I changed the large canister fuel filter on my 1987 300TDT, and now the engine will not start up. The engine cranks over, and it seems as though it wants to catch but it doesn't run. I have tried cranking the engine for over ten 20 second periods (with 5 minutes breaks in between), but it never catches. I have tried cranking the engine to the point that the battery is now drained. I'm charging the battery up so I can try starting the engine again, but I am worried about draining the battery again without being able to start the engine.

In order to minimize the cranking time and lessen the air in the fuel system, I poured the fuel from the old filter into the new filter. According to the Mercedes shop manual the OM603 engine is self priming. So how long is it supposed to take for the fuel system to prime itself? Is there anything else I can do to get it to start up?

I also have a couple other fuel system questions:

There is a diesel fuel heater/thermostat after the prefilter on the OM603. On my 300TDT, the previous owner bypassed the fuel heater/thermostat. I'm not sure what is wrong with them. The price of the fuel thermostat seems to be over $130. I'm not sure what typically goes wrong with the diesel fuel heater/thermostat. Is there a common failure mode for either the fuel heater or thermostat? Is there a way to repair the thermostat? I also live in California, so I was wondering how important the fuel heater is in warmer climate?

Finally, before I changed the fuel filter, the engine seemed to smoke on a cold starts and run rough for a minute or two after which it seemed to smooth out. What would cause this? My first instinct is that the glow plugs are not all working, but a mechanic that worked on my 300TDT for the previous owner supposedly replaced the glow plugs. Any ideas? It happens regardless of the ambient temperature.

Thanks in advance,

-Steve

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1987 300TDT smoke silver w/ burgundy leather interior
2000 VW Passat wagon indigo blue w/ beige leather interior
1985 Mustang SVO
1970 Chevrolet K10 fleetside, shortbed

Pausing 5 minutes between 20 second tires is a little long. Whatever progress you make will be negated by time. Try 10 second tries 10 seconds apart. The manual says to crank continuously for a minute or something like that. I can't see how that's not asking for trouble.

You might help your injection pump along. Crack the the lines into the injectors while you crank. When fuel leaks from a fitting, tighten it and crank again. It'll probably catch before you get fuel out of all 6 fittings but I find that if I don't help the priming along for each cylinder it can take a while of rough idling before it smoothens.

Oddly enough my 2 SDs never needed priming after replacing the fuel filters.

I was tempted to bypass the fuel thermostat when it sprung a leak. In my case either the plastic end piece cum fitting or the o-ring cracked when I replaced all the fuel lines. Turns out there's an inexpensive repair kit available at the dealer that includes both pieces. I needed it ASAP so I didn't check FastLane.

My SDL is that way when it's cold. I find that going through a couple of glow cycles, leaving the key in the on position for 10 seconds after the glow light goes off, works wonders. The glow plugs are pretty new and resistance checks out. Could be any of a number of things causing the cold start roughness. Lazy glow plug, lazy delivery valve, low compression in one cylinder, etc. Check the resistance through the glow plugs and consider new delivery valve seals if they're original. Otherwise, live with it.

Sixto
95 S420
87 300SDL

i know this sounds confusing....but I imagine you are suggesting that the fitting where the line attaches to the injector be loosened allowing air to escape.
I must ask though, how many of you guys do this alone? Do you have a remote starter button and if so, where do you feel is best to connect?



Fuel T-stat? What does it look like? Does anyone remove this?
And what is a Cum Fitting?



I am diagnosing a 'no start' condition with an 87 300TD. Ran fine, parked on the flat, week later, no start. I get a 'pop' maybe from one cylinder trying, but thats it. Was hoping to see priming procedure here. No luck yet. Will try opening lines while helper cranks.

Battery is fully charged.

__________________
85 300D 3 pedal. Current project.
83 300TD (need rear wiper assembly dead or alive)
84 300SD Daily driver
85 300TD almost 400k miles and driven daily.
98 E300D *sold
86 300SDL *sold and made flawless 10 hour journey to new home.

I do it alone. No remote starter. Loosen all the lines, crank for 10 seconds, tighten the fittings that are wet, lather, rinse, repeat. When at least 4 lines are wet and tight, the engine will stay running on its own.

It's an aluminum cylinder sitting on the driver side engine mount arms. Follow the fuel line from the small filter to the plastic end piece of the thermostat that's also the fuel inlet fitting for the fuel thermostat.

Other no start suspects include stuck IP fuel return check valve and clogged oxidation catalyst. To check the fuel return check valve, pinch the line from the big fuel filter back to the tank. If the engine starts, the check valve is stuck open. To check for a clogged cat, remove the plug on the #1 exhaust runner that takes a 17mm socket. If the engine starts, the cat is probably clogged.

Sixto
87 300D

There was quite a discussion about someone having difficulty getting one of these engines re-primed awhile ago and it should be in the archives. Also by dumping the old filter oil into the new filter I wonder about some junk in the filter being transfered like water in the bottom of the old filter etc. It might have dosed your pump. Should really only put clean fresh fuel oil into the new filter. Hopefully you got it running before reading this note or the archives help.

Or Diesel Purge.

Sixto
95 S420
87 300SDL

Just a note of interest. I got the idea of pouring the fuel from the old filter into the new filter from the "Mercedes-Benz E-Class Owner's Bible". The "Mercedes-Benz E-Class Owner's Bible" is written by Stu Ritter who is technical editor for the Star Magazine, as well as 25 year MBZ repair shop owner/technician. At the time I thought the idea was good, but I seem to be getting a different opinion from everyone else.

Thanks for the replies so far though.

-Steve

__________________
1987 300TDT smoke silver w/ burgundy leather interior
2000 VW Passat wagon indigo blue w/ beige leather interior
1985 Mustang SVO
1970 Chevrolet K10 fleetside, shortbed

What exactly is a 300TDT? is this a Turbo Diesel Wagon? Or is it just an '87 300D? I have seen the TD designation, and the DT designation, but never used in conjunction.

SteveM.

- PS - let 'er crank. Get a good jump start and crank for 30-45 seconds.

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'93 190E/D 2.5 Turbodiesel 5-speed (daily driver)
'87 190D 2.5 Turbo rustbucket - parts car
'84 Dodge Rampage diesel - Land Speed Record Holder
'13 Ram 2500 Diesel
'05 Toyota 4Runner

Jetmugg,

A 300TDT is a turbdiesel wagon. The 300DT is the turbodiesel sedan. The "T" tacked onto the end stands for Turbo. Mercedes-Benz uses this nomenclature when referring to the different models.

-Steve

__________________
1987 300TDT smoke silver w/ burgundy leather interior
2000 VW Passat wagon indigo blue w/ beige leather interior
1985 Mustang SVO
1970 Chevrolet K10 fleetside, shortbed

there is a junction block right in front of the battery, follow the positive cable, it connects to it.
jump the positive cable with the wire next to it, and you will get a crank.
if you have a remote starter switch, connect it there, (like 7.00 at autozoo)