Gererac model 09734-3 LP issue

[woodland_park]

hello, I'm trying to assist my neighbor with his LP fueled generator, but I don't have any theory about how it runs and I'm wondering if anyone could give me direction. Here's what I know. Using the start switch inside the RV (with the load breakers off), it doesn't start. At the generator, using the start switch and the LP prime switch, it will start, but stops as soon as the prime switch is released. He was told to replace the main board which didn't help, same issue. I believe both start and prime switches are good as I ohmed them out with a meter. I can hear the LP valve click when I push the switch and I get 12 volts on 1 of the terminals. The other must go to ground I assume. Thing is, the LP valve does not click every time I press the prime button.Should it? Is there a pick and hold circuit as well once the valve is energized? I need a little theory of operation and hopefully someone can help. Thank you

[woodland_park]

OK, we found the issue with the Generac LP generator not staying running!
There is a terminal block screwed into the frame about 8 inches below the voltage regulator. There are 4 blue 12VDC wires all labeled wire 14. 1 goes to the prime switch, 1 to J2 on the control PCB, 1 goes to the oil pressure and high temperature and the 4th I believe to a fuel pump that the LP version doesn't have. Anyway, the screw securing the male ends of the terminal block was gone and 2 of the wires had broken off the female spade terminal connector. I just stripped all 4 ends of the wires and wire nutted them together. Fired right up! Still need to order and replace the oil pressure switch, but the high temperature switch is at least in the game. So no switches or circuit board. Just connection, connection, connections.
Thanks for all the input!!!

[MEXICOWANDERER]

Oh the value of using a lightbulb 50 watt testlight. 12 volts will put a 4+ amp load on whatever a person is checking. Bad switch? KAH ZANG! found instantly. Saves diagnosis via shoveling banknotes troubleshooting.

[woodland_park]

still no joy on the generator staying running after releasing the "prime" switch. we're going to replace the "prime" switch as soon as it gets in. This is a 3 position switch with battery power coming in the lower terminal. When pushed it's supposed to bring the 12V to the center terminal, which in turn energizes the LP fuel solenoid allowing propane to pressure up the line to the carb. When pushing the switch, sometimes I get 12V at the middle terminal and sometimes nothing or something between 0 and 12V. The solenoid actuates"clicks" accordingly.Maybe it's some as simple as the "prime" switch. It ohmed out fine, but who knows once you put voltage and current through it. Stay tuned.

[NRALIFR]

Richard, I believe a model 09734-3 is a Primepact 66LP correct? I'm afraid I don't have any personal experience with that model. I'm only familiar with the Impact 36LP that's in my camper. There are a lot of similarities, though.

I CAN tell you that on mine, the PRIME switch does not really prime the engine with LP, it only opens the LP fuel lock-off solenoid, and that lock-off solenoid SHOULD be held open (by voltage) while the engine is running. There are many things that could cause the control board to shutdown the engine, and it does that by dropping voltage to the fuel lock-off solenoid.

The fuel lock-off solenoid allows LP to flow to the next component, which is a big round "pancake shaped device" that looks like an LP regulator. The maintenance manual calls it a secondary regulator, but it's not really a regulator (the LP fuel is already at the proper pressure at this point in the system) it's more of an on/off valve that only allows LP fuel to flow to the engine when there is vacuum in the intake manifold. Like when the engine is either cranking or running. It takes a different type of secondary regulator to be able to really prime your engine. But again, the lock-off solenoid should open every time you pres the prime switch, and stay open when the engine is running.

One thing that MIGHT be causing it to shutdown, and this is true on mine as well, is a bad oil pressure or oil high-temperature switch. Those are both located on the oil filter head (which is right out in front on your model), and a quick test you can do is to simply unplug them and see if the engine stays running without them. The wiring diagram for the 66LP shows those two switches wired in series (wire #85), and there should be a single-pin connector accessible that you can unplug to disable both of them. On my 36LP it's a purple wire.

Make sure you have sufficient oil in the engine first! The oil pressure switch is normally closed, and is held open by oil pressure, and the high-temperature switch is normally open and closes on high temperature. If either one is bad and is staying closed all the time, the engine will start, but will then shut down. That's actually one of the listed problems in the troubleshooting guide (section 8.1) for the 66LP. Possible causes are bad oil pressure or high temperature switch.

The Maintenance Manual I have for the 66LP is for a 09734-5, which is just a later model than the 09734-3 you are working on. There are probably a few physical differences, but for this problem it should be close enough. You may be able to find a -3 manual out there on the web somewhere.

I also sent you a PM.

:):)

[azrving]

I did deal with something like that. I had just typed a bunch of stuff and this half arse website quit again. How does a multi million dollar corp have such a lousy site. Maybe I'll be back tomorrow.