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  #1  
Old 09-26-2008, 02:34 AM
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OM602: No fuel on cylinder 4???

Hi everybody,

I just bought a 1991 300D 2.5. The car idles steady at 600-700 rpms, but misses. Also it lacks low end response - its very slow in 1st gear. The previous owner cleaned the injectors "after a bad tank of diesel" , but did not replace the heat shields. So on three injectors there were bubbles and fuel comingro the injector threads to the head. The car runs fine on the highway though.

I replaced the heatshields and cleaned the carbon on the injectors and the head. So now they seal fine. But the car runs on 4 cylinders. If I loosen the metal lines to each injector one by one, each one makes a difference in idle except number 4. I took off the metal line to #4 completely while idling, and it just drips like two drops per second. You can see the pulses from the pump, but barely any fuel coming out. The injector has carbon buildup, so the cylinder is running. Like i mentioned, on the highway the car feels normal. Also the clear fuel filter looks frothy, has air in it.

I ran two cans of diesel purge and changed the clear filter, same problem. I changed the injector with another one, same thing.

Should I replace the delivery valve o-rings/washers? I read on a forum that somebody had a similar problem with the car, and the delivery valves were not leaking, but the o-rings were bad...

Or my pump is out?

Thanks!

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  #2  
Old 09-26-2008, 08:49 AM
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I'd be careful if you do the Delivery Valve job. It can be messed up. I've experienced it when a pro fixed my om602's o ring (he only changed one and messed the pump up).

Anyways, if you try it, just read up. There's enough info here to make sure you can do it. Just follow the directions. Also remember the torquing procedure on the DV's... It's important.

That said, my 603 (similar engine but one more cyl) had a good lope to it especially hot. I changed the DV o rings and it cleared it right up. It wasn't leaking fuel (visibly) but the IP was taking in air on the plunger's down stroke since the o rings weren't making a good seal. There's obviously no way to 100% verify that but after the repair that's the only thing that makes sense.

That may or may not clear up your problem but for a few hours of work (removing the intake manifold, injection lines, and delivery valves) you could rule this out.

But... again be careful and extra clean or you could take any life the IP has right out of it. The job has to be done right and done carefully.

Hope that helps.... IP's live a long time in these cars. Bosch's inline mechanical pumps are the best ones ever made IMO. Cummins used them in the Dodges from 94-early 98 and they're also lasting a long time. The later stuff from Dodge/Cummins... not quite the case.
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Tom's Imports of Columbia MO Ruined the IP in changing leaky delivery valve O-Rings - Refused to stand behind his work. Mid-MO MB drivers-AVOID Tom's.
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  #3  
Old 09-26-2008, 11:43 AM
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How did they mess up the IP? I am afraid thats the case.
I will be careful, I worked on a couple of cars before.
Gotta buy the socket first though.

Thanks!

Quote:
Originally Posted by 777funk View Post
I'd be careful if you do the Delivery Valve job. It can be messed up. I've experienced it when a pro fixed my om602's o ring (he only changed one and messed the pump up).

Anyways, if you try it, just read up. There's enough info here to make sure you can do it. Just follow the directions. Also remember the torquing procedure on the DV's... It's important.

That said, my 603 (similar engine but one more cyl) had a good lope to it especially hot. I changed the DV o rings and it cleared it right up. It wasn't leaking fuel (visibly) but the IP was taking in air on the plunger's down stroke since the o rings weren't making a good seal. There's obviously no way to 100% verify that but after the repair that's the only thing that makes sense.

That may or may not clear up your problem but for a few hours of work (removing the intake manifold, injection lines, and delivery valves) you could rule this out.

But... again be careful and extra clean or you could take any life the IP has right out of it. The job has to be done right and done carefully.

Hope that helps.... IP's live a long time in these cars. Bosch's inline mechanical pumps are the best ones ever made IMO. Cummins used them in the Dodges from 94-early 98 and they're also lasting a long time. The later stuff from Dodge/Cummins... not quite the case.
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  #4  
Old 09-26-2008, 04:30 PM
compress ignite's Avatar
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DV O-Ring (+ crush washer + Spring) R+R

http://www.peachparts.com/shopforum/showthread.php?t=216067

http://www.peachparts.com/shopforum/showthread.php?t=200980&highlight=delivery+valve+orings
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  #5  
Old 09-27-2008, 09:22 PM
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I guess I gotta do a compression test... I loosened all lines one by one at idle and 1, 2,3, and 5 squirt fuel pretty good. #4 is squirting barely any fuel. But I opened the lines on my OM617 1984 300D ( which runs perfect), and they spray also barely any ( WVO car, by the way).
So I guess I will do a compression test tomorrow, because I have a feeling it might be a bad cylinder, although there is no blowby at idle.
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  #6  
Old 09-28-2008, 01:23 AM
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You state the fuel delivery on #4 is very sub standard in comparison to the others on that engine. That is your problem. No real reason to do a compression check. Stay with the low fuel delivery problem on number four.
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  #7  
Old 09-28-2008, 10:05 PM
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Location: DFW, TX
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Quote:
Originally Posted by barry123400 View Post
You state the fuel delivery on #4 is very sub standard in comparison to the others on that engine. That is your problem. No real reason to do a compression check. Stay with the low fuel delivery problem on number four.
You are right. I just did a compression on that cylinder and it is 360, measured through the glow plug hole with a Harbor Freight tester.
So I guess it will be the delivery valve o-ring/washer, or something else on the pump.
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  #8  
Old 10-01-2008, 11:43 AM
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Location: DFW, TX
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The socket showed up yesterday, and I pulled the delivery valves this morning.
What i found ( keep in mind prevoius owner told me the injector heat shields were nor replaced, supposedly the work was done at "Sam And Joes" in Arlington, TX)

- somebody used vise grips to remove the delivery valves before ( morons)
- when I removed the metal lines the fluid on top of the delivery valves was staying up, vs #4 drained immediately
- #4 was hand tight
- #5 was over tight
- #1 has a different spring than the rest - a lot shorter and weaker spring, shiny, not black like the rest

I am not sure if "Sam and Joes" in Arlington did the repair, or the previous owner is lying but this is rediculous - loose delivery valve and one wrong spring....

Now I gotta buy a spring from somewhere...
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  #9  
Old 10-01-2008, 09:56 PM
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Just find an injection repair shop near you and give them the Bosch part number for your injection pump (it will probably begin with 0400, stamped along with a few more sets of numbers). They can get you any part you need for it for a very reasonable price.

Edit: Make sure you replace the copper crush washers; they are the seats for the springs. The springs wear a seat into the washers so you need to start with fresh ones once you separate them.

I am not sure where you are located, but I got my parts from Seattle Injector Service, and they were very helpful.

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Last edited by shingleback; 10-02-2008 at 06:12 AM.
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