Bonzo400

OK, 1995 classic, with apexi PFC, bigger injectors, mapped, and exhaust, inlet, headers etc.


When car has been standing overnight, or even a couple of hours ( and is still reasonably hot in the water department - 60 - 70 degree C ) it takes 5 seconds or so of turning over to get it to fire up, then it runs rough for a few seconds ( not quite on 3 cylinders ).
Blip throttle and it clears , but with cloud of blue/black smoke from exhaust.
No emulsion in oil, no water use.
Drives fine once going!
New plugs at 0.6mm gap, MAF and Lambda recently.

Looks like going rich on cranking, or fuel leak into a cylinder wetting a plug that needs to clear, or water temp compensation is off at the temps?


Could it be :
Dodgy water temp sensors
Injector leaking into cylinder intermitently / releasing fuel pressure into cylinder when engine stopped?
incorrect values in PFC for cranking or temp correction ( but then why do it when still warm but stoood an hour?)
Oil leaking into valve/piston - valve seals failing? ( STi 4 heads )
FSE 1:1 fuel reg failing rich?

Any ideas?


Thanks

Bonzo400

Anyone?

As above, first attempt to start after standing for an hour or more and takes 5 seconds to fire, runs lumpy for 5 seconds and throws out white ish / blue ish smoke when throttle blipped. Engine may be cold or hot and same thing.
Only happens after standing for an hour or two.

DeanF

iTrader: (1)

Does the fuel pump whirr for a few seconds when you turn the ignition on ?? (Before cranking)
It almost sounds like your fuel is running back into the tank so taking a few cranks to pull it through & then lumpy for a while until the pressure stabilises.
There is a one way valve in the Fuel Pump on the fuel line exit pipe which should stop fuel pressure loss & run back etc .

Has your fuel pump been upgraded ?? The Walbro's seem to hold fuel pressure much better than the standard Pump especially if they have done 50,000 plus miles .

Dean

nickyrhodes

Hi,

I've read about this problem somewhere before. My 98 does it but not very often, say if i stall it in traffic and its hot it takes ages to start. Off the top of my head i cant remember what the cause was, may have been idle control valve as water passes through it if im thinking rightly. Also if you happen to press the throttle before you start it i get the same problem...

Agree with DeanF, definately check that out!! Someone else might remember the post im thinking about, it may have been off sidc forums...

EDIT: was prob this post i saw:

overfueling on hot start - Subaru Impreza Drivers Club Forums

Bonzo400

Thanks guys, had a look at that and is similar but not the same! Mine does it from cold and often after been stood over 30 mins, but is fine if it is turned off and back on in a few mins - starts like it used to on 1 turn over!

I have an upgraded Walbro fuel pump, and the fuel pump does whirr a couple of seconds before stoppiong as it primes / pressurises the fuel system - it does lose pressure after a couple of hours, but always has done ( as I found when changing injectors soon after stopping - fuel everywhee! ) and still starts once the 2-3 secs of whirring is complete.
BUT I have a FSE 1:1 fuel pressure regulator ... wonder if this is starting to fail and allowing over pressure or flow back to tank ... and as I have a parallel fuel hose fitted maybe that is plumbed in wrongly? But this problem occured well after those were fitted... Doh!


I am feeling it is a water temp sensor ( or wiring associated with it ) - there are 2, one to dash gauge and one to ECU which does aid control of enrichment / cranking etc - these were changed for 2nd hand items last year so may have gone again ...

I'll keep trying...

Matthew

Could be the crank or cam position sensors. Try cleaning both of them.

They often fail slowly, so will work when cold, and well enough when the engine is running, but it won't restart when hot. One way to check is to blast the sensor with some freezer spray when the car doesn't start. If it jumps into life then you've found the problem.

Matthew