85 300TD - Slow, Smokey, Irregular Power

[southofantarctica]

I recently picked up a pretty clean two tone wagon for $550 . The previous owner parked it for about two years, due to "Dropping oil pressure while at speed" (I have not had any evidence of this). The engine ran, with an obvious miss, and has enough blow by to make the oil cap fly off and do a pretty good imitation of a freight train. It also sent up a grey diesely smoke cloud that would put James Bond to shame. But for the price I took a gamble on the engine.

This being my 3rd om617, I felt good about my chances of being able get this one back to a point of being usable while I saved up for a replacement engine if needed.

So far I have:

Sent off my injectors off to be cleaned and balanced, done by Greazer. Helped all around, power, drivability and less smoke. Was told that the #2 injector was shot. Replaced with usable used unit.

While the injectors were out, I put Marvel Mystery Oil in each cylinder and cranked the engine over by hand, a little each day.

Adjusted valves, most weren't half bad, surprisingly.

I found that the miss was due to a loose prechamber nut on #2, tightened it up and made worlds of difference, no more miss, but still had poor idle.

Installed new rack damper bolt, cleaned up the neutral idle but still shakes bad in gear. (More tweaking will fix it I think).

New filters and oil change. Old oil smelled heavily of exhaust and slightly of diesel. But fine beyond that. Very Dark, possibly a hair thin.

Removed the Alda, seeing that it had been tampered with previously. Suspected that it was broken in the fuel limiting position, but no change after it was removed.

I have about 200 miles on the car. But billows continuous grey smoke, hot/cold, idle or at high RPMs. The power is very inconsistent. 1000-2000rpms is below average, but tolerable. 2000-3000ish is below average, usable. 3000-3500rpms the car actually to slow down. 3500-4200rpms is the best part of the power band, has some pull to it. Recently started to notice a 'ticking' above 2200rpms, only under load, about 60% of the time. Seems to change with the rpms. Happens more often when warm. Warm idle is 1.3 bar I would estimate. If the accelerator is slightly depressed when starting, it will start immediately, low of 35F. If no pedal is applied it will crank for 2-3 seconds before starting. All glow plugs are working. Operating temp is normal. Will be getting a boost gauge hooked up tomorrow, hopefully.

0-60 mph time is averaging 43 seconds. Merging is an exercise in prayer.


Any suggestions of what to do beyond driving it into the river?

[mannys9130]

I'd drip time the thing and see how that is. I'd also do a second valve adjustment in case your last one has been its only in a long time, and check valve timing.

[barry12345]

A lot of stuff will have to be checked out. The boost line is probably blocked with crud for the 0-60 times to be that slow. Or the turbo is bad or the linkage to the injection pump does not have the full range of movement it should. Or fuel supply or pressure is inadequate.

Personally I would do a compression check on the engine as the first thing to make sure the effort is worth it and you do not also have a cylinder problem. This avoids flogging a dead horse.

Otherwise it just sounds like an older unmaintained Mercedes diesel. Perhaps most are several small things wrong that are more labor intensive than cost intensive. I also wonder if your egr valve is stuck open?

That and the boost line are worth the checking effort prior to the compression test. Some of these engines have signifigant blow by. Of course that is not the best. Yet to me the important thing is the amount of miles per quart of oil. Also I assume you have had a look at air filter to make sure it is not saturated with oil?

A new standard I have come up with of perhaps an indicator of what is actually causing the blowby. We always assumed it was only the rings and bores. Old tired valve seal rubbers that have pretty much disentigrated with time and worn valve guides will not make an oil burner of these cars in themselves. Yet they can increase what we call blow by.

If you think about it they can add pressure to the crankcase. The turbo keeps the pressure at the bottom of the intake guides at a positive pressure Where on a gas car they are at a constant vacuum or negative pressure. The bottom of the exhaust guides are usually at a small positive pressure as well. So rather than sucking oil and air down them they can instead add pressure to the crankcase.

