Bad Injection Pump? - PeachParts Mercedes-Benz Forum

jake12tech · #1 06-12-2017, 02:53 PM

Ok, I'm working on a 95 e300 with a misfire. This is the third car I've seen with this problem on these om606s. The last two cars were a bad injector or bad fuel. Popped off the injection cover plate off the top the engine and the crossover pipe and started it. It has a dead misfire and it smokes out of the 5th cylinder out of the head. Car came to the place I work at and the other shop concluded it was an injection pump after throwing injectors at it. I plan to do a compression test, but out of curiosity how does a diesel usually behave with a bad IP? It does have 320k miles on it. I would think if a pump was bad, it wouldn't run at all and not just cause one cylinder to misfire?

The best part is the customer drove it here smoking and misfiring. This poor car...

OM617YOTA · #2 06-12-2017, 05:47 PM

Check the delivery valves!

jake12tech · #3 06-12-2017, 07:05 PM

I think you may be on the right path. The delivery valve sends fuel to the injector so I guess it makes sense. What would cause the smoke out of the head? I would think that's leaking compression. Or maybe a bad prexhamber? I wonder if it's a bad valve may be but I can't imagine one going out without a bunch of others

Mxfrank · #4 06-12-2017, 07:45 PM

I think the injection pump is the last thing to consider. Do a compression test, and based on the result you may want to do a leak down test. There are a lot of valve related things that can cause this. Such as a bad lifter, recessed seat, damaged valve, seat or prechamber. When I pulled the head on my 602, I found that three seats had divots blasted out of them. No idea how that happened, but I suspect that some gasoline was mixed into the fuel.

jake12tech · #5 06-13-2017, 12:36 AM

Quote:

Originally Posted by Mxfrank

I think the injection pump is the last thing to consider. Do a compression test, and based on the result you may want to do a leak down test. There are a lot of valve related things that can cause this. Such as a bad lifter, recessed seat, damaged valve, seat or prechamber. When I pulled the head on my 602, I found that three seats had divots blasted out of them. No idea how that happened, but I suspect that some gasoline was mixed into the fuel.

I think it's a bad valve like you said.. The pumps usually never go bad in these cars unless they're destroyed off of WVO. I think I'll find a compression test will tell me what's going on in that cylinder. I wonder how much damage the owner has done to that cylinder driving it like 20 miles with a misfire. I told him to stop driving the car and pay to have it towed.

Maxbumpo · #6 06-13-2017, 07:30 AM

Nine times out of ten, or maybe 99 / 100, a misfire is due to a problem with the injection cycle, and so driving the car isn't doing harm.

Double check the previous shops work if any doubt there, injectors are consumables and it is very easy to contaminate the hard lines with dirt and foul an injector immediately. If you don't have a pop tester for injectors, then swap positions of #5 to see if the problem follows. Bad delivery valves can be detected visually I think, I know that to be the case in several instances (myself and Diseasel (sp?)).

Smoke out of the head? Do you mean smoke coming up from the injector well, or do you have the valve cover off too? Smoke from the injector well points to possibly (a) fuel leaking into the injector well and certainly (b) poor sealing of the injector in the pre-chamber, allowing some compression gas to vaporize that fuel.

jake12tech · #7 06-13-2017, 08:12 AM

Quote:

Originally Posted by Maxbumpo

Nine times out of ten, or maybe 99 / 100, a misfire is due to a problem with the injection cycle, and so driving the car isn't doing harm.

Double check the previous shops work if any doubt there, injectors are consumables and it is very easy to contaminate the hard lines with dirt and foul an injector immediately. If you don't have a pop tester for injectors, then swap positions of #5 to see if the problem follows. Bad delivery valves can be detected visually I think, I know that to be the case in several instances (myself and Diseasel (sp?)).

Smoke out of the head? Do you mean smoke coming up from the injector well, or do you have the valve cover off too? Smoke from the injector well points to possibly (a) fuel leaking into the injector well and certainly (b) poor sealing of the injector in the pre-chamber, allowing some compression gas to vaporize that fuel.

Smoke is coming out of the injector well. I will be running a compression test later this afternoon let you know what I come back with. I think its pointing towards a prechamber the more I think of it. Not sure though yet. What would a leak down test tell me? Would that indicated specifically where the issues are whether it be a valve etc

Diseasel300 · #8 06-13-2017, 10:32 AM

If there's smoking coming up out of the head in the prechamber area, I certainly wouldn't suspect injection pump! Maybe someone did an injector and reused or forgot to install a new heat shield washer? Prechamber cracked? Something more sinister?

moon161 · #9 06-13-2017, 11:20 AM

You can loosen the hard lines at the IP or at the pump one by one and see its pumping or developing any pressure for the missing cylinder

jake12tech · #10 06-13-2017, 11:34 AM

Quote:

Originally Posted by Diseasel300

If there's smoking coming up out of the head in the prechamber area, I certainly wouldn't suspect injection pump! Maybe someone did an injector and reused or forgot to install a new heat shield washer? Prechamber cracked? Something more sinister?

Don't think it's a piston or a ring.. too low of mileage. I'll know more after the compression test. It is smoking out of the injector

Quote:

Originally Posted by moon161

You can loosen the hard lines at the IP or at the pump one by one and see its pumping or developing any pressure for the missing cylinder

Will check that in a few hours

moon161 · #11 06-13-2017, 12:58 PM

The IP on my 602 was not pushing any fuel at all to I think # 3and #5. One from a parts car is going in.

jake12tech · #12 06-14-2017, 12:29 AM

Zero compression on the problem cylinder.. going to do a leakdown test and see what's going on didn't have time to do that today

moon161 · #13 06-14-2017, 09:45 AM

Quote:

Originally Posted by jake12tech

Zero compression on the problem cylinder.. going to do a leakdown test and see what's going on didn't have time to do that today

Well, theres your problem.

jake12tech · #14 06-14-2017, 04:38 PM

Looks like a valve, going to pull the head and examine