81 Rabbit NA injection pump trouble

[ilikevwdiesel]

Just scored a really nice 81 Rabbit LS diesel. It runs good except for the idle won't adjust properly. If I adjust the throttle stop out it will stay around 1000 rpm then it hits a certain point and drops off to like 600 all within a quarter turn of the threaded rod. If I idle it up high and turn on the AC it lugs down really low and shakes. Is there something malfuntioning inside the top of the pump that could be fixed without removing the pump? I can remove and reinstall the pump cover that's no trouble for me but I have no clue on the inner workings. Anyone have any thoughts?

[Baron VonZeppelin]

run the tank kinda low then dump a quart or two into the tank...

Quart or two of what product ?

I was thinking of suggesting running an ATF treatment through it -
is that what you're meaning to say also RoR ?

That stuff does work some good magic often.
One guy even said his straitend out running good, and the wipers and horn started working again too. lol

If you can't wait to run the fuel out low, you can just run your Inj Pump supply and return hoses into a container of ATF. Letting it soak in the pump/injectors while full of ATF, for 12-24 hours is a good thing too.

I'd give it a go first before wrenching on the Inj pump.

[Rabbit on Roids]

sorry, atf... i was kinda tired when i posted that.

[ilikevwdiesel]

run the tank kinda low then dump a quart or two into the tank. i ran like 3 quarts through my audi when i got it and it made that thing run so much better. it wouldnt even hardly idle straight when i got it. haha, the audi that you turned me onto no less. if you end up running into serious problems, come on down and i will help you build a fuel pump for your new ride. i built the one on my car and its holding up well, just has a small leak from the top cover gasket, the tops been off too many times with too old of a gasket. lol.

dude I'm in Maine...you sure this post was meant for my thread?    anyways...I did stick the fuel line into a quart of ATF and let the pump suck the whole thing into it and let it sit overnite. It didn't help.

[Rabbit on Roids]

wait, got mixed up. sorry man. thought you were someone else. my bad. i may have been tired when i posted that 

[ilikevwdiesel]

anyone? maybe the pump has low internal pressure? hope I don't have to replace/rebuild it.

[Rabbit on Roids]

try re sealing it. might be sucking air at the pump shaft seal.

[ilikevwdiesel]

if it were sucking air there wouldn't it leak when it wasn't running? there's no air at all in the fuel supply line.

[Rabbit on Roids]

the input shaft on the fuel pump is in front of the vane pump, where there is SUCTION AT ALL TIMES. or should be atleast. if you had a lift pump, then it would be pressurized there and would leak, correct.

[ilikevwdiesel]

there's nothing wrong with any of the seals on the pump it doesn't leak or lose prime.

[Rabbit on Roids]

hmm. cause the only thing i can think of that would make it run like that is either air in the pump, or a weak pump. a vane or 2 or 3 might be stuck in the vane pump. or, try backing your fuel screw way out. has the fuel screw been messed with at all? thats all i can think of that will make the idle really hard to tune.

[ilikevwdiesel]

I messed with it till I'm blue in the face. backed out the fuel screw and no power, turn it in and it runs away. must have a weak vane pump that's all I can think of too. oh well have a (hopefully) good pump coming from the samba.