91 Jetta Diesel Idle/AC issue

[kenbt]

I lived without air conditioning for years. This spring, I took it to be repaired and when I got it back I tried to adjust the idle speed from inside the car. There was no effect on the engine speed when it was pulled out. The adjustment knob does move the lever on the injection pump.

Before the AC repair there was no reason to use the idle adjustment.   A while back I had to have by injection pump rebuilt after developing a leak after my first tank of ULSD. My pump was sent off, rebuilt and returned. When I picked up the car the idle adjustment/timing advance control was pulled all the way out.

Question. If the pump was reinstalled and timing set, with the knob all the way out, would this cause my problem?
What else could cause this issue?
Thanks for your thoughts
Ken

[Quantum TD]

Timing is supposed to be set with the cable all the way in.

If not, then the timing will be retarded with the cable all the way in, and your mileage will suffer. This will be the case, even though your current mileage is better than before the rebuild. This is due to 2 things: 1) no leaks and 2) calibration of the pump. So, overall your mileage may have improved, but with retarded timing, your mileage may not be as good as it can be.

There is a possibility that whoever installed your pump may have knocked off the idle-up lever. It attaches to timing-advance cable, and connects to a lever on the side of the pump. Most VW diesels after 1987 have the idle-up lever on the side of the pump.

It's also possible that whoever installed your pump, installed an off-the-shelf rebuilt pump, rather than rebuilding your original pump. If they did, then you may have an early pump which lacks the idle up. If that's the case, and the timing is already too far advanced, then pulling the cable with no discernible effect would be the outcome.

Perhaps someone can mine the archives to show pics of the idle-up lever.

[jtanguay]

i'd say just increase the idle by using the residual fuel screw and go with that.  unless it has the vacuum idle boost like the AAZ pumps do, it will shake with a/c on at idle.  i guess you could always retrofit one... because i dont think its a good idea to drive around with the timing boost always on...