87 300TD OM603 Injection Pump - PeachParts Mercedes-Benz Forum

jevansxb · #1 03-07-2022, 02:48 PM

I just recently acquired an 87 300TD, a rare beast indeed, for the ridiculous price of $500. This car is far from a driver yet, and I must admit I scooped this car up on impulse. It has a large laundry list of problems that need to get sorted well before it could ever be road worthy. Here is the general list, in order of importance:

1) Injection pump issue for cylinder #5
2) Clean/seal/install fuel tank
3) Rebuild SLS
4) Interior/doors/windows etc...

I did get the car running and actually drove the car onto the trailer to bring it home. Started working on number 1 above and here is what I have found. Number 5 cylinder is dead, and I have determined the #5 injector is not firing at all. With the car running and cracking the lines loose at the injector, all injectors are receiving good fuel pressure, ie each line spits fuel a couple of feet in the air, except for cylinder #5. When I crack open number 5, there is a weak dribble of fuel with LOTS of air bubbles. I have already taken #5 injector line off and removed the delivery valve nozzle and spring to clean them and make sure they are clear of debris. I noted there is rust inside the fuel system - the line and DV nozzle had signs of rust inside. There obviously has been some water exposure to the innards of the fuel system, which explains why the PO removed the fuel tank and never re-installed it. Short of replacing the IP with a good used one, is there anything else I can do to try and revive the existing IP? Can I remove the delivery valve under the nozzle for inspection? What would cause air bubbles on only one injection line? There isn't a lot of DIY info on mechanical diesel injection pumps or even much info on how they work. I obviously don't want to throw a bunch of money at this car, as it is never going to be a really nice car. Does anyone have a lead on a good used (cheap) injection pump for an OM603??

dieselbenz1 · #2 03-07-2022, 04:13 PM

I'd start by cleaning the fuel system by running a Purge or 2 through it before anything else.

jevansxb · #3 03-07-2022, 06:21 PM

Quote:

Originally Posted by dieselbenz1

I'd start by cleaning the fuel system by running a Purge or 2 through it before anything else.

Been there, done that. I know the importance of this step. I am trying to figure out why there would be air bubbles on only one high pressure injection line. Anyone have any insight on this? Could this be a problem with the delivery valve/plunger on this cylinder? I am hoping I can get the injection pump working again. If I have to rebuild the injectors AND source a new/used IP, well that is really going to hurt the wallet.

dieselbenz1 · #4 03-07-2022, 07:50 PM

Removing the side cover of the IP will allow up to see the rack move. Is it possible no. 5 isn't moving when the rest are, I don't know..

777funk · #5 03-09-2022, 06:25 PM

The good thing is you can compare the bad port with the good ones. If it were my car, I would make sure that everything under the delivery valves looks the same, moves the same (nothing's rusted stuck, spring broken, issues with the plunger), etc.

But I wouldn't do that until I was 100% sure that #5 isn't delivering fuel and I would be super careful while looking inside the pump. You don't want any debris in there and of course don't want to lose anything. IP work is generally pump shop territory for what it's worth. That wouldn't stop me from doing basic (careful) inspection. Now doing anything further like fuel delivery balancing, etc, I wouldn't mess with that personally.

Also, I wouldn't pull the pump from the car until I did the above and also as someone mentioned looking under the side cover.

Getting a good used pump is a gamble unless you know 100% it came from a good working engine.

jevansxb · #6 03-09-2022, 07:53 PM

Quote:

Originally Posted by 777funk

The good thing is you can compare the bad port with the good ones. If it were my car, I would make sure that everything under the delivery valves looks the same, moves the same (nothing's rusted stuck, spring broken, issues with the plunger), etc.

But I wouldn't do that until I was 100% sure that #5 isn't delivering fuel and I would be super careful while looking inside the pump. You don't want any debris in there and of course don't want to lose anything. IP work is generally pump shop territory for what it's worth. That wouldn't stop me from doing basic (careful) inspection. Now doing anything further like fuel delivery balancing, etc, I wouldn't mess with that personally.

Also, I wouldn't pull the pump from the car until I did the above and also as someone mentioned looking under the side cover.

Getting a good used pump is a gamble unless you know 100% it came from a good working engine.

Thanks Funk and DieselBenz! This is the kind of input I am looking for. Now the question is - am I safe to pull up the delivery valve without putting anything out of wack? I have seen youtube videos (Diesel Mercedes guy) who explains how to renew the dv o-rings and copper washers, BUT emphatically warns against messing with anything under the copper washers or you are "totally screwed." Since I don't want to be "totally screwed", I have resisted the temptation to remove anything under the copper washer, even though I can't see any type of setting which could get messed up. Short of loosing or messing up re-assembly of parts. I have no desire to mess with the balancing until I can determine why one delivery valve is not supplying hardly any pressure. Any idea what scenario could cause air bubbles in that one line? Are there any threads on cleaning and inspecting DVs? I am hoping there is some debris in #5 DV which is prohibiting fuel to fill the plunger.

jevansxb · #7 03-10-2022, 03:48 AM

Quote:

Originally Posted by 777funk

The good thing is you can compare the bad port with the good ones. If it were my car, I would make sure that everything under the delivery valves looks the same, moves the same (nothing's rusted stuck, spring broken, issues with the plunger), etc.

But I wouldn't do that until I was 100% sure that #5 isn't delivering fuel and I would be super careful while looking inside the pump. You don't want any debris in there and of course don't want to lose anything. IP work is generally pump shop territory for what it's worth. That wouldn't stop me from doing basic (careful) inspection. Now doing anything further like fuel delivery balancing, etc, I wouldn't mess with that personally.

Also, I wouldn't pull the pump from the car until I did the above and also as someone mentioned looking under the side cover.

Getting a good used pump is a gamble unless you know 100% it came from a good working engine.

Thank you Funk and Diesel Benz! This is the kind of feedback I was hoping for. I'd really like to take apart the delivery valves to see if I can find the problem, but I have seen several warning videos on Youtube cautioning not to touch anything below the copper washers or "you'll be sorry." I am having trouble finding much info or instruction on DV dismantling or inspection. Can anybody point me to any threads or DIYs on this subject?

Any ideas why I would be seeing air bubbles on only one injector line? If I am having air leaks I would expect to see air bubbles on all the lines.