Onan 7.5DKDFJ Generator Fuel Shut Off Solenoid

Pete Beau · 08-09-2016, 07:23 AM

My Onan generator won’t start due to the fuel shut off solenoid not pulling open on start up. If I manually open the solenoid it will start. Furthermore, if I hold it until it generates electrical power the solenoid will ‘hold’ open and shut off normally.

My question is the voltage to the (3) terminals on the solenoid. During cranking to start, the top lug (positive terminal) has 12.3 volts. The bottom lug (aux.) has 1.6 volts.

Running and the solenoid in ‘hold’ position the top lug has 14.4 volts and the bottom lug has .06 volts.
Are these readings OK and I have a bad solenoid?

Thank you in advance.

Pete Beau

Rich Biebel · 08-10-2016, 01:35 PM

Solinoid has a "pull" coil and a "hold" coil circuit....if it has 3 terminals on the solenoid.

One terminal is pull, one is hold and the other is common or ground.....

The pull coil gets energized during cranking. Drops out and hold coil keeps it energized once it's running and generating ouptput.

The higher voltage you see running is charging voltage....they have alternators....usually a little one like a Shogun....with a separate V/R-rectifier

Might just be a bad solenoid. Or possibly a control issue.

If it stays in once it's running the hold circuit is good.

I would use a voltmeter to see if the "pull" side of the solenoid is getting voltage during cranking.....

If it is the solenoid is bad.....
If it isn't the pull circuit has to be diagnosed.
A print from a Service Manual will be needed....

You could use a jumper and hit the terminal NOT energized when it's running on the solenoid with 12+ to see if it pulls in as long as the negative or common is connected to B-

A Fluke Voltmeter shows you DC polarity.......when something is energized.....I use it all the time to ID DC circuits that way....

Rich Biebel · 08-10-2016, 06:00 PM

Pete I looked in the print for your machine and the pull coil B+ comes from a relay. Not sure if it is on a board or seperate. Just track that aux. terminal wire back to it's source. Probably not as easy as it sounds but that is what you have to do. That is assuming the solinoid test we talked about on the phone proved the solinoid itself was moving once you externally powered the aux terminal....

08-09-2016, 07:23 AM	#1
Pete Beau Member Join Date: Sep 2002 Location: The Mo-ta City Posts: 245 Likes: 51 Liked 30 Times in 11 Posts	Onan 7.5DKDFJ Generator Fuel Shut Off Solenoid My Onan generator won’t start due to the fuel shut off solenoid not pulling open on start up. If I manually open the solenoid it will start. Furthermore, if I hold it until it generates electrical power the solenoid will ‘hold’ open and shut off normally. My question is the voltage to the (3) terminals on the solenoid. During cranking to start, the top lug (positive terminal) has 12.3 volts. The bottom lug (aux.) has 1.6 volts. Running and the solenoid in ‘hold’ position the top lug has 14.4 volts and the bottom lug has .06 volts. Are these readings OK and I have a bad solenoid? Thank you in advance. Pete Beau

08-10-2016, 01:35 PM	#2
Rich Biebel VIP Member Join Date: Jun 2007 Location: Northern New Jersey suburbs Posts: 2,275 Likes: 25 Liked 510 Times in 200 Posts	Re: Onan 7.5DKDFJ Generator Fuel Shut Off Solenoid Solinoid has a "pull" coil and a "hold" coil circuit....if it has 3 terminals on the solenoid. One terminal is pull, one is hold and the other is common or ground..... The pull coil gets energized during cranking. Drops out and hold coil keeps it energized once it's running and generating ouptput. The higher voltage you see running is charging voltage....they have alternators....usually a little one like a Shogun....with a separate V/R-rectifier Might just be a bad solenoid. Or possibly a control issue. If it stays in once it's running the hold circuit is good. I would use a voltmeter to see if the "pull" side of the solenoid is getting voltage during cranking..... If it is the solenoid is bad..... If it isn't the pull circuit has to be diagnosed. A print from a Service Manual will be needed.... You could use a jumper and hit the terminal NOT energized when it's running on the solenoid with 12+ to see if it pulls in as long as the negative or common is connected to B- A Fluke Voltmeter shows you DC polarity.......when something is energized.....I use it all the time to ID DC circuits that way.... __________________ Rich Biebel S/C 1479 Last edited by Rich Biebel; 08-10-2016 at 01:39 PM.

08-10-2016, 06:00 PM	#3
Rich Biebel VIP Member Join Date: Jun 2007 Location: Northern New Jersey suburbs Posts: 2,275 Likes: 25 Liked 510 Times in 200 Posts	Re: Onan 7.5DKDFJ Generator Fuel Shut Off Solenoid Pete I looked in the print for your machine and the pull coil B+ comes from a relay. Not sure if it is on a board or seperate. Just track that aux. terminal wire back to it's source. Probably not as easy as it sounds but that is what you have to do. That is assuming the solinoid test we talked about on the phone proved the solinoid itself was moving once you externally powered the aux terminal.... __________________ Rich Biebel S/C 1479