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HomeTech Articles > EFI Troubleshooting Document #1

Pelican Technical Article:

Electronic Fuel Injection (EFI)
Troubleshooting Document #1

 

EFI TROUBLESHOOTING CHART
Based on possibly occurring problems (fuel injection system only)

NOTE:  This chart identifies only problems pertaining to the fuel injection system.   However, before looking for the problem in the fuel injection system, make sure that it is not possibly in another part of the engine, such as in the ignition system.

 

Trouble Cause Correction
Engine does not start, fuel pump is not running. Defective pump connections, pump relay or connections. Check pump connector for good condition. Check if pump relay is functioning (switch ignition on and off, listen for relay noise). If necessary, use voltmeter.
Pump relay receives no current at terminal 86 (12V) because main relay is not functioning or wire is defective. Check with voltmeter. Repair open circuit.
Pump relay shows 12 volts at terminal 86, but terminal 85 has no ground. NOTE: Relay is active for only about 1- 1 1/2 seconds after the ignition has been switched on. Check with voltmeter; relay is wired from ground through control unit. Do not connect terminal 85 to ground without first disconnecting wire 19 leading to the control unit, otherwise the control unit will be damaged. If no ground is available to wire 19 (switch ignition on and off), replace control unit.
Engine does not start, fuel pump is running. Connection from wire harness (wire 18) to starter terminal 50 is defective. Check with tester with starter running.
Operator' s problem: Engine does not receive sufficient amount of air for starting. Cold start system defective. Start with wide open throttle. Check thermoswitch and cold starting valve, possibly spark plugs as well, if overrich mixture is encountered (wet or carbon fouled spark plugs). See 1.1-2/7, test step 19.
Open circuit in wire connection of temperature sensor. Check wires. Replace temperature sensor.
No pressure buildup in fuel main line (compressed fuel hose or defective pressure regulator). Check pressure with gauge: 1.96-2.04 bar
(1.96-2.04 atm) when starter is running.
Replace pressure regulator if necessary.
Defective diaphragm chamber in pressure sensor. Replace pressure sensor.
Engine starts when cold but stops again. Wire connector for trigger contacts in distributor not connected or wire broken. Connect tester and go through test steps
8,9, 10, 11, 11a (EFAW-tester) resp. 14
(VW1218). If necessary, replace wire
harness or trigger contacts.
  Defective trigger contacts. Replace.
  Also see "Engine does not start".  
  Defective pressure sensor. Replace.
Engine dies when car is in motion (usually pre- ceded by misfire). Trigger contacts have excessive resistance or are dirty. Connect tester. If test steps 8 and 9 (EFAW tester) or 14 (VW 1218 tester) show malfunctions, replace trigger contacts in distributor.
Defective connectors. Check.
Entire system malfunctioning. Pump relay failing occasionally. Loose connection in power supply line of pump or control unit ground. Check pump relay and associated wires with voltmeter (follow wiring diagram).
Engine running badly. one cylinder not working. exhaust trails white smoke, Stuck injector. Replace.
Bad connection in injector winding or injector.  
Engine misfires due to causes other than the ignition system. Loose connections, but also ground connections, in injectors (ground- related problems cause two injectors to malfunction). Check connections, replace injectors if necessary.
Corroded or loose ground connections in the electrical system. Check ground connections for firm seating and attachment; battery ground strap, ground strap connecting transmission with frame, and regulator ground.
Check if problem can be traced to the ignition system. Otherwise it may be periodic voltage drop (Voltage I and II) in control unit (loose connection also in multiple connector in control unit. Check continuity in wires 16 and 24 with the aid of voltmeter.
Engine does not produce its full power.


Poor power output and poor power transition.
Defective pressure sensor.

Regulating flap for crankcase vacuum binding.

Insufficient injection quantity over the entire range due to fuel remnant deposits on injectors.
Replace.

Free up.


Replace injectors (injectors cannot be checked with shop tools).
Excessive fuel consumption. Defective temperature sensor or high contact resistance, Check connecting wires. Connect tester and go through steps 1-12 (EFAW-tester) or 1-13 (VW 1218 tester). Replace defective parts after possibly performing supplemental tests.
Considerable rpm surging during idling (between 1000 and 2000 rpm). Leak between auxiliary air regulator and intake distributor. Check.
Leak at throttle valve housing. Replace gasket between throttle valve housing and intake distributor, possibly reposition.
Leak in connecting houses between the intake distributor and intake manifolds. Poorly seated hoses, possibly requiring replacement.
Uneven idling, very poor transition during acceleration. Engine out of adjustment. Check and readjust ignition timing, valve clearance, and idle speed.
Mixed up injector groups. Check if connections are properly attached to
ignition distributor and injectors.
Loose vacuum hose connections. Firmly connect vacuum hoses, replace if necessary.
Comments and Suggestions:
socal1200r Comments: I'm also having issues with my '73 914 1.7L not starting. It ran okay a couple of days ago, then I went to start it the next day, and it cranked over but wouldn't fire. Ran the battery down, found out it wasn't holding a charge, so installed a new battery. Same result, car turns over but doesn't start. From reading the posts about this, I'm seriously considering ripping out all the FI parts and putting a 32/36 Weber conversion on it. Should be MUCH simpler to maintain, and not have to worry about all these stupid 40+ year old FI parts...
September 17, 2016
  Followup from the Pelican Staff: I can't help without knowing what is missing from the system when you are trying to start it. When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and fuel pressure, volume, quality and engine compression. Once you figure out what is missing, it will be easier to diagnose.
- Nick at Pelican Parts
 
