MEP -004a. DC circuit breaker issues

[Rwf642]

I was investigating the reason for the dc circuit breaker not working on the front of the genset. I removed the cb without disconnecting the battery (really dumb move) it seems someone had wired all the wires to one terminal. (probably because the breaker is bad) none the less, I touched the ground to that terminal (I said it was dumb) sparks and now no power to panel which includes run/start/stop, panel lights test lights etc, etc. Where do I look for the problem? Is there a fuse or breaker or other fail safe? It looks like two of the wires go into a group going into a large distribution box, the other goes to the alternator. It still has 24 volts and is hot. The problem obviously goes into that big metal box. What can I expect if I open that thing up? Are there any fuses inside? Please help!!! Thanks for any insight.

 

[derf]

If you made sparks you need to find and fix the damage. If there is a fuse it should be shown somewhere in the TM. There isn't usually a fuse between a battery and a circuit breaker, though.

 

[Rwf642]

Thanks Def, I removed the connection box and found a huge fuse/shunt that was blown. I replaced it and I now have power back to the panel. The reason all this happened because I was looking for a cause for no power to the fuel pump, injector pump solenoid, oil pressure gauge not registering, fuel level not reading even in the run/battle mode. That problem has not gone away. Start of problem was...I removed the injector pump and injectors and sent them out for a rebuild. Everything was working then. I turned the run/battle switch to activate the fuel pump to service filter etc while injector pump was removed. (all worked well) pump is back and I reinstalled it. Tried to start and no fuel pump and others as mentioned. Frustrating!!!!
Thanks for your input.

 

[derf]

You may have shorted something like the glow plug harness or injector solenoid.

I only have a general idea of the workings of these gens.

 

[rosco]

Bump

 

[R Racing]

On the mep-003a they use the same switch for pump,start , and glow plugs ect. Cant remember if the mep-004a is the same ? if so could be a bad switch ?

 

[Rwf642]

Update- Problem with the dead genset is partially fixed. I removed the DC relay box and found a fried shunt. It is made of brass so with a little solder magic it is back to life. I am still having a problem with getting juice to the fuel pump, injection pump fuel cut off solenoid. I believe it to be the circuit board and relays in the DC relay box. It looks like it has been repaired before. I am almost sure the relay is bad on the board. The board has had wires soldered on the printed circuit board where the printed solder is missing. I back fed 24volts through the fuel cutoff solenoid and everything started working except the oil pressure light at the fault light panel. Oil gauge showed good pressure. Now I need to find the relay circuit board. Part # 6110-00-201-6015 aka 30554 69-768 anyone with advise on where to get one of these reasonably priced would be appreciated.

 

[ETN550]

Update- Problem with the dead genset is partially fixed. I removed the DC relay box and found a fried shunt. It is made of brass so with a little solder magic it is back to life. I am still having a problem with getting juice to the fuel pump, injection pump fuel cut off solenoid. I believe it to be the circuit board and relays in the DC relay box. It looks like it has been repaired before. I am almost sure the relay is bad on the board. The board has had wires soldered on the printed circuit board where the printed solder is missing. I back fed 24volts through the fuel cutoff solenoid and everything started working except the oil pressure light at the fault light panel. Oil gauge showed good pressure. Now I need to find the relay circuit board. Part # 6110-00-201-6015 aka 30554 69-768 anyone with advise on where to get one of these reasonably priced would be appreciated.

What's the fried R3 resistor in the pic? The K7 relay looks like one of the $150.00 Airpac units. If the K7 relay is only used on one side and the coil in it is good it can be removed and installed in reverse and will give new life. If it is used on both sides it can be swapped with another that is used on one side and then installed in reverse on that circuit. These are pretty good relays. Did you measure the coil in the relay as open? Or do you think you have a contact problem? They are very well built and hermetically sealed relays. If the short ruined the contacts but they are not welded shut then maybe swapping or reversing will fix it. A used one is probably the cheapest way to another relay. Someone parting out a control panel... I think they are very common. I have 4 in my 016B box.

 

[Rwf642]

The fried resistor is a 1500 ohm wire wound power resistor. I found a 1470 ohm and replaced it. When I flipped the board over to solder you could see the heat had made its way to the rectifier. The K7 relay looks like it has been in and out a few times. Someone glue it back in with blue RTV. I did not check the relay itself. The tests in the TM are a little tough to do with it out. Its hard to tell with the wiring diagrams which side is used. With all the damage to the circuit board I thought it best to replace it as a unit. The arcing did not do the damage to the relay. The arcing happened because I started looking for reasons why all of the sudden every thing stopped getting power. The CB was not working (wouldn't reset) so I pulled it without disconnecting the battery. All 3 CB leads were on one terminal. That obviously wasn't the problem. I haven't concluded positively that the circuit board is the issue, but with all the damage and previous jerry rigging I suspect it being the problem.

 

[PeterD]

Though a different form factor (pins and such) there is an automotive relay very similar to the K7 relay, and it is not expensive. I can check if you want, and let you know the number, but you'd have to either adapt a new socket, or figure some way to connect it up. The automotive relays are 12V but it would not be difficult to work around that since the coil current is very low a resistor in series would likely work just fine.

 

[Rwf642]

Peter, Thanks for the insight, but I don't think the relay itself is bad, I think the circuit board is bad. If the relay can be checked without power (because when you remove the cube you have no power to check with) I could put a DVM on it. But that would only tell me if they're stuck closed. I'd like to find a used circuit board with the relays already on it. Any help with that would be helpful. I tried to source it through WBparts and CTG the online line gov't part locator but had no luck.

 

[PeterD]

OK, see what you are saying...

 

[ETN550]

Peter, Thanks for the insight, but I don't think the relay itself is bad, I think the circuit board is bad. If the relay can be checked without power (because when you remove the cube you have no power to check with) I could put a DVM on it. But that would only tell me if they're stuck closed. I'd like to find a used circuit board with the relays already on it. Any help with that would be helpful. I tried to source it through WBparts and CTG the online line gov't part locator but had no luck.

A used board at a reasonable price would be a good thing to have. Those AirPax relays are obsolete but available at $150.00 so to have a board with them intact is worth something. Peter's 12v relay with a socket conversion would be worth it too. Might be possible to cut the case off the existing bad relays and build out from there with the 12 v relay and resistor along with it, retaining the original pin config to plug into the board along with the screw down arrangement.