Former VWDieselParts.com Forum

In my experience, the IP timing affects power, but not to the extent you describe. If the timing is in the range of enabling the engine to run, you should basically have the power you would expect.

Does this sound like a pump issue or an injector issue?

I think you've got the idea. I would check out injectors next. Personally, I'd replace the nozzles and do a compression test since you have to remove injectors anyway. As for the timing, it sound like your "knock" is what's called marbling here (based on the fact that it has gotten louder as you've rotated the IP towards the engine), it will get louder rotating more towards the engine, and go away as you rotate away. rotating away just until marbling goes away is a good place to leave the timing. ... tons of info here on that on this site.

Thanks Greg Lousy. I'll have to check the injectors I guess. That's where they have to be pressure tested at a shop, right?

My buddy had alot of black smoke and low power.
I took the timing light/pulse detector down there and timed it better.
It now has more power,.. it was slightly too advanced.
How are you checking the timing? Making a mark then test driving it? Or using a dial indicator?

I have not had any luck with the dial indicator. I'm trying to adjust it by sound. I have attempted to adjust all screws on the pump, over and over and over again. I'm hoping that maybe one of the injectors is bad.

I would probably replace the nozzles right off, just cause its pretty cheap and good to do anyway. or you could have them pop tested. or put injector lines on upside down with injectors on and watch the spray as someone cranks... you cant tell breaking pressure like this but you can see basic spray pattern and spot a real bad one.

Yeah, I think I'll try that first Greg Lousy. Thanks for the tips!

So, I took the injectors out and connected them to a working pump with the lines upside down. They each spray fuel out of them onto a paper towel. So, they seem to be working fine. Should I have a diesel shop test them for pop pressure?

professional testing would be a good idea. You need to check spray pattern, pop pressure, and make sure they don't dribble (leak) minimally. I bought rebuilt ones from Jack (forum owner) and saved myself the grief. Between that and a rebuilt pump from him my 82 runs like a top, even in spite of my one low cylinder. Total investment a little under $600 but well worth it for a car that has served me well for 13 years so far. Doesn't smoke unless I make it (floored at 3500 rpm) and keeps up with today's traffic lunatics pretty well.

Thanks for the reply bscutt. I'm trying not to dump more money into this thing, so if I can avoid paying for injector testing that would be nice. So far it looks like each injector is spraying fuel. My next guess is to make sure the delivery valves are working. If so, and I still have no power and black smoke, then is it possible that it's the pump itself? I have a recently tested pump that works great that I may just swap out and see if that helps. I should also mention that I did a compression test and each cylinder was well over 300 psi. Thanks everyone!

Ja, a pump swap is an easy diagnostic.

I doubt the delivery valves are the source of the problem... my understanding is that they mostly maintain line pressure between injection events, so that the IP only needs to pump enough fuel to pop the injector. If the smoke is dark, it is usually overfueling and a problematic delivery valve would likely result in less fuel and delayed at that, IMO.

Thanks Tyler Durden,
I will check the delivery valves next. If they work, then I'm swapping the pump. If that doesn't work, then I'll scrap the whole car. Lol. I will report back!
Thanks again!

So, I checked the delivery valves. They seem to be working fine. I still can't get any real power outta this thing. Could the pump be wearing out? I don't want to swap pumps because I'd have to swap out the accelerator arm as well as other parts on the pump. I'm pretty much out of ideas except taking it to my local diesel place. Anybody out there familiar with fine tuning these pumps? I thought maybe the accelerator arm is maybe in the wrong position too? Hmmm.