VinoVotary Comments: Ok, gotta put it out there since I'm at a bit of a loss! 73 2.0 had a stutter issue with acceleration around 2500 rpm, continued to get worse, so replaced vacuum hoses, cleaned and checked tps, replaced injector seals, cleaned fuel tank and lines, verified fuel pressure is correct. Replaced mps, new plugs, coil and wires. Has a crane ignition as well as hydraulic lifters. Now that everything is replaced or checked the damn car won't start unless the vacuum hoses are off the dizzy! Then I'll put the hoses back on and the engines begins to die and finally sputters to death?? Super super frustrating! What should I check now?
July 20, 2016
  Followup from the Pelican Staff: Check timing to be sure it is OK. If so, confirm there aren't any vacuum leaks. - Nick at Pelican Parts  
Seabeeparke Comments: I'm struggling with a 72 914 1.7l... car was running great, I had recently replaced the fuel pump, fuel filter, plugs, points,cap and rotor etc... I was driving and had a few instances were it fell flat on it's face for a second, no fuel, but then got it back and continued on. I decided to double check my filter and it was still unrestricted. I reinstalled he filter put the car back on the ground, and no start. Did a series of diagnostic checks and it seems that my injectors are not getting a pulse signal. Any advice on where to begin my search for the culprit? Is the pulse on the positive or ground side, does one of them stay constant or do they both pulse.
July 16, 2016
  Followup from the Pelican Staff: I don't have wiring to review for your vehicle. You should have a constant power and a pulsed ground. If not working, the engine speed sensor or DME may be faulty. - Nick at Pelican Parts  
retread Comments: Nick, Thanks.

It runs sort of OK at low speeds and idles sort of OK if you disconnect and plug the vac line to the MPC.

I have used vacuum leak finder spray, no issue found.

We did a mechanical TDC locate through #1 plug and remarked both timing marks.

I have put in three different known good distributors, and timed them with an Intelligent timing light in smart and dumb mode.

Yesterday I Pulled the ECU and checked the four wires7,8, 10, and 15 as I recall from the ECU and the MPC both for Continuity and short to ground. No issue found.

Even though I tried several "known or suspected good" MPC's, I am now looking for the MPC test Procedure.

This is a real brain twister. I have been working on these cars personally since 1974 and then as a small shop owner since 2002. this one is killing me.

Any thoughts will be greatly appreciated.

One last thought, The fuel pump is an aftermarket. Maybe I need to recheck the pressure to see if it is failing, because the issue has become progressively worse over time,
December 22, 2015
  Followup from the Pelican Staff: It's the case where everything checks out, but it is still broken.

Spray is not a good way to locate vacuum leaks. You will not find a small one using a spray, plus you have the danger of fire. Use a smoke machine when the engine is cold and warm. try increasing fuel pressure a bit by restricting the return, if a vacuum leak, you should be able to remedy it temporarily by adding fuel volume.

I would still also question timing if the engine is properly sealed. - Nick at Pelican Parts
 
retread Comments: I have been fighting a lean pop and poor running on this 1972 914/ 1.7 for months. Pyrometer pointed at # 3 so I figured injector issue. Replaced all four. No Joy.
Adjusted brain, No joy. Pumped up Fuel pressure, Worked for a little bit then no joy.Fuel Pressure still in FS.

Car idles and does low speed when

Drives me crazy. So far I have replaced the distributor, the MPC, four injectors. Car idles and does low speed if I disconnect the Vac line to the MPC. full rich stuff.

Have not done cylinder head resistor or anything like that so far.

Need creative help.
December 21, 2015
  Followup from the Pelican Staff: Lean pop is most likely caused by a vacuum leak or mechanical engine timing. Have you confirmed both of those items are OK? - Nick at Pelican Parts  
arg Comments: 1973 914 1.7,ignition timing adjustment procedure
October 13, 2015
  Followup from the Pelican Staff: Check here for what you need:

