wrxsti280

iTrader: (6)

I have a problem starting the car when cold. my94 sti version 1 wagon.

when it fires up from cold it appears to be running on 3 cylinders but it isnt as this has been checked, it idles at 200-300 rpm for a couple of seconds, but then fires up to it's normal idle speed, warm the car up and everything is fine.

we have checked so many things ranging from maf and coolant temp sensor to injector pulse width, and by process of elimination got it down to plugs, even though they had only been in 6 months. these have now been changed and the problem is still there although not quite as bad.

i got the old thinking cap on and the only thing i can come up with is a problem with the fuel pump and the non return valve. If i turn ignition on 2 steps and prime the fuel pump, then turn off and turn back on 2 or 3 times to prime the pump again and again, it fires first time and as normal as it used to do. my theory being that the non return valve isnt working properly and therefore letting fuel back out into the tank and when i come to start the car first time from cold it hasnt got up to pressure and is therefore having a problem starting.

what i would like to know is this, have i already proved my theory and is this even possibly the problem, because it's starting to **** me off a bit now.

any help greatfully appreciated.

steve

Jolly Green Monster

iTrader: (4)

have the coil packs been replaced?

I would suggest changing them if you haven't already.

Also worth grounding the block as this sometimes smoothes out cold running, although I wouldn't expect it to sort this problem but it might help a little.

Simon

wrxsti280

iTrader: (6)

coil packs were changed about 6 months ago, the car has got an earthing kit on but is not earthed to the block, it is to both suspension turrets at the front, both sides of the intake manifold and to the alternator.

is what i have proposed above a possibility?

Jolly Green Monster

iTrader: (4)

Having now ready your post fully.. sorry..

yes sounds like the fuel pressure regulator is possibly faulty..

Simon

wrxsti280

iTrader: (6)

thanks for your help mate, it's really getting to me, tried everything and everytime i think ive got it it comes back and bites me on the ****, damn subarus.

right, i will get this changed and see where we go from there, another good excuse to put a walbro pump in i suppose and make 100% certain fuelling is taken care of.

thanks again

Jolly Green Monster

iTrader: (4)

the fuel pressure regulator is on the drivers side fuel rail nearest the turbo.

unlikely to be the pump.. they usually fail fully or work.

worth also looking at fuel filter.. might be restricting flow.

Simon

wrxsti280

iTrader: (6)

spoke to harvey and he also suggested more likely to be fpr than pump, im gonna swap that and the pump to be on the safe side as a new walbro wont do it any harm.

it had a new fuel filter about 3 months ago, so i cant see it being that.