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462avi · Posted: Fri Jan 26, 2007 3:56 pm Post subject: Hot start problems

I have noticed a lot of posts recently regarding hot start problems. I think we should come up with a solution ourselves. I have two suggestions. One is to put a check valve on the fuel tank return at the fuel distributor. I know that this won't fix any fuel boil off problems in the injector lines but it will hold pressure through out the whole system. My second suggestion is to put in a momentary pushbutton switch on the dash that connects to the fuel pump relay. The idea being that you hold the button for a few seconds before you
start the car to prime the system for a longer period then the relay provides.
Just a thought. Anyone else got any ideas?

Geoff
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2005 C230K
2002 grand cherokee with 4.7L

Mike924 · Joined: 12 Aug 2004 Posts: 2601 Location: IoW UK

Ozzie has tried the check valve (pressure valve, actually) in the return line approach and it seems to have worked for him.

Running the fuel pump prior to starting does not work. I know; I've tried it. Running the pump for as long as 30 seconds still has no effect on the hot start performance.

If you want a switch on the dash, the thing to connect it to is the CSV. This will spray fuel into the manifold, bypassing the injectors and get the engine started. It may run lumpy for a while until the vapour clears in the lines, but it does this sometimes anyway.

The real answer is to change your fuel accumulator. It seems the diaphragm becomes porous over the years and hence fails to maintain the pressure during the critical cooling down period.
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1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

Ozzie · Posted: Fri Jan 26, 2007 6:03 pm Post subject:

Yes.. it worked but....... not if you have leaky injectors.
The fuel ends up in the intake manifold and no pressure remains in the injector lines.
I replaced the injectors, removed the pressure valve and now have no problems.
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Porsche 924 1984 (UK import) NA
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