http://www.pelicanparts.com/techarticles/tech_center_main.htm
I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 
Don Comments: I have a 1974 914 1.8 that has undergone a complete restoration. Engine starts but runs very rich. Does not smooth out at any speed. Have done all usual checks replaced all vac hoses-fuel hoses etc. Engine has been rebuilt with new temp sensor. When clamping fuel line to cold start valve engine will not start. Seems to be major problem with main FI system. Any ideas on what to check next?
September 19, 2015
  Followup from the Pelican Staff: What is fuel pressure? - Nick at Pelican Parts  
Andy Comments: Have a 1976 914 2.0L: Last time out engine ran great until it fully warmed up then it would intermittently sputter/lose power when trying to accelerate. Next time I pressed pedal it would accelerate fine. Next time sputter. Replace throttle switch just a few years ago and is good. Had injectors cleaned, tested, and new seals a year ago. Checked MPS vacuum a year ago and good. Checked distributor and all ok. Checked dwell angle and steady at 47 from 1200-2500rpm. Removed adv/ret hoses from Distributor to check timing and engine went up to 2500rpm which I believe its supposed to. It would run at 2500rpm for a while but then drop down to 1200 and jump back up. Kept going up and down. Checked timing and is dead on. Still need to check CHT sensor. I think an air leak causes the engine speed to go up?? My issue is that it goes down. What does the unsteady speed drops while adv/ret hoses are removed indicate? Could this be the cause of the sputtering problem when engine is hot?
September 14, 2015
  Followup from the Pelican Staff: The sputter could be from an air leak. I would start there, if you find the intake is sealed, I would check spark, fuel and compression on all cylinders. - Nick at Pelican Parts  
Starbear Comments: Problem resolved! Did several things though my impatience and frustration kept me from retesting after each one so don’t know if just one issue; suspect a few little things combining.
1. AAR valve checked out electronically OK, but used freezer/oven temp tests to get the disc moving back and forth. 2. Replaced 2/3 of the vacuum hoses have ordered remaining ones. 3. The hose one the fuel pressure regulator was on, but loose; cleaned and reconnected it. 4. Tweaked idle screw ‘faster’ a bit. 5. Cleaned pins on AFS unit. Will still send in AFS for rebuilding. Also noticed that I have a full second hose from the vacuum advance to the opposite side of the throttle valve – not on ANY hose diagram that I’ve ever seen. Have redrawn my own annotated, numbered, hose diagram. Whew!
August 13, 2015
  Followup from the Pelican Staff: Thanks for sharing your installation repair process and experience. These type of comments add so much to the Pelican tech community.
- Nick at Pelican Parts
 
Starbear Comments: 8/3 Inquiry cont'd. Thanks, Nick. Checked out Aux Air Regulator OK and just about done replacing all vacuum lines. Was working OK last night and will check PCV tonight and get back to you. Will probably get AFS rebuilt anyway original @ 41 yrs old...
August 12, 2015
  Followup from the Pelican Staff: Thanks for the follow up, keep us posted. - Nick at Pelican Parts  
kalani Comments: 75 914 2.0 ..rolling idle when throttled up it hangs at high rpms and slowly drops ?????
August 7, 2015
  Followup from the Pelican Staff: First, confirm there are no vacuum leaks. Sounds like the engine is trying to get control of idle. If there are none, you may have a faulty air regulating valve.- Nick at Pelican Parts  
Starbear Comments: More on 8/3 inquiry: Did another test - bypassed the aux air regulator by connecting the two hoses; kept the valve electronic connection on. Started fine though idle zoomed to 2800+ and stayed there. Reconnected hoses to regulator and got regular start idle followed by steady decline as warming. Sign that the valve is OK, but the air flow meter needs rebuilding?
August 4, 2015
  Followup from the Pelican Staff: Sounds like it may be OK. Have you checked the PCV valve? - Nick at Pelican Parts  
Starbear Comments: OK; THANKS, Nick! Will order today though catalog has it NLA and will confirm alt part OK. Might as well get air flow meter rebuilt, and replace rest of vacuum lines, too!
Onward....
August 3, 2015
  Followup from the Pelican Staff: No problem. let us know how it works out.- Nick at Pelican Parts  
Starbear Comments: RE: 8/3 inquiry - Ah... That the same as the aux air regulator #022-906-045?
August 3, 2015
  Followup from the Pelican Staff: Yes. - Nick at Pelican Parts  
Starbear Comments: Per 8/3/15 inquiry: Yes, it does. Street-runs fine; just doesn't hold idle after engine warms.
August 3, 2015
  Followup from the Pelican Staff: I would assume the idle control valve is it at fault then. - Nick at Pelican Parts  
Starbear Comments: Re a 1974 914-1.8; original owner, original L-Jetronic FI system. All of a sudden, as the engine warms, the idle drops, stutters, then dies. Idles just fine when engine is cold, before slowly fading. Checked vacuum boots one cracked; fixed, spark plugs OK and seals OK, head temp sensor OK, thermostat wire OK and various vacuum hoses seem OK, replaced all/most several years ago have worked fine until now, though have never replaced the four large, short ones on the four intake pipes. Adjusting the idle screw on the air control box has little/no impact. Condenser and points seems to be OK. Any suggestions – faulty aux air valve? Rebuild air control box? Replace all vacuum hoses again? Thanks!
August 3, 2015
  Followup from the Pelican Staff: Does it run well if you hold the idle using the accelerator pedal? - Nick at Pelican Parts  
kimbob Comments: hey- I have a 1975 914 with a 1.8. Every time I go into a corner, either way, the car sputters and I'm coasting through the corner, and then all of a sudden I get my power back and I'm good. I've replaced my fuel pump, and cleaned out my tank[it had a lot of rust deposits in it}. that didn't seem to make any difference. where do I go from here? thanks, Kim
July 19, 2015
  Followup from the Pelican Staff: First thing to do is find out why it is sputtering, what is going away. Monitor fuel pressure during the issue, if steady, monitor power to the coil when the problem is present. Let me know what you find. - Nick at Pelican Parts  
Kalani Comments: 914 2.0 starts and idles ...when i increase throttle it drops off the face of the earth .....help
July 11, 2015
  Followup from the Pelican Staff: To start, I would perform a fuel delivery system test. Check fuel pressure, volume and quality.
- Nick at Pelican Parts
 
randy in desert Comments: 71, 914 after 12/13 miles I lose power though might be vapor lock don't know. I live in desert runs fine up to 12/13 miles.1.7 engine.
June 29, 2015
  Followup from the Pelican Staff: Could be fuel delivery issue. I would perform a fuel delivery system test. Check fuel pressure, volume and quality.
- Nick at Pelican Parts
 
