Hello,

I inherited a MB Unimog with OM616.911 engine.
Suffers from what appears to have been described as "nailing". It became worse after the injectors were rebuilt at local Bosch injection shop. Planning on replacing the DV springs, o-rings and crush washers.

Questions:
1) torque specs and procedures for DV
2) IP adjustments for fuel shutoff. From what I can tell when throttle is shut all the way off the engine should quit. It doesn't, chugs along at ~400 RPM and we have to use the clutch to stall it. There is no 12V pull/hold plunger for fuel shutoff like I've seen on other diesels.

Thanks, Dan

I looked up in your stats it is a 71.

Look in here for the procedures on delivery valve O-rings and crush washers. The main thing to remember is that the delivery valve holders (sometimes called pipes in the manual) are in inch pounds not foot pounds or obviously the metric equivalents.

http://www.peachparts.com/shopforum/diy-links-parts-category/146034-fast-navigation-do-yourself-links.html

However, it is better that you check other things that can cause nailing.

Low compression caused by cylinder, piston, ring wear.

Valves needed adjusting (that effects the compression)

If it has a timing chain that stretches and changes both the valve timing (messes with the compression) and the fuel injection pump timing making. You can change the fuel injection pump timing but that won't correct out of spec valve timing. Look in the repair links on methods to check the timing chain stretch.

Fuel injection pump timing. Timing too late or too advanced can cause nailing.

Injectors can cause the nailing. You are presuming the fuel injection shop did a good job on them. You did not say if when they rebuilt them the put-on new nozzles.

Bad fuel can cause the nailing.

Are you having any smoke issues at any time while the engine is running?

Good luck

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84 300D, 82 Volvo 244Gl Diesel

Thanks for the link
Engine has been overhauled. Injectors were rebuilt at that time.
New bearings, rings, cam, cam followers

Don't know if new nozzles were used. The shop we used was a local Bosch authorized facility we used before and personally knew the rebuild guy (since passed away)

Multiple different stations (and states) of on road/off road fuel, no change.

It does haze, not the cleanest burning diesel I have.

It has always started hard, before and after rebuild. Yes, am fighting with some air in the system but even after running and warm doesn't start good and definetly sounds like one cylinder is working harder than the rest. It has new Bosch glow plugs as well.

Dad wished he had the pump overhauled when engine was torn down but never happened. His research was leaning towards DV for next step but never got around to it.

Today I stopped by my local Bosch pump shop and bought a gasket kit for the IP, they didn't have seals separately. They ordered a set of DV springs in case I find any broke/compressed.

If they installed new nozzles, you would have been billed for those.

What color is the haze? When my Volvo diesel sat for a year, I had had a haze of gray smoke at all speeds as it turned out in my case due to sticking piston rings. One time when I timed the fuel injection pump wrong, I got copious amounts of white billows of cloud like smoke. I turned out that when the fuel injection pump is too retarded what I thought was white smoke was me seeing the atomized unburned fuel.

Which brings us to something else. If it hazes at idle hold a bit of cardboard next to the tail pipe and pull the cardboard away and carefully smell it. It may smell like fuel or oil. Either one of those gives you a clue what is causing the haze.

It is tough to know what to say without being there. So, I can only speak in general.

Might be you have to go back to some basics. Line up the timing makes and see if the camshaft timing is within specs.
Recheck the valve adjustment
Time the fuel injection pump in your case using the drip method.
And see if it makes a difference.

To what extent was the engine overhauled. New pistons and liner? Or was it the same pistons and liners with a new set of rings?
Was the cylinder head fully overhauled meaning that the valves were removed re-ground and the valve seats reground and new valve guides as needed and new valve stem seals?

You might pull the injectors and take them to a different fuel injection shop and see if they will test them for free, getting a 2nd opinion. Find out before you go what your opening/pop pressure is for the injectors.

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84 300D, 82 Volvo 244Gl Diesel

I get that, however I wasn't billed. As stated I inherited this from my dad who has since passed away. Knowing the pump builder, if it needed parts he would have replaced them. Price wasn't a issue. I would trust he did it right vs a 2nd opinion from someone I don't know.

It did not get a complete rebuild. No pistons or liners. Extent of head work, don't recall. Knowing how meticulous dad was on details...I'd be surprised if the timing and valve adjustment was off. Will have to dig through his notes as he even kept a record of all the bearing clearances during assembly.

The "nailing" is random harsher diesel knock "cracking". If it was consistent I could narrow it down by cracking injectors. Replaced some leaking crush washers on the LP, pulled the relief spring on the pump and found it compressed to 21 MM stretched to 27/8 and now showing 13 psi at the filter head.

Have read enough threads about people finding compressed DV springs to consider it a legit concern. Wouldn't be surprised if there is internal pump damage as it was low on oil and had poor maintenance when we got it.

Need to flip the cab so I can easily access the side of the pump and check linkage and try to figure out why it won't shut off.

Raw fuel, know that smell. Trying to start the ole IH3500A in -20*F without a block heater.

Free....not likely.

This is not my first, or only Diesel, just my only old MB.
More familiar with setting timing and DVs on my P7100.

Best wishes.

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84 300D, 82 Volvo 244Gl Diesel

1971 would be correct.
Looked through many of the DIY links but none appear to address the fuel shut off for this model. It doesn't use the same setup as the 240D cars.

Have you had any experience with this model pump?

No. You might try also posting over here:Here's the place to discuss 1979 and earlier models!
Vintage Mercedes Forum - PeachParts Mercedes-Benz Forum

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84 300D, 82 Volvo 244Gl Diesel

I'll check it out, thanks again.