Bubbles in the fuel line!

[Cman]

On my 94 td jetta I've got bubbles coming the filter in the fuel line,, I checked all the hose clamps on the filter and they seem fine..

where are there any other conections that I can check??

Also does this car have an electric fuel pump in the tank like the older gas models??

Thanks Again.

[andy2]

The injection pump pulls the fuel from the tank through the filter there is no electric pump.If there is a leak in the system it will pull air in beacuse its under vaccum, a restricted fuel filter can also be the problem.Usually the problem is the plastic return fitting on top of the filter they can get cracked  or the o-ring uesd to seal it can also be not sealing well too.If you change the fuel filter be sure to lub the o-ring so that it will seal well.Air could also be coming out of the injectors return or inj pump as there could be a leaking seal on the pump or an injector problem.just look at the inj pump and verify that its dry and no fuel is leaking from it and then i would try a fuel filter. Always fill the new filter with fuel, then drive the car around for 10min to get any other air out of the system after the filter is changed. hope this helps

[mainer]

you might be lookin at the line that returns the fuel to the filter.
_________________
Mercedes 200

[Cman]

no its the the supply line..  ( the larger of the 2)

I'll take a look at the oring and inspect the plastic piece as well..

Thanks

Tom

[Peter]

it is perfectly OK to have small  bubbles in the system ...only if the bubbles  get large should you be concerned ..(maybe a new filter is needed)..you will notice problems  if your car starts missing...it never hurts to check for rusty fuel clamps along the whole line to ensure all will keep working fine...also check for rust on top of the tank were the hoses are connected too...leakage can occur there also....

On my 94 td jetta I've got bubbles coming the filter in the fuel line,, I checked all the hose clamps on the filter and they seem fine..

where are there any other conections that I can check??

Also does this car have an electric fuel pump in the tank like the older gas models??

Thanks Again.

[gropar]

With bigger hoses (generic injection hose from tank to filter), new colars and new return valve on the filter I got from lots o'bubles to none.

I just got rid of restrictions I could do without and everything was perfect! (I used to have bubles since I bought the car - -1.6td -- and after the engine swap -- 1.9td).

[toomanycars]

G'day... New member from Australia. Golfs exported to Oz have a fine mesh filter in the fuel tank. Don't know if this is true elsewhere. I've had problems with this becoming blocked with fungus.  Try blowing (gently) compressed air back from the line into the filter to the tank. Too much pressure and you'll blow the mesh filter off its mounting! Recently I had major bubbles between the filter and pump. I checked the usual things and put a clear hose between the steel pipe from the tank and the filter banjo. No bubbles there so I relpaced the filter. Perfect!

[1996jetta]

I just went through the same problem with my 1996 Jetta.

Mine was real tricky.  It only happened when the temperature was cold and it cleared up after the car warmed up.

It was so bad that I had to pull over after the car died and refill the fuel filter just to get the car running long enough to overcome the bubbles.

I went through the whole part by part replacement routine.  New fuel filter, new filter "T", new rubber lines, etc.

I tracked the problem down by splicing in a long section of plastic hose at the fuel filter and the fuel pick up lines.  

It turned out that the leak was in the fuel line to the filter.  There is a factory join to a section of rubber hose that is right on top of the fuel tank.  It has a metal crimped ring on it.  

I cut off the plastic tubing, replaced the brass insert, routed a new rubber hose from the fuel tank, and placed new worm clamps on it.

No more problems, instant starting, no more frustration.  

It turns out that this is the reason the fellow sold me the car.  He didn't tell me the problem when I bought it (on a warm spring day in 2004).  

Lots of luck and I hope you get the problem tracked down.

My question is:  Why is the one way in-line valve at the fuel pick up over $150 CDN?

kc

Comments welcome at [email protected]

[Dieseling]

I did the same thing as toomanycars.

Shortly after I bought my '85 Jetta diesel about 2 months ago I installed clear line from the fuel filter to the pump to see if there were any problems with fuel delivery & also to see if the fuel was obviously contaminated (questionable vehicle history). No problems with contamination but there were/are bubbles in the line & they got/get larger with higher rpm. Ran clear line from the check-valve near the fuel tank directly to the fuel filter to locate the source of the bubbles. No bubbles in that line but still bubbles in the fuel filter to pump line so I then bypassed the fuel filter completely, directly connecting clear line to clear line. No bubbles! Ergo, same conclusion as toomanycars -- it's the fuel filter -- but still haven't replaced it (waaaay too much money for this style at the local parts store, not to mention mess, so will be looking for old style at salvage yard & retrofitting). Runs fine, despite the bubbles.

OTOH, it wasn't running so well when I had the pump timing adjusted by ear & found out it was retarded by ~0.45mm!!! And I thought the continual stuttering at lower rpms was caused by the bubbles in the line! Runs so much nicer after I set it at ~0.93mm! Oh, & I was able to drop the idle rpm as well with the proper pump timing. Now have idle set at ~880-920 using photo-reflective (or something like that) reading tach.

[fspGTD]

Here are some posts from the old board covering the bubble-in-fuel-line topic that you guys should check out:
http://www.hostboard.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=4037&t=205

http://www.hostboard.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=4037&t=316

http://www.hostboard.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=4037&t=344

http://www.hostboard.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=4037&t=564