Pelican Technical Article: EFI Troubleshooting Document #1

Comments and Suggestions:

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

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

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

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

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

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

raulmga	Comments: i noticed a sweat or fuel mark around the fuel tank neck, is that a vacum leak???
July 22, 2011

hogfarm	Comments: how do I get the cylinder head temp sensor out
May 14, 2011

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

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

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

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

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

chi	Comments: how can you adjust the idle speed?
January 3, 2010

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

Pelican Technical Article:

Electronic Fuel Injection (EFI) Troubleshooting Document #1

Electronic Fuel Injection (EFI)
Troubleshooting Document #1