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Starter System Troubleshooting

Pelican Technical Article:

Starter System Troubleshooting


4-10 hr


$120 to $250





Applicable Models:

Porsche 911 (1965-89)
Porsche 912 (1965-69)
Porsche 914 (1970-76)
Porsche 930 Turbo (1976-89)

Parts Required:

High torque starter, transmission ground strap

Hot Tip:

Most starting problems are caused by bad grounding

Performance Gain:

Easier and quicker starting

Complementary Modification:

Upgrade to a high torque starter
101 Projects for Your Porsche 911

This article is one in a series that have been released in conjunction with Wayne's book, 101 Projects for Your Porsche 911. The book contains 240 pages of full color projects detailing everything from performance mods to changing your brake pads. With more than 650+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any Porsche 911 owner's collection. See The Official Book Website for more details.

At one time or another, everyone will have problems starting their 911. It's almost inevitable with older cars of any make, and Porsches certainly are not exempt. What do you do when the car won't crank? There are a few steps and procedures that you can follow to track down the problem. It is important to note that the subject of this project deals solely with the starter motor and it's electrical system. If the car is cranking, and won't fire up because of a fuel or ignition system problem, then you'll have to check some of the other troubleshooting projects in this book.

The first place to look for trouble in your starting system is your battery. The battery is perhaps the most important electrical component on the car, and due to its design and nature, is perhaps one of the most troublesome. Before doing anything drastic like replacing your starter, you should make sure that your battery is in good condition.

Is the battery more than five years old? Have you accidentally left the lights on and drained it down considerably? Are your lights dim? Does the battery sit for long periods of time when you don't drive the car? Do you need to charge it up every two months or so? If you answered yes to any of the previous questions, then you should take a long, hard look at the condition of your battery. Lead-acid batteries are not meant to be drained completely. If your battery has been drained, then most likely it has been damaged. The exception is a deep-cycle lead acid battery like the ones used in marine applications. These can be drained significantly, and still return to function properly.

Begin by checking the voltage on the battery posts using a voltmeter. Place the meter's probes on the posts of the battery, not the clamps. This will give the most accurate indication of the voltage in the battery. A normal battery should read a voltage slightly above 12 volts with the car sitting still, and no electrical devices on (the small trunk light in the front trunk shouldn't make a difference in this reading). A typical reading would be in the 12.6 volt range when the battery is fully charged. If the reading is 12 volts or less, then the battery needs charging or needs to be replaced with a new one. To be certain, you can usually take your battery to your local auto parts store for testing.

When the car is running, the alternator should be outputting anywhere from about 12.5 volts to about 14 volts. If you don't see any significant change in the voltage after you start up the car, then your alternator or voltage regulator could be faulty. If the voltage is high at the battery (around 17 volts or higher), then the regulator is most likely faulty and needs to be replaced. Overcharging the battery at these higher levels will cause it to overflow and leak acid all over the inside of your car.

Once you have determined that your battery is fine, you should make sure that your transmission ground strap is properly installed. The engine and transmission are mounted to the chassis using rubber mounts. While great for the suspension, the rubber mounts make lousy electrical conductors. To compensate for this, there is a transmission ground strap that electrically connects the transmission and engine assembly to the chassis. To accurately assess the condition of the ground strap, you need to crawl underneath the car after it's been jacked up, and take a look at the bottom of the transmission. If the strap is corroded or damaged, it might be best to install a new one. Make sure that you clean both ends of the strap and the areas that it mounts to on the chassis. With all electrical connections, it's a good idea to clean the area that you are mounting to with rubbing alcohol, and also to sand the area lightly with some fine grit sand paper. Doing so will remove any dirt, grime, surface rust, or other corrosion that may interfere with creating a good electrical connection.

Another problem area for starting is the starter, of course. The starter is a somewhat complex device for what would seem to be a simple task. There is a solenoid on the starter that both actuates the small gear that turns the flywheel and switches on the main starter motor. It is important to throw in a note of caution here. The starter motor is connected directly at all times to the positive terminal of the battery. If you accidentally touch the terminals of the starter with a metal object that is grounded, you will quickly generate a lot of sparks, heat, and enough current to fry your alternator and a large chunk of your electrical system. I have heard of two separate occasions where a person was working on their car, and their watch touched the terminals of the starter and the chassis ground. This literally caused the watch to become welded to the chassis of the car! The lesson: exercise caution in this area. Don't wear any jewelry when working on the car, and always disconnect the negative terminal from the battery.

