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Topic: Generator cranks but will not start (Read 750 times) previous topic - next topic

Generator cranks but will not start

My 7.5 Onan will crank over but I doesn't have power going to the fuel pump or solenoid. I jumped from the switch to the fuel pump and it works. Held throttle by hand I fired up. Can't find the reason I don't have power to the controls.
1992 Silver Anniversary Unihome 4000
WTBA. 350 hp Detroit, Allison HT 746
Build number 4022

Re: Generator cranks but will not start

Reply #1 –
Possible bad high temp, low O/P shutdown sensor? Blown fuse some where? Just a WAG don't know much about Onan
Bruce, Linda, and Macy
Zoey RIP 1/20/19
1999 U295 40' build #5400
2017 silver Jeep Wrangler, 1260 watts of solar on top
Moving around the country

Re: Generator cranks but will not start

Reply #2 –
Is it gas or diesel?
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Generator cranks but will not start

Reply #3 –
Diesel
1992 Silver Anniversary Unihome 4000
WTBA. 350 hp Detroit, Allison HT 746
Build number 4022

Re: Generator cranks but will not start

Reply #4 –

Maybe this will help

http://truckroadservice.com/barth_attachments/682105772_Onan_DKD_Service_Manual.pdf
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Generator cranks but will not start

Reply #5 –
I seem to remember that there is a circuit breaker that If tripped will keep it from starting.
previous 1984 35 ft ORED 250 HP 3208 Cat       
previous 1998 40 ft U295 CAI 325 hp Cummins
previous 2003 40 Ft u320 build #6140 450 Cummins M11.                                                         
1999 Mazda Miata
Ron, Nancy, Tipper the cat, Max The dog
1997 U 270 36 ft build number 5174 8.3 Cummins

Re: Generator cranks but will not start

Reply #6 –
What does the exhaust look like while the engine is cranking?
    White smoke = unburned fuel
    Black smoke = partially burned fuel
    No smoke = no fuel.

Open the oil fill cap to see what comes out while cranking.
       
If diesel cranks without starting it is not getting fuel. Crack an injector fuel line to see if fuel is getting to the injector while cranking. Be careful that is high pressure fuel. If no fuel check everything from the injector pump back to the fuel tank.

Tim Dianics
Pam Sapienza
Vader PupZilla Labrador Canine Beast (AKA Pup)
Columbia, MO
1996 U320 4000
2021 Jeep Gladiator, Diesel

Re: Generator cranks but will not start

Reply #7 –
Quote from: Silvbullet –
My 7.5 Onan will crank over but I doesn't have power going to the fuel pump or solenoid. I jumped from the switch to the fuel pump and it works. Held throttle by hand I fired up. Can't find the reason I don't have power to the controls.

What year is your 7.5 Onan generator? Assuming it is around early 1990, it has very similar issue as mine.
I was able to get the generator running by supplying the fuel pump with external 12V power and hold the solenoid. But there is no 12V power came from the control box.


I have to buy a new control board (Onan 300-2604) from flight systems for $200

Also, there are loose wires. I couldn't figure out which one is loose, so I hired an experienced Onan technician to fixed everything.

According to the technician,
    • Loose ground connection at A11 board
    • Loose connection @ K13+14

If you open the control box, you will see all wires are labeled with these numbers. You can try to to tighten all screws you can find and see if it can fix the issue.

Good luck!
1991 Grand Villa U300

Re: Generator cranks but will not start

Reply #8 –
I just bought the control board, I think I broke the start switch messing with it so I guess I will buy one of those.
1992 Silver Anniversary Unihome 4000
WTBA. 350 hp Detroit, Allison HT 746
Build number 4022