I have a Generac generator in my 1995 Damon Intruder (GN-480 Q-55).If I prime it on the gennie it starts and runs fine for about 1-2 minutes then quits, however if I keep prime switch down or press it for 3 secs every 1-2 minutes it runs fine.Gennie is providing power as fridge and lights go on after a few seconds and I switch breakers on.I replaced the fuel pump and filter (no change in symptoms)Gas tank is full.Same symptoms if I disconnect the low oil & temp sensors.I replaced the Prime rocker switch as it was cracked (the one I used has three positions and will stay ON unless switch to OFF). Thinking back I attached the 3 wires in what I thought was correct order but now I'm wondering if I could possibly have connected the 3 wires incorrectly.Should the fuel pump run continuously (I presume YES)? Should the control board take over the fuel pump once prime switch is released.Is it harmful to keep the Prime switch on?I was going to clean carb but someone suggested that is unlikely given symptoms, however I am willing to try anything as I am reluctant to delve into control board issues at this point.Thanks for any help.

The gas line from the main tank to the generator has probably deteriorated and sucking air into the fuel line for the generator.If you remove the fuel line going to the pump and try to siphon gas from the main tank you will probably see air bubbles and the line will not maintain a siphon.You can also supply gas to the pump from another tank to see if the gen continues to run after it starts.Do not remove the carb, that is not the problem.

Thanks for that suggestion.I have tried both from main and Auxillary tank.I replaced hose from T junction to pump and from metal tube to carb

Maybe you have figured out that it is the wires on the rocker switch? Otherwise I would put a multimeter on the positive wire to the fuel pump and see if it loses power when the prime switch is released. No power to the fuel pump might indicate a control board issue.

Good suggestion. I’ll try that.

The most common carburetor problem with small gasoline engines is a clogged primary/idle air or fuel passage/jet. The only way to repair this is remove the carburetor and disassemble it. Carburetor cleaning spray, even once it is disassembled is not adequate to clean the tiny passages. You need a set of fine wires/brushes. Sold on Amazon.

GENERAC GENERATOR ISSUE | Good Sam Community

Grit_dog
Navigator
Jun 07, 2022
SeligL wrote:
Another question if I can’t solve this problem, is it harmful to leave Prime on as gennie runs and works fine when Prime is on or pressed for 3secs every 1-2 minutes.

Prime should be a momentary switch, for obvious reasons.
If it stays on, you have the risk of the fuel pump running deadhead or leaking fuel or blowing out or blowing up your vehicle….if you ever forget to turn it off.
bounder39zman
Explorer II
Jun 08, 2022
The prime switch used on this Generac gen. has both NC(normally closed), and NO (normally open) contacts in the switch. in prime mode, the 12v on wire 15 is connected to fuel pump thru NO contacts. In run mode, 12v from control board connects to fuel pump thru switch NC contacts. Sounds like you just need to install correct switch, Generac part# 092113
SeligL
Explorer
Jun 08, 2022
Thanks bounder39zman. I have ordered a new Prime switch. What you write makes sense. I don’t think I mentioned that I replaced the cracked Prime switch with one I had as a spare at home. Didn’t really think it would be critical but maybe it is. So I’ll wait for new switch and see then. On my diagram there are wires 15 to fuse, 14A (RED) to Fuel Pump shutoff valve and 14 to terminal connector. (15 does not go to FP). When I connect new switch it looks like 14A goes to middle prong., bottom one? To fuse and therefore top prong to terminal connector. Please correct me as I don’t want to wire this incorrectly.
Many thanks.
Grit_dog
Navigator
Jun 08, 2022
SeligL wrote:
Another question if I can’t solve this problem, is it harmful to leave Prime on as gennie runs and works fine when Prime is on or pressed for 3secs every 1-2 minutes.

Edit, you replied while I was typing. Good to see yo're fixing it right.
Cant help with the pin outs on the switch, sorry
SeligL
Explorer
Jun 08, 2022
While I wait for new Fuel Prime Switch to arrive, looking at old cracked one I see 1a and 1b at each end prong and 1 in middle,
So I assume correct connection will be 14A (RED) to middle prong (1).
15 goes to fuse and 14 to Terminal Connector. Can anyone tell me if 15 or 14 goes to prong 1a (and other one will go to 1b).
Thanks
bounder39zman
Explorer II
Jun 14, 2022
Your wiring is correct. 14A to middle terminal (goes to F.P.)
14 goes to top terminal (from terminal on RUN B+ connector, has power from control board when running. wire 15 goes on bottom terminal, has batt 12V+ from fuse. when you push switch to prime, batt 12V+ is connected thru switch to fuel pump. When genset is running, 12V+ is connected to fuel pump (14A) from wire 14
SeligL
Explorer
Jun 15, 2022
Thanks bounder39zman.

Switch is due to arrive today.

Will hopefully connect wires correctly.
SeligL
Explorer
Jun 18, 2022
Finally received the new prime switch (Generac G092113 Switch from AP Electric & Generators) and wired it as bounder39zman indicated (and so clearly explained how it works).

It works fine now!!

I guess the "ordinary switch" I naively used to replace the cracked one cut off the few pump when in Run mode. This explains why it would run for only 1-2 minutes unless I kept on priming it.

So a BIG THANK YOU to you all for your help, especially bounder39zman
bounder39zman
Explorer II
Jun 20, 2022
Glad I could be of help. (I actually do this sort of thing for a living ...generator tech for 35+ years)
SeligL
Explorer
Jun 20, 2022
Thanks again.

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