Generac power generator not running

[staninlowerAL]

I encountered a problem with my Genrac 1750kw generator today, it stopped running while in use. Checked fuel and oil level, ok. Tried restarting and it will fire off and immediately shutdown in 2 or 3 seconds. Replaced the oil pressure safety shutdown switch with a new OEM switch, same problem. Anyone know a method to bypass the safety switch to test it? The switch has 2 wires. I don't know for sure but I think it is a n/c switch when running.

[RonT]

Try it both ways - disconnected and then shorted. The larger generac generators use a solid state intermediate device which shorts out the ignition circuit. The one on mine failed and I took it off. To test for this, follow the wire to the coil assembly and disconnect.

[Barnyard]

Stan, I am not familiar with that generator, but does it flash any type of code when it stops running. My motorhome generator kept flashing a code and when I finally figured out how to read it I found there was a coolant problem.

[staninlowerAL]

No code or visual signal that I can find. It's about 14 years old, always stored under cover. Gotta do some more investigating. TKS for the reply.

[outdoors4evr]

If it fires at all, then the safety switch is not an issue. The safety switch is designed to cut the ignition.
I'd start looking toward fuel. Try to get it started on starting fluid. Might need to clean the carb.

[staninlowerAL]

This one has a time delay oil pressure switch, according to the manual. Once the engine starts it will run to allow the switch to activate. If it does not then the engine shuts down. My delima is the gen had been running for about 45 minutes on fresh fuel when it abruptly shut down just like the kill switch had been turned off. Now it will start and run for a few seconds then die. I want to bypass the newly installed OP switch to make sure it's ok. Lack of info on the safety interlocks makes the troubleshooting difficult.

[staninlowerAL]

UPDATE: A friend who owns a small engine shop suggested that I try to "force feed" fuel directly into the carb to see if the fuel solenoid has malfunctioned. When I tried this it would not run at all, only backfired through the carb. Only success was a small fire in the throat of the carb (no damage done). Happened more than once, I'm beginning to think there's more going on here that I want to imagine. Looks like I'm going to be looking for someone who knows something about this GENERAC genset--32hp Guardian twin cylinder engine. My friend at the small engine shop does not work on the Guardian engines, can't get parts.

[ctltmp]

This isn't my advice, but I found it for your generator and thought maybe it could be useful.

If it shuts down after 4 seconds then it is likely the low oil pressure switch. If it shuts down after 2 seconds, then likely it is the rpm sensor on the flywheel. It can go bad or go out of adjustment. Check the sensor output while running , even if only 2 secs, you should get 0.4-0.6 v AC and the sensor should have 1000 ohms +- 10 % resistance. You can adjust the sensor to flywheel gap down to "one half turn" in Generac speak if the voltage output is not there.

[staninlowerAL]

Thanks for the info. I had not found any info about a rpm sensor on the flywheel. I have about ruled out the OP switch since I replaced it with a new GENERAC OEM replacement part #OC3025 with no change in the results.

[RonT]

Something Ctltmp said jogged a memory cell for me. My ONAN failed this way when one of the brushes got stuck and arc'd the slip ring. It did not see 60 cycles on the output after some period of time and sent a shutdown command to the engine. The diagnosis involved measuring the output or in your case plugging an incandescent lamp and observing while the start / shutdown takes place.

[staninlowerAL]

Hey guys, thanks for all the tips and suggestions. The good news is the genset is running and operating normally. The bad news is I have no idea why. After it would not start yesterday, I removed the battery and put it on a slow charge overnight. I reinstalled it this afternoon and it started and operates normally. I get frustrated when things "fix" themselves and I don't know why!!!! I suppose I should reinstall the new OP safety switch and rule out a faulty switch since it is running on the old switch now. Cheers!!

[staninlowerAL]

I thought I was done with this problem but that's not the case. Yesterday after running it for a couple hrs and welding it abruptly shut down again, no restart. This was similar to the first event in that it had been running for a couple hrs. I again waited until the next day (today, about 24 hrs) cool down, and it restarted without any problem. If this were a Cub I would suspect a failing coil since it seems to be temperature related. ☹️

[outdoors4evr]

You write about an abrupt shut down, but more detail may be helpful.
Did it shut down like someone turned the spark off? - RPM's ramped down to zero? Still could be the coil.
Did it shut down like something instantly stopped the piston? RPM's suddenly were zero? (can it turn over after it stops or is it temporarily seized)

Did the engine sound like it was laboring just before it shut down? Perhaps a mouse built a nest inside the heat shield cover and the engine is overheating due to the lack of airflow.

[staninlowerAL]

Thanks for the questions. No unusual sounds and the engine turns freely with the starter during restart attempts, does not seem to labor or turn slower than normal as if something is under load. The engine stopped as if the kill switch was activated (it has a rocker type 3 position switch-- kill/run/start and defaults to the run position). Attempts to restart result in the engine firing and running for a couple seconds but will not clear whatever fault causes the shutdown. I will have to remove the cowling to determine if there is anything restricting the airflow (not easily done). I hope the barn cats have kept the rodent population at bay, I've not seen any evidence but it's still a possibility. As previously stated, when everything cools down after about 24 hours it restarts normally. Plans are to do some more welding today and see if it reoccurs the third time. I'll post what happens.

[staninlowerAL]

Update: Ran about 2.5 hr this morning, no problems. Air temp was about 15 deg cooler than yesterday. ❓❓