This is driving me nuts. I've been trying to fix this since March. If I had the money, I would just buy a clone of my car without THIS CONFOUNDED PROBLEM.

Anyways, check THIS out.

I have a 1979 240d that runs GREAT! above idle. Seriously the fastest 240d I've ever driven, especially on the freeway. However, once this little demon reaches operating temp, the idle is deplorable. It rocks the car back and forth, and when you're behind the tailpipe, the exhaust makes a 'thump, thump, thump' sound. It sounds EXACTLY like as if the rack damper bolt was the problem, but 240ds dont have those. I have done EVERYTHING. I feel like I could have a Phd in Mercedes driveability if I figured this one out. Here's what i've done.

*replaced the nozzles and had the injectors pop tested (by mike_d, thanks dude!)
*checked the IP timing, according to the fsm, seemed fine.
*adjusted the valves, rechecked them THRICE, using the directions in the fsm.
*ran a purge through the fuel system.
*replaced all non metal fuel lines
*replaced the hand primer
*took out the tank and cleaned it out. ran mineral spirits through the hard lines.
*replaced both fuel filters.
*replaced both side motor mounts
*replaced heat shields, cleaned out prechamber before installing injectors.
*prayed
*checked idle with vacuum shut off hose disconnected, no change.
*compression test, great numbers. cant remember exact readings but all above 350 and close.

And I didnt shotgun all these things at once, I did them one at a time.

If anyone has any ideas or diagnostic procedures I could try, I would be so grateful. I'm desperate. This is my only car. There is a reward. If anyone can actually figure this out, I can pay you, and my girlfriend and I will make you a pie. And I make a good APPLE PIE.

Seth.

Time to pull the IP and bring it to a trusted diesel injection shop. Very likely delivery valve related.

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1982 240D auto
1978 300CD auto
1985 300D auto
1983 300TD auto
1984 Porsche 944 5 speed
1973 Opel GT 1900 4 speed
1967 Chevy C30 350 Sm420
1973 Mustang Grande Convertible 302 C4
1981 VW Pickup 1.6D Turbo 5 speed
1983 Rabbit 1.6D Factory Turbo 5 speed
Plus parts vehicles...

on a 240D i would do this. Find out which cylinder is missing, by loosening each injector line 1 by 1 until u find the one where the idle doesnt change much or any.

Loosen the 2 13mm nuts on that delivery valve holder, use a 15mm on the delivery valve and slightly turn it either way until the idle is smoother. BY turning it clockwise you give it more fuel, counter clockwise is less fuel.

NOTE: this is technically something that is to be set and adjusted ONLY on a bench tester. However on a NA 4 cylinder motor i think you'll be just fine.

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1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

I have an extra IP from a known good running (but overheated) engine. Is it easy to just r+r the pump? never done it myself.

I feel your pain. I gave up on an '82 240d for the same reason/syndrome. Car ran like a champ until it was fully heated up, then ran rough and smoked.

Was told by two wrenches it was a valve problem. Pulled the head, head was pristine.

Didn't someone cure this on another car by replacing the lift pump?

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

GOOOD idea. come to think of it, with all the removing and replacing the hard lines over and over again trying to mess with the injectors, i could have bumped the valves one way or the other a tad.

yeah the lift pump is one thing i havent tested yet. Thanks for reminding me about this, I had thought about replacing this with one from a donor engine but sort of forgot. Wonder if theres a way to test it. Cant find much on the threads.

I had the impression from reading the threads that it's a fairly recent wrinkle on these cars, I guess a function of age(?). I know that when I read it, I sort of mentally slapped my forehead and thought "the one thing we never looked at."

It really hurt to give up on that car. Though I ought to have mentioned that mine had been run on unheated WVO for a while and that is now known to be a lift pump killer.

Good luck with it.

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

I`ll be following this thread, I also have a OM616. runs excellent, "now". But never know what she will be doing down the road.

