Cummins Onan QG generator

[Stonne]

Hello RV Forum,

I am a new member here.

I have a Cummins Onan QG 4000 generator onboard my 2018 Jayco Redhawk 25R. The other day, I went to do a monthly startup, but the generator would not start.
The investigation found a mouse took up residence on top of the gen and chewed through two of the wires in the harness between the control board and the Fuel Cut-off valve and the other was between the control board and P6 of the generator (AC Sense L1). I lower the generator out of the RV and made repairs to the chewed wires. The generator will now start and run fine but there are now two issues that I need help with. First, the generator will not STOP from either the local switch or the remote switch, both will start the generator, the only way to stop it is to disconnect the battery or cut-off the fuel. The other problem is the fuel pump starts as soon as the battery is connected without pushing the primer button.

I hope I do not have to get a new control board. $700+. I am thinking that maybe the T1 ignition coil is not getting the, Ignition Kill, signal. But I have no idea why the fuel pump starts right away.

Any thoughts would be a help.

Thank you in advance.

 

[Henry J Fate]

First thought is the mice may have done more damage than you could see or possibly (no offense we all have been there) the repair was not done correctly. Before spending money for new stuff, it may be a good idea to drop the generator and have a closer look for something that may have been missed or repaired incorrectly.

Also....It is a good idea to screen the cooling air exhaust area and the air intake. I got bit by the rodents several years ago and they made a meal of my harness too. Since then I screen and no problem. It does restrict the air flow proportionately to the screening material used though. I designed mine to be removable for times when its not needed or the high heat temps.

 

[Stonne]

First thought is the mice may have done more damage than you could see or possibly (no offense we all have been there) the repair was not done correctly. Before spending money for new stuff, it may be a good idea to drop the generator and have a closer look for something that may have been missed or repaired incorrectly.

Also....It is a good idea to screen the cooling air exhaust area and the air intake. I got bit by the rodents several years ago and they made a meal of my harness too. Since then I screen and no problem. It does restrict the air flow proportionately to the screening material used though. I designed my to be removable for times when its not needed or the high heat temps.

Thanks, Henry; No offense taken on the repair comment. I went back and double and triple-checked my repairs to make sure that they were correct. The only place that I can not get to see if there is any mice damage is at the T1 connection. It is up inside the generator. All other wires appear to be in good shape. There is no other evidence of rodent damage. I will install screening around the inside of the housing before reinstalling the gen-set back up into the RV.

 

[DonTom]

. First, the generator will not STOP from either the local switch or the remote switch, both will start the generator, the only way to stop it is to disconnect the battery or cut-off the fuel. The other problem is the fuel pump starts as soon as the battery is connected without pushing the primer button.

Is the relay staying closed after you once start it? Won't open on command? Primary coil voltage won't go away?

This relay:



-Don- Reno, NV

 

[Stonne]

The 12 volts is at the solenoid coil during startup then drops to zero volts when the engine reaches normal running rpm's, about 2 seconds.

 

[DonTom]

The 12 volts is at the solenoid coil during startup then drops to zero volts when the engine reaches normal running rpm's, about 2 seconds.

Do the contacts then open? Could you have a melted together (closed) normally open relay contacts preventing the normal shutdown?

-Don- Reno, NV

 

[Stonne]

I have removed and bench-tested the solenoid. It works as designed.

 

[DonTom]

Is there a way to disconnect the remote cable and try to turn it off from the genny itself to see if there is a short in the cable?

Or with the power off, check the resistance across the open start switch with the cable still connected.

-Don- Reno, NV

 

[Stonne]

I have tested both of your suggestions. I have done a continuity test on all wires of the cable harness. There are no shorts or opens. The generator runs fine and puts out 122 volts @ 62.0 Hz with no load and 120.1 volts @ 60.2 Hz under load (AC). The only conclusion I can make, is that the control board is not putting out the 'Ignition Kill' signal that puts ground to the spark plug coil, which would stop the engine. I installed a battery disconnect switch at the generator housing which stops the engine when the switch is turned off. The generator is now back up under the RV as I will leave it as is. Thank you to everyone who replied

 

[DonTom]

I have tested both of your suggestions. I have done a continuity test on all wires of the cable harness. There are no shorts or opens. The generator runs fine and puts out 122 volts @ 62.0 Hz with no load and 120.1 volts @ 60.2 Hz under load (AC). The only conclusion I can make, is that the control board is not putting out the 'Ignition Kill' signal that puts ground to the spark plug coil, which would stop the engine. I installed a battery disconnect switch at the generator housing which stops the engine when the switch is turned off. The generator is now back up under the RV as I will leave it as is. Thank you to everyone who replied

It's good to check all other possibilities, and it seems you have. It sounds like you have figured out that your issue is on the control board and most likely is at this point.

-Don- Auburn, CA