Try replacing the glow plug relay with a good one then see if that helps. Same experience I had with my '83 300D until I replaced the glow plug relay...

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1987 300SDL 314K mi, counting; #22 Head
1999 E300Turbo 405K original miles
1997 E320 180K mi (Son's)
2002 ML320 (Son's)
1998 S320 140K mi (Son's) sold
1985 300SD 311K mi
1984 300D 324K mi (killed by a hit-n-run turd)
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I will check my glow plugs but i just dont get how they would be good enough for it to start when cold but not when its hot, the light comes on on the dash and does what it should.

As far as the fuel shutoff not releasing thats what i was thinking too, i just wasnt sure how i wanted to go about fixing it/testing it. I actually have had to step into the throttle a bit since the get-go to get it started. I tried pinching off the return line and it did not have much affect, same thing goes for unhooking a bunch of vac sources to really bleed the system to release anything that might be sticking and messing with me.

I have not ran a diesel purge through it. P.O. ran single tank wvo and I got the car with a full tank. After about the second tank of real-diesel I started clogging stuff up as i expected. My family owns an oil company so i went down and got some biobor and used that on a tank and then used some diesel kleen on another. The car runs great which is what makes me thing its something stupid, it feels power/accel wise about as strong as my 03 mkiv tdi 5-speed. The tank strainer is clean.

The previous owner already got rid of the EGR with block off plates and such. Air filter is new.

Totally bogus! I have a manual glow plug setup on my 617.952 and I never use glow plugs when the engine is hot....or even warm. As long as it hasn't been off for more than an hour or so, it pops right off.

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Current Stable

• 380SL (diesel)
• Corvette C5
• Manx
• Baja Bug
• F350 Powerstroke
• Auburn Boattail Speedster replica

Remove the oil fill cap and try to start hot. Too much base blow by pressure build up can affect the shut off valve.

It is a very easy test but usually seen at highway speeds. On the other hand these engines are just getting older and older so some things should be considered. I would consider this a very rare thing on your car but still a very remote potentially possible.

After you turn the key to glow, try pumping the accelerator pedal to the floor a couple of times to make sure the injection pump fuel rack is not stuck in the stop position, and then crank the starter.

Manual priming pump leaking?

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

I'm guessing you have to look at a fuel issue. When it's hot something expands.

that link is a wikilink; and the link you posted with a TDT is about the engine- not the car. Nothing on the rear of the car says TDT, and this link which is the same as yours calls the car a 300TD. All USA 300TD's from 1982 onward are turbocharged. Some other countries had the 912 version of the 617 until '86, others had the 952. DO you hear anyone calling their non turbo version a TDK?

It is a strange problem since diesels like heat, unlike sometimes fussy gasoline carburetors. I wonder if perhaps something with the lift pump when hot. Perhaps the piston seals get soft so it stops building pressure, at least while cranking, and perhaps at idle it does pump enough.

It would be real nice if there was an easy way to measure the lift pump pressure. I recall some guys have tapped thru a banjo bolt to add a pressure gage. Supposedly, 12 psig is "like new", but it would probably run as long as the IP gets sufficient fuel supply, maybe as low as 5 psig.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

I like this idea, will try for sure.

yah i ve done that, pretty much the first thing i try when any car wont start. No to the prime pump and it is the newer style.

If i get it started when hot it runs great though. I have a fuel pressure gauge in the cab so i can tell you exactly what my pressure is. It helps that i JUST rebuilt the pump but im seeing 11psi driving around/ 9-10 at idle/ 43 if you pinch the return (I was curious). Inline filter stays full, car does not maintain pressure on the gauge when car is off ( which is in line with what i ve read) and the gauge is T'd off the return side of the IP.

I do appreciate all the help. I have a mityvac on the way so im going to be able to do some definitive tests rather than assuming the new lines and stuff are sealing well. Its a bummer having a car that i can only use for stuff where i leave it running

FWIW my '84 wagon did not like to restart when hot- but it was the starter not engaging. All I'd get was a click. When it cooled off- sometimes 5, sometimes 25 minutes later- the car would start. I didn't do anything about it and it doesn't seem to do that anymore.

