Hey Guys! I'm new here, so if this is in the wrong spot I apologize.

Im looking for advice on an engine that is running rough with cylinder 1 being the culprit.

So my buddy who's a mechanic swapped an '84 300SD OM617A (according to seller has 135k miles) into my '85 G-wagen for me. We replaced the old OM617A that was in the truck since '06. It had some bad piston slap.
Anyways, during the swap we replaced pretty much all the seals and gaskets, including head gasket. We replaced the glow plugs, timing chain tensioner, water pump, thermostat, lift pump, lines, hoses, belts, filters, fluids, ect.
Came time to start her up and it would crank and was on the verge of starting but couldn't get it to start.

My buddy became busy with work and preparing for a baby, so I had the truck taken to a reputable diesel shop in town.

After being there an hour they gave me a call and told me they had it started! running pretty rough though. I guess during our valve adjustment we had them too tight. So they adjusted the valves to be in spec. They also had to mess with the IP and were able to bleed the system better.

Good news: it doesn't have any blow by and is running.

Bad news: it does have some white smoke, so unburnt fuel? And it's still running pretty rough.

So they did some more diagnosing and cylinder 1 is not getting hot and seems to be the problem. They said it seems like a problem with either the intake or exhaust valve, possibly stuck open or closed. They swapped the cyl 1 Injector and that didn't make a difference, they also cracked the lines for cyl 1 and that didn't either.

So they want to do a leak down test to determine which valve is the problem and then go from there, they said they will probably need to remove the head and have it and the valves machined so they seat properly and that should solve the problems.

Any thoughts on the problem? Has anybody ever ran into a similar issue with the valves? Do you think there are any other obvious things that could be causing the rough idle? Do you think cleaning and machining them back into spec will solve the problem?

Thanks guys!

I'm no mechanic and am new to the world of Diesels and OM617's so this whole process has been a learning experience for me. Thanks in advance!

This engine has clearance fit on the valves and pistons. If the valves are not completely closed the piston will hit the valve and close it. Leakdown test is a good idea. Cheap diagnostic that will isolate the problem. Go from there. The car not starting because of valve lash being wrong is not good. Most likely they where tight rather than open. Possibly on number one cylinder one of the valves was too open and contacted the piston and damaged the valve. The shop is giving good advice.

Thanks for the input!

We ended up pulling the head and finding a score on cyl 4 as well as several valves not seating right, so have decided to go through with a whole rebuild. I called several shops local to me and the quotes they gave seemed a bit high (similar to metric motors) and most were pretty backed up. So the engine leaves tomorrow for Metric Motors. Turn around time right now is about a month, so I will hopefully be able to finally enjoy this truck by my 1 year mark of ownership! Haha

Any recommendations for repairs/maintenance to perform while the engine is out?

We are going to make sure the cooling system is in tip top shape, flushing the radiator really good with some cleaner. It looks to be in pretty good shape from what I can tell.

The triple K turbo is getting sent off to a shop recommended by Metric in CA for rebuild as well. (very reasonable price too)

Injectors were pop-tested and came back as excellent condition.

The only other thing I'm thinking thats left to be serviced is the fuel system. New filters will be ordered, probably should flush the lines. I also should probably have the fuel tank drained and cleaned, any advice on this?

Thank you all in advance!

Kurtis

Because of the investment in the rebuild, if the rad is anything short of excellent I'd replace it with brand new. Same for the oil cooler lines, have them reconstructed with high end hose. Flush the oil cooler well.

Have the starter rebuilt unless it is excellent.

Inspect or replace/upgrade the battery cables.

Inspect transmission front pump seal for leaks if an auto.

Post pics and good luck!!!

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