[GMCnet] Onan No power to fuel pump

[Richard MacDonald]

Ran Onan over a hour for the A/C Sunday, today would not start. Checked filters and fuel available. Connected external 12v to pump and got fuel.
Suggestions ?


--
Richard MacDonald
Punta Gorda, Florida
76 Edgemonte TZE 266V102313
Howell TBI EBL


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[Matt Colie]

Oldngray wrote on Wed, 16 July 2014 15:50

> Ran Onan over a hour for the A/C Sunday, today would not start. Checked filters and fuel available. Connected external 12v to pump and got fuel.
> Suggestions ?

Richard,
The fuel pump is on the same circuit as the ignition.
Check for bad connections and even the ground at the mounting ear.

Matt - Underway to Evart


--
Matt & Mary Colie - Members GMCMI, GMCES
'73 Glacier 23 With 4 Rear Brakes that pull as they should
SE Michigan - Twixt A2 and Detroit

[Steve Southworth]

Oldngray wrote on Wed, 16 July 2014 14:50

> Ran Onan over a hour for the A/C Sunday, today would not start. Checked filters and fuel available. Connected external 12v to pump and got fuel.
> Suggestions ?

I your unit has not been modified then follow the wire from the fuel pump back towards the ignition coil. There will be a tube with a quick connect
splice in it. These are notorius for coming apart or failing. They are quite brittle and, generally, reconnecting them is not successful. Cut off
the old connectors and crimp on new quick disconnects. Use the insulated quick disconnects and throw out the tube that covered the old splice.
--
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI

[Richard MacDonald]

Mine was bad too, installed new bullet connector, still no power to pump. Engine runs when I connect external 12v to pump.

--
Richard MacDonald
Punta Gorda, Florida
76 Edgemonte TZE 266V102313
Howell TBI EBL

[Ken Burton]

You need to check pin 9 on the board. If there is +12 there when cranking then you have a wiring problem. Pin 9 feeds both the ignition and the fuel
pump.

Another quick test would be to jumper 5 to 9 and see if it starts. If it does then the wiring to the pump and ignition are OK and your problem is
back on the board.


--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

[Steve Adams]

Exactly what Ken said. Jump pin 5 to 9 to determine if wiring or board is at fault.
--
1978 GMC Royal
Eastern Pennslyvania
1968 Chevrolet C20 396 Camper Special
1969 Chevrolet C20 Camper Special
1985 Buick Electra Park Avenue
1992 Camaro 25th Anniversary Heretage Edition Black

[Jim Kanomata]

On the Onan, there is considerable vibration, so the board takes lot of
abuse.
It is not a bad Idea to carry a extra board and a 5 amp fuse.
Bridge rectifier is also another thing to carry with you.
Other than the fuse, they are not easy to acquire, not even our master
Cummins/Onan caries them.
In fact they call us or parts on these units.
We stock 2 type of boards; one is like the origniol and the other is with a
short harness for 76-78.
When Dwayne Simmons was alive he rebuilt them for us, but later they became
unreliable.
The new ones by Dyno Electric has been working well.

--
Jim Kanomata
Applied/GMC, Fremont,CA
ji...@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502

[Ken Burton]

I have repaired a lot of those boards in the past and believe me it is not worth the effort. Also the relay that fails most often is NLA (No longer
available). I tell people to go get a replacement board if they can not repair it on themselves. Jim stocks and sells the Dinosaur Electronics
board. I have one on my coach. I got tired of repairing the OEM Onan one. I think they are about $140 but check the Applied GMC Web site for a
price or call Jim K. direct. 1-800-752-7502.

Ken B.

jimk wrote on Thu, 17 July 2014 00:10

--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

[Richard MacDonald]

Have been under the weather this past week so not much into working on this problem.
Which Board do I check, inside control panel or the one on the Generator?

Where could I see a layout of the Board showing the location of pins and their numbers?

Thanks

--
Richard MacDonald
Punta Gorda, Florida
76 Edgemonte TZE 266V102313
Howell TBI EBL

[A.]

