Hi all, I'm in need of some help. I have a 928S 1984 Automatic (EU). The car has been in the garage for over 8 years untouched, was running fine before that.
Now that I'm restoring it I'm running into a major issue: The car won't crank with the key in ignition. I'll try to summarize the steps I've taken to find the issue (without succes so far)

• New battery has been installed.
• Ignition lights function properly
• When turning on the ignition the starter won't crank at all, no sound or anything. You do hear some relais switching.
• I shorted the pin connected to the starter from the 14 pin connector on the passenger side the starter DOES crank now. So the starting motor functions correctly.
• All resistors have been tested, cleaned and are functioning fine.
• The relais no. XIV for the starter motor functions correct. Tested it with 12v and functions correct. To be 200% sure I swapped out the other similar relais without succes.
• However: when I measure the power to the relais no. XIV when turning Ignition to start: There's no power on this relais. I haven't yet tried shorting this relais to test if that works yet.
• I noticed the following electrical systems do not function aswell: Brake lights, Headlights (do pop up but have no light), others lights do function. Front windscreen wipers do not work. Wiper fluid motor does work. Other electrical systems do seem to work fine. (Speedometer and RPM meter were malfunctioning in the past from time to time same as the Dynamo not working on low RPM)
• Automatic gearbox when in R the reversal light works, I'm unsure if there's a sensor preventing from cranking if it's not in Park or Neutral, but it seems to me this works fine.
• Modern automatic cars won't crank when brake pedal isn't pressed, but I don't think the 928S has that yet?

So I'd like to ask if someone has a clue if this has to do with a malfunctional ignition connection to the relaisboard, or could it be an ECU issue, or some other sensor preventing cranking?

Thanks in advance!

 

When cranking the iignition switch powers up the 4mm2 yellow cable in the 14 pin connector. If you powered up that cable externally and the starter motor duly worked then the problem likely lies between the ignition switch and the 14 pin connector. Chances are it is the ignition switch not making connection assuming battery power is getting to the ignition switch in the irst place

 

So it works (cranks) from the 14 pin to the starter, good job!

The ECU's will not prevent the engine from cranking, they just need to see the pulse from the flywheel sensor for them to provide Spark and then Fuel.
As for sensors there are none that will stop the engine from cranking, No brake peddle switch on any 928, however there is a Neutral safety switch located at the trans IIRC.
You stated that other things do not work, did you swap out the XBus relay, and check / clean all the fuses?

Dave K

 

Thanks for the info. That helps a lot. Yes checked them all, so maybe there's a problem in the connections from the dash to the relays. I am glad to hear it's not the ECU.
Since the Speedo and Rev counter are not working the dash needs to come off anyway.

 

There is also the possibility that the relays may not have been put back into the correct slots ,
use D100 and verify all the relays are in the correct locations
I would suggest you do a CE panel refresh

 

I agree with Stan and Fred, but based on your full description, including the other random electrical issues, I would look at the actual ignition switch. They do go bad, and when they are on the fritz all kinds of weird and seemingly unrelated electrical issues seem to occur. Not a real good way to test it, but I would swap in a know good one and see if things change. As Fred said I agree the issue is between the key and the 14. Pin. The ignition switch does alot more than just the yellow wire and starter, it essentially is the main Bus for the car. The X bus relay was added to handle the increasing load as cars progressed, but at least on some early x bus cars, it handles less than the ignition switch. On my 86 I did some diagram tracing and if I recall the xbus relay powers the fog lights and defrost and little more. The ignition switch still handled more.
FYI once you get those hard- to-reach tiny screws off to get the ignition switch detached from key cylinder, you can just swap in a test switch and use a Phillips screw driver to operate the switch like a it’s a key. No need the burden of reattaching everything to your key cylinder just to test it. Hope that makes sense.

 

With starter relay removed : Terminal 30 battery voltage. Terminal 86 battery voltage in start/crank from ignition switch. Terminal 85 ground, in park or neutral for automatics. Terminal 87 to starter.

 

From my notes

 

Starter relay circuit 87 goes to LH terminal 4 and pin 14 at the under hood connector and then to the starter. Circuit 86 directly to ignition switch, voltage in start/crank. Circuit 85 goes to gear select terminal 50 and will ground in park. Circuit 30 battery voltage.

 

Thanks so much for the replies all. Very usefull.

Hereby an update:

Dash has been removed and ignition inspected. I ran into the following thing:

I'll try my best to explain:

The current situation depicted below: "This is measured from the male side of the ignition ofcourse, but i drew it on the female connector"

• We have 2 red wires going to 30 (upper and lower)
• one yellow from 50 to the starter relay

On Key turn 3 (full start) as depicted:

• upper 30 does not contact 50
• lower 30 DOES contact 50
• All wires to starter relaysboard are functioning, no wire or circuit breaks.

My question: Is this the normal situation, or could it be the 2 red wires on 30 (lower and upper) have been switched on the female pin in the picture?
Might this also cause the windscreen wipers (front) not to function?

Thanks in advance

 

The starter relay 85 coil terminal connects to the transmission safety switch - this grounds when the transmission is in Park. You cannot start in other trans positions OR if this switch is disconnected - check this switch, there is a 6 pin connector in the spare tire well above and in front (wrt car) of the battery box. These wires from the switch are the thicker Violet & Violet/white wires there (middle Pins: 3 & 4) Violet - changes to Brown (Ground 31) on the car side, while Violet/White changes to Brown/Yellow on the car side. If the Brown/Yellow wire is not grounded (zero ohms to ground) the car will not start because the starter relay will never activate.

Alan

 

Thanks for the reply. The color codes of the car side do not match your description. I have a black & black&blue wire on that spot. Does ground though.

Whats the 4 pin connector for? Is that connected to the tachymeter/rev counter?

Thanks!

 

Well - a different approach is to just test the starter relay socket 85 pin if it is not grounded that is your problem.

The other wire there in the connector is for the kick down solenoid. Unfortunately the WDs for your year do not show colors, the '83 and '85 WDs that do - have quite different configurations. Later model years all have the 6 pin connector, manual cars will have a ground jumper at the connector (no trans safety switch).

Alan

 

[QUOTE=Alan;18917328]Well - a different approach is to just test the starter relay socket 85 pin if it is not grounded that is your problem.


So update: It's Cranking!!

​​​​Problem was indeed: bad connection on the 6 pin connector in the back from transmission. Big thanks to all! After cleaning it grounded on pin 85!
​​​​
Next challenge is getting it to run again. It did not fire up (yet). Putting the dash back first then going to check if we got spark and fuel.

I'll keep you updated!