MEP-831A Governor Control Replaced - no start

[DieselAddict]

Reuse is ok

 

[zapp]

Well.. got the fuel IP back installed and bled the system. It fired right up! . Of course, it can't be that simple.. At first I got an Overload/Short fault light come on and the engine turned off. I restarted and got a low oil sensor light and it turned off. I changed the oil, checked the filter, and it's the same thing. Low oil fault and engine off. Looking through the TM it just says if the engine has less than 15 PSI it will fault. Is there a way to test the oil pressure switch or something else I should be looking at?

Engine run and low oil fault:

 

[kloppk]

The OP switch's fail fairly often in the 831's.
Hopefully you actually do have oil pressure!

You can disconnect one of the wires to the switch to prevent it from reporting/falsely reporting that fault.
** If there is a real OP issue it won't shut down!

 

[zapp]

Yep, two wires on OP switch. I took 1 of 2 wires off and started engine. No low OP fault but actuator arm went back to magnet and turned off. Restarted and manually moved throttle/actuator arm which then resulted in overload/short fault. Starting to think this has more problems going on. Going to try and look at the electric diagram and understand the logic of where the signal is coming from to shut down..

 

[kloppk]

Shutdown comes from the A2 Fault Monitor. When a fault is reported to it A2 turns the K12 FAULT relay on. K12 is the leftmost relay behind the gauge panel. When tripped K12 will have an LED on it in. When that happens K12 removes power from the Governor Controller module causing the engine to shut down.
The OL/SC faults are detected inside the Inverter and those faults are sent to the A2 Fault monitor.
Unfortunately, the Inverters in these sets can be fussy and throw OL/SC faults when there aren't any.

 

[2Pbfeet]

FWIW: Generally, the L70s build oil pressure rather quickly, i.e. a a second or two, and with cold oil often to pretty high pressures. (A probable cause of the oil sensor failures in these engines in my own view.)

All the best,

2Pbfeet

 

[zapp]

Thanks a lot! Appreciate the detailed info! I'm trying to break this down in to smaller bites and step through to isolate. I noticed when I took a wire off the OP switch the magnet engaged and the engine stopped but K12 didn't have an LED on indicating it had been energized or a fault sent. Can the inverter be unplugged to determine if the fault is coming from it or test points? I've been searching and saw your thread on humidity impacting the inverter board and potentially sending an OL/SC.

 

[Light in the Dark]

@kloppk are these small sets like the larger TQGs, where you have to hold S1 till sufficient pressure builds?

 

[Guyfang]

NO.

 

[kloppk]

As Guy said no. The OP usually shots up to about 125 PSI quickly after starting. Way more than the 15 PSI LOP cutoff.