Oldngray wrote on Mon, 21 July 2014 15:28

> Have been under the weather this past week so not much into working on this problem.
> Which Board do I check, inside control panel or the one on the Generator?
>
> Where could I see a layout of the Board showing the location of pins and their numbers?
>
> Thanks

http://gmcws.org/Tech/dsimmons/onan/p04.jpg

What the diagram shows is that
pin 1 on the Onan board goes to connector 2 on the remote start/stop switch,
pin 2 on the Onan board goes to connector 1 on the remote start/stop switch,
pin 3 on the Onan board goes to connector 3 on the remote start/stop switch,
pin 4 on the Onan board is not used,
pin 6 on the Onan board goes to connector 4 on the remote start/stop switch,
pin 5 on the Onan board goes to connector 6 on the remote start/stop switch.

Note: Pins 1 to 6 have two pins each, one across the top to connect to the remote and another down lower, mixed in with the rest of the stuff.

Pin 1 is ground for the board. it is also connected to the remote, providing a ground to the remote switch.

Pin 2 is the input to the board for the remote stop function. Grounding this pin cause the board to shut off the generator.

Pin 3 is the input to the board for the remote start function. Grounding this pin cause the board to start the generator.

Pin 4 doesn't seem to be used in our application. Looks like another input into the same circuits that the oil pressure switch connect to.

Pin 5 is FUSED 12 volts from the battery.

Pin 6 has 12volts (fused) only when the generator is running.

Pin 7 is the ground side of the coil of the start solenoid. Grounding this point should cause the starter to engage.

Pin 8 is an A/C "generator running" input to the board from the flywheel alternator. (The other side of this AC signal is pin 5.) It disengages the
starter and "latches" the voltage provided to pin 9.

Pin 9 is the output of the board to BOTH the ignition and the fuel pump. If there is voltage here, the pump should be running and the points/coil
should have power.

Pin 10 has 12volts from the starter solenoid when the starter is engaged. It provides power to pin 9 when starting.

Pin 11 is UN-FUSED 12 volts from the battery.

Pin 12 is the input of the board from the oil pressure switch. The switch applies a ground when there isn't oil pressure. Just disconnecting this pin
disables the function.

NOW for the methods of jumping (bypassing):

The main differences in jumping is where the power comes from, all of them connect to pin 9 (electrically the same point as the + side of the coil,
the fuel pump and the fuel shut-off solenoid):

Method 1.) Some jump from pin 11 but it is better to use fused power on pin 5. It pin 11 works but pin 5 does not, look at the fuse.

Method 2.) The most popular spot is pin 5. You still use the button on the board to get the starter to turn. But you need to un-jumper the pins to
turn off the generator.

Method 3.) Relatively unknown method is pin 6. This disables the generator running and low oil pressure functions but maintains BOTH the start AND
STOP functions of the board. As the lower pin 6 is right next to pin 9, a short one inch jumper can be left in place with the cover on and genset
pushed back in the "Onan-hole." Be aware that if you try to start the generator but it doesn't start, there will still be power to the pump and
ignition until you press "stop." While all methods keep the power on pin 9, it is just easier to forget without a wire hanging off the generator.

--
'73 23' Sequoia For Sale
'73 23' CanyonLands For Sale
Upper Alabama

[Richard MacDonald]

Wow, now that is a Tutorial, now I will try to use it.

Thank you

--
Richard MacDonald
Punta Gorda, Florida
76 Edgemonte TZE 266V102313
Howell TBI EBL

[A.]

Oldngray wrote on Mon, 21 July 2014 18:43

> Wow, now that is a Tutorial, now I will try to use it.
> Thank you

Credit belongs to the late Duane Simmons. I copied it from somewhere and keep it in a text file in my GMC directory.

--
'73 23' Sequoia For Sale
'73 23' CanyonLands For Sale
Upper Alabama

[gene Fisher]

Read here
http://www.gmcmhphotos.com/photos/gmc-chemicals-and-tools/p55261-yuno-board.html

Erf

--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html

[Richard MacDonald]

I had a spare Board, Mr Onan now runs like a Champ. Thanks everyone for your help.