Two things jump out at me: the history of single-tank WVO use, and the OP's statement that he's got to pump the accelerator to get it to start. This points to a problem in the injection pump.

I'd recommend attempting a rebuild of the delivery valves (new springs, copper washers and O-rings if required in your car) and visual check into the top of the IP to see if there is significant gum/varnish etc. from the WVO. Caution on the delivery valve tightening procedure: be sure to read the FSM or ask here, there are two different versions (at least) of injection pumps on OM617.9xx engines, two different torque procedures. Messing up the torque on the delivery valves will cause the injection event to be wrong and the engine won't run correctly.

DO NOT under ANY circumstances remove or touch anything below the delivery valve, or your injection pump calibration is out the window. You need to be clean clean clean to prevent contamination of the injection system with dirt or debris which may clog / destroy an injector.

Rebuilding the delivery valves will do two things: allow you to visually check their condition and look into the top of the pump for WVO gum/varnish, and eliminate them as a possible source of trouble.

A less invasive approach that may help would be a Lubro Moly diesel purge treatment, using pure diesel purge in a temporary fuel container in the engine bay (be sure you don't mix up the fuel supply and return lines when done). Biodiesel (the real thing, VO that has been converted chemically via transesterficaiton) is also a terrific solvent and may clean up the WVO mess just as well as diesel purge. Seafoam is another product that may work, but I've never tried running that direct.

I *think* if your injection pump has the splined delivery valves, a special socket is required and the torque procedure is four stages: torque to 30 Nm, release; torque to 30 Nm, release; torque to 30 Nm; torque to 35 Nm, and then install the lock-down tabs.

If your injection pump delivery valves accept a normal socket, the torque procedure is different: It may be a single step torque to 40-50 Nm.

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

^^ Unfortunately i kinda thought this is what was going to be the case. I dont have to pump the gas though, just hold it at like 30% to start. I looked into the delivery valves because i found that my number 1 had some iffy threads. Where do i get a rebuild or buy new delivery valves ? I couldnt find a good source for rebuild parts. Thanks.

You can get the part numbers here:

Mercedes-Benz Teilekatalog (Ersatzteile online)

And then search around, either this site sells them or MB dealerships etc.

Note that there are different part numbers for California versions. Enter your VIN and that should give you the correct part numbers. In the diagram attached, you only want parts 41 & 47.

Attached Thumbnails

 

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

So i called my local MB and got number 41 and 59 but they no longer made number 47. I also need a part 29 because when i took it apart i found the threads were bad, unfortunately this is 170 dollars which is ridiculous.

Did you change your secondary filter also? Sounds like your filter is clogged again since you used biobor.

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'85 300D Cal 280,000 miles
'14 GLK 350 60000 miles

^^^well not in the last 20 miles but i ve had to do one a tank for a few tanks. I can see when they re going bad because i have a pressure gauge.

Updates: so after putting in all new glow-plugs and going through it all they work. Did some other things with a mitivac n stuff (fuel and vac system) and didnt come up with any results. All vacuum hoses are going to the correct places. Took off my injectors and fuel squirted out (except #1, more on that later) car started right up, better than before with 2 bad plugs. Turned the car off and went to do my liqui molly purge. I am currently halfway through this because the car did not like idling on the purge so about 2/3 of the way through I let the linkage back too much and it died. At this point it was up to around 80 (C i assume) on the temp gauge and would not restart. Did it in a clear bottle and it definitely cleaned some stuff.

Injector one didnt really squirt out like the others, i had to take out the delivery valve and primer-pump it to get fuel to there, i cranked some more once i could see fuel in the seat and nothing squirted out. I got it running and when i went to disconnect the #1 line at the injector to see what happens and the second i loosened it i got fuel out and the engine died. Think the ip is bad? there was some real gunk in the dilivery valve area and the car ran wvo.

At this point its getting to be a bit rediculous. I must be cursed with cars because i have all "reliable" that dont work; 03 vw tdi w/130k which is driving super super erratic (im like 99% new maf is going to fix it) and then a w123 "million mile car" that starts great, drives well, wont start when warm sooo essentially undriveable. My 3rd cars a toyota,a supposed reliable car, that i have consulted so many people in the community on and it still is gutless and idling all over the place after being parked for 15 min and running perfectly.