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Hard starting when warm

 
Old 10-06-2010, 09:53 AM
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tomu
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Default Hard starting when warm

1985S - Starts fine when cold or immediately after shutting off when warm. If I wait for 30 minutes when warm, it won't start for 3-4 hours.
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Old 10-06-2010, 12:35 PM
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BigAl1
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My thought would be to check the fuel pressure accumulator to see if the diaphram is leaking. This could allow the fuel pressure in the system to drop quickly after shutoff, thereby allowing the fuel in the lines on top of the hot engine to vaporize easier = vapor lock.
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Old 10-06-2010, 01:23 PM
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John Speake
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Check ifyou have spark when it won't start.
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Old 10-06-2010, 05:01 PM
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WallyP

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Find the fuel pressure regulator and the pressure dampeners (2). Pull each of the small vacuum lines on these units and check for any traces of fuel in the lines. Any unit with fuel in the vacuum line must be replaced.

The fuel system should maintain pressure for twenty minutes after shutdown. If the diaphragm in one of the units has a leak, this pressurized fuel will leak directly into the intake manifold, causing a "flooded" (very rich mixture) condition after a few minutes. After a couple of hours, the fuel will have evaporated, and the cooler engine will also start with a rich mixture, so the engine will start.
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Old 10-07-2010, 12:24 AM
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To help diagnose if the problem is excess fuel next time try to start with the throttle wide open. This is the procedure for clearing/starting a flooded engine.

If it starts you will need to find the source of the fuel and Wally's recommendations are where you should start.

If it doens't start don't assume it is not fuel, just that you still do not know.
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Old 10-07-2010, 02:55 AM
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safulop
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You say "it won't start," but how long are you cranking? If it is purely a fuel pressure problem, then if you crank long enough it will start, because the fuel pump will eventually repressurize the line. This is the normal failure mode (loss of fuel pressure) which causes notorious hard-starting in the 944. But if it really will not start at all, then I think you have to look for something else like the excess fuel getting into the intake.
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Old 10-07-2010, 10:02 AM
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tomu
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I have held throttle wide open and cranked engine long enough to build pressure. It doesn't fire, and after several hours, when it does start, it doesn't seem flooded. It starts and runs smoothly immediately. Could there be an issue with the fuel pump relay over heating?
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Old 10-07-2010, 10:07 AM
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John Speake
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....... check for spark when it won't start !
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Old 10-07-2010, 11:52 AM
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Try burping the gas cap.
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Old 10-07-2010, 11:57 AM
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R.Pires
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Originally Posted by tomu View Post
1985S - Starts fine when cold or immediately after shutting off when warm. If I wait for 30 minutes when warm, it won't start for 3-4 hours.
Hi

My car does exactly the same thing, but it eventually starts when warm with the throttle wide open and cranking for a few seconds.

Regards
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Old 10-07-2010, 06:34 PM
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Originally Posted by John Speake View Post
....... check for spark when it won't start !
It may pay you to listen to what John is saying, just a thought............
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Old 10-08-2010, 12:02 AM
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WallyP

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It always pays to listen when Speake speaks!
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