Another potential problem is the starter teeth on the flywheel or ring gear. If the starter seems to engage and spin up with a high-pitched whirring sound, then it is likely that the starter is not fully engaging the flywheel. This is especially prevalent with intermittent problems where sometimes the starter will work fine and then other times it will spin freely. The fix for this is to inspect the flywheel teeth, and to replace the flywheel or ring gear when the engine is out of the car.

When 911s have trouble turning over the starter motor, it is often because there isn't enough current to fully trigger the solenoid on the starter. This can be caused by a number of reasons. The most common reason is old wiring in the car. As the car ages, the wiring has a tendency to lose some of its electrical conductibility. This can be caused by the wires getting bent or crimped, or it can also be triggered by the constant heating and cooling of the wires. This tempering of the metal within the wires can directly affect their conductivity. With age often comes corrosion, and as we can see simply by looking at the Statue of Liberty, copper corrodes quite easily, leaving a light green layer that doesn't conduct very well.

The solution is to track down the problem in the wiring and fix it. Very often, tracing back the electrical connections from the starter, and carefully cleaning all the contacts will improve the situation significantly. While this can be a time consuming process, it's really the only way to track down these electrical gremlins. Chances are if you are having wiring conductivity problems with your starting system, then it's probably affecting other electrical systems as well.

The primary method of tracking down bad connections is to test them with an electrical multi-tester. Test the resistance across lengths of wires and connections in your car and look for any that are significantly higher than others. Chances are with a little cleaning of both the wires and the contacts the system will improve.

The electrical portion of the ignition switch is another source of trouble. This small part often wears out and fails after many years. Some symptoms of this problem is an ignition switch that requires a lot of force to start the car. Another symptom is headlamps that flicker on and off when you wiggle the key. For the replacement of this switch, see Pelican Technical Article: Replacing your Ignition Switch.

If you cannot find the problem causing your starting woes, there is a potential solution called a hot start relay kit. While this solution will work by bypassing some of the faulty wiring, it is basically a Band-Aid put on a much bigger problem. The hot start relay kit takes the power from the starter cable that is connected to the battery and uses it to turn over the solenoid. The relay is powered by the electricity that travels through the âfaulty' wiring. Since the hot start relay only requires a few milliamps of electrical current to operate, it fixes the problem of starting the car. However, as mentioned previously, if you have electrical starting problems you probably have additional electrical problems elsewhere. These are best tracked down and fixed, instead of glossed over.

Finally, if you have determined that the problem lies with your starter, you should replace it. The starter is relatively easy to replace: simply disconnect the electrical terminals and unbolt it from the transmission. See Pelican Technical Article: Engine Removal, Engine Removal, for a few more details on the removal of the starter.

You can replace your unit with a genuine Bosch rebuilt unit, or for about the same cost, you can opt for a quality aftermarket unit. The aftermarket starters are higher torque starters, weigh less, use newer technology, and are generally a really good bet for placement in your car. In most cases, the cost between the OEM and aftermarket starters is negligible. Compare the two before you make a decision. If you want to go with a completely stock 911, then stick with the Bosch unit. Otherwise upgrade to the aftermarket starter.

Another popular option for upgrading your starter is to install a 1.5 HP Bosch unit. The early 911s shipped with the Bosch 17X starter which is rated at only 3/4 HP. The later style Bosch 68X unit is a bolt-in replacement and offers much better cranking than the original 17X starter. New Bosch units are not available, but rebuilt ones can be found if you have a good used core.

The infamous transmission ground strap is one of the easiest parts on the car to overlook, yet can cause so many electrical troubles.
Figure 1

The infamous transmission ground strap is one of the easiest parts on the car to overlook, yet can cause so many electrical troubles. Since the transmission and engine mounts are insulated by rubber, the ground strap is the only significant ground to the engine. If the ground strap is disconnected or missing, then the current that turns the starter must travel through the engine harness or other small points of contact. Needless to say, this situation usually doesn't provide enough current to start the car. The white arrow points to the location where the transmission ground strap attaches to the transmission. The yellow arrow shows the chassis mounting point.

While upgrading to a high torque starter shouldn't be your first step in troubleshooting a difficult starting 911, it can be a worthy upgrade to a starter motor that has genuinely worn out.
Figure 2

While upgrading to a high torque starter shouldn't be your first step in troubleshooting a difficult starting 911, it can be a worthy upgrade to a starter motor that has genuinely worn out. The aftermarket starter motors offer higher horsepower, and are also significantly lighter than their factory counterparts.