That is why I use the premise of how high is the actual base oil consumption. The valve seal rubbers did not last thirty years on their gas cars but most of our cars still have whatever is left of the original ones still in there. Since the diesel valve guides also might suffer a little less lubrication than the gas engine guides. After a couple of hundred thousand miles one would wonder what shape they are in. The engine in general is not a real high reving one so even with a poor condition of them existing it will still seal the valves well enough.

Not increasing oil consumption that much at the same time. Conversely if the oil control rings are tired you will burn more base oil for the same amount of blow by.

[mach4]

Check the condition of the fuel pressure relief valve spring.

[southofantarctica]

Originally Posted by mannys9130

I'd drip time the thing and see how that is. I'd also do a second valve adjustment in case your last one has been its only in a long time, and check valve timing.

Another valve adjustment is probably a good idea. And I am planning on working on the timing later on in the month.

Valve timing = timing chain stretch...? I did a search for it and that was the best I could come up with.

[southofantarctica]

Originally Posted by barry12345

A lot of stuff will have to be checked out. The boost line is probably blocked with crud for the 0-60 times to be that slow. Or the turbo is bad or the linkage to the injection pump does not have the full range of movement it should. Or fuel supply or pressure is inadequate.

I have the ALDA removed, so a gunked up turbo line should be a non issue. The turbo might be on it's last leg, but I know that it is doing something. You can feel the additional power from the 2200-3000 range. Also, the linkage has been adjusted for full travel. I also have a uprated fuel overflow valve from Greazer. Supply from the tank could be a factor.

Personally I would do a compression check on the engine as the first thing to make sure the effort is worth it and you do not also have a cylinder problem. This avoids flogging a dead horse.

Great Idea.

Otherwise it just sounds like an older unmaintained Mercedes diesel. Perhaps most are several small things wrong that are more labor intensive than cost intensive. I also wonder if your egr valve is stuck open?

Had not thought of the egr valve being open. The vacuum lines have been disconnected from that.

That and the boost line are worth the checking effort prior to the compression test. Some of these engines have signifigant blow by. Of course that is not the best. Yet to me the important thing is the amount of miles per quart of oil. Also I assume you have had a look at air filter to make sure it is not saturated with oil?

Air filter is good.

A new standard I have come up with of perhaps an indicator of what is actually causing the blowby. We always assumed it was only the rings and bores. Old tired valve seal rubbers that have pretty much disentigrated with time and worn valve guides will not make an oil burner of these cars in themselves. Yet they can increase what we call blow by.

If you think about it they can add pressure to the crankcase. The turbo keeps the pressure at the bottom of the intake guides at a positive pressure Where on a gas car they are at a constant vacuum or negative pressure. The bottom of the exhaust guides are usually at a small positive pressure as well. So rather than sucking oil and air down them they can instead add pressure to the crankcase.

That is why I use the premise of how high is the actual base oil consumption. The valve seal rubbers did not last thirty years on their gas cars but most of our cars still have whatever is left of the original ones still in there. Since the diesel valve guides also might suffer a little less lubrication than the gas engine guides. After a couple of hundred thousand miles one would wonder what shape they are in. The engine in general is not a real high reving one so even with a poor condition of them existing it will still seal the valves well enough.

Not increasing oil consumption that much at the same time. Conversely if the oil control rings are tired you will burn more base oil for the same amount of blow by.

Good explanation, I hadn't see a case for it like that. I'm not terribly worried about the blow by, but noticed that it was significantly more than my other two engines.

Also, I was not able to get my boost gauge hooked up, HD didn't have all the hardware I wanted.

[barry12345]

Depending on the output pressure of the lift pump. You might want to install the old pressure relief valve for testing. I do not know what pressure the replacement ones are calibrated at. Yet obviously higher than the originals.

If you see output from that valve it is okay to leave it in for the testing. What I was thinking was if there is air involved it cannot partially clear through a constantly closed relief or overflow valve. All of the air instead would have to get processed through the injector lines. Just a thought though.

