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BionicBalls · Joined: 05 Jan 2009 Posts: 642 Location: Charlotte, NC

What are your thoughts on using a check valve in place of an accumulator?

I've got a check valve on order and plan on putting it in the fuel system between the accumulator and the fuel dizzy. I'm hoping that this will solve my warm start problem. If it does, do you think I can just eliminate the accumulator?
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1980 924 NA
1982 931

Ozzie · Posted: Wed Nov 04, 2009 6:12 am Post subject:

you should already have a check valve in the pump.
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Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

Rich H · Posted: Wed Nov 04, 2009 6:20 am Post subject:

What he said. Tux hasn't got a check valve and he doesn't have difficult hot start he has no hot start at all...
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1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

BionicBalls · Joined: 05 Jan 2009 Posts: 642 Location: Charlotte, NC

Well something is causing a void in the fuel system. Cold start is no problem, hot start is no problem, but warm start is. It will start up immediately, run for a second then cut off, and it then takes about 45 seconds of turning over to start back up.

What I'm gathering is that the fuel in the injector lines is enough to start it up and run for a second but there is a void between the accumulator and the dizzy that is then causing it to cut out and not be able to start until the void is filled.

I'm using the fuel pump from a 951 if that matters.
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1980 924 NA
1982 931

!tom · Posted: Wed Nov 04, 2009 8:14 am Post subject:

PORSCHEV · Posted: Wed Nov 04, 2009 10:41 am Post subject:

I have been called a hick before for saying it....but I will say it proud again. Wire your cold start injector to a switch and start it whenever you want. Simple solution to bad engineering, I call it.
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1976 924
5 lug conversion, 17'C2 wheels,custom body work,327 vette engine.

1978-#53 "D" track racer.

9XX Girl! · Posted: Wed Nov 04, 2009 10:56 am Post subject:

i will second that! fit a Audi 5000 TB and use the WOT switch. When it dont start, put your foot to the floor and crank away.

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924 (84) N/A 2 ltr - 5 Speed - BLACK - Project (looking for 200BHP, any ideas!)
924 (81) N/A 2 ltr - 3 Speed Auto - SURINAM RED (Metallic) - Near Original Spec (sticking with originality)
BOTH ON THE ROAD, BOTH USED EVERY-OTHER DAY

RC · Joined: 25 Mar 2007 Posts: 2637 Location: Australia

Then what happens when you`re driving and put your foot down? Runs so rich that if the motor doesn`t stall it leaves a big cloud of black smoke behind while you watch the fuel gauge drop.
May not be a huge problem if you drive like a woman

but most guys like to put their foot down even when not overtaking, going uphill, or entering freeways. A simple push button is probably the easiest & most effective hack.

BionicBalls · Joined: 05 Jan 2009 Posts: 642 Location: Charlotte, NC

tom, CIS pressures have been checked and are within spec so the pump isnt the issue. I'm going to try this check valve, and if that doesn't work then I'm going to wire the cold start injector to one of the switches on the center console, I've got three sitting empty.
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1980 924 NA
1982 931

Rich H · Posted: Wed Nov 04, 2009 6:14 pm Post subject:

You have classic hot start problems.
Use a classic hot start repair.

You say you have checked pressures, did you do a leakdown check?
Check all the injectors (5) and fuel lines are not leaking into the inlet manifold
(Pull each one after engine shutdown)
Check the check valve is installed and works
(Might be in the pump, might be seperate bolted to the pump outlet)
Check the accumulator diaphragm is intact.
(Take the screw out the bottom if you get fuel then you have a broken accumulator)
Check the accumulator is holding pressure
(The Accumulator should hold pressure for a set time, it's in the manuals)

Once you have done this then you can go hacking the system about and putting in another check valve if you really feel the need, despite the fact you have one already. If your old check valve works you will achieve precisely nothing.

The system works when its servicable. It doesn't work when it's broken. It's not a poor design, it's just fine, but it's 30 years old.

Don't bodge it - Fix it

Rich
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

9XX Girl! · Posted: Wed Nov 04, 2009 7:18 pm Post subject:

Rich H · Posted: Wed Nov 04, 2009 7:35 pm Post subject:

Neat fix. I found the Audi TB switch wouldn't fit intact and had to cut off the lower part of the case though. You got a pic of yours installed?
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

9XX Girl! · Posted: Wed Nov 04, 2009 11:01 pm Post subject:

gla924sem · Joined: 08 Nov 2002 Posts: 405 Location: Taylor, Michigan

Agree with PorChev

have been called a hick before for saying it....but I will say it proud again. Wire your cold start injector to a switch and start it whenever you want. Simple solution to bad engineering, I call it.

Did something similar years ago on the advice of a local Porsche repair expert in NW suburbs of Detroit. Chris at Munks was right on!!!!!!!!!

Connected my cold start injector to a dash mounted intermittent toggle switch. Starts every time. A few clicks of the switch and she starts cold, warm or hot!!!!!

RC · Joined: 25 Mar 2007 Posts: 2637 Location: Australia