Onan MDL3 won't shut down

[Wood]

Shot in the dark – thanks in advance. I’m not a mechanic.
model 12 5 MDL3A 31150A, serial A890 200 886

Symptoms – Will not shut down: stop switch / emergency switch, remote panel. Fuel must be cut in ER.

Summary - Solenoid contact get 12v when engine is running. Zero volts when Stop switch engaged but engine continues to run. With engine off and apply 12v directly to solenoid contact I can hear the solenoid engage / disengage and feel it at the throttle lever.

Data –
Generator runs properly. Oil, temp & voltage OK. AC voltage OK in all load conditions.

With battery power to the generator 0 volts across fuel shutoff solenoid contacts [There is no backfeed to the solenoid]

With preheat on 0.13 volts across solenoid contacts.

With engine start 8.5volts across contacts which builds to 12.5v+ as engine starts

With engine Stop or Emergency Stop voltage across contacts is 0v. RPM drops. AC voltage drops to ~90v. Engine continues to run.

With engine off disconnect 12v+ lead from solenoid contact. Impose 12v+ directly to contact. Can hear solenoid engage and disengage. Does not sound like a “clunk”. Sounds more like a “chirp”. When connecting/disconnecting I can feel the throttle lever bump. Throttle lever can only be moved 1-2mm between hard stops.

Resistance measures 4ohms.

Is the solenoid bad or is the linkage jammed up…..

I’m on a mooring and do not want to take this apart without a degree of confidence I can fix it. Plus – the solenoid is $300+

 

[Duetto]

hi,

i'm not familiar with this type of genset but i have 2 that at different times didn't what to stop. both were related to the fuel valve. on one, the fuel valve was sticking. i replaced and problem was solved. on the other it was the linkage to the run solenoid was too short so that when run solenoid was de-energized the short linkage didn't allow the fuel valve lever to fully retract.

hope this helps.

 

[Wood]

That's helpful. Thank you.

 

[Lepke]

I have a MDL3. The injector pump is a Stanadyne DB2. Manuals can be found online. Most are too big to post here. I had to replace the stop solenoid. $50 on ebay a few years ago. I don't think that's your problem.
I'd call a shop that rebuilds injector pumps.
Attached is a description of how the pump works. It's from a truck site and may be a little different.

 

[Wood]

Thank you.

The testing I did with 12v direct to the solenoid caused it to cycle a couple dozen times. The next time I ran the generator it shut off via the Stop switch and continues to work - for now.

I think the solenoid can be replaced without removing the pump so I am sourcing a solenoid and gaskets from some injector shops.

The lead seal is still intact on he assembly so it's never been apart in 32 years. There's probably diesel crud in the reservoir that houses the solenoid that can be cleaned out.

There's only 1500 hours on the unit. I don't want to remove the injector pump unless there' no option.