MEP-016B/C breaker tripping

[paramilusmc]

First off, this may not be a (B) series MEP-016, it has a Yanmar engine so it's probably a (C) model.

Anyways...

Unit was running great then all of a sudden shut down on its own. Found the DC circuit breaker was tripped. So reset it, flipped the main switch to its first position (Aux fuel) and in about a second trips the breaker again.

If I quickly turn it all the way to start it turns over and even starts to want to run for about a second, then it trips the breaker.

Swapped out the breaker, still trips. Made sure the batteries were totally charged, still trips.

All I can gather is that I have a short somewhere in the starting system since this is what the DC circuit breaker facilitates. TM isn't very helpful as it just states that if this occurs report it to higher level maintenance.

Unlike my MEP-831 I don't hear the fuel pump engage or run.

So, what's the likely culprit? What should I be checking?
Thanks in advance.

 

[Guyfang]

Unplug the Aux fuel pump and then see if it still happens.

 

[paramilusmc]

Unplug the Aux fuel pump and then see if it still happens.

OK, disconnected the auxiliary fuel pump, same results. I ran the unit manually with fuel poured into the filter housing and cracking the bleed valve so that it could eat without creating a vacuum, but without being able to turn the switch to run without the breaker tripping only allowed this for a few minutes.

So, what should I be looking at next in the system?

 

[Guyfang]

This is the S1 schedule. The only common terminal to all positions is terminal 11. Will the CB pop when the S1 is in preheat mode? So terminal 11 must be the wire from the 24V source to the S1. If the Preheat dosn't pop the CB1, then it will be s1-13, 14 or 15. So you need to see where they go. If the CB1 pops in preheat. then thats where to look. Preheat function.

 

[paramilusmc]

View attachment 961008

This is the S1 schedule. The only common terminal to all positions is terminal 11. Will the CB pop when the S1 is in preheat mode? So terminal 11 must be the wire from the 24V source to the S1. If the Preheat dosn't pop the CB1, then it will be s1-13, 14 or 15. So you need to see where they go. If the CB1 pops in preheat. then thats where to look. Preheat function.

Nope, pre-heat doesn't pop it.

 

[paramilusmc]

It was the fuel level switch.

Thanks Guyfang

 

[Guyfang]

Good to go!! Repairable? Wiring? They CAN, sometimes be repaired. Its a PITA, but sometimes its just the wire broke off under the canon plug. Four tiny screws, and take a look. The floats can not be it. They are more or less just holding magnets to open and close contacts. The contacts often go bad, but do not short to the tube. Its full of RTV. So give it a shot.

Had another thought. The cannon plug, itself. Sometimes the wires break off, in the plug end, on the wire harness side. Stick the plug into the float plug. That holds the plug , then you can unscrew the plug top. Open it up and see if a wire broke off and is shorted to the plug .