More air bubbles?

[Jay]

A while back I posted that within 24hours of owning the GTD I broke down on a motorway which seemed to be caused by air in the fuel lines, I got the car 'sorted' by having it bump started (tow started) and replaced the fuel filter, I've checked every few days or so and not seen any air bubbles since.

Now I don't often go on motorway/highways and today I did and had pretty much the same problem, the car lost all power & acceleration, it started to slow down, so I down shifted to 4th and the car regained power. I sat @ 60mph in 4th for the next 5mins then went into 5th where it seemed fine doing 60-70mph.

Just before I had this lose of power I had been doing 80mph to over take a dodgy euro driver in a lorry.

So what I'm wondering is if for some crazy reason I'm getting air bubbles in the fuel lines when going fast (IE 80mph) and what would cause this? Bearing in mind when it last happened the air bubbles were coming from the fuel filter into the fuel pump and we could see them in the clear(ish) fuel lines.

Could it be something in the fuel tank blocking the fuel pick up as the mechanic suggested (who came out to see why it broke down the first time), or something with the fuel lines or something else completely?

[Jay]

Anyone have a clue why I'm getting these air bubbles?

[theman53]

I would guess that you could have something like what you are suggestiing, but have you thought that it could be the fuel filter again? When I emptied the farm tank into my old rabbit I needed about 4 fuel filters before it finally stopped plugging them up. Some guys even put a vacuum gauge of some kind between the IP and filter to see if it is pulling too hard.

Other than that I would check for a very small leak that is very present when you are running it hard. Something that could introduce your air, but not let the system loose prime. Are you having hard starts?

[Jay]

I wouldn't have thought it to be a new fuel filter (what are the odds?), but it will be replaced again to be on the safe side, I've had a look around and I can get 5mm Braided Fuel Hose for £5 per meter which is probably worth it anyway, unless you guys rekon it won't make any difference to the normal 5mm hose at almost 1/3 the price.


Anyone got any good tips on checking the suction of the IP?

One of the previous owners used to use cooking oil of some sort, I know this as a fact, when we pulled the fuel pickup out the tank there was a load of gunk around the top of the fuel pickup that smelt just like cooking oil (we were undecided as whether it was veg or sun flower oil ), so I wonder if there is something in there blocking the fuel pickup and allowing air in...    I'll just have to not go over 60mph until I cure this.


EDIT: She starts up OK, most times with a puff of smoke, which is normal from what I've read even for some GTI gassers.

[Jay]

It had gone away for all this time then suddenly came back with vengeance!      


Had the recovery guys out to look at it, eventually got her tow started and then suddenly she conked out while filling in paperwork with him... so we tow started again and she carried on running... then conked out after filling it up with diesel, just outside the filler station... luckily Crazy Quiffs is right next to the filler station! woop!

So I went in and asked for some help, they came out to have a look, tried a few things then we towed her into their garage where I left her with them... I called them a few hours later as I hadn't heard from them - they had taken my number down incorrectly lol They had fixed it after 1.5hours, would have been a lot quicker if I hadn't told them a previous mechanic said it was the air bubbles causing the problems...

they traced it to the cable that runs to the IP that activates the fuel stop solenoid    Mine was making a bad connection, but is now sorted thanks to the guys at http://www.golfmk1.co.uk/

If you see a few air bubbles in your fuel lines and your car won't crank over - check the fuel stop solenoid cabling !  I felt so silly after that 

[dyoungen]

Have you thought of putting a pump just outside of the fuel tank so you are pushing the fuel into the filter instead of sucking it into the filter?

[Jay]

Yes, but I read somewhere it might mess up the dynamic timing and cause poor running   

[dyoungen]

That I"m not sure of. I have a Ford F250 with a 6.9 Diesel that I run SVO in and have a pump outside of the tank. I had converted an Isuzu to VO and used a pump on it to but I had a line that let any unneeded VO return to the tank so I wasn't forcing any extra into the IP.

[dennis]

Sometimes we see problems at the water seperator.

[dyoungen]

Sounds like the same problem we see on the old 6.9, water seperator. Most of the time the water seperator was removed and another fuel filter was used with the water seperator included.

[dyoungen]

Looks like I had the same type air intrusion problem myself. I bought the Jetta and drove it home. After I got it home I checked a few things and didn't find anything wrong. After that I couldn't get it to start. I've been checking out different things trying to start it but no go. Today I remembered that I had opened the water drain in the bottom of the fuel filter. I added some tranny fluid directly into the IP and the filter and she started right up. After going about 5 miles, she is running fine. I think I"ll just forget about the water seperator from now on.

[Rabbit TD]

Yes, but I read somewhere it might mess up the dynamic timing and cause poor running   

I just put a Mr. Gasket lift pump [4-7 psi.] on my Rabbit T/D a while back to see if it would make any difference for the starting problems I was having.  I really didn't notice any difference at that time.  I found an air leak which cured the problem, the pump actually found it for me by presurizing the line a little to make it visibly leak.  I noice absolutely no difference with the pump running or not either for starting or driving 75 mph and it doesn't change the mileage either.  It does make things a little easier when changing  fuel filter or changing the IP or whatever along those lines though.   

[monst]

I had air in the systemmmm.......
Really what it ended up being.. was rather interesting.....

I was told to run the car from a bucket of fuel...
So I got some fuel line ran the feed and the return
into the bucket...... the feed I ran from the bucket
to the filter........ ran car for about ten minutes....
  no bubbles............
put it back together...... drove for awhile ..... bubbles.....
   So anyway....
Down near the fuel separator underneath the back of the car
there were two inline check valves....... on the fuel feed and
return.   I checked them.... the feed check valve was malfunctioning...
and causing a restriction....
  So when this happens.... the pump will suck and suck and suck.....
pulling in air.... from where ever it can..... In my case at the fuel filter
at the O-ring for the warm fuel return........
    My car is an the A2...... but I have even heard of this happening
to A3's...  I believe the check valve here is in the fuel pickup in the tank...
A friend of mine said he had to run a drill bit through it to disable the check valve...

   Anyway, that is what I came across...
Oh yeah, the check valve cost like 50 bucks so I eliminated it from the line...
I was told that It absence in the fuel line may cause difficulty at start up
If it does, I didn't notice it. no biggie

[arb]

Oh yeah, the check valve cost like 50 bucks so I eliminated it from the line...
I was told that It absence in the fuel line may cause difficulty at start up
If it does, I didn't notice it. no biggie

My caravan conversion does not have a valve anywhere outside the IP. Works great.