Author Topic: fuel system HELP please (Read 3634 times)

biojetta · « **on:** February 11, 2008, 08:55:58 pm »

Here's the story, I have had the head and the injection pump rebuilt. I took my '85 jetta out for a drive and it ran fine I had to adjust the tranny linkage due to a new clutch and tranny rebuild it has 458,000 km's on it. I take it out again for a drive, everything is good then all of a sudden the system is sucking in a lot of air. I limp it home and start checking the fuel system. I by-pass the fuel filter (new) in the engine compartment (just in case), check the fuel lines for dripping or wetness. I drain and re-tighten the water separator by the right rear wheel. I pull the cover in the trunk for access to the top of the tank. Nothing is jumping out at me. I then pressurize the tank and push fuel back up to the injection pump. Try and start the car and it runs for a few seconds, dies and is still sucking a lot of air. I went to the dealer and they suggested a check valve by the water separator but, that doesn't make sense as it should still run fine it would just bleed back to the tank when shut off. Can anyone offer any suggestions to this one. I have experience with diesels but, this has me baffled, short of replacing all the components.

Vincent Waldon · « **Reply #1 on:** February 11, 2008, 09:12:51 pm »

Air leaks are a royal pain for sure... too bad the whole system isn't translucent.

Unfortunately it could be any component, any fitting, or anywhere in between. The usual suspects seem to be:

1) the fuel filter itself... this section takes the most abuse since the filter gets changed many times over the life of the car.

Is the water drain tight ?? Are the hose clamps secure ? Are the ends of the rubber hoses at the filter cracked ?

2) the water separator.... the plastic housing is prone to cracking as it ages, it has several fittings and o-rings, and it can get hit with road debris.

Best bet here actually is to bypass it completely and then remove it... they are no longer available and were discontinued on more recent models (ie the early 90s !) since the quality of diesel fuel had improved dramatically during that time.

If it's not those two things then you need to go to round 2: all the other hose clamps, the line itself all the way thru the body, and perhaps even the fuel pickup tube inside the tank.

The fact that it suddenly got bad suggests something "broke" as opposed to slowly got old... I'd personally start with the water separator since it's gonna give out on you eventually, one way or the other !!

biojetta · « **Reply #2 on:** February 12, 2008, 08:04:51 pm »

Thanks, Vince I'll eliminate the water separator initially and go from there. Do you know of a place to get the fuel line other than the dealer? Don't want to pay gold prices. I am also in Edmonton so if there is somewhere local that would be great. What would you recommend using to join the two fuel lines together and what would the size (od) be?

Thanks again.

Quantum TD · « **Reply #3 on:** February 12, 2008, 09:04:04 pm »

As a worst case scenario: if you don't find the source of the air leak, it may be that whoever rebuilt the pump may have used a wrong seal (input shaft) or didn't seal it properly. A car can run fine when not straining to pull from the tank, but stall/suck air forced to.

I just had a 1984 Rabbit running off a squirt bottle under the hood (the car had sat for about 10-15 years). Then, I cleaned out the tank, blew out the lines, put on a fresh filter, primed the pump and filter again and the pump wouldn't suck fuel from the filter/tank, despite the fact that I could pull it with my vacuum, and blow it throught the gas filler cap.

I installed a good used (but recently rebuilt) pump, and it started sucking from the tank just fine. I think the input shaft seal on the original pump was passable to start, but it was sucking air when confronted with the duty of sucking all the way from the tank.

The check valve the dealer speaks of may be an issue. It's located under that trunk inspection cover. I'm not sure if all MK IIs got them, but I know that the later ones did. It's connected to the "out" fuel line from the tank, and it keeps fuel from draining back to the tank. If it's sucking air there, then that's your problem. But if it's just faulty (i.e. not keeping backpressure) your IP should pull and hold fuel just fine: especially after a rebuild.

Either way, you should see fuel leaking if you're pressurizing the tank. I'd say, get one of those hand-vacuum pump kits. I got one at Harbor Freight tools for about $20. It comes with a brake-bleeder kit, which will allow your to suck fuel from your tank, through your filter and see if air bubbles are coming through. If they do, then you know the problem is in your fuel delivery system. If not, then the problem is in the pump, and I'd suspect bad input shaft seal.

