Too much of a good thing, MEP-803a wouldn't stop!

[m32825]

I set out to change filters and fluids this morning and decided to run the unit briefly to make sure everything worked beforehand. It started up and ran just fine, as expected. Then I turned the master switch to off... and it kept running!

After taking this in for a few seconds I hit the emergency stop switch... and it kept running!

I had less than a gallon of fuel in it, so it was just a matter of time before it came to a stop. While it ran on I started investigating and found that the fuel solenoid linkage had become unattached from the lever. I moved the lever to the off position and the unit shut down. Whew!

I had previously noted the linkage was loose and tightened it, this time I used some Loctite on it. Now it starts and shuts off like it's supposed to and I'm hopeful I won't see this problem again!

-- Carl

 

[Blackbear]

Interesting, I wonder by opening the side door and flipping that toggle switch, I forget what it's called wouldn't that work too?

 

[AfghanVeteran2010]

Interesting, I wonder by opening the side door and flipping that toggle switch, I forget what it's called wouldn't that work too?

Dead Crank Switch?

 

[Blackbear]

It has been a while since I've looked at it but I think there are two switches, one is dead crank.

 

[m32825]

Interesting, I wonder by opening the side door and flipping that toggle switch, I forget what it's called wouldn't that work too?

Good idea, that's where I was headed when I spotted the linkage problem. That might have done it, but something was keeping the fuel pump going with the other two switches off, so maybe not...

-- Carl

 

[Bmxenbrett]

I bet the fuel rack got jamed up or the linkage for the shutoff wad binding. Did you see the fuel shutoff move?

 

[m32825]

I bet the fuel rack got jamed up or the linkage for the shutoff wad binding. Did you see the fuel shutoff move?

No binding at all... the linkage totally disconnected, leaving the fuel shutoff in the "run" position. Manually moving the fuel shutoff to the "off" position stopped it.

-- Carl

 

[Bmxenbrett]

I bet the fuel rack got jamed up or the linkage for the shutoff wad binding. Did you see the fuel shutoff move?

 

[Guyfang]

Have seen this problem before, on the 802A and 803A. One way to stop it if you THINK the electric fuel pump is still running, is to simply unplug the electric fuel pump. But it is still going to run for a bit, until it empties the fuel filter bowl. Remember, it a diesel. Fuel, compression and air. That's all it needs. That's why all diesel engines have a fuel cut off solenoid.

If it didnt shut off with the S1 start switch or the S17 emergency switch, S10, the Dead Crank isn't going to matter any way. All it would do is cut out the fuel cutoff solenoid, just like the S1 and S17 would do.

If you think that the fuel pump is NOT being turned off, go to J3 Diagnostic cannon plug, pin K to ground with your multimeter. Voltage present? Then the pump is still energised, probably a stuck relay. No voltage, then it's always possible that due to the rack being in the full full position, that the vacuum caused by the consumption of fuel to the engine, continues to draw fuel. The fuel pumps have a check valve in them, but it only prevents fuel from flowing BACK into the tank. I once saw a 60 KW, with the rossa master IP stuck in the full fuel position run at the speed of sound, with EVERYTHING turned off. The only thing preventing it from blowing sky high was the linkage. Rather foolishly, that's just what we removed, in an attempt to shut it down by hand. Had to change our underware after it came apart.

The linkage often vibrates loose. Mostly you notice it because your engine oscillates, or tends to run high and low on the hertz meter. So you fix it before it falls off. I think the linkages came originally with a nut and washer holding the knob to the slider linkage. I believe at some point later, that was changed to a self locking nut, to prevent that problem.

 

[Haoleb]

Probably an easier way to stop it is just to cover the intake hose and cut off the air. Like a runaway diesel you pretty much just have to cutoff any air. Then you wont have to bleed the fuel system like you do running it dry. Then there is always manually moving the fuel cutoff solenoid linkage.

People sometimes have a similar issue with the 12 valve cummins diesel in my truck. The fuel cutoff either gets stuck on or off and it will not shut off or not start. But simple solution with these all mechanical diesels just move it by hand

 

[Daybreak]

Howdy,
I believe I know exactly what he experienced. The shutdown solenoid has a black thumb screw type nut. With all the shaking going on, it vibrated loose and fell off. The electrical did its thing, and the solenoid moved, but was not attached to anything to actually shut it down.

I was almost in the same boat, but caught the black knob just when it fell off, and re-connected it and all is well. And tight.

 

[Bmxenbrett]

Probably an easier way to stop it is just to cover the intake hose and cut off the air. Like a runaway diesel you pretty much just have to cutoff any air. Then you wont have to bleed the fuel system like you do running it dry. Then there is always manually moving the fuel cutoff solenoid linkage.

People sometimes have a similar issue with the 12 valve cummins diesel in my truck. The fuel cutoff either gets stuck on or off and it will not shut off or not start. But simple solution with these all mechanical diesels just move it by hand

It sounds easy and works but the intake to the engine on thesr are way up in there and can run on very little air. I had one rev way up in me...still cant remember how i got it shut off as i was running around trying anything. The rack ended up being stuck in the engine on that unit.
Theres a plug on the front cover by where the shut off solenoid connects i recommend having that off next time u start it..and a flat screw driver handy

 

[m32825]

Howdy,
I believe I know exactly what he experienced. The shutdown solenoid has a black thumb screw type nut. With all the shaking going on, it vibrated loose and fell off. The electrical did its thing, and the solenoid moved, but was not attached to anything to actually shut it down.

I was almost in the same boat, but caught the black knob just when it fell off, and re-connected it and all is well. And tight.

