New Pump Appears to have Stopped Pumping Fuel

[rabbitman]

I don't think the mk1s have a check valve.

[Doakster]

I don't know where to turn with this problem, I decided to remove the check valve completely, and plumb that section with new fuel line thinking that would solve the issue.

After doing that, the car did run for a while, but I still get the stalling, i almost have to leave the cold start out to get the idle up to keep the car running.

I've replaced all the fuel lines at the filter, except the line going to the pump with the banjo fitting, I pressure tested that and it's good. I can easily blow down the supply and return lines, so there is absolutely no restrictions from the tank to the filter, or from the filter to the pump.

I've seriously looked at everything in the fuel delivery system and can't find any leaks or blockages, is it possible for the pump itself to be sucking in air??

I can still see a few slugs of air that are in the supply line to the pump, how long should it take for all the air to get out of the system after you have break the system to work on it?

I'm at my wits end.

[Doakster]

Just did a little more trouble shooting.

I had black rubber line on the return line from the pump to the filter, so i installed some temporary clear line.

Re-primed the pump, started the car, and it ran for awhile, small amounts of air were in the supply line from the filter to the pump, so one would assume it should clear up.

On the clear return line there was mass amounts of air, to the point the line was milky white and never cleared up.

After about 5 mins, it's like the pump gets air bound and just stops pulling fuel, chokes off and the car dies.

I've checked, and re-checked the inlet and outlet banjo bolts on the pump and they are tight.

I can only assume the pump is sucking in air somewhere.

[Doakster]

Remove the fuel line from the tank pickup.  Plug it.  Try blowing into it and sucking on it.  Does it maintain pressure?  Try that for the return as well.

I think i'm going to block and pressurize the lines to 5-10 psi or so and see if there are any leaks.

Also, when running the pump there are only a few air bubbles that will migrate through the supply line to the pump, but on the return line it looks like a milkshake, seem like there is a lot more air on the return side of the pump, then is actually going into the pump, leading me to believe air is sucking into the pump is self somewhere.

[Vincent Waldon]

But did you see any air when you ran the car from a bucket?

[Doakster]

But did you see any air when you ran the car from a bucket?

There wasn't much, so I'm going to retest with that method today, and pressure test all my lines to the tank. I can see where you're going with that question.

[Rabbit on Roids]

thats why i like the lift pumps so much, cause they run at about 5 psi, and thats enough to show a leak. and if a leak shows, its easy to fix. ever since i put an electric lift pump before my fuel filter, ive had no fuel system related problems. when i got my car, i fought fuel system problems for the first year.

[burn_your_money]

Just because a line doesn't leak when you have it pressurized does not mean it will not leak under vacuum unfortunately.

What year is your car? If it has the fuel filter with the return valve thing in it that could be the problem. They recirculate the fuel back to the pump until it gets to a certain temperature. This also means that it recirculates the air.

Do you still have the water separator hooked up? That thing can cause a major restriction and increase the vacuum in the lines and cause air leaks. If you still have it try bypassing it. It is a useless device, only the mk2 diesels have it.

[Vincent Waldon]

Yup, this is why the bucket test is a good differentiator... if you can get the engine running clean with no bubbles etc from a bucket you're pretty much ruled out the pump and return lines as sources of air, and can proceed to go over the rest of the system with a fine-tooth comb.

I say "pretty much" because I suppose it's possible that a leak might only show up under the higher vacuums of pulling all the way from the tank... but I've never heard of a pump circuit with an air leak that doesn't show up when running off a bucket.

Tyler is on to something btw... the thermo T can be a pain.. the o-ring can degrade or jam sideways as it's being installed, the T itself can crack, and it also lets air on the outlet side (say, from the injector return lines) bleed into the intake and confuse things.