Another indication was did you observe any difference at all with the new relief valve? If none the fuel pressure supplied could have been too low to open either of them. Or perhaps is not enough to open the enhanced one. It s pretty obvious you probably have some form of fuel starvation with the times posted. You might need a fuel pressure gauge to get a clear picture of what is going on or to reduce possibilities.

Also keep in mind that too much blow by pressure can partially or totally shut down the injection pump. I have no ideal if you can run these engines at speed with the oil filler cap off as a test. I would make sure at least my crank vent hose was not badly gunked up internally.

There was another test with some possible risks for too much blow by. Basically it was to close off the vent hose and see how long the engine ran until it quit. You would have to look it up but ten seconds was about the normal amount on an old engine I think I remember. It was also suggested that this test might damage some seals but I have no opinion on that. Many used it when going out to examine an example of a car with this engine in it.

I have used it in the past myself. Too much base pressure starts to control the injection pump shutoff. No ideal if this was intentional in design or not.

[southofantarctica]

[QUOTE=barry12345;3567569]Depending on the output pressure of the lift pump. You might want to install the old pressure relief valve for testing. I do not know what pressure the replacement ones are calibrated at. Yet obviously higher than the originals.

If you see output from that valve it is okay to leave it in for the testing. What I was thinking was if there is air involved it cannot partially clear through a constantly closed relief or overflow valve. All of the air instead would have to get processed through the injector lines. Just a thought though.

Another indication was did you observe any difference at all with the new relief valve? If none the fuel pressure supplied could have been too low to open either of them. Or perhaps is not enough to open the enhanced one. It s pretty obvious you probably have some form of fuel starvation with the times posted. You might need a fuel pressure gauge to get a clear picture of what is going on or to reduce possibilities.

Also keep in mind that too much blow by pressure can partially or totally shut down the injection pump. I have no ideal if you can run these engines at speed with the oil filler cap off as a test. I would make sure at least my crank vent hose was not badly gunked up internally.
/QUOTE]

There was improvement when I installed the uprated spring. Also, I don't think that I have the old one anymore either, so putting the old one back in is a null point. I do not think that I have any air in the IP that hasn't worked out.
With the amount of oil that gets blown out, I would have to get creative if if tested without the oil cap. I'll look into that more tomorrow.

[mannys9130]

Yes, most people check valve timing to determine timing chain stretch. In your case, since the power is so wildly irregular, it would be done to verify that the cam is in the correct position. This needs to be done with the injection pump as well to verify that the injection event is properly set. Drip timing is what most people do. You can read about that online or in the manual.

Something's just not right. You have to do a few broad scope checks to see which thing is the issue.

[chasinthesun]

My only slow car symptoms was fixed from the banjo bolt at the back of the intake being clogged ,onced cleaned out it was a new car. Oh ,forgot about the linkage piece that hooks to the injection pump ,thats another one ,if the piece is loose with play the rolling jointed piece on the assembly is rotten,made of some hardened rubber that deteriates over time and wont give you the correct throw a new one gives resulting in slack from foot peddle to rev on the rack of the injector ,easy fix and easy to look for as calpriets,just wiggle the rod coming to it and if theirs play it needs replacing .I would add fuel lines into the replace catagory items ,rubber lines maybe restrickting flow internally,had a 190e with this issue and of course filters including the tank screen.
This car was being sold out of Houston ,correct ? Thats a good deal for a running car ,not to mention a wagon ,did you get the coil spring compressor he was also selling w/ the car?

