Diesel help

[GeraldD]

Hi My mechanic is stummped. I have an 1981 VW Rabbit pickup with a 1986(?) golf non turbo diesel engine. My problem happens only at higher revs. I can feel a vibration on the gas pedal and the truck seems to speed up or rev up on its own. All moter mounts are new. If sitting still in neutral and I push on the gas slowly the engine will rev up corresponding to the push on the gas then all of a sudden it seems to take off and rev up on its own. By letting go of the gas the engine slows down normally. My mechanic has checked the timing a couple of times and all seems normal. Any ideas would be appreciated. Thanks...G.D.

[TT225]

Could it be that a wire is tight/sticking?? Is it harder to press on the gas??
jon

[GeraldD]

Oh no gas is very easy to push, no binding at all. Thanks...G.D.

[ProjectPurity]

man, this is digging this up from the deep, but have you checked your tank filter? I had kind of the reverse problem: I would get to high RPMs and then the fuel would cut followed by a rev once the fuel came back. I tried checking everything fuel related and then pulled the little 100micron screen filter inside the tank. It was gummed badly. Try removing that. Hey, anything's worth a try

[trev0rbr]

it's running away, get a cam splash guard off an aba or a later 8v mk2 or a g60. then call it good

[stevethefolkie]

pull your throttle body and clean the heck out of it - you've probably got an accumulation of oily buildup that's causing your throttle to open and close slower than it should - you wouldn't feel the resistance at the pedal BUT it would impact how the engine revs -

[trev0rbr]

oh yeah now that read the whoel thing, sounds like what was said above. or it could be even a sticky governor. but it's soemthing at the injector pump

[stevethefolkie]

with a diesel the engine speed isn't governed by the fuel so much as by the amount of air allowed in - if the plate is sticking you'll get the slow rise and fall -

Another thing to check is that your water accumulator (that gets the water out of the fuel) isn't full - water + diesel can = big mess ... been there - done that - got the scars to prove it!

[ProjectPurity]

if the plate is sticking you'll get the slow rise and fall

Not quite sure what you mean by "plate" the VW diesel 1.6l doesn't have a throttle body per say, it's got an intake manifold that goes straight to an air filter box.... that's it on the intake side. The fuel system is far more complex than the air induction system (that's even a stretch to call it complex).

When the injection pump goes bad, or gets badly varnished up, it will start sticking which will cause the symptoms that were mentioned. I have a friend that pulled apart the IP from an Isuzu diesel to replace a part of the high pressure head (the area of the IP that distributes the fuel), that's not a fun process, but it certainly will teach you that many problems with a diesel fuel system can be found within that pump (which is why a TDI IP can go for $1500!). His throttle was sticking before the rebuild and now it's fine.

Maybe grab some biodiesel or some diesel kleen in a white or grey bottle (both are decent, but the white seems to do better at actually cleaning things out).

Another thing to check is that your water accumulator (that gets the water out of the fuel) isn't full - water + diesel can = big mess ... been there - done that - got the scars to prove it!

I'll second that!