Warm start problem..
 

The car is a 2004 impreza wrx sti type uk with around 80k miles .

I have recently had an issue where the car would start and drive fine. i filled up with fuel went to start it again and nothing. the starter turns over but engine does not fire.
I realised i could not hear the fuel pump priming as it should so waited a while ..approx 30 mins with me trying to start it several times. after some time suddenly the whirring of the fuel pump and hey presto it fired into life.

then drove some 90 miles home . turned the car off and out of curiosity tried to restart it and no fuel pump priming noise and no start.

i am a bit puzzled . can anyone advise on this please?

Failing fuel pump or bad wiring

You ARE keeping your right foot clear of the throttle pedal when starting, aren't you?

Yes I always start the car with right foot clear of the accelerator.

if it is the fuel pump failing, can it happen as described .ie. car runs fine then fails to reprime and will not start then starts fine and there is no change in engine performance after it started.

i find it strange that when the pump does prime and the engine starts it is as if nothing happened.

I had this exact problem with a c class merc turned out to be the crank sensor not sure if same with scoobies but thought I'd mention it

I had a very similar problem on a classic,bad wiring on the plug that fits on top of the pump/tank.
I took the inspection hatch off and listened while the car was running,wiggling the wires I could hear the pump cutting out.
Also had a faulty pump on a different occasion and could just hear that cutting out when I stuck my head in the boot.
On a classic(think newage is the same) there is also a connecting block under the rear bench seat which is worth inspecting.

One thing you don't want is the pump cutting out when on full boost,it can kill an engine,so I would advise staying off boost until you find the fault.

many thanks for your replies.

I shall investigate the wiring tomorrow .

I removed and cleaned the crank sensor . there was some soot and debris present but made no difference upon refitting.

ill post up anything i find .

As neeko said try swapping out the crank sensor, my rally car did exactly the same. Seems like it gives off wrong voltage when warm but fine when cooled off a bit.

My merc used to start fine in a morning then if I turned it off for any reason like u say petrol station it wouldn't start again until left to cool down

okay quick update. ordered a new crank sensor but pulled the old one out and tested the resistance both when engine is cold and when warm ...readings were .19kOhms and 0.2 kOhms respectively ...looking around on internet seems to be within range but a new one has been ordered. light was fading so i couldn't see much about the wiring but the idle was jumpy and when revved did misfire and pop a bit..

does this still sound like the crank sensor is at fault?

Lets hope so now you've bought one. All I can say is, the symptoms you describe were exactly the same as I experienced and the sensor fell apart when I removed it.

I certainly hope so too. The car has been perfect in my two years and 12,000 miles of ownership.

I have new spark plugs and fuel filter to change also. Whilst I doubt these are the culprits I am sure changing them can only be a wise move.

If the CPS is not the issue I have some other suspicions to be ticked off...Please let me know if I'm talking sh*te here...

1)Bad fuel pump...If this was failing sure engine temperature would not influence it's operation. I only suggest this as when engine is warm the pump fails to prime and I get the crank no start issue .

2) Fuel pump relay , ignition relay and main relay...Cheap ish to replace . Failing relays with dry joints can cause gremlins and after some light reading these may be the next port of call.

3) First and foremost check all wiring related to sensors and fuel system.

Fingers crossed the crank sensor will solve it.

Many thanks for your help with this. I hope to post a successful report later after work.

Swapped the crank sensor over on my lunch break . Was unable to test warm engine restart as had to hurry back but did notice that when i press the accelerator the revs are all over up and down and side ways.

starting to get really worried now.

So the car would not start warm or cold when I tried to start it after work.

I fitted new spark plugs and fuel filter . Plugs looked good , and filter did not seem blocked.

Still will crank but not start.

It's going to have to go to a garage and probably cost dearly :/

thanks for your help .

Have you not checked the fuel pump wiring then?
Have you tested the fuel pump? You can take it out and test or just run a positive wire to it in situ.

not yet ..just came in for a coffee and a cry haha. ill nip back out and have a look. the pump seems to prime fine now ...can hear it when i turn the key before cranking it.

ill be back .

Defo pump bro not a big job it'll start first time soon as you put one on I had 3 turbo 2000's that did the exact same thing not costly bro just tKe your time it's more patients you'll do it no probs:thumb:

If you can change the plugs the pump is a doddle :thumb:

Cheers for your encouragement.

So the pump can still prime but be too weak to supply fuel??

I looked over the harness in boot . Contacts are clean and shiny.

The four wires on the harness. Black, black/yellow, black/ red and last a blue possibly black blue I'm tired
Can someone confirm what these are

Im struggling to get at the relays to test them . Had the lower dash off but can't get my hand behind to unclip them

As every good story has a beginning middle and end I shall let you in on my latest findings and hopefully draw a close to this saga.

After testing the fuel pump , by disconnecting the fuel filter outlet and diverting it into a bottle away from the battery ( probably not the safest method?) I concluded I do have a working fuel pump.

When cranking the car again I noticed my 3/4 tank of fuel has over a few days of f***ing about cranking and priming has turned into 1/4 of a tank ...so I've got a fuel leak .

Sniffed the oil and it smells of fuel . So I guess I've got a dodgy injector stuck open .

I'll strip the injectors tomorrow, inspect and send them off for cleaning. It should be a quick turnaround so hopefully it's case closed.

I've not been able to test fuel pressure so I couldn't rule out a faulty regulator but the loss of fuel kind of obviates this possibility.

Thanks again and any comments are welcome.

Let us know if it wer defo the injectors or owt else pal wen you've sorted it with the outcome please thx:thumb:

I wouldn't have thought a sticky injector would stop the fuel pump from priming?
Hope it sorts if mate :thumb:

Injectors have been cleaned, weren't the cause of the fail to start and im back to square one. Spoken to a couple of people and they suggest the cam sensor. I just need to know if anyone can add to this as I'm losing hope with this. I'm happy to spend money on a solution but not obviously keen on piss ing in the wind.

Just replace the pump and take as an upgrade if nothing else it'll be taken off the list 100% :thumb:

So I've been away for several months and have turned my attention back to my car. Long story short it has been diagnosed with a faulty fuel pump controller. I've been told this part is unique to each vehicle (sounds funny ) and I will have to order new from subaru. I am glad my car will be fixed but does this sound right to you guys . I'd have thought I could just get a good used unir and plug n play ????

I would say plug and play.

I'd ring Matty the breaker on here not only will he have the part which will be much cheaper than the dealers he will give you any other info or help you need on the matter :thumb:

I've been in touch and he's been very helpful . Thanks for the heads up and cheers matty if you're reading this .