Jon Comments: I have a 1970 1.7 that the previous owner put a 1.8 motor in it. all of the intake and fueling components are 1.7 D jetronic. engine was having severe fuel diluted oil and running rich overall. I did the usual like check timing, check for vacuum leaks, fuel pressure injector contacts, TPS, valve clearance, compression, injectors, etc. the oil dilution problem seems to have gotten better after I set the dwell, timing, and fuel pressure, but it still seems to run rich and stumbles a bit around 3000 RPM and lack of power above 4000 RPM. I put vacuum on the pressure sensor and found a very small leak down. I took the pressure sensor apart and found the gasket on the main diaphragm was open a bit so I resealed it. I also noticed that there is an adjustment on the diaphragm. Is this adjustable? otherwise it starts and runs excellent.
May 30, 2015
  Followup from the Pelican Staff: I don't recall it being adjustable. If you found a tear, replace it. As this may be the cause. The other thing that comes to mind is leaking injectors. - Nick at Pelican Parts  
FerrariguyMa Comments: I have a freshly rebuilt 2.0L in my 912E, the engine is running D-Jet from a 914 and I am running into two problems. 1 at 3000-4000 rpm the engine "stumbles and bucks" and problem 2 is the engine once hot does not like to keep an idle and if it does stall is very difficult to restart. Any and all ideas, suggestions both welcomed and appreciated!
May 11, 2015
  Followup from the Pelican Staff: Sounds like a timing or misfire issue. The hot restart issue makes me lean toward timing. I would start there. - Nick at Pelican Parts  
fuugi Comments: Having issues with a 74 914 1.8 l-jet, got the car not running, fuel and starter was hot wired. Got car running the proper way idle and revs with head temp sensor disconnected, when connected car will not start or run. Temp sensor is new, any suggestions...thanks
May 3, 2015
  Followup from the Pelican Staff: It's possible the signal wire to the DME is shorted. I would disconnect DME and inspect the wire. - Nick at Pelican Parts  
Nate Comments: 73 Porsche 914 2.0 liter. Won't start and when it does it only runs for a few seconds. Timing set statically. Getting strong spark on all cylinders. Getting fuel through the injectors. Fuel pressure 30psi. CHT set up with variable resistance pot to 1400 ohms to simulate cold start. MPS ohms out correctly and holds vacuum. Any recommendations?
December 4, 2014
  Followup from the Pelican Staff: If you have spark and fuel, it has to be compression. Check engine compression and timing. - Nick at Pelican Parts  
brno Comments: i appreciate that page
November 15, 2014
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
Stevo Comments: Nick, you asked me if there are any "fault codes". How do I determine that?
If I spray gasoline into the air intake the engine runs fine.

Thanks
October 9, 2014
  Followup from the Pelican Staff: Sorry about that, I got ahead of myself. At times I forget what vehicle I am working with, as I answer so m any questions. Your vehicle cannot display fault codes.

I would perform a fuel delivery system test. Check fuel pressure, volume and quality.if fuel pressure or volume is low, check power and ground to the pump. - Nick at Pelican Parts
 
Stevo Comments: I have a 914 fuel injected 1.7L with a new fuel pump. The car will start and run for 3-4 seconds and then stops. If I pump the gas pedal very quickly I can get it to run for 6-10 seconds but runs very badly. Can you provide a direction.
October 8, 2014
  Followup from the Pelican Staff: I can't help without knowing what is missing from the system when it won't start. When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and fuel pressure, volume, quality and engine compression. Are there any fault codes? Once you figure out what is missing, it will be easier to diagnose.
- Nick at Pelican Parts
 
Paul10 Comments: I have a loose wire white near the fuel filter in passenger rear 911 1974s can anyone help. The car is suddenly loosing powers seems like fuel starvation.
Starts and runs ok intermittently but when power is needed it stalls

Many thanks in advance :
July 31, 2014
  Followup from the Pelican Staff: Can you find the other end of the wire?

If you suspect a fuel issue. I would perform a fuel delivery system test. Check fuel pressure, volume and quality. - Nick at Pelican Parts
 
Cpl620 Comments: 71 914 with a 1.7 d-jet. The car started to have trouble starting. I thought it may be a hot start situation and tried the gas to the floor. it took maybe 3 cranks each about 5 seconds before it would start, and progressively got worse longer intervals until it just won't fire. This took a few days fron the time it started to it not starting at all. It runs like a top when it starts, good power, no back firing, timing is dead on. I thought maybe oil got on some connections since it does leak, that didnt fix it. Fuel pump is working. A friend mentioned the ignition condenser maybe? but that seems odd since it still pulled strong when it did fire up. any ideas?
July 28, 2014
  Followup from the Pelican Staff: Ignition makes sense if it starts when held to the floor. I can't help without knowing what is missing from the system when you are trying to start it. When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and pressure fuel, volume and quality. Are there any fault codes? Once you figure out what is missing, it will be easier to diagnose.
- Nick at Pelican Parts
 
kpax914 Comments: Help; 1973 porsche 914 1.7 ignition system all new with overhauled distributer. however doesn't idle well, cleaned chkd TPS, ok. disconnected TPS runs ok no acceleration. F.I. harness brand new W/soldered conns. Removed hose from MPS runs rich. Should I suspect ECU?
July 13, 2014
  Followup from the Pelican Staff: Have you checked timing and vacuum leaks? - Nick at Pelican Parts  
aaronmvw Comments: Help Anyone?

