OM617 Performance/Maintenance Items
 

Hi,

I have a 1984 G-Wagen (ground up resto) with a swapped in OM617A from a car that lived in a field near the end of its life. With 480,000km (300,000 miles) on the clock and being thoroughly ignored it had all the usual problems- leaking oil, lots of smoke, poor starts, wouldn't stop, etc.

I actually thought it would be a "temporary" motor because of the high mileage, but now its running great, starts easily (even well below freezing), slight blowby, and with some engineering now stops without incident. I'd like to perform all the "wear" work on the motor so it just keeps running. I'm assuming that if I maintain this motor I could get another 400,000km without a rebuild.

There are only three problems I have at the moment. 1) Light smoke at idle and 2) low power on the freeway (can't maintain 60mph on hills) and 3) high fuel consumption (about 14mpg, I'm expecting 20mpg from prior experience). The G does weigh a lot more than say a 300D, but I know I can get more out of this motor.

So far, I've done the following:

- new GP's
- new gaskets at oil pan, valve cover, oil filter housing
- valve adjustment
- diesel purge (twice)

I'm considering, in rough order:

- injector rebuild
- timing adjustment
- timing chain
- vacuum pump

Does anybody have other thoughts, based on my goals of keeping this motor running for several more years + giving me the slight performance boost over what I see now?

Cheers,

Michael

An injector rebuild may be a good start. A timing adjustment with the mileage you mention would only be a band aid fix without the chain being replaced.

If there is any chance it needs a new chain .. that is a relatively cheap insurance policy. Be sure to replace all things which touch that chain if you can.. tensioners, rails, etc.. sprockets if you are able...
Then set the timing by the correct method.... the position of the number one valve...
that is cheap and will give you a baseline for the rest of the improvements.
I would do just one operation at a time....then you can tell what it was that made a difference.

ALDA cleaning?
Linkage hitting full stop?
Compression test.
Clean/poptest injectors.

If your top speed is 60 MPH, sounds like it is starving for fuel. Have you replaced the fuel filters?

Also be sure to check for full travel of the linkage from the accelerator pedal.... many a person on the forum has ' discovered' 20 mph more top speed just from that system...

The W123 rubber throttle bushing can easily cause the lack of full throttle travel due to its design and failure when it wears out. The W126's are not as likely to have throttle travel issues.

Is this a turbo or N/A motor?
I got 800k miles out of a N/A but in the end it was very sick. The motor had been properly maintained from new. I wish you luck with you dream of another 400k miles! If i were you I would consider a low mileage second hand motor if you are short on cash. It sounds like you have a nice G with a motor thats close to its use by date.

He's talking kilometers, not miles. Note that he's a fellow Brit from Canada (Canadians and Australians are all Brits, aren't they? :-0 ) and they went metric long ago.

Frozen rings might lead to the blowby. Folks have had success running water injection to loosen the rings, but it's not trivial. Check compression. And plan to replace the engine at some point. If you're not getting velocity or mileage it may be the most expedient path.