Yep, that's what happened!

-- Carl

 

[Farmitall]

Had that likage fall off one of my sets also.

The lever appears to be of soft metal so over tightening could strip out the threads. I tightened mine and used some red loctite on it.
If it falls off again, I'm going to figure a way to put a bolt from the inside facing out and use some stop nuts to jam things together tight.

As for shuting off the air......it doesn't always work on a diesel engine.

While responding to a fire one night, the first due engine company was laying lines and the pump operator was putting the truck in pump gear. The green light on the pump panel came on to tell the operator that it was OK TO PUMP.
Well, he throttled up and the truck went back into road gear, running down and pinning a firefighter underneath it. The engine was revving......maxing out rpm wise. This happened just as I was pulling into the driveway at the scene. I watched him get run over.

I jumped on top of the truck and knocked the rain cap off the filter intake and stuck my helmet over it cutting off the air then emptied a water extinguisher into it to saturate the filter.......it still ran!

The truck was old and the engine very worn( the truck had no business being in fire service) ....later investigation revealed it had two small cracks in the intake manifold and so when the intake was blocked/restricted, it started sucking crankcase oil by the rings and valve guides along with enough air for combustion. It was billowing thick black smoke with no sign of shutting down.....meanwhile the rest of my crew was conducting a rescue to lift the truck to get the trapped firefighter out from under the truck's frame and muffler.
I stabbed a cut through a rubber boot that connected the air filter duct to the intake manifold and injected two full pressurized water extinguishers and a very large dry chemical extinguisher into the intake and it finally shut down.

The firefighter was rescued by the others in my crew using the jaws to lift the truck enough to pull him out. He suffered multiple fractures and second degree burns and was out of work for around a year. He recovered fully and returned to work.

This truck is probably the exception to the rule, but it took alot more than just blocking the air intake to stop the engine. If it hadn't shut down my next action was going to be to stick a hydrant fed 1 3/4 inch water line into the intake and hydraulically lock the engine up. It was junk anyway....and after the investigation, it was scrapped (10 years and a million dollars worth of medical bills too late).....and it almost cost a man his life.

 

[DieselAddict]

A co2 fire extinguisher will do it reliably.

 

[Farmitall]

A co2 fire extinguisher will do it reliably.

Yes probably in an engine that had an intact intake manifold where the co2 wasn't diluted by air leaking closer to the intake ports.

I hope not to have the occasion to find out..

 

[Guyfang]

A co2 fire extinguisher will do it reliably.

As as long as you have one handy, and no one has used it to cool the beer down.

 

[windyhill]

Have seen this problem before, on the 802A and 803A. One way to stop it if you THINK the electric fuel pump is still running, is to simply unplug the electric fuel pump. But it is still going to run for a bit, until it empties the fuel filter bowl. Remember, it a diesel. Fuel, compression and air. That's all it needs. That's why all diesel engines have a fuel cut off solenoid.

If it didnt shut off with the S1 start switch or the S17 emergency switch, S10, the Dead Crank isn't going to matter any way. All it would do is cut out the fuel cutoff solenoid, just like the S1 and S17 would do.

If you think that the fuel pump is NOT being turned off, go to J3 Diagnostic cannon plug, pin K to ground with your multimeter. Voltage present? Then the pump is still energised, probably a stuck relay. No voltage, then it's always possible that due to the rack being in the full full position, that the vacuum caused by the consumption of fuel to the engine, continues to draw fuel. The fuel pumps have a check valve in them, but it only prevents fuel from flowing BACK into the tank. I once saw a 60 KW, with the rossa master IP stuck in the full fuel position run at the speed of sound, with EVERYTHING turned off. The only thing preventing it from blowing sky high was the linkage. Rather foolishly, that's just what we removed, in an attempt to shut it down by hand. Had to change our underware after it came apart.

The linkage often vibrates loose. Mostly you notice it because your engine oscillates, or tends to run high and low on the hertz meter. So you fix it before it falls off. I think the linkages came originally with a nut and washer holding the knob to the slider linkage. I believe at some point later, that was changed to a self locking nut, to prevent that problem.

MEP-803A ran flawlessly this last storm for over 24hours. went to shut it off and it wouldn't. went inside, messed with a few things and came back out, a few min later is slowly died. After a search I found this thread, sure enough I went out and the black knob / bolt linkage had rattled loose! some blue lock tight and tightened her down and it works like a charm now!!! Thanks for saving me I'm sure a lot of time figuring it out!

 

[CallMeColt]

MEP-803A ran flawlessly this last storm for over 24hours. went to shut it off and it wouldn't. went inside, messed with a few things and came back out, a few min later is slowly died. After a search I found this thread, sure enough I went out and the black knob / bolt linkage had rattled loose! some blue lock tight and tightened her down and it works like a charm now!!! Thanks for saving me I'm sure a lot of time figuring it out!

This is what will happen if the linkage comes off most of the time. It will empty the fuel filters as they're slightly above the injection pumps, so it knows no better & keeps going until starved. If you have a siphonage issue, you probable have something more serious going on.

In my opinion, that is why the electric lift pump was designed in & not the mechanical, so it would prevent the less knowledgeable end user (military) from having a runaway unit if the shutoff solenoid failed. I have seen incorrectly installed injection pumps not shut down as well & it prevents them from destroying the engine completely due to running dry of fuel before major damage is done. Wouldn't always be the case!

 

[dav5]

As as long as you have one handy, and no one has used it to cool the beer down.

Guyfang it sounds like you have first hand knowledge of this happening.