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

20 Replies

garym114
Explorer II
Jun 07, 2022
The pump runs when the gen is running. Prim just gets gas to the carb for it to start.
SeligL
Explorer
Jun 06, 2022
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.
Grit_dog
Navigator
Jun 06, 2022
OP, I’m not well read enough to say why you’re fuel pump doesn’t stay running.
But the fuel pump should be on all the time it’s running and it does not turn on and off.
If it’s a control board thing, you could bypass to make the fp run all the time but make sure it is wired to shut off when motor is off
Grit_dog
Navigator
Jun 06, 2022
theoldwizard1 wrote:
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.

Re read his description. Carb ain’t gummed up.
SeligL
Explorer
Jun 06, 2022
Thanks oldwizard1.

I’ve been thinking of tackling the carb but does it seem likely that it’s the carb if it runs while fuel pump is on via Prime? I’m thinking it’s likely that the fuel pump is not on if Prime is off.

I presume if that’s the case it’s something in the Control Board, but I’m hoping there is something simple that I can fix to get fuel pump to run when Start is on without Prime.

Can you or someone else please clarify:
When Start pressed fuel pump should run
Does the Control board take over this function or should the fuel pump be on directly from the Start switch.

What does Prime do other than energize the fuel pump? Does it also activate the choke?

I’m not sure I can fix this if it’s the Circuit board.

Thanks for your help.
theoldwizard1
Explorer II
Jun 06, 2022
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.
SeligL
Explorer
Jun 06, 2022
Good suggestion. I’ll try that.
Son_of_Norway
Explorer
Jun 06, 2022
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.
SeligL
Explorer
Jun 06, 2022
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
garym114
Explorer II
Jun 06, 2022
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.

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GENERAC GENERATOR ISSUE

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