ajc283

Dear Rennlist members,

I have been coupe'd up like everyone else and decided to tackle a few problems on the 928 over the past several weeks. I have a restored '78 928. I have owned this car for more than 20 years and have gone through my share of problems. But the starting issue as of recently has been a really depressing problem. Hopefully someone can help. Here is the story:

About two months ago I go to start the car and the starter would not turn off after the key is returned to 'key-on' position from the far right starter engage. So, I assumed that the solenoid on the starter went bad. I removed the starter and ordered a re-manufactured Bosch. I received the starter, reinstalled the starter and went to start the car and only would get a click...from the solenoid I assumed. So, pulled out the starter, tested outside the car by energizing the hot terminal to the terminal on the solenoid where the yellow wire connects and the starter was bad. Replaced the starter with another rebuilt Bosch unit. Just after installing the unit, I went to start the car and the starter worked for several tries, then went back to the solenoid clicking on start position when testing. Also, I removed the coil wire so the car wouldn't fire when testing the starter. My first guess was to check all grounds, so I went and cleaned the battery ground, cleaned and checked engine strap, and cleaned and checked all wiring at 14 pin connector, all were good. Tested again and same thing, starer would run after several attempts, then it would only click after several tries. I recently bought a new battery for the car and I kept it on a trickle charger so this component is strong. Then I decided to check the wiring under the dash board. I found a spliced yellow wire near the steering column that looks like it was from someone removing an older car alarm. Splice was intact but not excellent, so I removed the crimped terminal and soldered a new wire to replace the splice with solid solder to ensure no movement and good contact. Tested the start function and same thing, starter would engage a few times, then it would only click (solenoid noise). I am dumbfounded on this problem. I am guessing the next area would be to test the voltage of the yellow wire at the 14 pin, then at the solenoid??? Could my newer battery be bad?? I am measuring 13.3v at rest, and when the headlights are turned on I still had 12.8v with the engine and alternator not runnning. The newer battery is not as large as the older one, the autoparts stores locally don't carry the huge older type. Maybe the cold cranking amps are not enough to engage the solenoid?? Anyone who has any input I am greatly in appreciation!!! My car almost never sees a shop and I have removed the engine, suspension..etc all major problems, but this has got me stumped. The car ran and started well before the incident of the "stuck on" starter. Also, I was thinking maybe there is a relay problem?? Not sure the '78 year cars have a starter relay?

Shark2626

Possibly either the relay or the ignition switch.


ETA Here is your relay / fuse chart:

https://www.928gt.com/t-7879fuse.aspx

How have you owned and driven the car that long without it? Amazingly lucky of you!

ajc283

Can't be the relay because its a manual transmission car and the relay at XV is a bridged wire. I replaced the ignition switch when I redid the engine about 20 years ago. And power seems to be going to the starter solenoid, I hear the 'click' when the key is turned to start.

Mrmerlin

Well lets try working the other way
put the car in neutral. set the E brake and block the wheels.
Separate the 14 pin connector. in the engine bay,
NOTE your going to be pulling the engine side of the harness free from the car side,
the engine side is the side with the pins .

Now with the pins pointing towards the lower connector find the pin thats the furthest to the front of the car, and the closest to the right fender
This pin is the one with the thick yellow wire in it #14 you wont be able to see this unless the top half back side of the connector is removed and you dont need to remove the back half for this test

touch the tip of this pin to the hot post,
this will run your starter and its how you will know your starter system and power supply is good, or not
please report your findings

ajc283

Great idea! I was going to test the voltage at the starter solenoid but this eliminates me crawling on my back with tester and not having to ask my wife for help

Just went down to the car and tested at the 14 pin connector. Yes, I found the starter runs on the right passenger male plug when touched to the jump post (with a huge spark..lol) So, I am guessing the problem is probably upstream??

Mrmerlin

yes OK ,
now go to the resistors on the fender well,
one is a 6 and the other a 4 ohm
see if they both have continuity and the correct resistance
If your not sure where they are google it

https://www.google.com/url?sa=t&rct=...inO9i4b01xTD-P

ajc283

Following up with the requested Resistor check: I decided to remove the wheel and gain access to remove the resistors completely. The top resistor measured 0.8 ohms, and the bottom resistor measured 0.6 ohms. Both were in good physical condition with no corrosion and wiring appeared good.

ajc283

I have read inconsistent quality of the rebuilt Bosch starter. Can anyone confirm problems with poor quality on their Bosch starter rebuild? I am thinking that maybe my Bosch starter was not rebuilt well, even though I am on the second starter with similar problems. The starter solenoid seems to be the culprit.

Shark2626

I don't believe that Bosch "rebuilds" starters or alternators like an independent local shop might do, they "Remanufacture" them with new parts (certainly solenoids) and use the same quality standards as when manufacturing a new one. It is the same quality as New.

Technically (actually) this is now your third starter, the original and then the two replacements, and they all exhibited the same behavior. I would not suspect the starter at this point. I suppose that if you were to bench test this latest one and it failed, I would tend to suspect that your car is damaging the starters.

SeanR

I've encountered two of the reman Bosch units that did not excite the black/yellow trace wire and when I've got an early car that will not start as you are describing, I take a test light and touch that pin on the starter as someone is cranking it. If you don't get a full 12v, you aren't going to get the car started. As the wires on your starter are most likely old, telling the two apart is fun. The yellow one should be on the bottom, black/yellow should be just above it.

ajc283

The first replacement reman Bosch I tried several weeks ago would only make a solenoid 'click' sound. It would never fully engage the starter and turn the engine. The second replacement reman Bosch I rec'd from a different supplier (Pelican parts) actually intermittently engaged and turned the engine. However, after cycling on/off several times it would only 'click' and make the solenoid noise and not turn over the engine. This makes me believe maybe the starters were rebuilt, but maybe the shops are not rebuilding the solenoids. I am considering returning this starter and buying an Imi mini starter. Before doing that, I will test the line voltage on the yellow wire on the starter while someone engages the 3rd key position to see if I'm getting 12v. (Subsequent post have this idea). Does this make sense?

Shark2626

Yes. Good luck!

cemetery gates

When you get the click only measure the constant hot 12v at the starter and see how many volts you are getting there. If not around 12v, check the positive terminal at the battery and associated connections.

CG

GregBBRD

All strange 928 electrical issues (especially ones that have high current passing through them) start with a new ground strap from battery to chassis, especially if it happens to still be original. Remove the end that attaches to the chassis....inside where the tool kit sits. Look at the hole that the bolt/wing nut passes through. If you can't see flat braided cable and you can only see the brass "sides", replace the cable with one from....one of us who solve problems and sells parts.

ajc283

Update: Finally received some parts to finish some of the troubleshooting. Installed the following yesterday, new ground cable from chassis to battery, installed both new resistors inside the engine bay 0.4 ohm, and 0.6 ohm. Both replacements did not change the starting problem. I still have the solenoid click. I will jump the 14-pin yellow wire (male end) again today to the jump post to check for continuity from the 14-pin to the starter, if the starter fires properly I am assuming the problem is now at the key switch or from the key to the 14-pin connectors. And ideas on testing this segment?