'84 Rabbit diesel (non-turbo) rebuilt injector pump problems

[npmilani]

Hello all!

I've got an '84 Rabbit diesel that recently needed a rebuilt injector pump.  I foolishly had someone do it on eBay and they sent me back a turbo pump. So I have a pump of unknown integrity.

After having a very experienced VW diesel friend help me install and time it (timed to turbo specs) the car wouldn't start.  Very little fuel making it to 3 injectors and nothing coming out of 1.  After some troubleshooting, we found that the diesel return line was plugged and promptly unplugged it.

We've since replaced the fuel lines in the engine compartment with clear lines, so we can see if we're getting any air into the fuel lines. I even bypassed the fuel system by filling up a jar of diesel, running the pump inlet and pump return line directly into the jar to see if the problem was the fuel system.

After priming the fuel intake line and trying to start it multiple times, I'm at the point where I can get it to briefly start but not stay running.  It starts very roughly, revs up immediately and quickly stalls within seconds.

I did manage to finally get it running but only after I started it and immediately floored the pedal.  It did keep running and maintained a speed slightly higher than idle (maybe 1500 RPM??) with the pedal held at full throttle.

If I then ever-so-slightly let up on the fuel, it would slow down - so it seems to respond to throttle changes - but anything more than slightly letting up on the throttle would result in sputtering and eventual stall unless I returned to full throttle.  Basically it needs nearly full throttle to stay running.

Since it does actually start and (kind of) run, I might guess that the fuel pump is okay but maybe the timing is off.  Suggestions?

Thanks,
Neil

[fatmobile]

Try turning in the max fuel screw... or at least check how far in it is turned.
 I forgot to turn it in after putting an injection pump top on and it did the same thing.

[npmilani]

Try turning in the max fuel screw... or at least check how far in it is turned. I forgot to turn it in after putting an injection pump top on and it did the same thing.

Thanks for the quick reply!  Refresh my memory: is the max fuel screw the short one that sits by itself, above the injector output lines but below the return fuel fitting?

Come to think of it, I did mess with that a little bit while troubleshooting.  Do you recall which direction increases or decreases fuel flow - clockwise or counter?  Maybe I should turn it all the way in and gradually loosen it until I get something?

Thanks very much for the tip!

[fatmobile]

Yes, that's the one.
 Turn it in for more fuel.

[jtanguay]

Maybe I should turn it all the way in and gradually loosen it until I get something?

really don't recommend doing this... i'd say keep testing while gradually screwing it in.