MEP-003 malfunction

[Dock Rocker]

I bumped into a problem yesterday that I hope you guy can help with.I went out yesterday for its bi-monthly test run and I had an issue. Probably a big one.

I cranked it up as usual. It cranked flawlessly as it always has. No issues so far. I did about a 20 min run to get things warmed up (that’s really not a problem as it’s 95 with 10000% humidity in Mississippi)

I put a 50 amp RV style panel on the trailer and plumbed it into the genset. It’s worked fine until now. I plugged the house power line into the generator and threw the breaker on the genset. I then threw the breaker on the RV box. Everything worked fine for a minute then I saw an arc flash from the ground on the body of the genset under the control panel. See the picture for what I am talking about.

At that point the idle started going up and down on the genset and it quickly died.

I started checking things and I found that the female side of the 50 amp plug that I plugged into had given way and slipped back into the box. Basically I didn’t have the plug completely plugged into the female side in the RV box. I could not see this when i plugged it in but that’s what happened

I unplugged and killed all of the breakers and tried to restart the generator. It cranked but the idle fluctuated wildly and it died within 30 seconds. When I tried to restart it the fuel pumps do not prime and the starter doesn’t engage even when slaved.

I got fed up with it and walked away before I doused it with gas as it was hot and I wasn’t happy.

Fast forward to today. I tried it again and same thing. No pumps and all that’s happening is the fuel shutoff is disengaging

Now I traced the wires from the body ground looking for bad spots and found none. I pulled the ground lug off and unhooked the ground wires and cleaned them up good as well and the lug itself. I re-torqued the lug and wires.

Now this is where it gets weird. After cleaning the grounds and changing nothing else when I turn it to the prime/ or run position it immediately throws the emergency breaker.

I checked inside the control box for obviously burned or singed parts and they are all clean as they were new. It feels like there is a short somewhere in the 24 volt system that is keeping it from turning over but i am not sure.

Any ideas where to start? Any input would be greatly appreciated!






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[DieselAddict]

In addition to anything you find in a TM to troubleshoot, I would check the +24v supply in the control cubicle to ground with a meter. If you are tripping the DC breaker you have a fault somewhere. Assuming you find one I would then disconnect the VR and check again. My gut is to look at anything surrounding the VR first. That is one of the components that would take a beating in that kind of scenario.

 

[justacitizen]

i would disconnect all of the 24 volt connections from the starter and fuel pumps and see if the DC breaker still breaks then if it doesn't i would add each one back one at a time and recheck . if it breaks with everything disconnected you probably have a short in the harness. don't forget to disconnect the exciter.

 

[Dock Rocker]

I have had the TM’s out and highlighting the areas I think are pertinent. I am not going to he able to do any real testing until Saturday. I hope between the TM’s and the mental horsepower here I can get to the bottom of this.


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[Dock Rocker]

have you checked to make sure the DC breaker on the control panel is working as it should?

I have tried it in the on and the off position with no joy. Beyond that I have not checked it.

That is on the list of things to look at.

I haven’t been able to find the intersection of no crank / no starter engagement at all and the electrical issue created by the bad plug connections.

Stated differently weather it’s making power or not what’s keeping the motor from turning over?


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[jamawieb]

I had a unit do this one time and it was the ground stud for the ground rod, that you are referring to. It was loose and arched causing the same symptoms. Unplug the fuel pumps and then go to prime and run to see if the breaker trips. I bet one of the capacitors on the fuel pump shorted. If that fixes it, just cut the capacitors out because you don't need them.

 

[Dock Rocker]

I had a unit do this one time and it was the ground stud for the ground rod, that you are referring to. It was loose and arched causing the same symptoms. Unplug the fuel pumps and then go to prime and run to see if the breaker trips. I bet one of the capacitors on the fuel pump shorted. If that fixes it, just cut the capacitors out because you don't need them.

That would be so awesome if that was it. I will give that a try ASAP.


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[Dock Rocker]

I had a unit do this one time and it was the ground stud for the ground rod, that you are referring to. It was loose and arched causing the same symptoms. Unplug the fuel pumps and then go to prime and run to see if the breaker trips. I bet one of the capacitors on the fuel pump shorted. If that fixes it, just cut the capacitors out because you don't need them.

Well part of the problem is solved. Guyfangs email and your suggestions Were spot on for the circuit breaker. I unplugged the number 1 fuel pump and no more breaker. Number 2 pump and the auxiliary pump do not cause a short. Will probably snip out the capacitor and see what happens.

The next problem is that now it will not turn over at all. The fuel pumps prime, the fuel solenoid opens but nothing happens at the starter.

Any suggestions on where to go next? I was doing this on a slave from the hmmwv to rule out any potential battery problems.


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[jamawieb]

I would use a screwdriver and jump the starter to see if it actually works because it grounded directly to the ground stud. If it does engage with the screwdriver, then look at the crank solenoid inside the control cubicle.

 

[Guyfang]

Before you jump the starter, try this.

Check from pin 26, on the S1 to TB5-9, for 24 volts when the S1 is in the start position. If there is not 24 volts at the pin 26, then the S1 is bad. If there is voltage there, but not at TB5-9, then you have a wire problem. If you have 24 volts at TB5-9, then go to K1-A1 and see if there is voltage. If you have 24 volts on the K1-A1, and the K1 does not engage the starter, then it can be that the K1 is bad, or the wire from K1-A2 is no longer making a path to ground. You have to check it. Remember, K1 is what allows the starter to engage. The path from the S1 to the K1 is a straight path, in the start position.

 

[Dock Rocker]

I wanted to bring this thread to a close and thank Guyfang. He not only took his time help a hard headed tech-dummy he even lead me to the solution.

You can see from the post above a got a bad connection to the house disconnect switch and I saw flash from the ground lug on the frame of the machine. After that the unit died and I was getting a fault that was kicking the circuit breaker on.

The fist issue was the fuel pump. I cut the silver box out of the fuel pump and that fixed my circuit breaker issue.
After some serious coaching from Guyfang we went through testing the control head and everything checked out. And told me to test the signal to the starter solenoid and that was good. The issue was that the starter would not engage. Turns out the starter solenoid was dead.

I got the starter rebuilt and back in yesterday and I am running again and making power.

Thanks again Guyfang!!! I owe you one!


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[uscgmatt]

Thanks for posting the conclusion. It's good to know the outcome was a good one.

 

[justacitizen]

I hereby create and bestow upon "Guyfang" the ATTABOY award. Thanks Guyfang and ATTABOY!

 

[Guyfang]

I only work for beer!

 

[Dock Rocker]

I only work for beer!

Anyone know how to get beer delivered to Germany?


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[Guyfang]

Yeah, come visit!! The chubby fellow in the middle will appreciate it!

 

[DieselAddict]

Yeah, come visit!!View attachment 738062 The chubby fellow in the middle will appreciate it!

Careful what you wish for!

I'm going to be in China for September. I'm hoping to make a run through Europe next year.

 

[Guyfang]

I will be here unless I croak!!