Comments and Suggestions:
Aaron Comments: After nine months of not starting my 1967 912, after a repaint, I attempted to start it and nothing. I checked all the terminals and placed the battery charger on the car. With the battery charger, in the start position, the car started. I purchased a new battery and again the car would only start when the battery charger was attached to the battery. I installed a new starter and again the car would only start with the aid of the battery charger. I cleaned the negative terminals on the cable going from the chassis to the transmission and again the car would not start without the aid of the battery charger. Checked the new battery and it is good. Your assistance would be greatly appreciated.
February 15, 2018
my 912 Comments: can some one help,I need to know the distance the starter motor gear travels on a 1967 Porsche 912 , I have measured a distance of about 12 to 13 mm,and found that distance to be short of what I require .only grabbing about 2mm on fly wheel ,which isn't enough to start the car. its a 12 volt starter and correct flywheel 12 volt 109 teeth .
December 19, 2017
  Followup from the Pelican Staff: I don't have that info. Possible to bolt flat steel to starter mount and measure to gear. Then compare to your measurement.
- Nick at Pelican Parts
Neil McCaw Comments: Anybody know where to find a 9 tooth starter gear/ starter
to fit my '91 911 with a '95 G50 6 sp. and a lightweight
clutch out of an '87 930.? Many thanks for any info.

