Hi!
iI have a 78 euro spec car with some starting problems. Hope someone can point me in the right direction to solve this.
The car starts perfectly when it’s cold, but when I stop the car after a drive it won’t start again. The starter don’t want to engage, but if l use a batterypack on the positive terminal under the hood, it’s starts. I have changed the battery, so that’s new. When the car has cooled down, it’s starts.
Does anyone has a clue what this can be?

 

Start with replacing the starter relay. Notorious for failing on 928s and inexpensive to replace.

 

Thanks!
I will try that.

 

Check the connections at the starter, the main ground to the right side of the engine and the ground strap to the battery.

 

Thanks for the tip!
Did check the ground strap to the battery, but will check the others.

 

The ground strap can hide corrosion under the outer rubber surface. A new strap is not expensive and probably better option than trying to do a continuity check while bend and flexing the old strap.

So the engine turns when hot, but won't fire, is that correct?

 

All the instrument lights up, but nothing happens when I turn the key to start. But when the car has cooled down it starts as normal.

 

By any chance when this happens is the AC on? I know on warmer days if I stop my 78 while the AC is on and go to restart it with the AC switch on and the car still warm I get no cranking at all until I make sure I slide the AC switch to the left to turn it off. Not sure why this would be the case, but It does seem to be a consistent issue on my car

 

I will try this tomorrow, after a drive.
Thanks for the tip!

 

This is a complete SWAG but maybe your starter solenoid is requiring more juice to engage the starter after it gets hot. Sounds logical right? But it’s just a guess and I’d hate for you to buy one and it not solve your issue.

Also, is it an automatic? They have a starter relay; manuals just have a jumper. Unfortunately I don’t see another relay like it in your CE panel to swap as a test.

 

I did think about this, but wasn’t sure. My car has manual transmission.

 

I had a similar issue on my '84 that after the car warmed up (about 20 minutes) it would cut off while driving. Turned out to be that the fuel injection relay would stop working when it got warm. Thus why I suggested you look into changing the starter relay in case it is failing in a similar manner.. You can swap the horn relay with the starter relay to check.



EDIT: Just saw the above post about your car being a manual. So what I wrote above does not apply but will leave their in case others have a similar issue with their auto. It's possible your ignition switch is going bad in a similar manner, but that is more difficult to replace unfortunately.

 

There's no starter relay in a '78 manual

 

I just Googled it for you, apparently there really is something called Heat Soak. They make heat shields and heat wrap for the solenoid to protect it from exhaust heat, but I’m thinking you would be wasting your money on those because your solenoid is probably on its way out. You can buy it separately but getting a full remanufactured starter is best. How old is yours?

Google “starter won't work when my engine is hot” and read what others say before you throw money for a new starter at the problem.