« previous next »
Pages: [1]

Author Topic: Bubbles in fuel return line  (Read 1683 times)

Offline maxp

  • I live here
  • *****
  • Posts: 614
  • J reg 8v digi gti
Bubbles in fuel return line
« on: 24 May 2009, 17:02 »
Have been having problems starting the car when hot.

Looked under the car, found out there were quite a few bubbles in the fuel return line.

On priming the pump (1st click) i see more bubbles appearing,

There is a slight smell of petrol when the car does finally start when it's hot (took about 8 tries this afternoon- but once started is fine)

Im betting in on it being a faulty fuel pressure regulator.

Does anyone agree with this or can offer insight?

Logged

Offline mattkh

  • I live here
  • *****
  • Posts: 554
Re: Bubbles in fuel return line
« Reply #1 on: 24 May 2009, 21:40 »
Hi
Does the fuel pressure regulator on the fuel rail have a vacuum pipe ?
If it does, take it off, have a rag handy and check to see if it spurts any fuel. If it does then the diaphragm is faulty and may be the cause of the air bubbles.
Logged

Offline maxp

  • I live here
  • *****
  • Posts: 614
  • J reg 8v digi gti
Re: Bubbles in fuel return line
« Reply #2 on: 25 May 2009, 13:17 »
Just tried it, vacuum is sucking fine and nothing was coming out.

Argh any ideas? Maybe it could be blocked or a have a split in a seal?
Logged

Offline rubjonny

  • 10k hero
  • *
  • Posts: 16,349
  • Hello, my name is John and I'm a dub addict.
Re: Bubbles in fuel return line
« Reply #3 on: 26 May 2009, 10:41 »
has the ecu temp sensor been replaced recently? if not go buy a new one from VW.  check you get a spark when hot, the fuel rail and fpr dont tend to go wrong.
Logged
Hello my name is John and I'm a dub addict.

Offline maxp

  • I live here
  • *****
  • Posts: 614
  • J reg 8v digi gti
Re: Bubbles in fuel return line
« Reply #4 on: 26 May 2009, 11:31 »
Yes it has-ish (few months). How would that affect bubbles in the fuel line though?
Logged

Offline rubjonny

  • 10k hero
  • *
  • Posts: 16,349
  • Hello, my name is John and I'm a dub addict.
Re: Bubbles in fuel return line
« Reply #5 on: 26 May 2009, 12:06 »
my thinking was the bubbles arnt anything to worry about and the cold start is being caused by something else ;)
check over all your fuel lines for cracking and splits, especially the fuel rail ones at the ends, plus make sure you have no leaks.
Logged
Hello my name is John and I'm a dub addict.

Offline maxp

  • I live here
  • *****
  • Posts: 614
  • J reg 8v digi gti
Re: Bubbles in fuel return line
« Reply #6 on: 26 May 2009, 13:23 »
There are quite a few of them! Say 1 cm of solid bubble for every 10cm of petrol. Shouldnt a fpr totally remove all these bubbles as they would make the circuit pressire too low?
Logged

Offline rubjonny

  • 10k hero
  • *
  • Posts: 16,349
  • Hello, my name is John and I'm a dub addict.
Re: Bubbles in fuel return line
« Reply #7 on: 26 May 2009, 14:39 »
youre only seeing fuel that has been returned to the tank, if there isnt enough pressure to open the fpr it wont send anything back to the tank see.
Logged
Hello my name is John and I'm a dub addict.

Offline maxp

  • I live here
  • *****
  • Posts: 614
  • J reg 8v digi gti
Re: Bubbles in fuel return line
« Reply #8 on: 26 May 2009, 14:48 »
ah so it only really matters that the supply to the rail has good pressure then.
Logged

Offline rubjonny

  • 10k hero
  • *
  • Posts: 16,349
  • Hello, my name is John and I'm a dub addict.
Re: Bubbles in fuel return line
« Reply #9 on: 26 May 2009, 15:51 »
exactly! not saying these bubbles are definitly not a problem, but i dont think they are.  maybe you have a loose fuel line somewhere introducing air into the system?  as i say, check you get a good spark when the engine is cranked over hot.
Logged
Hello my name is John and I'm a dub addict.
Pages: [1]
« previous next »