Here is a good thread on the 616 lift pump rebuild. several links to check out.

http://www.peachparts.com/shopforum/diesel-discussion/295121-616-lift-pump-rebuild-questions.html

Charlie

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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

never ran on wvo, but did run on bio-diesel, which still makes me suspicious. ive seen what its done to my rubber fuel lines. i wont be able to get to this until friday, but i promise to keep you all updated!

awesome thanks!

X2 That is good advice.
Any competent Fuel Inj. technician (old enough to have worked on these cars) and worth his salt, will tell you immediately by listening to the engine whether worn D-Valves are the problem.

At your peril!

“79Mercy” - That is absolute nonsense to advise the O/P to loosen the metering element flange and alter the original calibration settings WITH A WRENCH!! before you have even the slightest idea what the problem is and then you tell him he’ll be “just fine”! Clearly you have no insight whatsoever into pump calibration procedure. There is more than enough balderdash posted on fuel injection in the archive here without you adding to it.

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Beagle

You need to provide more detailed information before anyone can really help you.

1) How long you had the car? Mileage?
2) How long has it had this problem? Did it start suddenly or gradually? Since you bought it?
3) You say the idle is worst when hot (that points to D-Valves) – Is it rough at start up?
4) Did you re-set start of delivery or did you just check it? Are you certain you got it right?

In order to have a smooth idle the fuel volume to each cylinder must be identical and since the volume is extremely small at idle (about 4mm³/cyl) it is a very delicate and precise setting procedure.

The most common Fuel Pump related causes of rough idle are:

1) D-Valve – worn or scored piston and/or leaking valve. (VERY common - remove check/replace D-Valve)

2) Metering Element – worn or scored piston or bore. Most common on #1 due to dirt having fallen into piston helix when removing D-valve to set spill timing! (Replace element $$$$$)

3) Advance (centrifugal) timing device -- Worn, broken or weak springs etc. (rarely gives trouble).

4) Unqualified interference with the calibration settings!! Far and away the most common reason these cars have come to me for all manner of faults with these MW type pumps. I rarely get these old 123 MB’s through my shop these days but in the ‘80s and ‘90s due to the legendary acceleration of these 616/7s old wives tales abounded on how to increase performance by adjustments to Calibration, Boost, ALDA, Max fuel stop all total hogwash of course.

A rough idle does not necessarily mean that ANY of the cyl’s are missing and this would be the case with worn D-Valves. I would suggest that you take the car to a respectable shop near you as I mentioned above and ask him to listen. Any competent Fuel Inj. technician (old enough to have worked on these cars) and worth his salt, will tell you immediately by listening to the engine whether worn D-Valves are the problem.


There is no harm in checking your lift pump although I doubt it has anything to do with your rough idle. Remember over 90% of fuel pumped by your lift pump is returned to the tank through the by-pass valve for fuel pump cooling. Simplest way to check the lift pump is to remove the hose at the steel return line to tank and hold it into a small container. You should see a strong flow out of it even at idle. This is also a good way to check condition of filters – a dribble means its time to change them. Lift pumps very rarely fail but if the pre-filter is ever omitted they can quickly clog with crud.

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Beagle

Well the calibration of the injection pump itself and sequential timing of the pumps elements sounds good or the engine would not idle well cold. When the pump is hot from operating may be a different story. Fuel is thinner and thermal expansion has occured.

If you could identify the cylinder by the loosening of each injector nut would be nice with the engine hot and idiling rough. If you cannot isolate it to one cylinder time for a little trouble shooting. At hot rough idle is their air coming through the return line from the injection pump?

Best test is to submerge the return line in a container with a little fluid in the bottom of it. With the engine running rough you should not be processing air as well at the same time. You can redo the test with the system cold for comparison if there is any doubt.

The test to see if it is cylinder specific is important in my opinion.

He doesn't say whether it does idle well when it is cold - that is why I asked him.


Yes, I agree, it is important but until we have some background it is premature to take stabs in the dark and tell him to do this or that. The original post has very little to go on.

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Beagle