Project 240d cranked after 14 years- runaway diesel - PeachParts Mercedes-Benz Forum

dinman · #1 03-10-2018, 01:38 AM

'83 240d. Has been sitting for 14+ years. I have had it since January but haven't messed with it much, well today it started. Instantly became a runaway diesel. Sounded smooth, not much smoke, and I was able to cram rags into the intake to stop it within 30-45 seconds. What usually causes this? Could an improperly installed throttle linkage do it? Did I possibly damage the engine? It sounded smooth shutting down

Before cranking I have-

Changed both fuel filters

Running off a tank of new diesel/diesel purge mix in separate canister

Valve adjustment

Going to look into it more tomorrow

optimusprime · #2 03-10-2018, 04:52 AM

You should look for a vacuum leak. I think these have a valve to close the engine down by vacuum ,no vacuum then it wont close down

barry12345 · #3 03-10-2018, 06:32 AM

Just the rack in the injection pump stuck open is a good possibility. Could be burning base oil as well as fuel but I doubt it. Most these injection pumps have an inspection plate that can be removed to inspect the fuel rack.

It can just need a helping hand and lubricant to get the rack freed up. The lever on the outside of the injection pump does not totally indicate the position of the rack inside the pump.

Fourteen years sitting could easily cause this. A true runaway is when the base oil becomes the fuel for the engine. Had this occurred you possibly may have been too frightened to get it shut down. In a true runaway the engine can sometimes rev up till it self destructs.

Personally I would not attempt another start until the fuel rack freedom is checked. Then even if you think you have solved the issue. Have a real quick close off for the intake system at hand. Also do not force the rack. As I am unsure of somehow the items it controls could be seized. Hitting it with penatrating oil and letting it work awhile would not hurt anything if it is stiff or really stuck.

I just do not know if that is even a possibility. Others with more knowledge can respond though. All I really know is that it would be the first place I would look into if it were my car. As soon as that is solved checking for seized up or very lazy pistons in the brake calipers would be next on my list. Plus you may want to clean the bulk of any rust off those rotors if there.

A lot of this is climate related. It is really great that even here in eastern Canada. A diesel engine can sit that many years and there is a possibility it will not be seized. Yet it will still be an all day sucker to deal with many of the problems. That result from sitting in this climate even for partially that long.

Hopefully it is just a simple problem from sitting unused for so long. Just my thoughts on your issue. Nothing to take to the bank. As like a bad check my thought could bounce.

tdoublenastywitit · #4 03-10-2018, 08:40 AM

Is it really a run away diesel or is it just your idle stop bolt, linkage is out of adjustment AND your vacuum shut off is not working?

I think if your linkage was disconnected or way out of spec your manual engine shut off won't engage.

This is the first thing to check.

If it's a real runaway diesel and it's running on motor oil u got a bigger problem

dinman · #5 03-10-2018, 09:28 AM

I think it really was a runaway. I've never heard one of these rev this high, and it lost a considerable amount of oil. I've never seen a runaway before.

It cranked, idled smooth for maybe 1-2 seconds, then full throttle.

dinman · #6 03-10-2018, 10:27 AM

To add^- I cant get the idle knob on the dash to adjust. At least I guess that's what it is, my 300d doesn't have that. So the stop won't engage because it's caught by the cable running to the idle knob. Maybe that caused it? I say I lost a lot of oil- it was on the low part of the stick, which I would think that if it really was running on it's own oil, it would suck up alot more than that. Maybe I'm wrong.

torsionbar · #7 03-10-2018, 11:27 AM

You said it was sitting for 14 years, do you know the reason why it was parked? Could it be related to the runaway condition you experienced?

barry12345 · #8 03-10-2018, 12:46 PM

New facts add possibilities. The range of the idle adjuster on the dash of the car. Really does not normally have a very broad range. More of a fine tuning effect than anything.

You can eyeball the lever on the side of the injection pump to see if it is at the stop or lowest point. So it may be a true run away if it is.

Then a test is in order. Make sure to disable the fuel system. Perhaps by loosening all the nuts at the injectors. Stuff some rags under them to catch the fuel.

You may find a better and cleaner way to disable the fuel supply. You just have to make certain it is effective.

Then the car should start and run on wd 40 sprayed down the intake throat. Have a helper present to place a piece of wood or whatever over the throat if it does run away.

The helper will also be useful in cranking the engine over after a glow plug cycle. If you plug in the block heater and it still works. Would pre warm the engine making the wd startup easier.

