MEP-805B speed controller no output

[brad.boudreaux]

I’ve purchased a low time MEP-805B from a fire department. The fire department could not get the unit running so they auctioned it off and purchased another. The generator would crank but not start. Speed sensor light would not come on while cranking so I pulled the MPU and got no output when testing with an oscilloscope. I replaced the MPU and now get the speed sensor LED blinking while cranking. The TM troubleshooting indicates to replace ESD5551 is the DC power OK and speed sensor LEDs are functional and the overspeed light is NOT on. I replaced the ESD5551 unit but get the same results. The TCM102 board shows a CMOS low voltage fault but I’ve read that that issue should not prevent the unit from starting. I’ve had no luck finding any more information on the CMOS fault. Does this fault prevent the unit from starting ? is this a low battery voltage on one of the boards (like a coin cell ) ? Here are some of the details
• Unit will crank but not start
• Overspeed LED is off , DC power LED is on
• While cranking the speed sensor blinks
• Engine will run if I apply power directly to the throttle actuator
o About 8 volts will give me 60hz with no load.
• TCM board shows a low CMOS voltage fault. I’m unable to find any direction on how to correct this and not sure if it prevents the generator from starting.
• Actuator LED does not ever light up (running or cranking)
• The Crank termination LED lights up when running engine (powering actuator directly)
o I am thinking this is an indication the MPU signal on the ESD5551 is good
• Replacing the speed controller ESD5551 did nothing.
• When running the engine with direct power to actuator , the generator produces voltage and the contactor open/close functions.
Any help getting this generator running or information on the CMOS voltage fault would be appreciated

Thanks

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