Greetings,

My 1983 300TD (OM617A) was accidentally run on approximately 50/50 gas/diesel for about 50 miles. Now it makes a loud noise, sounds a little like injector nailing but way louder, in time with engine RPM. Switching back to pure diesel didn't help (there may be some residual gas, but I did drain the fuel filter). The noise happens even holding down the stop lever and cranking it over, turning it over without it running. The sound seems to come from the front of the block somewhere - not sure where.

The engine sounds pretty normal except for the noise, and it even drives around the block ok, although I'm reluctant to drive it anywhere this way. I haven't run a compression test yet. Blowby doesn't seem to have increased. It still starts about like normal, so I doubt the compression has dramatically decreased. There was a lot of soot coming out the exhaust pipe while it was running on half gas. It ran rough with gas in the system, but with diesel it doesn't seem to shake any more than usual.

It's a rust-free car, and I've replaced all the suspension bushings and whatnot, so if the engine is toast, a new used one is a possibility. I used to have a good low-mileage OM617A with the wagon head in a rusted out car, but sold it - too bad.

Any speculation about what may be wrong would be appreciated.

Post a video clip so people can hear the sound. Won't get any definitive help without it.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

A loud sound like you describe is usually a good sound, meaning not something deep in the engine. My engine made a strange sheet-metal sound that was faint at idle and greatly increased ~2500 rpm. I couldn't track it down, but knew it couldn't be serious. I thought most likely the fan clutch, so bought a new one. With the fan belt loose, I spun the alternator and found the sound was the alternator's fan blades barely hitting the tensioning bracket.

I doubt that driving moderately on 50/50 mixture for 50 miles would have damaged the engine. Some talk like gas is "more potent", but it has less energy content. I think a bigger concern is that it offers little lubrication for the injector pump, but you still had diesel in the mix for that.

I forgot to check the alternator fan. The engine was shaking really bad on the gas/diesel mix, it could have wiggled something loose.

Normally the car runs with about 1 oz/gallon of two-stroke oil, to help the injection pump out. I actually added the usual dose of two-stroke about a day after it was filled, but didn't notice the unusual smell.

I'll get a video up later unless it's the alternator fan.

Did you drain the fuel tank also?

__________________
'85 300D Cal 280,000 miles
'14 GLK 350 60000 miles

The alternator fan looks clear, but I didn't take the belts off and spin it. A/C compressor started dragging and preventing the car from starting about a year ago, so I took the belt off and never fixed it properly (didn't work when I bought the car anyway). Perhaps a good diagnostic step at this point would be to remove the other three belts - reduce the number of rotating items and see if the noise goes away.

Video here:
OM617 noise after running with gas/diesel mix - YouTube

The stop lever stays down in the video because the spring that returns it is missing. It's missing because the casting on the injection pump that would normally retain it is broken. It hasn't seemed worth replacing the injection pump (or it's housing) over that detail.

The fuel tank is not drained yet. It's running on a separate container of diesel in the video. For a while, I was running it off a 1-gallon can of diesel, but then I had to move it out of the garage for a while, so I made a little plastic tank out of an old oil container.

Here is a video of the noise:
OM617 noise after running with gas/diesel mix - YouTube

The alternator fan doesn't seem to be hitting anything, but I didn't take the belts off and spin the fan yet. Probably would be a good diagnostic step to remove all the belts and see if the noise goes away.

The injection pump casting that holds the thing that returns the stop lever to the normal position is broken. It hasn't seemed worth replacing the injection pump over, and it means I can turn the engine off and crank it over.

Do you have a stethescope or a long screwdriver? If so put it on the valve cover and see if you can tell if the noise is coming from the valve train. It sounds like something in the top of the engine to me. Not a rod or main bearing. Put it on the vacuum pump and listen to that also. Watch out for the belts.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I did that earlier, but the car was outside, it was dark, and I didn't check the vacuum pump because I was worried I'd jam the fan. Anyway, I just redid the test, here are the results:

Valve Cover: I can hear the noise, but it's pretty loud in general in the garage
Vacuum pump: The noise is very strong here. But what would the vacuum pump have to do with the fueling mishap? Coincidence? Shaking?
Exhaust manifold: Sounds good.
SLS pump: Sounds fine
Other accessories: Sounds fine
Injection pump: Sounds kinda weird, but I've never listened to one of these before, could be normal.

The noise gets maybe a touch louder with the valve cover cap off, but it's not a super dramatic difference.

Has the car ever had a valve adjustment?

I think your next step will be to remove the valve cover and see what's going on.....if your lucky, the gas mixture caused a lot of carbon to burn off the valves and after adjusting them all will be fine...

If your not lucky, you will have a bent valve or broken guide....

Any new smoke from the tail pipe?

Also if you get the car sounding good again....let's do some maintenance..... Get rid of that red top battery and let's replace that injection pump....get rid of the spring.....

__________________

Sounds like a broken piston or a loose wrist pin to me.

__________________
'83 300D, 126K miles.

cooljjay: Last valve adjustment was about 12K ago. There was extra smoke when it was running with the gas mixture, but the smoke is back to normal (minimal) now. Valve adjustment fix would be great - I'll try that shortly (might have to be tomorrow evening).

rscurtis: The only way I can think of to test that is to pull the engine out and look. If I can't find a fix anywhere else, that's what I'll do...it'll be an opportunity to replace every last gasket and seal and hose at once instead of doing them as they fail.

Would the noise from a broken piston/wrist pin lessen with the injector line loosened so it wasn't firing?

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Update: Pulled the fan and power steering belt in preparation for taking off the vacuum pump. But I don't think it's the vacuum pump. The sound is very loud even turning the engine over by hand. Resistance from compression isn't that bad at the point the sound occurs.

Doesn't appear to be any of the accessories on the front of the engine.

I'm reluctant to fully disable the car in my garage at the moment, because I have to replace a head gasket on a different car this week, and it's snowing outside.