My 914/4 ran fine, and then one day it just suddenly died.
Checked the injectors, and they are not getting power. However, the fuel system is completely pressurized. Could it be a bad relay or ECU? I know the temp sensor or pressure sensor may also have something to do with it too.

Any help is greatly appreciated!
July 3, 2014
  Followup from the Pelican Staff: COuld be bad main relay. Do you have spark, what is the fuel pressure? - Nick at Pelican Parts  
smokey Comments: engine starts sometimes but dont stay running
July 1, 2014
  Followup from the Pelican Staff: You didn't mention what vehicle you have. I can't help without knowing what is missing from the system when you are trying to start it. When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and pressure fuel, volume and quality. Are there any fault codes? Once you figure out what is missing, it will be easier to diagnose.
- Nick at Pelican Parts
 
Kevin Comments: Thx Nick.
I previously changed plugs, wires, fuel lines, rotor, points, condenser, rotor cap, did a valve adjustment, new fuel filter. Cold compression test between 130-140 at cycl. Got the car running then stopped after starting half dozen times.
I did notice the plugs were wet. Any ideas?
April 9, 2014
  Followup from the Pelican Staff: If wet, likely losing spark. I would test for spark at the coils. if none, check at the coil. - Nick at Pelican Parts  
Kevin Comments: Under Corrections for Engine Does not Start, Fuel Pump is Running there is a referrence to - wet or carbon filled spark plugs See 1.1-2/7, test step 19.
I may have this issue but I am looking for the reference and test step information to follow. Can you tell me where this info is?
Thx
April 8, 2014
  Followup from the Pelican Staff: You will want to check for spark if the plugs are wet. This flow chart looks like it is from the factory, the referenced tests do not appear to be present. - Nick at Pelican Parts  
bill Comments: 1985 944 engin only runs when hot wired diretly to fuiel pump . hot wired at fuiel relay pump rum but wold not start engin pleas help
February 2, 2014
  Followup from the Pelican Staff: I would start by jumping the replay, does it run? If so, check operation of the relay. Is it being commanded ON, and when it is does power get sent to the fuel pump? - Nick at Pelican Parts  
Dirk Comments: I will answer my own question and hopefully give some usefull information: No, the fuel injection systems for the 1.7 and 2.0 liter engines are not interchangable. Not only are the actual fuel injectors different, but also the part sizes and layout of the system.
October 31, 2013
  Followup from the Pelican Staff: Thanks for the follow up. We appreciate it. This is great information.
- Nick at Pelican Parts
 
Dirk Comments: Can I use a d-jetronic fuel injection system that has been removed from a 1.7 liter engine and use it on a 2.0 liter engine? If it works, what kind of adjustments do I have to make?
October 30, 2013
  Followup from the Pelican Staff: Here is the solution you came up with:

I will answer my own question and hopefully give some usefull information: No, the fuel injection systems for the 1.7 and 2.0 liter engines are not interchangable. Not only are the actual fuel injectors different, but also the part sizes and layout of the system. - Nick at Pelican Parts
 
Arum Comments: I have problem with my 3.3L 930 87 it won't start it only happen for the past few days. Previously the Same thing happen but was okay after persistent cranking it continue to be running but after over few days it wont start again. It also smell fuel.

Last few months I have replaced all the relays on the engine side and CDI and was okay. Could you advise what to check?
July 20, 2013
  Followup from the Pelican Staff: I can't help without knowing what is missing from the system when you are trying to start it. When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector flow and pressure fuel, volume and quality. Once you figure out what is missing, it will be easier to diagnose.

if you have fuel delivery but no spark, check the signal to the coil.- Nick at Pelican Parts
 
adriansgp4 Comments: I have a Porsche 914, 1.7. It starts, runs OK, but when cruising it surges a bit, and will only accelerate reasonably if the accelerator is "pumped" gently.Acceleration without pumping is poor. I have replaced all vacuum lines, fuel hoses, points, plugs, injector seals etc. I have adjusted the timing/distributor, and tried the throttle position switch in various positions but is doesn't seem to make any difference. Any suggestions please.
Thanks
Adrian
Australia
February 5, 2013
  Followup from the Pelican Staff: Troubleshooting 914 fuel injection is a long-lost art. Though one thing you haven't mentioned is the air pressure sensor, these have a habit of having the internal diaphragm brake and then they no longer function properly. You can test the unit by pulling out and pulling a vacuum on it. This is also as simple as sucking on it with your mouth. If the unit holds pressure then it's still good. If you can suck a lot of air out of the unit then it's most likely bad. As you mentioned the throttle switch also gets worn out you can take a multi-tester and test each individual location on the throttle switch to make sure that it's functioning properly. The copper contacts inside the switch have a tendency to wear out over time and can create the surging problem that you are experiencing. - Wayne at Pelican Parts  
aircooledfool Comments: I just bought a 72 1.8 914 won't pass emissions. It spits fuel out the exhaust on to ground leaving blackish residue. I have not done any motor work yet not knowing were to start.
November 26, 2012
  Followup from the Pelican Staff: The first thing to do is make sure that the engine oil is not fuel diluted: This is caused by excessive unburned fuel in the cylinders running past the rings into the crankcase. You can check for oil dilution by simply smelling (and looking at) the oil dipstick. If it smells of gasoline and looks black and very runny, you have serious oil dilution and should change the oil before you try to run the engine any more.

