240D difficult start, dies in gear - not injectors - PeachParts Mercedes-Benz Forum

pdrayton · #1 09-20-2010, 09:56 PM

Yep, my baby beater has me stumped.

1983 240D A/T veg car. Was running fine,. then lost some power, now doesn't want to start. I have to spray some air intake cleaner in the air filter to get it started.

2nd symptom is that when I put it in gear, the revs drop and it stalls. It's like the tranny is engaging too hard. I'm not sure how the torque converter affects this or what adjustments there are to make. I checked there were no leaks to the tranny cap thingy (modulator?). Fluid level is good, newish filter and fluid.

3rd symptom - when revved up, it slooooowly returns to idle. And occasionally after idling for a while, the idle will go up slowly (from about 1000rpm to 2000rpm in about 5 seconds) or down slowly.

4th symptom - glow plug light only comes on occasionally. I've tested the resistance of the glow plugs - all around 1.1Ohm. I replaced one recently. But the not wanting to start happens even when the engine is at operating temp, so I'm thinking it's not the glow plugs. Could be my battery is weak and the starter is not turning over fast enough?

I've checked the fuel supply is good, and I've replaced and balanced the injector nozzles. Also replaced the fuel filter. I unscrewed the ALDA 1 turn, should I try removing it maybe? Not sure that is any good for a 616.

Vacuum supply is 23inHG, I forgot to check what it is going to the modulator, but I don't see how that will affect it starting.

I'm at a loss. Any ideas? I got it going and took it for a ride by keeping my foot on the accelerator when putting it in gear so it wouldn't stall. Rides fine, like it used to. Just dies when I stop and it's in gear. Could it be something about the altitude adjustment I read about ? (or is that the ALDA adjustment)

Help, I need this baby to tow my fishing boat. No fishing til she's fixed because the truck is waiting on a ECU before it can do the job. But I prefer pulling into the boat dock with my Merc. It's much cooler, and trucks and boats are such a cliche.

scottmcphee · #2 09-20-2010, 10:04 PM

3rd symptom is the most interesting, is the linkage returning to its idle stop or getting stuck or what?

Pop the ALDA off while diagnosing if you're concerned about it, just unscrew it off there. The only good it can do is restrict fuel in low RPM conditions. ALDA is your altitude compensator.

pdrayton · #3 09-20-2010, 10:17 PM

Thanks Scott. I'll take the ALDA off tomorrow and see what happens.It doesn't have any vacuum lines going to it, never has since I've had the car.

Yes, the throttle linkage all returns to normal (Idle stop), but the idle doesn't. I thought it might be air supply, so I cleaned the filter (K&N), but no change.

I read before this is a low power problem - could be bad injectors, bad IP, or bad compression. Seems unlikely since it happened in such a short time.

Biodiesel300TD · #4 09-20-2010, 11:44 PM

Have you changed the fuel filters at all, and have you checked the tank screen? Sometimes you can pull fuel fine with a vac pump, but when you actually get the car running it can't supply enough fuel.

pdrayton · #5 09-21-2010, 12:10 AM

It does the same thing whether I run it from the diesel tank or the WVO tank. I put a prefilter in front of the lift pump and it stays full, and there is good return from the ...um.. return line. So Idon't think fuel supply is the problem.

I've been reading about guys using naptha or turpentine to do a diesel purge - clean the ip and injectors and combustion chamber. I think I'll try that....

I'm thinking maybe the WVO has gunked stuff up.

Biodiesel300TD · #6 09-21-2010, 12:21 AM

Quote:

Originally Posted by pdrayton

I'm thinking maybe the WVO has gunked stuff up.

Probably. ATF will clean things out as well. Lubro Moly's Diesel Purge is another good product for clean out a fuel system.

pdrayton · #7 09-21-2010, 07:48 AM

Yeah, I have ATF type F in the diesel tank. I read that regular ATF doesn't have the cleaners that the old type F has. Also heard that Diesel purge is mostly something like naptha or turps.....

barry123400 · #8 09-21-2010, 09:20 AM

Quick test. Close off the fuel return line from the injection pump. There may be plenty of fuel in the injection pump but no retained fuel pressure. That could occur if the relief valve was all gunked up, It is probably not it but easy to check.

Biodiesel300TD · #9 09-21-2010, 10:29 AM

Quote:

Originally Posted by pdrayton

Yeah, I have ATF type F in the diesel tank. I read that regular ATF doesn't have the cleaners that the old type F has. Also heard that Diesel purge is mostly something like naptha or turps.....

You need to run it straight. Putting a bottle in a 20 gallon tank isn't going to do much for you. You need to stick the supply and return fuel lines into the bottle and run it that way.

scottmcphee · #10 09-21-2010, 12:36 PM

Quote:

Originally Posted by barry123400

Quick test. Close off the fuel return line from the injection pump. There may be plenty of fuel in the injection pump but no retained fuel pressure. That could occur if the relief valve was all gunked up, It is probably not it but easy to check.

I double that: pinch the return line from the IP.

Get the car switched to diesel while your diagnosing this.

If there was a chance of veggy cross contaminating a diesel fuel filter, replace the diesel filters.

Also slow run-down to idle suggests you're sucking fuel in the airstream. Anything can be fuel... like motor oil, or heavy crank case gasses.
Check the venting and air stream. Open the air intake manifold to atmosphere and run the car. (Keep objects away from being sucked into the engine, like your hat.)

pdrayton · #11 09-21-2010, 06:12 PM

I ran the baby on a quart of Naphtha to clean it out. The erratic idle was more erratic, but other than that samo samo. Then I checked 3 of the glow plugs - all good. Then the starter crapped out and I couldn't get it going again.

I'll check the IP return next time I get it going.

Vacuum to the tranny modulator is fine - from about 10 to 2 at WOT (this is how I set it up before and it worked fine).

I think there is a power issue - could be the ip not having enough fuel, we'll see....