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deepthought · 12-09-2012, 04:05

I have an Mercedes OM-636 engine. The other day when we where out it started making a popping sound and seemed like it was loosing power. It sounds like its from the air intake. So I shut the engine down and made a quick check of all the usual fluids (oil, radiator) everything seemed fine.

I tried to start it again but it wouldnt start. So I went back to the engine and started checking again. And found the Fuel filter looking a bit dirty so I removed them and replaced them with new ones.

Tried starting again and it very hard to turn over. I almost have to hold the starter on for 20-30secs to get the engine cranked over.

Anyways it started but still with the noise and if I have it in a lower idle and put it in gear it will die.

I made it back and as we where getting back there was a bit of white smoke coming out. so we dropped anchor and shut down the engine for the night.

Yesterday again I got it started with difficulty when I started it a lot of black suit falls into the water from the exhaust. And now there seems to be more of a blackish smoke.

Theres no metallic knocking sound no water in the oil or oil in the radiator.

There is gas going to each of the injectors the internal fuel filter is clean.

I was playing around this morning with it and cranking it a little and noticed that the number #4 (last glow plug) felt burning hot while the others where cool but I am not sure if that is normal or not.

I brought it to a yard here where we currently are anchored and they want 1000eurs just to take the engine out and then go from there. It seems a bit high so I am hoping I can find some suggestions or I will sail back 100miles to another mechanic if I have to since I know his prices where reasonable.

Any help would be greatly appreciated. Can give any more info if requested or post pics or videos of anything if needed.

Can also try anything and post results.

Thanks

vientoman · 12-09-2012, 04:27

you say "There is gas going to each of the injectors the internal fuel filter is clean"

maybe that's the problem......it a diesel isn't it? . ,mainly just kidding....I know you meant "fuel". I once filled up my "gas" volvo station wagon with diesel because the station accidentally installed a green handle on the gas pump. It got me down the highway far enough that I had a looooong walk back.

Wish I could offer some eacellent advice but I'm sure you;ll get some helpful hints from ll the experienced people on this forum. I love mercedes diesel engines. It's probably something simple and it can be resolved easily once it's diagnosed.

good luck......although luck has nothing to do with engines.......

S/V_Surya · 12-09-2012, 04:54

Since the problem started suddenly I am going to rule out adjustments to injectors or pumps. You need to do a compression test if you can before pulling the engine. There are two things that make a diesel go fuel and compression. My guess is a blown head gasket.

terrylad · 12-09-2012, 04:55

Why would the mechanic want to remove the engine? Is it inaccessible?

White smoke can be either unburnt fuel or steam, and this sounds like unburnt fuel, as you've checked for typical blown head gasket symptoms.

Unburnt fuel can be caused by faulty or gummed-up injectors. Sometimes you can identify a faulty injector by loosening each injector fuel line nut, in turn, so that the fuel squirts out while the engine is misfiring. The faulty one will have very little or no effect on the engine's running.

Not sure about the glow plug. See if you can disconnect it and if the symptoms change, chances are its affecting the engine.

A faulty injector pump can also cause these overall symptoms. There's very little one can do with IP's, other than remove the unit for testing in a diesel workshop. Either way, you'll need to get hold of a competent mechanic with facilities to test and if necessary, rebuild the failing components.

Your symptoms don't sound like dirty fuel problems, or air or water in the fuel issues. But you should eliminate those possibilities anyway as a matter of course.

Good Luck.

Charlie · 12-09-2012, 06:35

I have an two Mercedes diesels in automobiles. I have used this website to help me Mercedes Diesel Maintenance tips Have you checked the airfilter? The mixing elbow? Did you take on fuel recently? Have you tried using a Jeri can as a direct fuel source?

gjordan · 12-09-2012, 16:57

Popping back thru the air filter would indicate a burnt intake valve, and that screws up the whole air flow to the engine which would give you more power loss than the loss of 1 cylinder would. The hot glow plug is probably a completly seperate issue. They are supposed to get hot.VERY HOT. A Mercedes will start with 2 faulty glow plugs, but you are probably down to only one working which is real hard to get the engine started. The glow plugs might just be a wiring or corrosion problem, but a compression check is the first thing you should do. NO! actually the first thing you should do is get far away from the yard that wants to yank your engine. I have had Mercedes diesels in cars and one in a boat and they are a really good engine, but the parts are expensive. Keep us posted as to the outcome._____Grant.

**Ex-Calif** · 12-09-2012, 20:56

Misfiring can be anything from air filters, dirty fuel, injector timing, piston blow by, valve blowby, timing or failure to blown head gasket.

I would not be pulling the engine immediately but there are a lot of troubleshooting steps for this one.

I would sail back to your known/cheaper mechanic. I mean it is a sail boat after all, right? And at 28 feet you should be able to anchor and sail without an engine. May need a tow for a marina entrance perhaps...

deepthought · 13-09-2012, 05:17

We are drifting today to try and make it back the my last mechanic. The engine does start just very very hard. But this morning when we where leaving I sprayed some WD40 in the intake as we where turning it over and it kicked over pretty fast. I seem to have plenty of RPMs just loss of power if I try to do anything or turn the throttle down it will die. Have to keep it revving fairly high. The engine seems to get around 5deg hotter then normal. I just used it to keep off the rocks as we where pulling anchor.

Thanks for the tips Ill be trying to make it to the mechanic and hopefully he can diagnose the problem better then me.

@gjordan: I tried to remove the one glow plug that was getting hot but think I broke it because I couldnt get the wiring off it and the screw is just turning. Didnt take the plug out and its no longer getting hot. Found I can get new glow plugs for around $50 for a set of 4. So I will just replace them at the same time.

Thanks again.

Tingum · 13-09-2012, 05:48

I'll go along with gjordan. Might just be two unrelated things, a faulty glow plug, which you would not notice with all good cylinders and a compression problem, (valve Piston) The compression check is the cheapest diagnostic start, followed by an oil sample, then depending on the results, pulling the head. Hopefully there is some working room as pulling the engine should be a last resort. Those are very tough engines and a major failure is very rare. How many hours running time on it??

donradcliffe · 13-09-2012, 05:50

I've heard of Mercedes breaking valve springs--you might pull the valve cover off and take a look.

biggles72 · 01-05-2013, 04:14

And the problem was..........?????????????

deepthought · 01-05-2013, 04:16

Stopped working and was too much to repair. Removed it

no longer a problem.

biggles72 · 01-05-2013, 04:40

Thanks for the reply.

I am in the same situation except besides being a little smelly runs perfectly well. (perhaps needs an exhaust seal tightened?) I inquired to get it rebuilt from that company in the UK, and sadly they no longer offered rebuilds of the OM636.

Can only buy rebuild kits which is no use to me as I do not know any diesel mechanic I would trust to rebuild it here in Thailand anyway.

So the answer. Just keep on motoring and trust she gives me years more of trouble free smooth 2 liters per hour motoring.