Troubleshooting Thread for “7” Mep-804a

[Jeep Nasty]

Back again, I had to take a break from “5” because I’m not ready to pull the generator head off yet to check the windings.

I was able to get”6” Running and producing power with no issues so far.

This one is “7” just due to the number written on the side.

This one was missing all the filters and had all the fluids drained out of it. And also had a very old mouse nest. I filled everything up got the appropriate filters and attempted to crank it when I turn S1 to the start position I can hear the relay click but it will not crank.

It does operate properly through the dead start but I cannot get it to crank through the S1.

I have gone through the trouble shooting section entirely on the fails to crank and I am now at the point where as best as I can tell it’s an issue with the S 14 crank disconnect switch.

When I engage S1 to start I am receiving battery voltage at terminal 19 but I am receiving no voltage coming out of terminal 18. Which would be the voltage needed to go to the K2 relay to close that relay and engage the starter.

My question is right now is the crank disconnect part of the blue box governor control unit or if I open up that box is there an individual component inside that I can replace. Or is there something else I should be diagnosing prior to disconnecting or opening that blue box.


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[Guyfang]

Back again, I had to take a break from “5” because I’m not ready to pull the generator head off yet to check the windings.

I was able to get”6” Running and producing power with no issues so far.

This one is “7” just due to the number written on the side.

This one was missing all the filters and had all the fluids drained out of it. And also had a very old mouse nest. I filled everything up got the appropriate filters and attempted to crank it when I turn S1 to the start position I can hear the relay click, (this is probably the preheat relay) but it will not crank.

It does operate properly through the dead start, (S10, Dead crank) but I cannot get it to crank through the S1.

I have gone through the trouble shooting section entirely on the fails to crank and I am now at the point where as best as I can tell it’s an issue with the S 14 crank disconnect switch. (The S14 is part of the A5)

When I engage S1 to start I am receiving battery voltage at terminal 19 but I am receiving no voltage coming out of terminal 18. Which would be the voltage needed to go to the K2 relay to close that relay and engage the starter. (Have you checked, tested and properly replaced the MPU?)

My question is right now is the crank disconnect part of the blue box governor control unit, (A5, yes) or if I open up that box is there an individual component inside that I can replace. (There is nothing in the GCU to be fixed or replaced.) Or is there something else I should be diagnosing prior to disconnecting or opening that blue box. (Do not fool with the GCU.)
If the MPU is bad or mal adjusted, the set will not start. So start there. Then, since you have a good set running, you also have a test bed. Its rare that the S14 part of the A5 goes bad. But if you think its bad, simply but #7's GCU into your "test bed", and see what happens.)

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[Jeep Nasty]

That’s the schematic I used to determine that there should be voltage when cranking through 19 and 18 as that should be a closed circuit until the mag pick up registers the proper speed to shut off the starter.


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[Guyfang]

The MPU produces AC voltage. No input from the MPU, no run. Did you test the MPU output yet?

Put the schematic in here to keep us from having to look for it later.

 

[Jeep Nasty]

The MPU produces AC voltage. No input from the MPU, no run. Did you test the MPU output yet?

Put the schematic in here to keep us from having to look for it later.

Engine won’t crank at all using S1. So no way to measure output. I did check that resistance was in spec.

I found this in another thread and did check pins 1,3,5 on A-5 with S1 in start position.

I have proper voltage at pin 1 but no voltage a 3,&5 with s1 in start.

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[Guyfang]

Engine won’t crank at all using S1. So no way to measure output. (Wrong. You said you can turn the engine over with the S10. So try that) I did check that resistance was in spec.

I found this in another thread and did check pins 1,3,5 on A-5 with S1 in start position.

I have proper voltage at pin 1 but no voltage a 3,&5 with s1 in start.

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[kloppk]

No power to A5 terminals 3 & 5 is likely due to relay K21 not closing with S1 in START.
Check for ~24 volts at the following points in sequence with S1 in START.
S1-7
Diode CR4 Right end
Diode CR4 Left end
Relay K21 terminal A