Injection Pump re-seal and prime

Hello,
Vehicle is 96 passat wagon B4 with 260K. Injection pump was leaking so I resealed the 2 top seals only. I marked the location of the quantitative adjuster as carefully as possible and reinstalled in the 'same' place. I then hooked up the mityvac to the return line to refill the system with diesel. I watched a couple of vids and it looks easy. When I try however, i get a mix of bubbles and fuel. I've put about 20 psi on this and it seems to just keep pulling air and fuel. And when I disconnect the vac, the system seems to suck all that air right back into the return line and into the IP. Am i missing something basic with the set-up of the mityvac? I currently have it set like its bleeding brakes, i.e. with a reservoir cup and a short piece of hose running down into the cup. Any assistance is greatly appreciated.
Thank you,
Tom

You are already doing the right thing by pulling fuel into the pump via the return line.

One reason for bubbles can be other leaks, either at the pump, the filter or the line leading to the tank.

One way to prime the pump only would be to take a container of diesel kleen and run a line from the pump inlet straight into the container. That way you can eliminate any air leaks from the filter back to the tank.

Also, a plugged / dirty fuel filter can cause similar issues - restriction in the fuel filter can cause one to pull excess vacuum to draw in fuel, and this can increase the chance of ingesting air.

Are you getting bubbles in the clear line leading into the pump?

I had the same problem with mine. Turned out to be a leaking IP head seal allowing air into the IP, rather than pulling fuel in from the filter. I still have bubbles in the feed line from the filter to the IP, but at least it primed and runs, albeit a little rough still.

Yes, I'm getting air in the clear line leading to the pump. Damn, the car ran perfectly before I replaced the seals... It starts now but only runs for a couple of seconds----likely due to a bunch of air in the system. Any idea why when I remove the hose from the return line there's such a big reverse suction that introduces more air into the system? Or how to prevent that from happening with the mityvac?
Thanks again.

I'll own up to a bone head mistake I just made.

Removed the pump to do the seals. Got it all back together. New lines between pump and filter.

Sucked on the line from the thermo tee on the filter until I got fuel.

Hooked it up to the pump.

Sucked on the pump return line until pump filled with fuel and hooked that line up to the filter.

Tried to start it. No go. Remembered the injector lines were removed.

Cracked the injector nuts and cranked until they had fuel.

Started right up. Ran for about ten seconds and quit. Doesn't stumble to a stop, just quits. Big air bubble between filter and pump. No foam in the return line.

Shrugged, repeated sucking on lines, started again for about ten seconds and quit again. Again big air bubble. Again no foam in the return line.

Now I'm getting concerned. Thinking plugged filter but why all of a sudden? Doesn't seem like an air problem.

Anyone got it???

Thermo tee is the return!!! I had them mixed up. Swapped them and good as new.

KLXD said:

I'll own up to a bone head mistake I just made.
Anyone got it???
Thermo tee is the return!!! I had them mixed up. Swapped them and good as new.

Click to expand...

D’Oh!!!

I replaced the fuel filter as it was due anyway but that didn't help my vacuum problem. I decided to loosen the IP and adjust it slightly to see if i could keep it running. It worked. Now here's another question: it's obviously out of whack and needs the vag-com to get sorted out but i need to drive it approximately 10 miles. Is that going to do any harm?

Thanks.

Should be ok.