87 300D won't start

I am helping someone else troubleshoot their 87 300D. I have an 84 and am very familiar with it, but not sure what parts transferred over through the generation change.
The engine turns over but doesn't try to start. They have replaced the fuel filters. I have sent them an E-mail askign if they are sure they got the air out of the filter, but they have not answered. I don' think that air was the problem since the car ran fine, then wouldn't start, and only then did the they change the filter.
They have taken off the intake manifold and ensured that there is nothing obstructing it. The entire intake system is clear.
I have two ideas. Either the injector pump is bad, or the switch to shut the fuel off on shut down is stuck in the shut off position. I have sent them instructions to crack open a fuel line and check for fuel. Do those switches fail and get stuck in the shut down position though? I've never experienced that, and have heard of several people having them not work and have seen two cars where it wouldn't work. But I've never experienced a 300d where that swithc prevented startup. Does this happen?
If so, how do I check that? Is there a lever that it pushes on? If it is faulty, and I remove that switch, will the engine then be able to start or will there now be a gaping hole in the back of the IP?
I have not yet seen the car. Any knowledge I can get before actually seeing it would be appreciated since I doubt we will have internet access where it is.
Thanks a ton, Bill
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Has anyone checked the simple stuff????
Like whether the glow plugs are working - that's the usual cause of a diesel's sudden no start.
As more things are disturbed the murkier the trail becomes so please stop ripping everything apart! At the end there will be only a colossal mess - of parts, not a motor.
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I have a 602 engine and the fuel flow is achieved by use of vacuum to open the valve and hoses that branch off the brake servo hose and connect to the rear of the ignition switch and fuel pump. The rubber connectors can perish over time (or get removed) and prevent the vacuum from being achieved.
The same test regime has to be applied to any diesel that wont start - fuel and air first, after that go looking for serious problems.
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Alway check the glow plug system... always. Every glow plug should be less than 1 ohm... Make sure the glow plug fuse is good. Chances are... a couple of their glow plugs are dead.
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The injection pump usually lasts no less than the engine. Also, due to its cost and the labor involved, let it be the last suspect.
The shut off valve uses vacuum to activate. If there is anything wrong with the vacuum system, it is usually not stopping, instead of not starting.
I would agree on others' suggestion: check glow plugs first. The relay is on the left side fender, black, about 10cm * 10cm and 3cm thick. Open the cover and check the ohm between the 6-way connector and a good ground. Each socket should show about 1 ohm. If they are OK, check the fuse, and if there is 12 volts when key is turned to Run position.
Since the fuel system has been opened, air has come into the fuel hose. The worst case is that it may take a minute of cranking to bleed.
BTW, OM617 (your 84) shares no part with OM603 (87 300D). However, the design principle is similar and the basic debug is alike.
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My 1982 300 TDT became almost impossible to start when the EGR valve stuck open. It would start by push starting, but the starter motor just wouldn't get the tired motor with 396,000 miles on it turning over fast enough for it to start with the EGR valve stuck open.
So if the glow plugs are working fine and you are able to determine that the engine is getting fuel, check the EGR valve.
To check if fuel is being delivered you can slightly loosen one of the injector tubes leading to an injector and then turn the engine over and see if squirts of fuel come out.
I spent $6000 to get my engine remanufactured and spent 4 months removing and replacing the engine in my spare time (I have 3 vehicles). The new engine still didn't run right, although the super high compression of the new motor meant it would start, but it didn't run right at low RPMs because I had used my same EGR valve and it was still stuck open. The manual just suggests checking the vacuum valve. That was working, but the shaft in the EGR valve was stuck or maybe the valve was burnt, but it just didn't seal.
With my car I just removed the EGR valve from the intake manifold and replaced the stock gasket, which has a hole in it for the gases to pass through, with one I made from exhaust gasket stock that did not have a hole in it (except for the bolt holes), thereby eliminating the EGR from the engine, period. This works great, and where I live in the sparsely populated Eastern Sierra, the increased N02 in the exhaust does not matter.
The guy who remanufactured the engine and Karl, one of the experts on this list who is a retired Mercedes Service Manager, both assured me that it will not harm the engine in my 1982 300 TDT to eliminate the EGR valve. Non California cars from that year did not have EGR valves anyway.
I don't know if this would be safe for your car. Also, if you have to get your car smogged it probably would be a bad idea. We do not have to have smog tests here in Inyo county.