Of course if the engine starts reving and after you stop feeding the wd 40 in. It continues to do so. This is an absolute test to determine if you are burning base oil or not.

Once you prove it is either the injection pump or the engine is burning the base oil. Is far better than looking at the wrong cause.

Technically if the car had a runaway with the last owner. He probably could not have got the engine shut down before damaging it. I would not try to guess what base oil may be being used by examining the dipstick. Far too subjective to start with.

You are very lucky so far. The engine could have totally seized up in that long inactive period. A combination of moisture and air could have caused substantial corrosion in the piston ring lands. Locking the rings signfigantly in place. Leaving the engine with not even enough compression to even get started.

A few last obscure thoughts. The early 240d 616 engines had a line from the vacuum pump to the intake. If the diaphragm fails base oil can be fed into the intake system.

It would mean in your year that someone installed an earlier engine at one point. It created this problem and variations of it. So they changed the output of the vacuum pump exiting it to the crankcase. Before 1982 I believe.

You do not want to see oil in that line if it goes to the intake system especially. The only effect if the oil filled line was going back to the crankcase. Would be a low or no vacuum issue.

A failure of the modulation valve on the automatic transmission models can allow transmission oil to be sucked into the vacuum system as well. Once again you would see red oil in that line if this was the case. If it could reach the combustion chambers it would burn as fuel. I just am very unsure if it could reach the cylinders. Thinking not very likely or possible.

It was a little curious that the engine idled fairly normal for about two minutes and only then took off.. Anyways better minds and more experience members will probably post on your thread than myself. Give it a little time to see what they think.

Do you know, suspect or see any evidence that the last owner used waste vegetable oil as fuel? It was becoming popular about that time that car was retired. If it was used it changes the approach to the problem.

leathermang · #9 03-10-2018, 04:45 PM

We used to mention run away engines on here.. once in a while....
Larry Bible told about his adventure... it was going so fast he was afraid to get up close
so he was down behind the fender reaching over to try to turn it off
What we started suggesting in situations where the car is new ' to us '
was taking the air cleaner off and having a board to quickly apply to cut off the AIR..
as an emergency measure..
hope nothing was damaged...

dinman · #10 03-10-2018, 06:06 PM

Thanks for the replies guys.

It was super scary. I was waiting on something to explode. But it was unbelievably smooth.

Previous owner was a older woman who parked it due to not being able to drive anymore. It was supposedly running when parked. Car was flooded about 3 years ago, I would say up in the floorboards.

Sadly, I was starting it today and it fired, then died, then upon starting again, I believe the starter died. It just makes a grinding noise now, even with the key off.

Diseasel300 · #11 03-10-2018, 06:24 PM

I'd be willing to bet that the fuel rack is all gummed up in the injection pump. When I went through my IP saga in the SDL, I had one that did the opposite of what yours is doing, it would sort of idle, but refused to increase revs at all. Disassembling the IP showed it all gummed up inside, wasn't WVO residue, but oil that had just turned to varnish. Probably could have been cleaned up and gotten working again, but I said screw it and sourced another IP.

Simpler=Better · #12 03-12-2018, 01:23 PM

Probably just gummed up. Fill the IP with some PB blaster(instead of oil) and pop out the delivery valves(you bought new sealing washers, right?) and check that everything is clean down in there. Don't forget to drain the PB blaster and refill with oil.

It was probably just revving to redline. They're impressive at 5k all right!

x3 on the wooden block at the ready to shut it down quickly.

dinman · #13 03-14-2018, 11:19 AM

Everyone.... It started!! And did not run away. Very short video but it's as smooth as could be. My 300d I jumped it off with isn't even running in this video, that's all the 240.

Maybe the injector cleaner soaking in the IP helped unstick it? It starts up very nicely now.

Now I need a glow plug relay

https://youtu.be/O2TDACU1qq8

leathermang · #14 03-14-2018, 11:48 AM

Before you switch back to the in car tank...
I suggest you check for stuff growing in there...
If you unhook your fuel line at the bottom.....
and pull all the things attached to your tank
You can do a good job of spray blasting it IN PLACE....
I took mine out...and to the car wash...
but once I looked closely I could see I had clear shot at cleaning it in the car...
search for Biobar and other liquid killers you might need..
and blow out all the lines before getting out on the road...

Shortsguy1 · #15 03-14-2018, 04:50 PM

Leathermang mentions "Biobar" in his last post, but I am pretty sure he means Biobor.