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Starting aan 80 931 when the engine is warm/hot

 
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jpdorfer  
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PostPosted: Sun Jun 16, 2002 1:46 am    Post subject: Reply with quote

Over the past 24 months I have been on a journey rebuilding/restoring my 931. The engine has had a total rebuild. It starts with no problem. However it will not restart once the engine has run for a few minutes. Any suggestions??

JayD (jpdorfer@aol.com)
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gohim  
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PostPosted: Sun Jun 16, 2002 2:57 am    Post subject: Reply with quote

Does the engine die, when it won't restart, or does not not restart after the ignition is shut off?

What is/are the symptom/s of the non-start?

No Fuel At Injectors or Fuel Pump No Run?

Starter Doesn't Turn?

No Spark?
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jpdorfer  
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PostPosted: Sun Jun 16, 2002 3:01 am    Post subject: Reply with quote

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jpdorfer  
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PostPosted: Sun Jun 16, 2002 3:02 am    Post subject: Reply with quote

The engine dies and will not restart.
The fuel pump and accumulator are new and they are functioning.
It has spark, and fuel at the injectors.
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jpdorfer  
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PostPosted: Sun Jun 16, 2002 3:04 am    Post subject: Reply with quote

The starter works fine, the engine just will not catch.
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Paul  
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PostPosted: Sun Jun 16, 2002 7:17 am    Post subject: Reply with quote

Verify that the fuel filter (near the windshield wiper motor)was installed with the flow arrow pointing towards the rear of the car. Probably not your problem, but it only takes a minute to check. If it was installed backwards, they fail inside and the broken parts block the fuel flow. Once the engine dies, the parts fall away from the opening and the engine restarts and runs until the loose parts block the flow again.
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gohim  
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PostPosted: Sun Jun 16, 2002 10:27 am    Post subject: Reply with quote

If everything was as you described, the car would start and run.

So, obviously, something is not working.

The starter spins, it has spark, it has fuel, and it has run, so you don't have a broken timing belt.

Have you verified that the timing belt is timed correctly (probably not the problem).

I would replace the fuel pump relay with a new one, or take your fuel pump relay, and stick it into another 931 and verify that it is good.

The engine runs on a different circuit when starting the car, and if it starts, then dies when you let the key flip to the "ignition on" position, the problem could be in the fuel, or ignition systems.

And the first part you should check is the fuel pump relay as it is a common failure component of the fuel system.

[ This Message was edited by: gohim on 2002-06-16 09:30 ]
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jpdorfer  
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PostPosted: Mon Jun 17, 2002 10:55 am    Post subject: Reply with quote

Thanks for the info. I have an extra relay I will try that. Another thought, I have not changed out the distributor cap. Would that have an impact??

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Smoothie  
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PostPosted: Mon Jun 17, 2002 11:19 am    Post subject: Reply with quote

Read the FAQ[Technical] above, under "Hot Start Problem Fix" and "Car Won't Start/Run Properly:".
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larso  
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PostPosted: Mon Jun 17, 2002 9:21 pm    Post subject: Reply with quote

Probably not the disturb cap, but since it is SUCH a cheap part, just change it...change the coil if you want too, not too expensive, but my guess is that it's a fuel problem. Cars that will not start with the spinning speed of the starter, but that will start at a rolling start when hot, have fuel problems. When you are driving, and the car is hot..turn the car off while coasting, then put the key back in to run position (but not cranking). If the car kicks back in, but will not start when parked using the starter, not enough fuel is being pumped. If the problem does still occur when you try this rolling start, then it's an ignition problem, heat related problem (relay getting hot, coil getting hot etc.)

The only reason you would try this rolling start method, is if you do not want to go through ALL THE tests and all the havoc of using a fuel pressure gauge, and wasting all that time. If you do find it to be a fuel problem (car starts when doing a fast rolling start), then do all the pressure tests...but save yourself some time and if it isn't a fuel problem you don't have to do the tests!

Of course the other problem could be that your starter motor isn't turning fast enough, in combination with fuel problems.

One thing to note about doing the rolling starts though: I've heard that turning the car off while its coasting is not a good idea because it will ruin your cat. But SINCE I live in HORRIBLE Canada, I could give two shits if my cat destroys, I'll just take it off and leave it off! No emissions tests in horrible Canada. But stay away from Canada, it sucks here!

[ This Message was edited by: larso on 2002-06-17 20:22 ]
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jpdorfer  
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PostPosted: Tue Jun 18, 2002 11:50 am    Post subject: Reply with quote

Thanks for everyone's input. I have changed the relay and it is running better, now I only have to wait five minutes or so to get it to start!! Hey thats progress. I am going to revisit the timing tomorrow after work with someone more experienced than I. Oh yes --the filter is set in the correct direction. And I will take a look at the FAQ sheet on this subject.

At this point in time I am happy to have all the oil leaks stopped. One needs to be a master plumber to put the oil lines together on this vehicle. I think the elves in the Black Forest must have one to many beers when they designed the 931 power train!!

I had to have the block bored out for 87 mm pistons. Any comments regarding break in?

JayD
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numbers  
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PostPosted: Thu Jun 20, 2002 9:06 am    Post subject: Reply with quote

JP, sounds like the standard hot start problem that these cars are famous for. Thke Smoothie's advise and read the FAQs.
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