Mep802a won't shut off!

[KnuckleDuster]

Hey fellas, recently purchased a 2009 mep802a off gov deals and got to working on it. Ended up having to rebuild the engine, got that done and it fired up beautifully. Makes power but I've got two issues. Oil pressure gauge is pegged at 80 and stays there even when off. I know it's not making 80psi of oil pressure. It's definitely an electrical fault. And also, I can't get the machine to turn off! Once fired up I can switch it to off, hit the dead crank off, and hit the emergency stop. It doesn't stop running until I physically pull the fuel solenoid out and kill the fuel going to the pumps. Once the engine is stopped then the fuel solenoid snaps back forward. All the switches so far have tested fine. I am having a hard time navigating the diagrams to start tracing wires. Anyone experience this yet?

 

[WWRD99]

Hey fellas, recently purchased a 2009 mep802a off gov deals and got to working on it. Ended up having to rebuild the engine, got that done and it fired up beautifully. Makes power but I've got two issues. Oil pressure gauge is pegged at 80 and stays there even when off. I know it's not making 80psi of oil pressure. It's definitely an electrical fault. And also, I can't get the machine to turn off! Once fired up I can switch it to off, hit the dead crank off, and hit the emergency stop. It doesn't stop running until I physically pull the fuel solenoid out and kill the fuel going to the pumps. Once the engine is stopped then the fuel solenoid snaps back forward. All the switches so far have tested fine. I am having a hard time navigating the diagrams to start tracing wires. Anyone experience this yet?

The place I'd look is the TM section of the gensets. It has tons of info on where to look and troubleshoot. I am assuming it didn't run when you got it but if it did was the oil gauge working and the switch?

 

[Guyfang]

Open the control panel and pop the CB1, (DC Control circuit Breaker. Then look at M7, (Oil pressure gauge) and check that:

1. M7-I has wire # 137J
2. M7-S has wire # 130B
3. M7-G has wire # 100AN ans wire # 100AP

Then look at the row of plastic relays in front of your eyes. on the far left, is not a relay, even though it looks like one. Its a switch. S-14, (crank disconnect) I have several times seen a set not turn off, because there was a relay in this position. The switch has a red reset button on it. The relays do not. If this is not the problem, then we can really start to troubleshoot.

@Ray70 and @kloppk

 

[Digger556]

That's a good bit of info I will squirrel away for later.

 

[Ray70]

On your oil pressure issue, it sounds like you are saying the gage is stuck all the way up ALL the time.
Running, OFF, S1 at Start / Run and not running.
If so, first check the wiring as Guy said. Also confirm +24 on the I terminal and ground is on the G terminal
the S terminal is the sense wire going to the sending unit and should have resistance to ground when measuring the wire disconnected from the gage.
If it's an open circuit or shorted to ground, the sending unit is bad.
If everything above checks out good, then see below:

An 09 will have Beede gages in it.
If at any point while the power was on, you lost the ground signal, or the sensor signal, the gage will peg itself all the way up and the needle can get stuck against the side of the gage body. Look closely at the tip of the pointer, is it touching the inside wall of the gage body?
If so, remove the gage, loosen all the nuts on the studs so that the gage's internals are loose from the case a little bit, then tap the gage against the palm of your hand to shake the needle loose.

Once you get the needle loose reinstall the gage. Turn S1 to prime / Run. If the gage immediately pegs itself again, ( and all 3 wiring connections are good ) the gage itself needs to be replaced.

 

[kloppk]

The leftmost item in the row of relays is the S14 Frequency Trip Switch. The case looks like a relay but look closely and you should see a printed circuit board inside it.
There isn't any reset button on it.

The other relays to the right of it are relays and all are the same part number.

If you can take a picture of the row of relays and post it up it will help us help you.

 

[KnuckleDuster]

On your oil pressure issue, it sounds like you are saying the gage is stuck all the way up ALL the time.
Running, OFF, S1 at Start / Run and not running.
If so, first check the wiring as Guy said. Also confirm +24 on the I terminal and ground is on the G terminal
the S terminal is the sense wire going to the sending unit and should have resistance to ground when measuring the wire disconnected from the gage.
If it's an open circuit or shorted to ground, the sending unit is bad.
If everything above checks out good, then see below:

An 09 will have Beede gages in it.
If at any point while the power was on, you lost the ground signal, or the sensor signal, the gage will peg itself all the way up and the needle can get stuck against the side of the gage body. Look closely at the tip of the pointer, is it touching the inside wall of the gage body?
If so, remove the gage, loosen all the nuts on the studs so that the gage's internals are loose from the case a little bit, then tap the gage against the palm of your hand to shake the needle loose.

