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OM617 Low Speed Stalling?

Started by amilio, 02 November 2023, 08:22 PM

amilio

Hi all, my sister and I are completely stumped on this issue. A few days ago the car began running roughly at idle when cold, but would smooth out. Then yesterday while braking to a stop, the engine suddenly turned off. This issue also occurred twice before while she was backing the car up, only then it was the brake sensor light that came on for some reason instead of the battery light.

Oil level is good, battery/alternator is good (first thing I had her do was replace the voltage regulator, which was pretty worn down). My initial thoughts are that there is some kind of issue with the shutoff valve, or a fuel blockage (tank screen)/air leak that clears up at higher speed. I had the valves adjusted in July, but maybe they are too tight? I also had the primary/secondary fuel filters replaced then too. I saw a video that made me think it could be the lift pump or other IP check valves.

The issue has continued to occur somewhat randomly when coming down to a stop. If anyone had advice on what to check it's greatly appreciated!
1979 300 SD "Liesel", 282k Miles

daantjie

I would check out mercedessource vids on YouTube if you have not done so already.  Kent is a huge dieselhead and he has tons of videos on diesels and related issues. 
Daniel
1977 450 SEL 6.9 - Astralsilber

amilio

Yes, that was what made me think of the lift pump. I've been watching his vids since before I bought the car, hence the voltage regulator; he said the only time he had ever been stranded in a diesel was when the voltage regulator got too worn down. I definitely feel it's a fuel issue, it would just be great to narrow it down before I have the shop give it a go.
1979 300 SD "Liesel", 282k Miles

amilio

I was able to get a video of what happens right before the engine cuts out. There is a major "stutter" when the throttle is released.
1979 300 SD "Liesel", 282k Miles

amilio

Good update is that the shop seemed to be able to figure out the issue; the primer pump had developed a leak, so that was removed and cleaned/resealed. They also cleaned out the vacuum shutoff. Not quite sure what that last one entails, but regardless, that seems to be what the problem was as it's running well now.

On a side note, has anyone noticed that replacement voltage regulators seem to be taller than the stock one? Both replacements (Monark and Hella) had the plastic shroud up 2CM higher on the teeth so seems like it rubs. Haven't had any issues, but seems weird.
1979 300 SD "Liesel", 282k Miles