Hi, my E300D has started to hesitate and blow blue smoke under light to medium acceleration at speeds 30-60 mph. The blue smoke happens at the same time as the engine hesitation. It almost feels like the car is going to die, but the hesitation goes away with more pedal. Hard acceleration is very good with no smoke. The engine is also recently started making a hollow knocking sort of sound with each revolution (not too loud, but very noticeable at idle).
I bought the car with 267k miles, now has 284k. It has run well up until the hesitation started 3 weeks ago. I replaced all the fuel lines and o-rings (including the injector pump o-rings). Also just replaced the MAF sensor, fuel filter and screen, and did a diesel purge. I did have a check engine light prior to the MAF sensor replacement. No CEL now, but the hesitation/blue smoke is still there.
I’m thinking it may be a clogged injector? Maybe another diesel purge would help. Any suggestions are much appreciated!

welcome to the forum!
I'm sure a member with that style engine will be along shortly with more specific help for you, but those fuel line o-rings are a pain in the butt to seat... also, the bracket that holds the prefilter in, tends to leak air... you did change the prefilter right?

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Yes, I did replace the pre-filter screen, and the o-ring too. I don't think there are any air leaks - no bubbles are showing in the fuel lines. I have a 50 mile highway drive to work. The hesitation/blue smoke happens the same when the engine is cold as when it has been driven 50 miles. Seems like it might be a clogged fuel injector, but not sure. The hollow knocking sound seems it may be coming from the injector pump, but I can't quite tell. Thanks

This is so unusual, as the OM606 is a great engine.

One of the common problems when changing fuel lines and pre-filter is that the new pre-filter does not come with the O-Ring, and sometimes people miss that detail and install the screen without the O-Ring. I am glad to see that this is not the case here.

When you say 'including the injector pump o-rings', do you mean the delivery valve seals at the top of the injector pumps? If so, I suspect that you have a delivery valve issue here; perhaps one of the valves is not seated properly or something. From what you describe, it sounds to me like a fuel issue!

Why don't you try to isolate it to one cylinder? With the engine running at idle, back off the fuel line at the injector one at a time and listen for that cylinder to cut out. If one of them does not respond you have found which delivery valve to investigate. This will also ensure that all the air is purged from the system as well (to be double-sure).

It may also be an injector, but the test above may point that out too.

To keep it simple, will you check the air filter first? Perhaps the engine is being starved of air. Is the turbo working OK?

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'98 E300 DT
'87 190D 2.5 turbo RIP
'92 S500 Sold
'03 3.2TL-S A-Spec

I replaced the 6 o-rings and copper crush washers at the delivery valves on top of the injector pump. It does seem to be some sort of fuel delivery issue. I will try your suggestion of backing off the fuel lines one at a time at each injector while idling to try to isolate the problem. I will let you know! Thanks

Did you use the "torque, back off and re-torque" procedure when you installed the DV holders? If not, they can develop a leak internally and cause a leak because it retards the injection in that cylinder.

Bad news is that you'll have to remove the manifold again to re-torque...

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

When I did my delivery valves, I had read a few posts on the forum that stated that you could did not have to replace the crush washers. Before I did the job, the engine was as smooth as silk. After finishing the job, it would run, with a lot of shaking and nailing. I redid the delivery valves again with new seals and new crush washers, and used the proper torque procedure, and it was back to its old self, quiet and no shaking. I know its a pain to do the job all over again, but outside of the time you put in, its not expensive, and may solve your problems.

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96 E300d

The OM606 in the W210 is drive by wire system. The fuel cutoff is by a solenoid valve on the face of the IP.

There are 3 fuel hoses going to this valve and an electrical connector. On the backside of the valve is the 4th port going into the IP. This is your fuel feed into the IP and if that o-ring is leaking it can be causing an air incursion. Note the fuel goes through the shutoff valve twice. Once between the prefilter and lift pump and the second time between the main filter and the IP. This last connection is direct through the back of the valve body into the IP body.

On my car I have clacking idle and definite clacking up to about 1250 rpm under load then it smooths out. I have changed all the fuel hoses and replaced the prefilter and pre-filter o-ring. The last thing I can think of is that o-ring behind the shut off valve.

I have the o-ring for the shutoff valve/IP connection on my workbench and plan to replace it this weekend and will let you know how it goes. The o-ring costs about $2.50 and my MB dealer had it in stock.


For info, the fuel flow goes like this:
Tank -> fuel preheater (in the top edge of the head) -> prefilter -> shutoff valve -> lift pump -> main filter -> shutoff valve -> IP -> IP return/injector return/filter air bleed -> tank

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

I had driven the car 100 miles earlier in the week after I replaced the o-rings and crush washers coming out of the injector pump last weekend. During that drive, it was making the knocking noise and hesitation/blue smoke on acceleration. Then the car sat for 4 days.
I was ready this morning to loosen the lines to the fuel injectors, one at a time, to try to isolate the problem. However, when I started her up this morning, I was surprised the hollow knocking noise was gone. I took it for a test drive and found it was running smooth, with much less hesitation/blue smoke when I step on the pedal. I’m thinking it may be just air in the steel fuel lines as suggested by shingleback. I’m guessing when the engine cooled down, it may have sucked most the air out of the steel lines. Hopefully it continues to get better as I drive it over the next few days.

Update. I've found the source of the hollow knocking sound. The black plastic cover on top of the engine was bolted down too tight. One of the steel fuel lines was tapping against the cover making the noise. I loosened the rear two hex bolts, and the noise is gone. That was about as easy as it gets!

Whoa, not so fast.

Make sure the injection hard line clips and retainers are all present.

If you don't have those all intact, then your steel hard lines will vibrate and fail.

BTW I still haven't changed out the shut off valve o-ring yet, I had to go to Taiwan for work, and I just got back.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

I did a good diesel purge today on my '98 E300 with 285k miles. Started with 2 cans of the Liqui Moly. I ran it for about 20 minutes at various RPMs. The return got very dirty, eventually turning black. Please see attached photos. Is this normal? I stopped the engine before going through all of the Liqui Moly because it got so dark. The engine does run smooth now.

Attached Thumbnails

   

diesel purge is a solvent mixed in with the fuel, it cleans varnish and soluble sediment from the fuel line internals, and on a car with a lot of miles, yeah... it's going to show black purge return. it's normal. if you are worried, dump that, and put another two cans in, and run it again until it gets low. then change the fuel filters again, and purge the fuel clear!

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!