[southofantarctica]

Originally Posted by chasinthesun

My only slow car symptoms was fixed from the banjo bolt at the back of the intake being clogged ,onced cleaned out it was a new car. Oh ,forgot about the linkage piece that hooks to the injection pump ,thats another one ,if the piece is loose with play the rolling jointed piece on the assembly is rotten,made of some hardened rubber that deteriates over time and wont give you the correct throw a new one gives resulting in slack from foot peddle to rev on the rack of the injector ,easy fix and easy to look for as calpriets,just wiggle the rod coming to it and if theirs play it needs replacing .I would add fuel lines into the replace catagory items ,rubber lines maybe restrickting flow internally,had a 190e with this issue and of course filters including the tank screen.
This car was being sold out of Houston ,correct ? Thats a good deal for a running car ,not to mention a wagon ,did you get the coil spring compressor he was also selling w/ the car?

Yes, it was near Houston. I wish I had known he had a spring compressor for sale! I just bought one a week ago....

ALL my linkage is good. I know exactly what you are talking about with the ball type thing on the firewall. Had that problem with my first 300D. Caused big problems like you said.


I looked at the fuel prefilter, after about 30 miles of driving it is already chock full of crud. The original filter was extremely dirty, but I thought it was mainly just old. The tank is an issue that will have to be addressed. Might solve a goodly number of my problems if I had free fuel flow, like Barry mentioned earlier.

[chasinthesun]

Tank issues are pesky problems ,if you eliminate it as one of your problems you can work forward knowing it was addressed.I bought 2 nonrunning vehicles that were proven tank issues at the end.The tank for the wagon being a flatter one will give rise to more issues ,more area to rust if fuel has evaporated over the time sitting , the biggest enemy to the tank, that grud just sitting their until new fuel is introduced is an awaiting gremlin.A radiator shop will sometimes take on the cleaning of a fuel tank.

[barry12345]

We never see any growth in diesel tanks as far north as I am. Or at least is far less prevalent. I have never seen a case. Causes a world of grief though in hotter climates apparently.

Car deserves a complete fuel system cleanout. At least more labor intensive than cost.

That said I would first run and drive the engine on a jug with the pickup and return line in it. This simply because you noticed a power improvement with the enhanced relief valve. This to me is not consistent in some ways.

You want to localize the problem of where it is originating at although the fuel system cleanout will be needed. In fact the jug may indicate it is the only problem. Still I would not want to clean the fuel tank out to find I still had a problem at this point.

Just because it is a fair amount of work and can wait. The jug test is not rocket science. This test may also indicate if the lift pump needs cleaning or kitting as well.

I trouble shoot in ways that may seem different at times. I do not think I am lazy. Instead just do not like to do a lot of work until I am satisfied it will all work out well.

I also do not expect others to do as I do. In this case it would give me a chance at evaluating any additional problems or the lack of them at the lift pump and beyond. You can never be sure of what you might run into on very old cars . Put new fuel into the jug if you go that way. Bad fuel or fuel with a lot of water in it may also be in that tank. Mind the crud.

Even just dividing things up can make things easier. Hopefully your total problems are just the tank filter and a dirty tank.

That pesky improvement with the new relief valve to me should not have occurred. Basically if the engine was starving for fuel increasing the relief valve pressure release unless the old one was totally shot should not have done anything. At the same time some effects cannot easily be accounted for.

[southofantarctica]

Originally Posted by mannys9130

Yes, most people check valve timing to determine timing chain stretch. In your case, since the power is so wildly irregular, it would be done to verify that the cam is in the correct position. This needs to be done with the injection pump as well to verify that the injection event is properly set. Drip timing is what most people do. You can read about that online or in the manual.

Something's just not right. You have to do a few broad scope checks to see which thing is the issue.

Ok, I'll do some deeper digging on how exactly is need to do that. Try to get some readings this weekend.

[Maxbumpo]

EGR valve stuck open will stay stuck open regardless of vacuum line disconnected. I've had a stuck open EGR valve, and it produces the exact symptoms you describe (low power, smokey exhaust). It doesn't NOT contribute to the blow by.

Fashion a plate to block off the exhaust feed into the EGR (use steel not aluminum).

Keep marching through the other items mentioned, I'll bet the engine is basically sound but may have high oil consumption. Oil is cheaper and easier than a replacement engine.