924Board.org

[rat]

Little bit of an annoying one.

From cold, attempting to start the car will often fail.

The symptoms have me scratching my head a little. I can churn the car, leave it for 5 minutes, try again and it will not start.

If however, I remove a single spark plug the engine will instantly spring to life on 3 cylinders. The plugs when pulled are wet with fuel.

Once it has fired like this, replacement of the plug results in the engine instantly firing up and running smooth as anything, running at 1200rpm until warm and dropping to about 900ish.

Turning off and starting again from warm after 5-20 minutes results in an instant start first try.

Leave the car for 24 hours and same problem again, spark plug out, start on 3 cylinders, replace, starts fine..


Where should I be looking to try to diagnose this?

[rkn]

So it starts fine with any one of the plugs removed, or a specific one?

If you are getting too much fuel at cold start, it may be fx:

- Control pressure (WUR)
- Cold start valve open for too long
- Running rich, in which case the additional fuel from the CSV is drowning the engine.

First simple test is to unplug your CSV and see how your car cold starts. If it starts well without the CSV, then you are probably just running rich.

Best do a pressure test though.
_________________
1980 924NA ROW

[rat]

It seems to be the same with either of the front plugs, I've not tried with the harder to reach ones at the back. Will try unplugging the wur see what that does.

I was wondering along the lines of the non-return valve or accumulator not keeping the system pressurised, but the fuel on the plug, I think, rules that theory out.

I was expecting the car to start, even if too rich. I couldn't see what difference the removing of one single spark plug would cause to allow it to suddenly start..

[stevekat]

The car cranks faster with the single plug removed. This may help clear the flooded condition easier. Try holding you foot to the floor when cranking the engine after it floods to see if the car starts without taking out the plug. This allows more air into the intake system and often helps a car that is flooded start easier.
_________________
"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.

[Piper]

Did you get anywhere with this mate? I'm having similar problems that came on all of a sudden. When left over night it's a pig to start. Eventually starts after 5 or 6 tries with full throttle.

Cheers!

[rat]

Hi Piper, no further. Work, house hunting and a major family crisis have taken priority.

I'm wondering along the lines of something sticking in the fuel distributor, and perhaps it needs a clean out/new o-rings. Once started it runs fine, and will often start first turn of the key.

I ran the car for a year without problem, then parked it at my parents where my dad was the one to report this problem. It would of course start first turn of the key every time I came back to it.

It has now however repeated the symptom a few times with me present. The spark plug removal causing a change in pressure I'm sure is key to it somehow.

My only way to prove/disprove the alternate theory of flooding and the higher speed cranking allowing it to start would be to try repeating it with a semi flat battery and getting it to start reliably.

I'm hoping the house thing will be resolved sooner rather than later and then I can get a couple of weekends to rip into the thing. I'm thinking a CIS pressure tester may be a key bit of kit I'm missing though.