Lumpy cold start since fuel pump change *NOT SOLVED >:|*

[Connor H]

Hey chaps, so my car is spinning quite a few times before firing up and chugging/revving a bit mad on start up since i got the APS fuel pump.

Started up on a dime no issue before.

Any one have any idea what it could be? I put all the O rings and stuff back where it was (Took the pump out, two O rings nestled in the bottom of the pump basket, one on top of the pump itself once fitted in the basket.) the pump didnt come with any diagrams to show where they were meant to go... all clamps were tight on the hoses as far as i could tell.

Cheers

 

[Reggie Cupra TDi]

its probably forced a bit air through the system so the fuel pressure isn't correct, although it primes the air is still trapped, i would be tempted to crack one of the nuts on the fuel rail to release some of the air maybe and then prime with turn of the ignition and nip it back up. i had this on a ford i did the fuel pump on a couple of years ago and it worked. hope this helps.

 

[Connor H]

its probably forced a bit air through the system so the fuel pressure isn't correct, although it primes the air is still trapped, i would be tempted to crack one of the nuts on the fuel rail to release some of the air maybe and then prime with turn of the ignition and nip it back up. i had this on a ford i did the fuel pump on a couple of years ago and it worked. hope this helps.

Thanks mate.

I had a theory it was air but im a first timer with fuel pumps .

Any particular nut on the rail to crack? Will do this tomorrow and update.

 

[Reggie Cupra TDi]

trying to see if i can see any compression fittings where it attaches to the top of the injectors, that's where need to be cracked, on the mondeo i did they were on the top like in the picture so was 2 min job,

 

[Connor H]

trying to see if i can see any compression fittings where it attaches to the top of the injectors, that's where need to be cracked, on the mondeo i did they were on the top like in the picture so was 2 min job, View attachment 18927

Yeah I’m a little lost at where to release, I would have gone in and whipped a fuel hose off lol


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[Reggie Cupra TDi]

maybe someone else can shed some light on this, wouldn't want to point u in the wrong direction buddy, mine was a diesel so it could be totally different to petrol setup pal,

 

[Connor H]

maybe someone else can shed some light on this, wouldn't want to point u in the wrong direction buddy, mine was a diesel so it could be totally different to petrol setup pal,

Of course mate and thank you for the advice so far, at least I can look into bleeding air out the fuel system


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[Connor H]

No luck yet, double checked the tightness on the massive plastic collar nut thing that tightens the pump down.

It does however start nicely if i turn the key, spin it once, before turning it off and repeating.

 

[Woody_72]

Just a wee heads up. If you are cracking loose any nuts on a diesel, be extremely careful. The injection pressure on a modern common rail is well north of 30,000 PSI. It would do you a lot of harm before you even felt it .

 

[Connor H]

*UPDATE*

I finally sorted it simply by stumbling upon an installation manual for a different but similar pump, and realised i missed a pretty important and basic step,

I attached the fuel out line THEN primed it., therefor locking the air into the system introduced by changing the pump.

Whipped off the out line from the top of the pump assembly, primed it into a jug, line back in. Jobs a goodun

 

[Reggie Cupra TDi]

glad you sorted this mate, thankfully it was air trapped in the end nice one...

 

[Connor H]

UPDATE 2

The problem pretty much returned straight away, dies on first start second start fires up perfect.

I tried running the fuel into a jug in the engine bay this time today and still no luck fixing it.

I guess at this point there is air getting in somewhere near the pump? Either that or the pump is a pile of crap

next step is to take it out and reinstall it making sure everything is in the right place.

 

[Reggie Cupra TDi]

ahh damn best of luck with that fingers crossed for you

 

[Connor H]

ahh damn best of luck with that fingers crossed for you

Took the whole thing apart double checked all fittings and fixtures, even changed the o rings on the pump back to the original ones...still same problem.




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[elviscat]

Hi Conner did you get to the bottom of it? I wa thinking of replacing pump next, after having similar problem with my BAM. I have found to date if i prime the pump twice by turning key (pump prime, not starting the engine) key out door locked, unlock door key in prime pump again bingo starts perfect.
Else very, VERY lumpy, spluttering start for first 10 seconds. ECU does not give a misfire, new plugs installed etc, I guess meaning fuel related.

 

[Connor H]

Hi Conner did you get to the bottom of it? I wa thinking of replacing pump next, after having similar problem with my BAM. I have found to date if i prime the pump twice by turning key (pump prime, not starting the engine) key out door locked, unlock door key in prime pump again bingo starts perfect.
Else very, VERY lumpy, spluttering start for first 10 seconds. ECU does not give a misfire, new plugs installed etc, I guess meaning fuel related.

Not only did i not get to the bottom of it, but the APs pump died late last year so i chucked the old OE one back in, and it still does the same.

i found if i prime it and give it 6-10 seconds it fires up pretty nicely, other than that i just got used to it lol.