As for the causes of fuel dilution and other malfunctions, check out this tech article: http://www.pelicanparts.com/techarticles/914_EFI_troubleshoot/914_efi_troubleshoot.htm - Nick at Pelican Parts
 
Mitch Comments: Sorry this is Mitch again. It is a 914-4 on the fuel pump problem, thanks
October 2, 2012
  Followup from the Pelican Staff: Ok, thanks. This tech article explains a number of electrical tests you can do: http://www.pelicanparts.com/techarticles/914_EFI_troubleshoot/914_efi_troubleshoot.htm

You need a repair manual with wiring diagrams so that you can diagnose electrical problems such as this one. - Nick at Pelican Parts
 
Mitch Comments: I do not hear the fuel pump relay click on when I turn on the ignition. I replaced the relay board, relays and the voltage regulator. Fuel pump still does not come on, fuel pump works I checked it by direct wire. Flasher is flashing through the dash light indicators when I turn on ignition and flashes through the relay board. I would also like to know how to find termanel 86. I also replaced the ECU unit. I am at a loss! Please help, thank you, mitch
October 2, 2012
  Followup from the Pelican Staff: Thanks. See the response to the follow-up clarification. - Nick at Pelican Parts  
Mike Comments: soooo I c u have a 911-615-109-01 relay. is this relay for both the power supply and fuel delivery for fuel injection on 1971 914 1.7. and what is a 911-615-108-01 for?
August 11, 2012
  Followup from the Pelican Staff: 911-615-108-01 shows up s a fuel pump relay. - Nick at Pelican Parts  
g.i. Comments: i own a 1973 914 2.0 porsche in which it is in the mechanic shop for installing new 4 injectors.is it best to take one from /injector/ car and match it up with a new one .are there model or part numbers on each injector,so we get the right injector,what should the psi fuel/oil be set or read..we have seen 2.0 bar and 1.5 bar.what is layman terms.is there any thing else that should be done while changing out injectors...please advise..
July 6, 2012
  Followup from the Pelican Staff: It is best to replace them in sets and from the same application.
1.5 bar = 21.7 PSI, 2 bar = 29 PSI. Not 100% sure but you might be able to find a Bosch or the vendor part# on the old injectors. - Nick at Pelican Parts
 
gi Comments: what is the normal oil/fuel pressure on a 914 2.0 1973 porsche,mechanic does not have a manual to check these 2 items.injectors are bad all 4,shooting out fuel after car is shut down..
June 27, 2012
  Followup from the Pelican Staff: Fuel pressure is 28 psi. A manual is essential if you're going to work on these vehicles. - Nick at Pelican Parts  
Jose Comments: I have a 1975 Porshe 914. The engine cranks but the fuel relay keeps burning out. Any thoughts on locating the short. Does anyone have similar experiences that was able to locate the cause and the fix? Any informations is useful at this point. Thanks!!!
June 26, 2012
  Followup from the Pelican Staff: I would start by checking current draw at of the pump. Should be about 2/3 of the fuse rating. If the fuse isn't blowing, it has to be a high current draw, yet not high enough to blow the fuse. - Nick at Pelican Parts  
914 2.0 Comments: is it ok to use injectors from a 1.7 in a 2.0
February 26, 2012
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799. They should be able to look up that information. - Nick at Pelican Parts  
Karl Comments: my 94 Chevy Lumina APV is injecting fuel into the throttle body even when I don't press on the gas pedal
January 13, 2012
  Followup from the Pelican Staff: This is a forum for European cars, primarily. Sorry. - Nick at Pelican Parts  
John K.B. Comments: My '73 914, 1.7 has developed a fuel leak at or near the injectors on the passenger side. It came on suddenly. A month ago I replaced the fuel lines from the tank to the rear and the fuel filter. Is there a quick fix for the FI leak?
November 28, 2011
  Followup from the Pelican Staff: Once these injectors become leaky they need to be replaced. If the fabric-covered hose that supplies fuel to the injector is leaky, you can grind off the crimped-on metal clamp and replace the fuel hose with equivalent high-pressure hose. But it is just as likely that the plastic of the injector is cracked and leaky. - Nick at Pelican Parts  
sloroger Comments: Same problem as Milton, November 19th! What is that triggers sets of two injectors to fire? I'm thinking that if I could just diagnose this it might be easily fixed, but I'm stumped. Please help me identify the component that triggers the injectors to fire in sets of two.
November 21, 2011
  Followup from the Pelican Staff: There is a second set of points in the distributor on a plate below the regular ignition points. These are used to trigger the injectors in pairs. - Nick at Pelican Parts  
Milton Comments: I currently have only the #3 and #4 cylinder running. I replaced the injectors with new ones. They all read 3 ohms at the brain box connector. The trigger for the fuel injectors looks new, and fuel is at 30PSI. Could there be air in the line? I also seem to be getting spark my timing light was flashing on #1 and #2 wires. When I remove the injector wires it still runs the same....baffled!! Any suggestions?
November 19, 2011
  Followup from the Pelican Staff: Be sure to check the basics: Engine compression. - Nick at Pelican Parts  
J Marshall Comments: Have a 1974 914 1.8l with all original fuel injection. Started with the flick of the key and ran perfectly. Had to take it to the body shop, where it was for six months. Go to pick it up today and it starts easily and idles. But when you press on the gas pedal it will "jump" up to about 3000 rpm then shoot back down to idle. Completely lacking enough power to move.
No work was done to the engine while it sat there. Mystery to me. Could they have somehow messed up my airflow sensor by trying to start it with the gas pedal pressed.
I'm also getting a pretty heavy clicking when I attempt to give it gas. Sort of reminds me of what the valves would sound like until the car warmed up-except now its not going away.
Any help appreciated.
October 26, 2011
  Followup from the Pelican Staff: This car has L-injection. Make sure the air boot between the mass air flow sensor and the intake is solidly attached and not cracked. - Nick at Pelican Parts  
RSZ914 Comments: I have a 1974 914 1.8. Pulled it out of the garage the other day, no problems. 1 hour later went to start but would not. Engine "cranks" fine, but never fires. Pleant of gas and the fuel pump is new. Now several days later and still does not start, so That should rule out vapor lock. Any ideas?
September 3, 2011
  Followup from the Pelican Staff: I can't help without knowing what is missing from the system when you are trying to start it. When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and pressure fuel, volume and quality. Once you figure out what is missing, it will be easier to diagnose. - Nick at Pelican Parts  
raulmga Comments: i noticed a sweat or fuel mark around the fuel tank neck, is that a vacum leak???
July 22, 2011
  Followup from the Pelican Staff: Could be a liquid fuel leak. I would inspect it closely. - Nick at Pelican Parts  
hogfarm Comments: how do I get the cylinder head temp sensor out
May 14, 2011
  Followup from the Pelican Staff: Try this tech article:

http://www.pelicanparts.com/techarticles/911_cyl_head_temp_sensor/911_cyl_head_temp_sensor.htm - Nick at Pelican Parts
 
Paul Comments: Where would I find the loation of the fuel pump, and fuel pump relay on a porshe 914 1971
April 9, 2011
  Followup from the Pelican Staff: If the pump hasn't been relocated, it should be located in the engine compartment below the battery (fuel filter is there too). The fuel pump relay is located on the relay board on the left side of the engine compartment. - Wayne at Pelican Parts  
jonnie Comments: 1982 928 porsche wont stay running i tried new computer fuel pump can hear the injectors spraying when i jump them but not when car is turning over but if we jump the relay panel the car try to run but not good enough to burn the gas off the plugs getting wet all the relays are new it get gas up through the rails hope you can help me thanks
February 17, 2011
  Followup from the Pelican Staff: The car needs spark + fuel + compression + timing to get it to run. Sounds like you are missing fuel. The fuel injectors are triggered by the computer, which gets its information from the sensors (camshaft / crankshaft?). I would check those sensors first and then go from there. - Wayne at Pelican Parts  
hotwheel Comments: can anyone help. 1972 914 I have been having problems with my cars idle after it's been running for about 25 min. The book says it's the fuel mixture and when I take it to the shop the mechanic tells me the heads were loose and the valves were tight. My question is if the heads the first time came loose and leaking oil were the gaskets still good enough to re-tighten instead of getting new ones. Every time I take it in he has to tighten up the heads and readjust the valves. He also says that the pressure sensor my be bad and he make the car run richer but within a week the same thing happens again. Has anyone had this problem and can you help.
February 12, 2011
  Followup from the Pelican Staff: Sounds like you need a new mechanic to start. I haven't really heard of a problem with the heads being loose on these engines - I hope that he is not overtightening them each time. You cannot use a static torque method to tighten them, you have to use running torque with lubricated head studs. Actually, any time after assembly, the torque values are not terribly accurate, but that's a different story for a different day.

He should be able to measure your mixture on a CO machine, and he should also be able to test your pressure sensor for proper operation. If he can't do this, then you should probably find a mechanic who can? - Wayne at Pelican Parts
 
detoxcowboy Comments: The above recomendation for the 914 2.0 thermo=time switch causing low idle after 5 minutes is wrong. The thermo time switch only operates at ambient temps of 15-32 degress farhenhiet, in other words when its snowing or at that level of environment.. and then it only operates when the key is in the start position..
July 14, 2010
  Followup from the Pelican Staff: Thanks for the input on this one. We appreciate the help. - Nick at Pelican Parts  
bill Comments: bill 1.7 914 runs good after warm up idle very hi 2000 rpm no power after 3500 rpm changed FI contact points in dist a couple of month ago went away now it back again fuel pressure 36 psi good plenty of power to 3500 then bog's down checked points ok timing ok no vacuum leaks driving me crazy but lets see thanks bill
May 9, 2010
  Followup from the Pelican Staff: You said you checked fuel pressure, i would give fuel volume a look. A pint in 30 seconds is a good rule of thumb. Also check exhaust back pressure. You want no more than 0.5 psi.- Nick at Pelican Parts  
David Comments: Question [if you have time]: I have a 74 914 1.8 that once warm and under deceleration or downshifting has an irregular but recurring set of pops in the exhaust. Almost sounds to my like it is running rich but certainly can't confirm that. Injector firing problem? The car runs and idles great when cold or warm.

