still trying to figure out air leak

[hjalbert]

I have replaced and double clamped every piece of fuel line from the IP to the metal line that goes back to the tank. I also replaced the filter, and the the filter head. I am getting air bubbles in the fuel from some where before the filter when I rev the engine. (I can see this through the clear line right after the filter. And when I turn the engine off, The fuel line is emtying, either into the filter, or the tank, but generally in the morning it takes a good 12-20 seconds to start, so I think it i going to the tank.

I looked under the car, and the only place there is another connection (supply side) is the fuel hose thet goes into the bottom of the tank (that is the supply I hope). Is this a standard size hose? it looks bigger on one end. I guess it could be leaking in the metal lines themselves, but are there any other places to check before I replace those? thanks

[Fatmobile]

A clogged fuel line can cause bubbles in the fuel line.
Put a vacuum gauge on the fuel line and see how hard the pump is pulling. A vacuum gauge will tell you so much. I try to make sure all my VW diesel driving friends have one hooked up and mounted on the dash.
I can't remember what you are working on (another good time to ask people to put their vehicle in their signature) but if it's a Rabbit, the in-tank screen could be clogged.

[hjalbert]

Sorry about the lack of a sig it should be there now. I am working on an 82 rabbit car. What I dont get, is that is the lines were clogged, or the tank screen clogged, would it allow the fuel to go back to the tank? this is what is happening, in addition to the air being sucked into the IP while running... Im confused. I will add the vacuum guage. do you have a pic of your set up? I will have to look at your site. thanks

[Fatmobile]

Yeah, if the vaccum is high when you shut the engine off, it will suck fuel back to the tank. I saw this on an extreme case of clogged fuel lines I was just working on.
I would suck fuel through the filter and the vacuum would quickly pull the fuel right back towards the tank.
High vacuum will cause air in the fuel to expand into bubbles. Some people think it's because air is leaking in due to the high vacuum but that's not always the case. The high vacuum will cause the air to expand into bubbles large enough to see.
There is a picture of my vacuum gauge connected to my input banjo.
It's on the temp sensor page of my website. Click on the www below.
vvvvvvv

[hjalbert]

this makes sence. I hope it is the problem. Would it be advisable to attempt to blow the lines backwards with compressed air? My air bubbles are sometimes the length of green beans......about 1 inch or 1 1/2.

[hjalbert]

I am an idiot. last night I forgot to purge, because I thought I was leaving again. Now the car will not start....I ahve cracked the injectors, and am currently charging the battery. Never been this bad before....

[libbybapa]

If you keep it up, you'll lose your super-model figure.

Andrew

[hjalbert]

one pot of boiling water solved that problem. to bad its too late now to find a vacuum guage

[Fatmobile]

this makes sence. I hope it is the problem. Would it be advisable to attempt to blow the lines backwards with compressed air? My air bubbles are sometimes the length of green beans......about 1 inch or 1 1/2.

I don't think that would do you any good at all. It would just blow the in-tank screen off it's perch and then there's a screen with even less surface area that will clog even quicker.
You'll need to pull the fuel sender and the in-tank screen.

I use a purolator electric fuel pump with a clear fuel filter in front of it to "vaccum" around the pickup area.
It pumps fuel through the filter and back into the tank.
Last one I did this on, I thought it would be a 30 minute job. It took 7 hours. The car used to be a gasser and had sat for years. When I got the fuel sender out and went to pull the in-tank screen .... there wasn't one. I figure someone did the compressed air trick.
The small screen below it took all the crap and eventually broke through and the whole fuel line filled with crap.
To clear it out I used the fuel pump and ran a hose up to the engine bay to backflush the fuel line. It would clog and I'd have to use compressed air to break through, then run the pump till it clogged again. Vacuuming fuel and chunks out of the tank and pumping filtered fuel back to the engine bay. It finally quit clogging so we ate some pizza and let it run for awhile, backflushing the fuel line and sucking up the chunks as they flowed back into the tank.
I ended up staying overnight. Luckily I brought a spare in-tank screen with me. Installed it, took it for a test drive and the vacuum jumped up to 15. We had a system now so it didn't take too long to get 2 final and big chunks out of the fuel line.
Next test drive it was at 0.
I figure you probably have vegetable oil in your diesel tank. I've seen that before too. I had to pump all of the vegy/diesel fuel into the vegy tank and fill the tank with clean diesel ... on another friend's car.

Next time you forget to purge, pull the "OUT" bolt and replace it with a normal banjo bolt so the vegy can be purged from the pump.
Most of the vegy will quickly be removed from the pump and you can put the "OUT" bolt back in.

[hjalbert]

The car had sat for a while before I bought it, so I bet you are right on the junk in the tank. Regarding the veggie in the tank, I am sure it ahs happened, because even though I use two three way valves , I am human, and my switch times could use fine tuning. from now on I will err on the side of letting diesel go to the veggie oil tank instead of the other way around. I will enjoy cleaning out the tank! (riiiigggghhhhtt). thanks for the advice!

[Fatmobile]

Your return line banjo bolt says "OUT" on it right?

[hjalbert]

yes it does say OUT

[taygan]

I've been having bad bubbles below freezing on the 1994 1.6TD FrankenJetta. It used to be a gasser, so I think I've got to clean the tank.

You'll need to pull the fuel sender and the in-tank screen.

I assume this means dropping the tank?

I use a purolator electric fuel pump with a clear fuel filter in front of it to "vaccum" around the pickup area.
It pumps fuel through the filter and back into the tank.

Is this with the tank off, or down the fill tube? Is this a pump from a vehicle, or a transfer pump? What size hose do you use?

I ended up staying overnight. Luckily I brought a spare in-tank screen with me.

Where did you get the spare screen? Should I assume I need an in-tank screen added since this was a gasser?


Thanks, Taygan
Chugiak, AK

[Fatmobile]

Those instructions are for the A1 body style ...pre '84 Rabbit and Jetta, ...
I've never messed with the tank on a '94 but if it's like the '91 Golf, the fuel level sendor is in the rear, under the carpet. You don't have to pull the tank to get to it. On the pickup you will though
I don't think there's a fine screen in the tank. At least not fine as a screen in a Rabbit ... and it's part of the fuel pickup. Instead of part of the tank, like in the Rabbit.
Since yours was a gasser, was the in-tank fuel pump swapped for a diesel pickup?

Is this a pump from a vehicle, or a transfer pump? What size hose do you use?

I got the purolator electric fuel pump at Napa.
The input threads are 1/8" NPT, I like to screw on a 3/8" barbed fitting because bigger stuff can fit through it.
There's a short piece of hose going to the clear plastic in-line filter and another piece of tubing (clear tubing here would allow you to see if stuff is bridging just before the filter) goes to a piece of metal tubing bent just right to get back into the corners and "vacuum" out the crud.
Having a spare screen was just luck. I had it from another tank and threw it in the "tank cleaner" box when it was laying around. If I see another one laying around, I'm going to make sure it gets thrown in the box.
...so pull the fuel level sender and let us know what you find.

[taygan]

Okay, I can spin the ring, but can't seem to find the spot where it will come out. The sender moves aroudn a little undeneath it, and there are 3 ridges that are flush with the outside of the ring.. The other 9 ridges stick out. I tried lining a flush ridge up with the arrow on the sender, but it won't come out.

Any help? Is there only one spot where the ring will come off or 3 spots?

1994 1.6TD Jetta gas conversion