Injection pump will not prime

I have read about all of the problems with IP, but I can't find my problem...

I have a 2001 jetta TDI. After letting it sit for about 1 week I found it would not start. The clear fuel line to the IP was empty so I guess I have a leak somewhere. I used an oil extractor as a vacuum source and verified that I can pull fuel through the fuel filter. When I put the vacuum on the return line from the IP I can't get any fuel to come out of the pump. The vacuum holds pretty well so it is not a gross leak that is preventing the fuel flow. I used the starter to rotate the pump a few times with the vacuum on the return line and still no fuel out of the pump.

Any ideas of what could be wrong?

It often takes a LOT of vacuum to pull fuel through the pump... Make sure that there's no air leak that could be subotaging your efforts - when I did this a week or so ago, I had left a couple of the injector lines loosened (anticipating the next step in starting the car), and was advised to close them up...

Just keep on trying...

Yuri

agree with yuri about needing lots of vacuum, even then its comes out begrudgingly....not a good sign that you lost prime, if you fuel filter isn't fresh I'd change it, its one of the cheapest things you can do to work on your problems

Everything hooked up except the return fuel line. Tighten all nuts on hard fuel lines. Hook up interinjector lines, and small return line to IP. Stick an old glowplug in the return fuel line.

You know fuel flows easily thru the filter, and it is fully primed. You know that the fuel supply line to the IP flows fuel easily. You know that the case pressure relief valve is intact. You know that your fuel shutoff valve is good.

Hook up large tubing of mityvac to the metal return line fitting. Pump, pump, pump..............Your goal is fuel in large clear mityvac line with only small bubbles (BB sized) coming out of the metal return line.

Can't get fuel or won't hold a vacuum? Start thinking about an air leak at the pump head seal on the IP. Stick a 12v+ jumper wire from the battery to the fuel shutoff valve and see if you get fuel.

Won't pull fuel at all, and you absolutely know the IP is has no leaks? IP is toast. Send for rebuild.

paramedick said:

Won't pull fuel at all, and you absolutely know the IP is has no leaks? IP is toast. Send for rebuild.

Click to expand...

Careful with that bit of advice: it's too easy to give up on the pump without exhausting all the other possibilities...

Yuri

maybe the check valve inside the fuel tank got stuck opened position.
anyway,fill up the fuel filter with diesel then crack the 4 injectors, then try start the car until fuel start spreeing .close the injectors that flow fuel.
until the 4 injectors did this ,the car must star.
forget the priming proses ,its a complete joke (for me)

Thanks for the advice. I am not using the hand pump. I have one of those air powered vacuums for extracting engine oil and I was using that. It pulls a pretty good vacuum. I will see if I can pull a harder vacuum and hold it longer. I think I only did it for 5min or so before.

On the issue of the check valve. I did not see that in the manual. I will look again when I get home. Given that when I pulled fuel through the filter and then released the vacuum the fuel drained back that would indicate that the check valve is not operating. Is there really a check valve?

ymz said:

Careful with that bit of advice: it's too easy to give up on the pump without exhausting all the other possibilities...

Yuri

Click to expand...

Perhaps I should have gone farther. These check are automatic to me....I added the next paragraph to previous post.

You know fuel flows easily thru the filter, and it is fully primed. You know that the fuel supply line to the IP flows fuel easily. You know that the case pressure relief valve is intact. You know that your fuel shutoff valve is good.

If fuel still won't flow, the IP is toast. I see it a couple of times a year. Same IP primes/work flawlessly when they come back from DFIS.

It's automatic for you... I remember how much effort (vacuum) it took to pull fuel through my pump that had been sitting for 8 months... I would have been tempted to give up were it not for the hints I got from you and MOGolf...

Yuri

I got great help from Jeff Robertson last year on a car that air locked. Sometimes you have to suck all the air out of the pump, bubble at a time to get them to work, especially on pumps that have dried out from long lack of service.

Set up a fuel source to the 'in' pipe on the I.P. I have a small funnel with a piece of fuel line that works great. Keep the funnel full Use a MiteyVac or equivalent and draw fuel out of the return line on the I.P. Keep sucking until no bubbles come out of the pump. This can take a while... 1/2 hr.

That usually gets the circuit going. I also make sure that the o-rings on the thermostatic 'T' are good. An air leak there will put you right back where you started.

When you have a solid fuel flow at the I.P., loosen the line nuts on the injectors and purge them. Tighten 1/6th turn and it should start.

Why not just remove the plug on the side of the pump and fill the pump manually. I almost never use a might-vac. Although they are great tools.

I just changed my TB, Fuel Filter, etc ... anyways, i didn't know i had to fill the fuel filter, and my IP ran dry. You need a LOT of CONTINUOUS Suction .... a good 20-30 minutes before it'll draw fuel, dont dispair !! just be persistent and it'll draw the air out and start drawing fuel. Make sure you top up your filter before attempting to start. You may need to crack injector #3 to bleed the air out, thats what i did with mine and she fired right up !!

Had one towed in today that lost prime had it running in 5 minutes. It does not take 20 minutes there is more than one way to skin a cat.

Make sure the sending unit in the tank is good. This car had a bad one and it was sucking air. Put a might vac right to the sending unit outlet nipple and if your getting air and not fuel its bad.

USUALLY, it doesn't take long to get the prime back... sometimes, it's a BEAR.

I've had it both ways. When it's bad, it's very, very bad. When it's easy, anybody can do it.

Thanks for all of the advice. I got it started. If found that filling the filter was not enough. I had to take the inlet line off the filter and fill it with fuel and then pull a suction as suggested by Franko6. I don't know why just filling the filter did not work for me. Anyway, now I need to find the leak. It is difficult to clean the fuel pump to see which seal is leaking, especially since I expect it will be a small leak and therefore I have to clean it well. Any cool tricks out there on finding the very small leak? Thanks!

Its usually the pump head seal leaking. Wash all around the pump let it dry, run the car for a while check for leaks. Then let it sit overnight and look for leaks again. But it could also be leaking threw the return back into the tank.

My fix for a stubborn airlocked IP was to remove the cut-off solenoid and pull fuel there first, THEN the return line....easy-peacy!

Thank you KROUT

Thanks KROUT. My '03 Jetta has been sitting a while because it wouldn't start any time that I let it sit for any length of time. I think it was the Tee at the fuel filter. Put a new one and a new filter on and could not get the IP to prime. So I tried your method. Was a pain getting it in that little hole, but after that I cracked the injectors open and she started spraying fuel. Thanks for the tip, because I don't have a mighty vac.

If the seals are good in the IP...
Uhhh replace the check valve (or get it working) on the return line on the injection pump. There's your problem! If the check valve on the output of the injection is clear you will always prime the pump in under two minutes.