87 300TD OM603 Injection Pump
 

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??

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.

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..

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.

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.

I've pulled the plungers out (used a typical 'magnet on an antenna' tool if I remember right). Just don't damage them in any way or you'll regret pulling them. Don't get any debris in there. I'm sure I've seen a video on pulling the pump apart but it's been a while. I wouldn't dig deeper than you feel you need to. Don't take too much apart at a time and take pictures as you go.

Air bubbles could indicate the element is not getting much fuel. Close off the return line from the injection pump. It might get more fuel pressure available

. A wide open delivery valve might be pulling air back into the line as well. Submerge the end of the line in fuel and watch if the bubbles stop.

Initially I thought where could he be getting the air from?

I also considered that the piston in the element might not be going far enough down to get enough fuel out of the fill port. That would not explain the air in the fuel though. I did think. It could account for very low volume though perhaps.

If there is any indication the car had been using WVO as fuel mention it. I just about discounted not enough fuel pressure as it is a six cylinder engine.

I kind of remember if a fuel supply problem existed. For an unknown reason some owners reported the last element on the injection pump was not delivering fuel properly. Never made a lot of sense to me but that is what they claimed. I still have a problem with the air. Even if the element was badly worn I would not expect to see air.

Very insightful Barry12345! I like your explanation of how air could be getting drawing back in through the line. I will try submerging the line and see what happens.

I think there is a good chance this car was run on wvo at some point in its lifetime. It does have an Elsbett sticker in the rear window. Although I haven't found any WVO equipment on the car, I have removed a couple small harnesses and small relays from under the hood which were obviously not OEM. I do know the 5 injectors which are squirting fuel are not working very effectively, as it does smoke and nail more than it should. I am sure I am going to need to rebuild all 6 injectors to have a good running car.

So it looks like I am going to be diving into the DVs and trying to find out what is going on with number 5. I will pull them apart carefully, cleanly and one at a time. Not going to be able to dive into that next week. I will post an update then.

Thanks for all the input I have received so far!!!

Not ideal but in a way WVO use is a possible answer. Animal fats accumulate in the base of the injector pump.

I would get a good solvent in the base of the pump. Let it sit for awhile. Like a day or two. Try to rig up something that gathers up the output of the injection pump output. To see what was in there.

There is a chance the port in the element is pretty well obstructed with crap. . Guys have reported blobs of stuff coming out of injection pumps that were on vegatable oil. After solvent soaking.

That sticker was not put on the car for fun. Injectors may be bad as well. Pump may or may not have damage. Until you know if there is anything inside that injection pump, leave the lines loose. You do not want to pump what might be dissolved through the injectors. After a good soak. It will not start on five cylinders. The injection pump cannot reach proper pressure. The injectors may be a mess. Or worse the engine itself May be damaged.

That WVO system killed a lot of these cars. We went through a huge amount of simular cases on site years ago. It got so bad one of my early questions was it now on vegatable oil or had been. People would come on site but never mention this. It was probably in their minds like being caught in the washroom with a copy of playboy to them. .After the usually massive problems occurred.

Technically you can run vegatable oil. The rules to do so are pretty strict. Most users did not obey them. Before anything I might run a compression check. Engine may not be damaged but you cannot do all kinds of things only to find out later it is. To me it changes how you approach problems. Give me a little time to think. I will try to post more later this evening. You want to pump the solvent in with the lift pump. As buildup on the lift pumps valve seats is nor uncommon with WVO.

I just got back in from a long highway trip this evening. So I kind of need a break before my brain starts to function better. Rule number one is water is like sandpaper going through the injection pump elements. Many WVO users did not dewater their fuel. Took a huge amount of injector pumps out. In many cases the thicker viscosity of the WVO allowed the engines to run, On diesel fuel the elements could not make pop pressures. I really think already you should see if you have decent compression. Unburnt vegatable oil would get down into the rings and turn into glue. Imobilizing the rings. Taken to extremes cylinder walls were vertically scored. So if you have poor compression a ring soak is job number one. To see if you can get the compression up if it is low. I would temporarily forget the fuel system.

Wow, thank you for all of this brain storming, Barry, I really appreciate it. I have been camping all weekend otherwise I would have replied earlier.

Before I left, I decided to run a small bottle of Magical Mystery oil I had laying around. It is currently in the injector pump right now. It did not make any difference in the way the car runs. I have not run the car in about 3 or 4 days. When you say a good solvent, what is best to use?

I have the day off, and I just bought a diesel compression test kit. I will start by pulling the injectors and doing a cold compression test to see where I am at. I will update with my results later today.

Laquer thinner and acetone are two solvents used. For the injection pump. Hoping for a decent compression check. It is possible. You are in a warmer climate. Essentially chemical action falls off very fast under 70F degrees.

Good News! Here are my cold compression numbers (psi):

1-380
2-360
3-420
4-400
5-410
6-440

I know lowest to highest is more than 20%, but at least the compression isn't low! I attribute the high numbers partially to descent engine health, and possibly to carbon build up from running WVO. Yes, there are definite wvo signs - nasty grease build up around a couple of leaking injectors.

I know the injector nozzles are ruined from wvo, so will be rebuilding them with new nozzles etc.

Now back to the injector pump. What is the best way to go about this? I haven't pulled the DVs yet. Should those be pulled before pumping solvent into the injection pump? Should I just use the lift pump to pump in the solvent? Which is better to use? Lacquer thinner? Acetone? A combination of both?

Both dissolve animal fats. I prefer laquer thinner as a universal type solvent.I guess there are two ways to fill the injection pump. Hand pump but the oil in the filter must be displaced.I might take the secondary filter off and dump the contents. Fill it with the solvent and install..

Or remove the relief valve and gravity feed the solvent in through the last fuel line to the injection pump. Let it soak for a couple of days. See what gets expelled from the pump. It is far from a certainty yet with an open injector line that fifth element should be producing fuel output.

It is kind of a pain yet at the same time if a car was on vegatable oil. You have to make sure there are no accumulated animal fats in there. You found rust in the injection pump. Water in the fuel kind of explodes off the injector tips and this can damage them.

Like most of these cars we purchase there is usually not enough history. I dislike suggesting things that make work for others. To me with my limited understanding I just am not sure how that number five element seems to be doing almost nothing.

I have never heard of a cam lobe going bad in one of these in line injection pumps, Since number one and six elements are producing you have not had a cam bearing support failure.

I do not know if we have ever had a case of a sticking delivery valve either. Sticking open I mean.to me this one is a little strange. I am also thinking that maybe the control arm for that element is disconnected inside the injection pump.

The baseline you established on the engine gives some hope. At least so far there does not seem to be any solid indication the Injection pump needs replaced either.