[Giles@PerformanceDiesel]

Hi Andy

Sitting on my Dad's couch in the UK reading about your problems.
best thing to test the pump is the "bucket test" and feed the pump seperately and the return
back into the bucket. prime the pump and then run the car on the other source of fuel
you will get air in the return of the pump for quite a while.
pumps can't make air and they will leak before they suck air unless their source is
blocked off
hope you get it running
Giles

[Doakster]

Hi Andy

Sitting on my Dad's couch in the UK reading about your problems.
best thing to test the pump is the "bucket test" and feed the pump seperately and the return
back into the bucket. prime the pump and then run the car on the other source of fuel
you will get air in the return of the pump for quite a while.
pumps can't make air and they will leak before they suck air unless their source is
blocked off
hope you get it running
Giles

Hi Giles, thanks for the reply and the suggests, I'm pretty sure I found the problem. After some more trouble shooting this is what i found.

- Ran the car with supply and return on a can of diesel right to the filter, car ran ok, at first the supply line had no air going into the pump, the return line eventually cleared of air after 5-10 mins of idle, but when revving the motor I would get a surge of air coming out of the return line, and no air going into the supply line of the pump. To me that points to the pump sucking in air.

- Next i pressure tested the supply and return lines, i found the sensor on top of the water/oil separator was leaking badly, ok thought i found the problem, i completely removed the separator, and re-plumbed the lines, I re-pressure tested and the supply and return lines held fairly well. Tried to run the car off the fuel tank, it would run for a while but did the same thing as the can test, surges of air on the return side of the pump.

-I went a step further and ran a brand new rubber fuel line directly from the fuel tank and to the filter, i even pulled the pick up unit and stuck the line directly in the tank so the cars supply line is completely bypassed. The car did the same thing, would barely run and still had surges of air in the return line of the pump. In this case there was absolutely no blockage of fuel to the pump.

So now i know that it is not my fuel lines, i completely bypassed them and ran the car directly from the fuel tank and tried a separate can of diesel and got the same result.

After all this i am getting large surges of air in the return line (looks like a milkshake when i rev the motor), and very little if any fuel in the supply line again leading me to believe the pump is sucking in air.

So I decided to pop off the timing cover and what did I find?

A leaking pump shaft seal. A small amount of diesel was present only on the bottom side of the timing cover, directly below the pump pulley. And I was able to reach my finger in behind the pulley and feel diesel directly below the pump seal.

So at the very least i need to get this replaced, and based on all the troubleshooting i did, this better be the solution, I've looked over the entire fuel system and bypassed the entire fuel system, that's not the issue.

Also the car runs slightly better and longer before it dies on a can of diesel, rather than pulling fuel from the tank. My guess on this is because on the can of diesel is doesn't need to provide as much suction compared to the longer run of line that is needs to pull a suction on when going to the tank.

It's just too much of a coincidence that the car ran great on the pump for 60 miles or so, died and this issue has come up, and before the new pump i never had a fuel delivery/blockage issue.

Any other comments are appreciated. 

[rabbitman]

You sir, are having bad luck Sounds like the seal is leaking really bad, I've heard of them leaking fuel out but never heard of it sucking soooo much air that it quit.

I bet once the leaky seal is fixed it'll work fine.

[Doakster]

You sir, are having bad luck Sounds like the seal is leaking really bad, I've heard of them leaking fuel out but never heard of it sucking soooo much air that it quit.

I bet once the leaky seal is fixed it'll work fine.

This car has been the death of me, worst luck i've had with any vehicle.

I just went out and stuck my finger underneath the seal again, i can get a good pool of diesel to develop on my finger.

I seriously have looked at the ENTIRE fuel delivery system and bypassed the ENTIRE fuel delivery system, this is the only issue i can find.

[Doakster]

How tight is your timing belt?  Overly tight and it will trash that injection pump bushing extremely quickly and cause the seal to fail in the way you describe. 

I tightened right to the recommendation out of the bentley, so that it can be twisted about a 1/4 turn (45 degrees the bentley says) between the cam pulley and the IP pulley. I tightened it to that spec when i first installed the pump and that is still the tension as it stands right now.

[burn_your_money]

How hard do you have to try to twist the belt 45 degrees? I usually set them so I can easily twist 45 and if I try hard I can almost get a full 90 out of them.