924Board.org

[ourkid]

I drove for 7 miles today,stopped for 5mins then tried to start again.It did fire,but because i noticed the boot was open i turned the engine off almost straight away....

Then it wouldn't start up again.
I cranked until the battery got tired,then gave it a rest.I couldn't smell fuel at all under the bonnet (pump was running).I'm new to 924's but have picked up on the so called "hot start problem" whilst scanning various forums.So i unplugged the blue 2 pin connector which plugs into the tubular "valve" on the back end of the intake manifold/plegnum chamber.
The car then fired up first time and ran smoother than ever.

So,what causes this and how can i fix it?

Thanks,
Ade.
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1983 924 N/A

[Rich H]

You have a problem but it sounds like cold start/warm up regulator/TTS issue.

A hot start is when te engine is properly hot and won't restart after 10-15 mins (Long enough for the fuel pressure to drop so you get vapourised fuel in the lines) the 5th injector you disconnected is the cold start valve and should only be firing for 8-10 secs, it could be that its leaking and causing you to run rich.
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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

[Smoothie]

No, what happened there isn't conclusive of a hot start problem.
I've had it happen a few times myself, where if it doesn't keep running on the first start, re-starting becomes more difficult. Actually, on the restart you may find you have to do things differently. I have two guesses on what's happening, first is there's fuel left over from the cold-start valves' first dose from the initial start and your second attempt is giving it another dose and leaving it too rich - second guess is that the thermo-time switch is already open on the second start attempt, so you don't get another dose from the cold start valve. Whatever it is, the solution is the same - hold the throttle pedal to the floor while starting until it kicks in. Doesn't work for Ozzie, but it seems to work for the rest of us.

BTW- That was the CSV (cold start valve) that you unplugged. The fact that it started with that unplugged suggests that my first guess is right, and the problem was too much fuel caused by multiple actuations of the CSV.
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[ourkid]

Thanks for that,
I've read carefully through both replies and it's starting to make sense.I cut the engine before it had chance to really start,then decided that pumping the gas would be a good idea to get it going again,compounding the problem.It's running fine now so at least i'll know what to do next time!
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1983 924 N/A

[Smoothie]

I also found that it's best to press and hold the pedal to the floor -before- activating the starter for the second or subsequent attempts.
Turning the key first, then pressing the pedal down doesn't seem to work as well.
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[JackRabbit]

i can't understand how so many people with what at first seems like the same issue are discussing decidedly different symptoms... my '79 924 ran for it's first 1000 miles out of hibernation with no "hot" or "cold" starting problems... now although it always fires up after it has sat for the night, if I drive it somewhere far enough for it to get hot and then leave it for an hour or two... it doesn't wanna start...

I've tried starting with the pedal to the floor with no success.. As I'm not mechanically advanced enough yet, I hesitate to tear into the engine compartment.. but the problem seems to show no signs of improvement so I guess I'm gonna have to sink or swim.
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'79 Porsche 924
'05 Honda Civic
'07 BMW K1200R
'78 Honda Express
'52 Willy's
'58 Wheel Horse

[Ozzie]

There are many causes for the hot start problem starting at
the fuel pump
the accumulator/s
the regulator in the CIS
the WUR
the CSV
the injectors

it could be any one or combination of causes.

As it is caused by the fuel vaporising in the fuel lines in the engine bay it could also be a cooling fault.

I wont go into specifics here as it has been covered many times before.
A search will reveal all.
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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

[Chrenan]

You can always take my approach, crack open your wallet and your tool box and replace all the fuel components until the fuel system works to your satisfaction. After replacing the WUR, CSV, injectors, accumulator, fuel pumps, fuel pump relay, filter, and every fuel hose I touched in the process the car starts great everytime. The only original part is the fuel distributor. All of these cars are old now, and regardless of how they've been cared for any original parts in the fuel system are well past their best-before-date.
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1987 951 - M193 Version for Japan

[Ozzie]

I replaced pump, filter, regulator seals and injectors before mine ran fine.
Not as expensive as some.

WUR, fuel dissy and accumulators are not cheap.
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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

[Min]

my car gave me a choice, do what chrenan did, or update the fuel system. I updated it to EFI and it starts no problems

Min
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Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting.

[Mike924]

@JR: Start with the accumulator(s)...
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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