Agreed, and that is what I was trying to rationalize out.
Had the engine oil level gone down or started similar, my supposition would have been different.

I did get the hood open last night, so hopefully today I might have some compression numbers.

Onto another thing that’s bugging me...
When I cranked the motor over, there was no fuel ejected from the lines where I disconnected them from the injectors.
I expected it, and got nothing. What I did get was fuel gushing out of the IP side of the motor.
Thoughts?

__________________
2009 Mercedes ML320 Bluetec

Get a helper to crank the engine or whatever. You have to identify the pretty much exact location. Where the fuel is coming from. I have never actually seen one of this models engines.

Fortunatly it does not sound overall like you have an internal engine issue.

If I could not establish where. I would close off the relief output of the injection pump. Apply some pressure on the input of the injection pump. If it would not hold say 10 or 20 pounds pressure. I would get a good used injection pump.

From your description you do not only have external leakage showing. You have also fuel getting inside the engine. I suspect it is either the injection pump or the lift pump. Your choices are extremely limited with the fuel pre heater bypassed. As you mentioned.

I personally prefer testing unless a problem is really obvious. You could also disconnect the output of the lift pump and do the same test on it by putting some pressure on the input. I suspect strongly one or the other will not hold pressure. Where they both must to function.

Just my two cents worth. Actually I like this problem from the aspect of what it may cost to repair. Good used injection pumps for that engine should be available fairly cheap if needed. Yours I believe is a pretty rare failure yet things happen. I believe your overall situation is far from dead.

There is no fuel pressure being developed in the base of the injection pump to feed the injection pump elements. So there would be no fuel coming out the injector lines.

To see what the eventual problem is / was .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Any chance that gasoline got mixed with the diesel fuel?

I though I added but did not. If pressure testing the injection pump and anything comes out an injector line. Just screw on an injector.


Otherwise the pressure might be going in a port to the element and travelling up and out the line.

Thats kinda what I was thinking...
Thanks for the conformation!

Thanks for the thought about "gas" dilution, but I filled it myself, about 200 miles ago, so I doubt it.

Ok, so its been a fun couple of days...
Got the hood open...
The Amazon $70 8MileLake Diesel compression test looked great...
If only it worked.....
After I ordered, I spotted multiple NEGATIVE reviews of that tester saying it did not have a pressure retention valve in the gauge....
Some were older, so I hoped/thought maybe it was a bad batch or it was a fault they had fixed...
WRONG!

Every compression the gauge went up and back to zero...
Its weird, as I see a pressure relief button on the gauge head... as did others...
Anyways, its a great set with loads of adapters.... but useless, so don't buy it!
It went back in the mail to Amazon today... as I rolled past HF and picked up their $30 unit... well, $23 after the 20% coupon.

Got it home, checked it for "Compressed Wuhan Virus", put on my mask, and got to work...
The $23 Compression Tester wins, but NOT good news....

Here are the numbers(cold obviously):

#1 = 220psi
#2 = 305psi
#3 = 440psi
#4 = 435psi

So, now we know that its more than a fuel issue, which may have been it, up until the runaway moment...

I'm not sure what a healthy OM601 motor should show on compression test, but I do know that 10% variation across cylinders is the accepted standard.
Either way, I am actually impressed that 3 and 4 are reading 435 and 440 psi with almost 1/4 Million miles on this motor!

So, we have maybe:
1/ Blown HG? Maybe between #1 and #2, although I would expect those two to be more equal, given that scenario.
2/ Piston/Ring damage?

Guess its not a dirty fuel filter, as was suggested over on "Another Forum"....

Tomorrow I think I will do a quick oil injection on 1 and 2, and see if that makes a difference.
I could also do a Leakdown test, but its lots of fiddling about getting the cylinders to TDC... and might not gain me much more info until the head comes off.
Will also drain the oil, and see how that looks.
FWIW, the coolant level is fine, but tomorrow for fun, I might also do a cooling system pressure test.

Comments?

__________________
2009 Mercedes ML320 Bluetec

Do the leakdown test next .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Adjust the valves and try the compression test again.

A leak down test is not only more accurate but also more reliable but a good leak down tester made by OTC is expensive. Most cheap ones are low pressure only which should still be good enough. You start at number 1 on compression stroke (if you can't see the camshaft through the filler cap you may have to try and rotate 360 degrees if you get a bad reading on exhaust stroke) and then you go in the firing order rotating it 180 degrees between cylinders. Balancer should have markings for both tdc and 180.



Hydraulic lifters on the OM601, doesn't need adjustment

Well, I was hoping that would have caused the low numbers.

Only have a HF leakdown tester, but better than nought.
Think I might do a quick Oil injection test beforehand on 1 and 2, and see what happens for fun.

So, at this point, a good guess is I am in to pull the head off.

I have an original MB OM 601 Service manual to hand...
It only discusses leakdown tests and 25% max pressure loss.

It also only discusses head removal with the engine out.

__________________
2009 Mercedes ML320 Bluetec

Why?

Leakdown will tell you if you have a blown gasket between cylinders or a blown gasket between the cylinder and the coolant passage. Just listen to where the air is leaking out. You can even do this test without a tester just put air into the cylinder

Diagnose first fix second

Doesn't that mean I'm pulling the head off either of those 2 scenarios?

My concern would be if its leaking into the crankcase, telling me I lost a piston ring or such... that would be a deal breaker and it will be going to the JY...

__________________
2009 Mercedes ML320 Bluetec

Cheer up! The head is aluminum, so nice and light.