Neil McCaw
June 5, 2017
  Followup from the Pelican Staff: Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
Camp Comments: Hi
tried to start my 73 Targa after a few weeks.
Power comes on and all electrics working on fully charged batteries, fuel pump buzzing, all good ... however when I turn the key only one click ...try again and just a click... not sure what it is as it's never happened in the 10 years of ownership . Could it be starter or solenoid ? Tks
May 23, 2017
  Followup from the Pelican Staff: Could be. BUT - I would voltage drop the starting system cables. Could just be a bad connection. If they test ok, check the signal to starter, replace if not running when activated.- Nick at Pelican Parts  
Scott Comments: I'm having fun. I have a 1968 911 with a 2,4S/901 drivetrain which delivers only a dreaded clicking sound when attempting ignition. The battery in service when the problem first surfaced was 3y old so I replaced it and the new one checks out fine. The car had this issue 5 months ago and I was able to get it started and drive it back to the house about two hours later without issue*; the problem again presented itself immediately after shutdown. It does not roll except in neutral. *There was a multitude of potential fixes occuring at the same time during the issue's first appearance so what actually "fixed" it was not readily apparent. The clutch, starter, tranny and related components have all been rebuilt or replaced within the last 18 months. If I wasn't working nearly 90h/week I would tear down and diagnose but as it is I don't have time for much else besides sending up a flare. Thanks in advance for any ideas.
February 26, 2017
  Followup from the Pelican Staff: Haha you ARE having fun! Most of the time this issue is caused by a bad ground at the gearbox to body, or by bad ground straps at the batteries. Also check to make sure that the ignition switch is dry. You may want to buy an electrical portion of the ignition switch (assuming the grounds and starter B+ are good and clean free of corrosion) you can easily unplug the connector and plug in the new one, then turn it with a screwdriver and see if your problem goes away... - Casey at Pelican Parts  
pcar71 Comments: the smoke was white, and the wiring harness that goes toward the generator was warm. i didn't get as far as to turn the ignition on, this was just after making the initial connection of the battery. the generator did not get water, btw.
December 12, 2016
  Followup from the Pelican Staff: White would indicate steam, most likely. Disconnect the battery. Inspect the area of the smoke, confirm the harness is not melted or overheated. - Nick at Pelican Parts  
Pcar71 Comments: I have a 71 911t, recently flooded with 2' of water. After drying the car out for 3 weeks, i decided to connect battery, had alot of smoke from engine compartment immediately, disconnected battery of course now, what next? Could it be water in starter?
December 3, 2016
  Followup from the Pelican Staff: what color smoke? Could it have been steam? - Nick at Pelican Parts  
Andrei Comments: Hi Nick. I have a 1985 930 Porsche and an electrical problem...Sometimes now more often starter doesn't engage no sound, nothing when i try to start the engine. This happens usually when the engine is hot after a long trip. If i connect a direct 12 + wire to the starter yellow wire engine starts just fine. I wouldn't use a "Hot jump starter relay" or new home made wires to correct the problem, any ideas would be greatly appreciated! Thanks!
October 2, 2016
  Followup from the Pelican Staff: Sounds like either the wire is failing when hot or the connection. I have seen cables and wires fail, try replacing it. - Nick at Pelican Parts  
Pokey Comments: 1986 911-has been running great. Always started on first hit. Recently there could sometimes be a slight delay between turning key and start up. Intermittently, it would not start but then try again and it would. Now turn the key and all I get is a click solenoid trying to engage. No start. Removed starter twice to inspect recent Bosch rebuilt - bench tested perfect every time. Installed back in the car and issues persist. Battery tested fine and is 100% charged. Car will bump start fine on first hit. Issue seems to be isolated to starter circuit only - but not the starter itself or the battery - suggestions?
August 18, 2016
  Followup from the Pelican Staff: You likely have a battery cable issue. I would voltage drop test the positive and negative battery cables. - Nick at Pelican Parts  
Rolf Comments: Have had my 1972 911 T stored for about 4-5 months in a climate controlled garage. Tried to start the other day. Lights at dash come on, you can hear the buzz in the engine compartment and just a click when you fully turn the key. Does not turn over. Never had a problem with the same scenario for over 40 years. Any thoughts?
July 18, 2016
  Followup from the Pelican Staff: Sounds like maybe the starter has failed. To be sure, voltage drop the battery cables to the engine and starter. Then check the signal to the starter solenoid. - Nick at Pelican Parts  
Larry Comments: My 1986 911 twice has not started a second time after being driven 20 to 24 miles. I've stared on compression or jump start and the next time it started right up. My mechanic couldn't figure it out.
February 24, 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. Are there any fault codes? Once you figure out what is missing, it will be easier to diagnose.
- Nick at Pelican Parts
Wiz Comments: 82sc Replacing starter with a hi-torgue, My stock starter has just onr large power wire on cellenoid post, I am told the wiring on the high t orque is different. It has the blue covered bolt on starter and a large bolt on cellanoid. Can any one help? Thanks
October 11, 2015
  Followup from the Pelican Staff: I don't have info on that. Check with the starter manufacturer. - Nick at Pelican Parts  
Joes911 Comments: Just had Pelican hi torque starter and batt cables changed on my 76 911s with 3.2 l motor. Spin is fantastic! No more worries about hot crank! Js
August 31, 2015
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
mike Comments: cant start my 68 912; has been stored all winter in a dry but very cold place. engine turns over and bat is ok. Could have some for of gas line freeze? I checked today and the gas line coming in to the filter is bone dry
March 29, 2015
  Followup from the Pelican Staff: The engine cranks but does not start? First thing to check is for rust in the fuel tank. Purchase fuel tank sending unit gasket...Remove fuel tank sending unit, look with a flashlight the inside of the tank should be clean and silver with no rust. If that looks nice and clean, try very liberal pumping of the accelerator pedal when trying to start the car. This is required when starting after long periods of idle time. Pump the accelerator numerous times before trying that first crank. Once the engine starts to turn over continue to pump the accelerator rapidly. You may need to use a battery jumper pack to continue the cranking process and pumping. Usually this will get the car started. If you can spray a brief squirt of starting fluid in each of the carburetor barrels that may help get her going too. If those things fail, it's time to check for spark and make sure all carburetor barrels are receiving the proper fuel flow. - Casey at Pelican Parts  
pete Comments: I have a 84 carrera that has intermittent electrical starter problems, Afterlooking under the the dash I found a black wire about 20 gouge or somewhat larger that was very hot at one time melting the insulation to a point where i can see the metal wirer the wirer has no current flow at this time but al the doors and deck lids including glove box has no current What is the black wirer for? and where does it go please help
October 27, 2014
  Followup from the Pelican Staff: I am not sure what wire that is. I would grab a repair manual. It will have the wiring diagram.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
Terry Comments: Lately, my 1969 Porsche 912 starts when cold, but often the starter will not engage after having been driven. Dash lights come on, but just a faint click when I turn the key. Sometimes it restarts if I wait a few minutes. Any ideas?
August 18, 2014
  Followup from the Pelican Staff: The starter itself may be faulty. I would check for the start signal to the starter from the ignition switch, when the problem is present. If it is good, voltage drop test the positive feed, if that is good, the starter is likely faulty. - Nick at Pelican Parts  
NYNick Comments: My 78 SC starts right up in the morning, but requires multiple attempts while turning over to get it to fire after being driven. Ideas?
April 22, 2014
  Followup from the Pelican Staff: Sounds like it could be fuel delivery issue. I would perform a fuel delivery system test. Check fuel pressure, volume and quality.
- Nick at Pelican Parts
Leo Comments: Hi, on a 46f degree morning my car didn't have enough current to start. Took the battery for testing and recharge and again everything was normal. After a few days, I checked the battery with a volmeter and showed 12.2v, after starting the engine the clamps showed 12.3v, but when I turned the a/c, headlamps, and stereo the readings where 11.7v.
Could this mean an alternator or regulator failure?
August 17, 2013
  Followup from the Pelican Staff: Yes, it sounds like your alternator is not charging. It could be the alternator itself or the regulator. - Nick at Pelican Parts  

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Page last updated: Fri 2/16/2018 02:03:35 AM