THanks,

David
April 6, 2010
  Followup from the Pelican Staff: Check the exhaust system junctions for small leaks. - Nick at Pelican Parts  
Enzowho? Comments: This question may have been answered but I'm havin a hard time with a 1983 928S not starting. I've replaced the fuel pump and all applicable relays. I have power to the pump relay and the injector relay. There's fuel pressure at both rails but it appears as though the injectors are not firing. They aren't wet. I can get the car to start with starting fluid down the intake manifold and as soon as that runs out the motor dies. I fixed a broken wire to the temp sender, and replaced two loose ground wires. I suspect the injector computer is not working but I don't know if it's a ground problem or the computer itself. How can I test it? There is a large wire on the driver's-side front of the engine bay that has a female terminal on the end that is connected to nothing and based on the distance it can travel, I can't find anything in it's reach that it might connect to. I don't know if this has a role in the running of the motor or not.. Any suggestions would be appreciated. Thanks.
March 23, 2010
  Followup from the Pelican Staff: have you checked the fuel injection relay? I have seen these corrode and blow fuses. - Nick at Pelican Parts  
Mike Comments: I have a 77 911S. When lightly depressing the gas pedal, in neutral, my rpm's quickly go up to 3000, hover there for a few seconds and then come back to normal idle. I would only expect them to go up to 1100-1200. This also happens when shifting, although once in gear everything seems fine. Engine runs strong otherwise. Any clues?
Thanks,
Mike
January 13, 2010
  Followup from the Pelican Staff: You could have a vacuum leak or need to adjust your idle setting. This forum thread has some great information:

http://forums.pelicanparts.com/porsche-911-technical-forum/625887-startup-idle-rpm-all-time-1977-2-7-cis.html - Nick at Pelican Parts
 
chi Comments: how can you adjust the idle speed?
January 3, 2010
  Followup from the Pelican Staff: Please specify the year and model of your vehicle. - Nick at Pelican Parts  
Brian Somers Comments: I have a 76 914 and when I first start it, it idles beautifully, then after about 5 minutes the idle starts dipping and almost cause the engine to stop running. It will occelate between 0 and 1000 rpm until the engine is warmed up, at which point the idle sits perfectly at 1000rpm. Any ideas of things to check?

Thanks,

Brian
November 8, 2009
  Followup from the Pelican Staff: On the 2.0L 914, there is a thermotime switch that controls the cold start valve. It's supposed to operate it when the car starts and when it's warming up. If the switch shuts off when it's not fully warm, then it will affect the mixture and cause the "hunting" that you are experiencing. This may not be the problem, but it's the first place I would look. The switch is in our catalog: http://www.pelicanparts.com/catalog/shopcart/9144/POR_9144_FULint_pg2.htm - Wayne at Pelican Parts  
Jarret James Comments: 1975 Porsche 914 1.8
Have spent the last six months trying to find why I have power surges.
Usually resulting into intense power drop all the way to 4000 RPM, Severe
bucking which feels very dangerously unstable, almost kills the engine if accelerator is not yielded. I thought it was the cylinder head temp. sensor replaced it.
I find it very strange that on a drive through the woods the car can have such a split personality. A couple of turns later the engine is running the best it has in years? The next a trucker is going to run over me...
Have also just tested another ECU, inspected all main gas lines and main electric supply lines and electronic ignition, pug wires, cap, plugs valve adjust, well what next?
Struggling daily driver.
August 10, 2009
  Followup from the Pelican Staff: I would suggest that you assume nothing at this point. Make a check list and look at everything. Very often overlooked are the wire harnesses in the engine bay, which can become heat hardened and sometimes work, and then sometimes not. Run a compression check and valve adjust on the engine too, just to take any mechanical issues out of the equation. Hope this helps! - Wayne at Pelican Parts  
Vic Comments: Help, anyone?

1982 Porsche 928, fuel system problem. Got the car from another, was told it was working prior to replacement of timing belt. I completed the timing belt replacement, fuel pump, filter and relay was replaced by previous owner.

Engine will not start, but runs nice when fuel is put in the intake filter area.

Ignition spark is fine
Air intake is fine
Compression is fine
No exhaust restrictions
Fuel is getting to the injectors
Injectors removed cleaned and spray is fine

Getting 12V to each of the injector terminal wires, not sure if this is normal? I was under the impression that a negative is needed to activate the injectors. I repeat both wires are positive when the ignition is on. Very little pulse on the wire when trying to start, looks like not enough current to activate the injectors?

Green wire is fine, connector was replace
Tach on dash not working, was told 1982 does not effect EFI?

Any assistance is greatly appreciated, like to get the car running to give to my son.

Thank you,
Vic
May 18, 2009
  Followup from the Pelican Staff: First step would be to take the injectors and place one into a glass jar to see if they are indeed firing. Also, check the fuel pressure - fuel may be getting to the injectors, but the pressure may be too low. - Wayne at Pelican Parts  

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