Had a a search and seems that I may need a ECU coolant sensor, but it seems wired.
With the ignition on normally hear the fuel pump prime but have to switch off then on to prime then it turns over for a while before starting, once started sputters a bit before running on cold start as normal, once warm starts on the button.
Car is a 2002 bug STi normally used at weekend so sits all week and just started this, one cel light or codes.also walbro pump fitted late last year and ngk 6's plugs
Any ideas?

 

Was the walbro fuel pump new or did you buy a second hand one?

 

New, supplied and fitted by Slowboy Racing

 

Could be a fuel pressure issue. Its worth letting the pump prime 3 or 4 times before cranking. if it starts ok after that then get the pressure checked. Could be pump,fpr or a leak

 

Would it not be the same when warm?
Can start the car cold (as above) then switch off and leave for while and starts straight away

 

Mine does the same, if I don't use it for 4-5 days I hear it fuel up and it struggles to fire up, once it's run for a few seconds it's fine. Solution for me is use it everyday!

 

Had two coolant sensors go on my last Scooby. Both times would start perfectly when cold but would not start once warm.
With having to prime twice would seem to be some sort of fuel issue.

 

I was thinking the fuel pressure is dropping away slowly. So after a day or two theres none. I know mine takes about 2 days to drop completely(have gauge)

 

Seemed to start fine this morning, does seem as it is fuel related.
Had it on the diagnostic pc at the workshop today and checked all the sensors, all ok
Even checked the resistance readings both hot and cold all with in spec.
Fuel pipe connections all good, maybe new fuel pressure regulator?

Is the standard one the small inline black one near the filter?

 

Left for a week,same issue, primed twice and still turned over for about 10 seconds and spluttered into life, left for couple of hours and fine, does seem like fuel issue??

 

Try changing the fuel filter see if that helps

 

that's a fuel pulsation damper not a regulator.

usually located on the end of the fuel rail at the turbo side of the manifold with a small vac line to it

 

Already done

Cheers this will probably be the next item to replace

 

i think there was an ecu update dealers could do to fix the bad starting

 

No good for me as it has different map

 

Left for 24hours and started fine, see what happens after two days then three!
Does seem fuel related may swap out the plugs and see

 

Still the same today,any ideas?

 

Idle Control Valve. Unscrew & clean valve & housing.Check the small O ring is not perished/damaged & is sealing ok.

10 minute job.Worth a try.

 

Idle is fine at both cold (high revs) and at normal idle, wondering is there a fuel check valve anywhere or the fuel regulator.

 

Anyone? There must be a solution to the problem

 

Full list of what's been checked so far?

 

All of the above

 

Now replaced spark plugs,fuel filter and been round all the electrical connections and pipe connections all good.
Still same issue on cold start up when left for more than a day.

 

How does it run if you start it from cold and try and drive straight off? Any holding back? or shaky idle if you were to stop at a junction or anything within the first half mile?

Is it literally just the starting that's the problem or does it run shaky when it's cold?

And when it's warm it starts fine?

 

Just the first cold start, let it run for less than a minute and stop restarts fine, no issues when warm/hot, no idle issues either.
No issues driving when cold or warm.

Yesterday I had to crank for good 6 secs then in came to life slowly, like its on couple of cylinders this lasts for 1-2 seconds then idles fine.

 

I had the same issue, I replaced the spark plugs, cleaned throttle body, cleaned the maf, checked for vacuum leaks, replaced the fuel filter and fuel pressure regulator and still doesn't start right away from cold start but once started you can shut off and starts first crank same issues as OP. I first thought I found the culprit when I replaced the fuel pressure regulator but few days later it started doing it again and so I suspected my fuel pump check valve is faulty since the fuel is bleeding off when left overnight. I installed a new Walbro 255lph fuel pump 2 days ago and seems to have fixed the issue. I will monitor and report back after a week of observation if that did it. Otherwise my next move is to check my fuel injectors O ring.

 

My fuel pump was replaced last year for a Wallbro 255, wonder if it is on its way out?
Next for me will be FPR, done the throttle body and MAF already.
Think trip to specialist is on the cards.

 

Yeah, my Walbro FP was installed back in 2010, I was reluctant on replacing it but still did it anyway so now I have another pump that is unsure if it's good or not. My car seems fine but not really sure if that really fixed it so let us know what your specialist finds.

 

Same today, engine cranking for long time until it burst to life.
Done a diagnostic check and no codes stored or pending but would not complete check on the O2 sensor, would this be the cause?
Bugging me now, def electrical no issues with the fuel system, or mechanical? Compression test?

 

You still haven't tried my 'stick on the throttle' trick, have you!

JohnD