Bubbles in the fuel filter

[JP-009]

I have just replaced the fuel filter in the Mk1 (because the old one was clogged up - my bad), but there are now bubbles comming up through the filter (from the tank going to the engine).

I assume this is a bad thing? I have now done about 15km and she now missfires occasionally. Will this sort itself out eventually? or do I need to do something about it? (Sorry for my silly question)

[BL33SU]

just a question, what happens to the car when the fuel filter is clogged up? does it drive differently or any thing noticable?

[h100vw]

I wouldn't worry about the bubbles if the engine runs ok.

If the filter becomes restrictive to the fuel flow, you may find performance inhibited under high load/max output conditions. In an extreme case the engine may be damaged if it is run weak for any length of time. I am sure that you would notice the lack of performance before that happens though.

Gavin

[brackie]

Drawing in air

Bubbles means that you're drawing in air somewhere beween the filter and the tank. Check all hose clips first.

[syncro]

I've had that before and it seems OK.

[BL33SU]

I wouldn't worry about the bubbles if the engine runs ok.

If the filter becomes restrictive to the fuel flow, you may find performance inhibited under high load/max output conditions. In an extreme case the engine may be damaged if it is run weak for any length of time. I am sure that you would notice the lack of performance before that happens though.

Gavin

could it cause the revs to cut out when i give it?

[h100vw]

Maybe, but there are plenty of other things that are more likely to be your problem. Fuel filters get changed so infrequently and even then cause few snags.

VAG-COM scan first job.

Gavin

[JP-009]

It’s a weird intermittent thing that only just started after it rained early last week (before that, the engine ran smoothly and sweetly).

I changed the fuel filter because the engine died on a couple of occasions – and all the intermittent surging and power loss seemed to indicate fuelling problems. That’s why I checked the filter to begin with, and found that it was all green and gummed up.

But now I can see bubbles when the engine is running, and when I drive the car, engine revs don’t appear to influence the problem (which is still there). I can give it full throttle and revs (6k) and she runs great - so it seems a bit weird to me.

Will check all hose clamps for any leaks, but if bubbles aren't a problem, then I'm not sure what to look for next...

[86gti]

my mk1 has bubbles in the filter too.. doesnt cause a problem.
i actually think its fairly normal.noticed this back in the old days of playing with Pintos and escorts.... usually find if you hold the filter (if you can) they will stop. mostly vibration that causes it.

the surging sounds like you might have some moisture in the works (spark not fuel)

[syncro]

From an Autobooks workshop manual;

"Note that from may 1980 a fuel reservoir was fitted in the line from the fuel pump to carburettor. This reservoir ensures that only fuel free of vapour bubbles is supplied to the carburettor."

[gldgti]

nice work syncro,

bubbles in your fuel filter shouldnt cause an issue. your carbie (you have a carbie engine??) has a float chamber which fills up with fuel and that is where fuel is mainly drawn from. if air is getting into the fuel system, it might lessen the efficiency of the system and not fill up the float chamber quickly enough, so after you gun it you might find you have a few low power moments.

mollins' yellow mk1 has a bit of an issue with fuel starvation because we're sure there is something solid inside the tank that occasionally gets sucked over the pickup - by blowing back through the line the problem goes away!

[JP-009]

Got the little Mk1 back (after a long and painful journey to Pete's house of miracles). He said that he replaced the condenser and re-seated the jets in the carby (?). Pete did agree that the bubbles shouldn't cause any problems.

Anyway, She runs like she should – crisply and smoothly – which is great. Now we are back on the road and having fun again, YAY!!!