AHU TDI A.S. on Injection Pump

Hello everyone,

About 2 weeks ago, i was accelerating onto the interstate and my car, a 98 jetta tdi, lost power, but was still making boost, so i knew it wasnt limp mode. It made a terrible “clattering, diesel knockish” type noise and thought it was a stuck valve or jumped a tooth on the injection pump. I could still maintain interstate speed, but it was hard, even with 15psi of boost.


All of a sudden the damn thing put me back in the seat (as i was almost pegging the accelerator trying to maintain speed til i could pull off) as it regained power. It went a few days without doing it and then it started back doing it, but would usually stop doing it if you pegged the accelerator on the interstate. Now its doing it again, but this time it wont get out of this “funk” its in.

After some research and wire wiggling, I found that wiggling the 3-pin harness by the injection pump harness seemed to make a very noticeable audible difference while idling. Tracing that, I found that to be the Advance Solenoid for the pump. Which requires you to remove the pump to get to it...which is not something I want to do if I don't have to. Is there anywhere to purchase just the harness and I can rewire it in? or just the connector and I can re-pin it? What has everyone else done to fix this issue?

Abacus, this might be something you can answer for me...

The wires and sleeve are potted into the valve. Likely the sleeve broke at the point where it leaves the potting causing one of the wires to fail at that point.

You were due for a timing belt anyway weren't you?

as far as what failed or where the problem is i wont comment.
i do know VW has this 3pin connector, i dont happen to have part# on hand. 1 suggestion, if you need connector, take a trip down to your local VW dealer and have him look up part#. i know mine has on parts pic blow up. is like $17.

I'm having the same issue where on the hwy boost is around 12 PSI while doing 75 mph. Not sure what is going on. Boost use to be around 8 PSI at 75 mph. Car all stock with no mods. Around town the car drive great with no issues and pull as it should.

Rosebud, check your lines to the wastegate.

a small hole had melted in my hose because it had fallen down against the manifold at some point. The outer fabric looked ok but when I pulled on the hose, it separated and the hole revealed itself.

My car would run great in town but on hwy it would sit at a higher boost than normal and occasionally go to limp mode.

ketchupshirt88 said:

Rosebud, check your lines to the wastegate.

a small hole had melted in my hose because it had fallen down against the manifold at some point. The outer fabric looked ok but when I pulled on the hose, it separated and the hole revealed itself.

My car would run great in town but on hwy it would sit at a higher boost than normal and occasionally go to limp mode.

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Thank you Sir, will check that tomorrow.

ketchupshirt88 said:

Rosebud, check your lines to the wastegate.

a small hole had melted in my hose because it had fallen down against the manifold at some point. The outer fabric looked ok but when I pulled on the hose, it separated and the hole revealed itself.

My car would run great in town but on hwy it would sit at a higher boost than normal and occasionally go to limp mode.

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RoseBud68 said:

Thank you Sir, will check that tomorrow.

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@ketchupshirts88 Well checked the line to the waste gate as well as all the other line to be sure and all good. Does the waste gate use vacuum or pressure? I have a Mitty Vac if vacuum.
Thanks in advance.

The wastegate uses pressure and should start moving at 8-12 psi.

I'd pull on each one of the wires and see if they separate. I've seen too many of these VW connectors have broken wires just inside the connector. If you find one, just de-pin it and solder it back together. If not and it still happens, I'd de-pin them all, connect them individually and protect them with tape, then go from there.

i take an adjustable wrench, its a small one, put to size, it goes over 'thick' part of wastegate lever where the rod connects. try not to let it snap, and see that it moves. can be hard to see and reach back there.

iluvmydiesels said:

i take an adjustable wrench, its a small one, put to size, it goes over 'thick' part of wastegate lever where the rod connects. try not to let it snap, and see that it moves. can be hard to see and reach back there.

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Not sure I understand this. Use the wrench to manually move the rod to see if it move freely?

not the rod, the rod its self is too thin, dont bend it. there at the wastegate lever, at the end of the rod should be a thick transition from the rod, the wastegate lever, its attached to the rod.
take a look

iluvmydiesels said:

not the rod, the rod its self is too thin, dont bend it. there at the wastegate lever, at the end of the rod should be a thick transition from the rod, the wastegate lever, its attached to the rod.
take a look

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Yeah, sorry but I'm not following you.

Should really start a different thread on your wastegate problem. Doesn't have much to do with the OP's question on the Advance Solenoid.

1998TDIMonster said:

Tracing that, I found that to be the Advance Solenoid for the pump. Which requires you to remove the pump to get to it...

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I don't see why you need to remove the pump. Remove the rear backing plate from the pump and then the 2 bolts holding the solenoid in place and remove the solenoid. They are often a bugger to get out. I haven't done one on a car but I can't imagine it requiring the pump to be removed. I have spare solenoids if you need one. Just PM me.