Just my $0.02

biojetta · « **Reply #4 on:** February 16, 2008, 07:19:30 pm »

So, here's an update. I have now replaced the fuel supply line from the tank with removing the water separator by the rear wheel completely all the way to the injection pump and the small lines between the injectors and still sucking air in. I wouldn't think the return line could affect this but, not 100% sure is this possible? I have removed the injection pump to return it to the rebuild shop to have them check the pump and confirm things. If nothing wrong I would be totally baffled.

biojetta · « **Reply #5 on:** February 19, 2008, 06:01:03 pm »

I took the pump to the shop and apparently I had my timing belt to tight and it destroyed the transfer pump and scored some bushings, oops. I guess I won't do that again.

jtanguay · « **Reply #6 on:** February 19, 2008, 06:15:39 pm »

Quote from: "biojetta"

I took the pump to the shop and apparently I had my timing belt to tight and it destroyed the transfer pump and scored some bushings, oops. I guess I won't do that again.

hmmm this sounds interesting... i'm having almost the same issues as you. i replaced the rubber line from the plastic going to the pre-heater return (injection pump side of the pre-heater) and my car ran fine after that for a few days... now i can't get it to start no matter what. i've replaced pretty much all lines going to the fuel filter... injector no.1 squirts pretty damn good, and the others just dribble... i'm getting quite a bit of air in the return line at shut down.

how are we supposed to measure the belt tension? with that $40 tool??? did you have it on super tight or was it just slightly tighter?

thanks

rabbitman · « **Reply #7 on:** February 19, 2008, 06:57:07 pm »

That's what I did also, only mine ran fine but the belt would track off center, it was only 6 months old when it did it. The other thing is that if you tell them you didn't use a gauge (that's the first thing they'll ask you) they'll say "oh, it was over tightened" and you can't prove a thing :x . The only way is to have them tighten it for you. It's maddening 'cause there's nothing you can do about it. I didn't take it to them to put the belt on though 'cause they're almost 4000 miles away. Good luck

biojetta · « **Reply #8 on:** February 20, 2008, 01:57:48 pm »

To jtanguay, I guess I had the belt pretty tight, I guess I'll have to look at getting one of those gauges.

To rabbitman, These guys do strictly pump rebuilds they as far as I know do not work on the vehicle but, I am going there later this afternoon to pick up the pump and I'll ask them ( for curiosity sake).

The air in the line that I was getting was in the supply line not the return line so when I get it back I'll put it in and see what happens from there. Hopefully all goes well and I can finally get my wife off my back and her car back to her ( it's only been two months ).

biojetta · « **Reply #9 on:** February 20, 2008, 10:01:15 pm »

I have it all back together and it runs great but, I seem to be leaking fuel out the small return lines between the injectors. The injectors are brand new if makes any difference. Can anyone offer suggestions for repair or is this normal? Rabbitman the shop GSL Diesel in Edmonton here where I had the work done also does shop work on vehicles ( fuel systems only).

Vincent Waldon · « **Reply #10 on:** February 20, 2008, 10:15:48 pm »

Nope... not normal but cheap to fix.... the lines get old and cracked and then leak.

Al at Basco Automotive on the south side (433-5101) stocks the hose... get a couple of feet and you can replace those suckers and be good for another 200K km.

Holler if you get stuck.

Vince

biojetta · « **Reply #11 on:** February 21, 2008, 07:20:35 pm »

I forgot to mention that those lines are new as well. Here's what's been done so far. the fuel supply line from the tank has been replaced completely (removing the water separator by the rear wheel), injection pump rebuilt (twice), new injectors and, new lines between the injectors. So, Vince I'm a little stumped now as I have never had to deal with this type of return system with any of the diesels I've worked on.

Vincent Waldon · « **Reply #12 on:** February 21, 2008, 07:36:04 pm »

Hmmmmm..... strange. No worries... it's a machine... it will *not* beat the collective wisdom of the interweb !

Perhaps we can narrow this down a bit with some nit-picking (and seemingly random) questions:

- is it leaking at all injector sites ?
- leaking at the base of the injector, at the joint in the middle of the injector body, or all the way down the injector ?
- are the high pressure lines that bolt on to the top of the injectors nice and tight ?
- were new heat shields used when the injectors were installed ?
- are they factory-new injectors, or did someone rebuild older bodies ?

My favorite trick iwhen I'm confused as to where a leak is coming from is to get a can of spray brake drum cleaner (Canadian Tire in a big blue can or Princess Auto in a red can) and hose down the area of interest... it will wash away old diesel/oil/coolant and leave the area nice and dry. Getting someone to start the engine while you stand on guard with a flashlight might help you decide where the leak really is.

biojetta · « **Reply #13 on:** February 21, 2008, 07:43:29 pm »

I'll have to try the brake clean thing on Monday. I have something else going on this weekend. I'll get back to you.

Thanks Vince