Once you get the needle loose reinstall the gage. Turn S1 to prime / Run. If the gage immediately pegs itself again, ( and all 3 wiring connections are good ) the gage itself needs to be replaced.

Alright, tested all the wires, they all check out okay. Signal removed from gauge ohms at 240. 23 volts at the gauge and ground is perfect. Attached photos are the gauge with key off, as soon as I switch it to run position, and the photo of the start switch. It is indeed there. So I'm thinking the gauge is bad. Now, any ideas on the fuel solenoid not turning off?

 

[KnuckleDuster]

The leftmost item in the row of relays is the S14 Frequency Trip Switch. The case looks like a relay but look closely and you should see a printed circuit board inside it.
There isn't any reset button on it.

The other relays to the right of it are relays and all are the same part number.

If you can take a picture of the row of relays and post it up it will help us help you.

Photo posted

 

[Ray70]

Once you turn off S1 / E-Stop and / or dead crank, does EVERYTHIN continue to operate normally? Fuel pump, gages, panel lights etc? Or do you loose all the DC controls as expected, but the solenoid is still pulled in and engine still running?


BTW, your picture is correct, left most "F.T Relay" is the correct part.
And I would agree that your oil pressure gage is dead.

 

[KnuckleDuster]

Once you turn off S1 / E-Stop and / or dead crank, does EVERYTHIN continue to operate normally? Fuel pump, gages, panel lights etc? Or do you loose all the DC controls as expected, but the solenoid is still pulled in and engine still running?


BTW, your picture is correct, left most "F.T Relay" is the correct part.
And I would agree that your oil pressure gage is dead.

Just checked it, and yes it appears everything stays on and keeps working normally

 

[Ray70]

And once you manually press the FSS lever, the engine dies, FSS pops out and does the panel power shut off at that point?

 

[KnuckleDuster]

And once you manually press the FSS lever, the engine dies, FSS pops out and does the panel power shut off at that point?

Yes that is correct

 

[KnuckleDuster]

And once you manually press the FSS lever, the engine dies, FSS pops out and does the panel power shut off at that point?

But something I find strange is that if the engine is off and I just cycle through s1 functions everything works normally. And If I just bump the start but don't allow the engine to actually start, when I switch s1 back to off the solenoid closes and the panel turns off.
It's only when it's running that I have the issue

 

[Ray70]

Here's my thoughts so far.
Somehow you are getting power back feeding through either the oil pressure switch circuit or the engine fault control circuit.
Whatever path it is taking its bypassing the E-Stop , Dead crank and S1 switches.
This is going to take a little studying of the schematic.

 

[Ray70]

I wonder if it could be possible that you alternator is shorted internally, sending power backwards through the field excite wire, back to S1 while it's running? You could try removing the Field wire off the alternator and see if anything changes??

 

[KnuckleDuster]

I wonder if it could be possible that you alternator is shorted internally, sending power backwards through the field excite wire, back to S1 while it's running? You could try removing the Field wire off the alternator and see if anything changes??

I'll give that a shot soon and let you know what happens. This is certainly an interesting situation.

 

[KnuckleDuster]

Here's my thoughts so far.
Somehow you are getting power back feeding through either the oil pressure switch circuit or the engine fault control circuit.
Whatever path it is taking its bypassing the E-Stop , Dead crank and S1 switches.
This is going to take a little studying of the schematic.

Ray can you help me out with the alternator wiring? I've got no wires on the stud labeled "excite" or "ac tap"

 

[Ray70]

Sure, so Let me tell you how to figure some of this stuff out.
Open the oil filter side door, that schematic inside the door can be a life saver, Look for G2 near the upper right.
It will show wire 137T going to the excite ( left ) side of the voltage regulator mounted on the back of the alternator.
Then 100AE goes to the ground stud on the back lower right of the alternator, along with the black pigtail from the right side of the voltage regulator.
Then wires 180C and 180D go to the + or BATT stud. mid-left of the alternator body ( the one with the insulating washer where it comes out of the alternator case. )
Take a look and compare yours and see where your wires are at now, perhaps something with the wiring is causing you issue??
Send picture if at all in doubt.

 

[Ray70]

If wire 137T is on the Batt. stud on the alternator, that could very well be causing all your problems, plus a few others you probably don't even know about yet!

 

[Guyfang]

Pictures are good.