air bubbles

[juleshs]

i keep geetting a lot of air bubbles in my fuel lines, as this a bad thing?
also if my fuel pump is not timed properly will it be noisy?  aaz

[96jetta]

did you replace the fuel filter?

[juleshs]

yes new filter

[96jetta]

how bad is the mix between fuel and air?

[juleshs]

if by mix you mean how many bubbles, well since i have been building this car (about 4 years) it as mostly been sat ticking over i took it to the mot station about 5 mile round trip. there have always been a lot of bubbles, in the clear pipe between the filter and the pump there is always some bubbles there but doesnt seem to effect the perfomance

[8v-of-fury]

Bubbles will with out a doubt cause performance issues. If the engine thinks its getting X amount of fuel from the pump according to the RPM of the engine, and its really getting 70%X (fuel) and 30%Y (air) it is going to hinder performance substantially. Say the engine is spinning at 1800 and is receiving the appropriate fueling to do so.. now you add air in to the fuel and it is only getting enough fuel for 1500 rpm.. You will push the peddle more but you will get less power. It's just a bad thing, lol.

Check all your fuel lines. Did it have air bubbles before replacing the filter? check those connections especially. Add a clear line before the filter so you can see if it is coming from the filter or from the filter to tank section.

[Golf/Jetta]

my AAZ does this. replaced all fuel lines/rubbers and still have the problem today..
are they big bubbles or tinny..
tinny bad
big OKż

[8v-of-fury]

my AAZ does this. replaced all fuel lines/rubbers and still have the problem today..
are they big bubbles or tinny..
tinny bad
big OKż

What? 

ANY BUBBLES are bad  There should be no bubbles whatsoever in the fuel system. You have a leak somewhere, it is advised that you fix said leak

[8v-of-fury]

There should NEVER be any air in the fuel entering the engine.  The amount that is O.K. is NONE.  

Beat ya to it Andrew 

[veedubcanuck]

My 93 does the same. I see the odd bubble (one every maybe 8 sec.) Done it since day 1 when the car was new. Never had an issue.

[8v-of-fury]

My 93 does the same. I see the odd bubble (one every maybe 8 sec.) Done it since day 1 when the car was new. Never had an issue.

That is an issue. Feed or Return line?

[ezekiel]

There should NEVER be any air in the fuel entering the engine.  The amount that is O.K. is NONE.  

Truth.

You all need to replace your copper crush washers, most likely.

[Vincent Waldon]

O-ring at the return tee on the fuel filter is another common suspect, for those vehicles so equipped.

[macka]

when I got my car it was a beast to start because there wasn't an O ring in the tee.