[Vwdiesel] 82 Rabbit diesel - injector pump lever is "sticky"

[Joe]

I've got an 82 Rabbit diesel whose injector pump was replaced (by the
previous owner) in mid-2007 with a remanufactured pump from Parts Place Inc.
Car is from Wisconsin, and was run on biodiesel as well as regular diesel.
I'm running it exclusively on diesel.  I've owned it for about 2 months now
and have put about 3K miles on it.. Gets 42 MPG at 70 MPH.  It's developed a
"sticking" problem on the accelerator which I've determined is the pump
lever itself, not the cable.  Once the engine is warm, I can pop the hood
and grab the lever, increase the engine speed, and it will slowly (like it's
gummed up) return to the idle position.  If I move it too far, the engine
will race and I have to forcably push the lever back to idle.  It will
return to idle by itself eventually, but I don't like to race the engine
that high.

Now I suspect this has been an issue with the pump from the beginning, as
the previous owner had also purchased an accelerator cable about 6 months
later but never installed it.  I looked closely at it and it appears to be
the wrong cable (adjustment at the firewall, not at the pump like the
original).  However, I've adjusted the original cable and gave it a generous
shot of WD-40... The cable moves quite freely.

So is it possible that the return springs on the remanufactured pump are
orginal and somehow weakened?  I'm thinking about installing an additional
return spring bolted to the passenger fender, just for safety's sake as I do
wish to drive this car frequently.  Or is this a symptom of a more serious
problem which will cause the pump to fail?  Indeed, am I causing more damage
by using it?  Any input is appreciated.

Joe