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I didn't think to say that the glow plugs had been checked. That was actually the first thing he checked. Then the fuel filters. Then the air filter, then the intake manifold.
I told him to check that the fuel filters didn't have air in them and to try cracking open an injector line to do two things-check to see if the IP was sending fuel to the engine and to get any air out that might have gotten in the line.
I'm just trying to get a list of stuff to try if the injector line cracking method yields no fuel at the injector.
As far as the shut off valve, I was aware that it operates using vacuum and not having vacuum will make it so that the engine won't shut off. My question is can the valve wind up stuck in the shut off position. Not because of a lack of vacuum, but just by wearing somehow, or a spring pops off or something like that. If it were to stick in the shut down position, then no fuel would flow. Anyone know of this ever happening?
Thank you for the help everyone.
Bill
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The shut-off is by pulling a lever (or rod, I forget) inside IP. It is not natural for it to stuck that way.
Is there fuel leaking? How old is the fuel hose and the thin bleeding hose on top of injectors? Are they wet or you can smell diesel? If there is leaking, air may be sucked in which can cause no start.
Is the inline filter (normally clear color) filled with fuel? Any air bubble? Was the previous one very dirty (sign of contamination, possibly algae)?
How many miles on the clock? Is low compression a possibility?
I thought 87 should be OM603 (6 cylinders). OM602 is 5 cylinders. The EGR on OM603 (not sure about 602 but possibly the same) is bolted to the air charge pipe (immediately out from turbo, before the flat pipe carrying the air across the valve cover). However, too much EGR may stall a running engine but I don't think it will make it no start. Before engine starts, there is no exhaust. Whatever flowing thru EGR valve still contains lot of oxygen.
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I actually didn't know that the 86 is the 602 and 87 was the 603. I have a W123 car with the 617 and am not that familiar with newer stuff. I messed that one up.
As for the EGR, it doesn't have oxygen at startup, but once it starts turning over and firing at all it will be oxygen poor, so I could see it producing a half-assed running engine that sounds like it wants to start and the starter can get it to turn over quickly, but it never actually runs on its own without the starter. I'm not saying that this is what is happening. I'm just commenting on my theory of how the EGR would affect starting.
I wouldn't think it would be lack of compression. The car ran fine one day and had always started up easily, then wouldn't start the next day. I'd think that lack of compression would gradually degrade starting.
Bill
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Diesel needs two things to run: fuel and compression.
I agree with you on that the compression should degrade gradually. Also, the fact that the engine ran fine a while ago but not now (when it is hotter). The chance to have low compression is unlikely.
Let's go back to fuel. Make sure there is no fuel leaking. I had an incident when leaking hose allowed enough air to get in and caused no start. If the hose is original, it definitely needs replacement.
Another possibility is injection timing. The timing is not easy (unlike OM617) to check by DIY due to special tool. But this is a mechanic thing and it should also degrade gradually (unless the timing chain jumped).
The OM603 (same as 601 and 602, but different than later diesels) is simple mechanic controlled machine. There is some electronic on it but it is mainly for emission control, in my opinion. You can disconnect all those electronic and the engine should still run.
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Well, the mystery is mostly solved. The stop lever looked like it was a little depressed. So he tied the stop lever up and tried starting the car. It started right up and ran fine. Now it won't shut off though. I know with my car, and I assume his car allso, the engine is shut down by a vacuum operated doohicky that gets vacuum once the ignition switch is set to off. So I think it is clear that somethign is wrong with the shut down circuit.
I theorize it may be one of two things. The doohicky is stuck like I postulated before, or perhaps the valve in teh ignition switch that allows vacuum to go to the doohicky is acting up. Maybe the no start prolem surfaced because that valve allowed vaccum by, but then didn't vent back to atmospheric pressure once it was supposed to, and now that valve in the ignition isn't operating at all.
I'm going to have him apply vacuum directly to the doohicky to see if it still works. If it does, then the ignition switch it suspect. If it doesn't work, then we have a winner.
Thank you for the input guys.
Bill
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Great job! Keep going and get it fixed!
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He ran a piece of fishing line through the vacuum lines. checked all the fittings, and made sure all the plugs and connections in teh area were good. The car now works as it should. It's still not apparent where the problem was, but now it is gone.
Thank you all for the input.
Bill
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So where is the EGR valve on the 602?
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