| Onan Fuel Pump Mystery [message #176473] |
Thu, 12 July 2012 13:34  |
gbarrow2
Messages: 765
Registered: February 2004
Location: Lake Almanor, Ca./ Red Bl...
Karma: 3
|
Senior Member |
|
|
Onan Experts,
My Onan has run fine for years. Now it will start and run for 30-45 seconds and then die; as if running out of gas.
I jumpered between #5 and #9 terminals on the board. Pump runs fast at first and then slows as it pressurs up.
I ran a hose from a gas can to the pump. Same symptom. I removed the bottom of the pump; filter screen is clean- small amt of stuff in bottom of filter cap.
Reinstalled filter and removed discharge hose from pump. Jumpered 5&9 pump runs and discharges what seems like sufficient fuel. Not a steady stream- it sputters but puts out a lot of fuel.
Reattached hose- Starts up and then dies.
If I try to start again immediatly takes a while of cranking before starting.
If I let the pump run a bit before starting; it will start right away then die as it runs out of gas.
I bought a replacement pump but before installing thought I'd see if there is a simple solution that I'm missing.
Any suggestions? Thanks
Gene Barrow
Lake Almanor, Ca.
1976 Palm Beach
|
|
|
|
| Re: Onan Fuel Pump Mystery [message #176475 is a reply to message #176473] |
Thu, 12 July 2012 13:53  |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
|
Senior Member |
|
|
Hi Gene.. maybe drop the carb bown and clean and squirt carb cleaner up towards the inlet valve as you raise and lower the float. Squirt the passages. just thinkin..
| gbarrow wrote on Thu, 12 July 2012 14:34 |
Onan Experts,
My Onan has run fine for years. Now it will start and run for 30-45 seconds and then die; as if running out of gas.
I jumpered between #5 and #9 terminals on the board. Pump runs fast at first and then slows as it pressurs up.
I ran a hose from a gas can to the pump. Same symptom. I removed the bottom of the pump; filter screen is clean- small amt of stuff in bottom of filter cap.
Reinstalled filter and removed discharge hose from pump. Jumpered 5&9 pump runs and discharges what seems like sufficient fuel. Not a steady stream- it sputters but puts out a lot of fuel.
Reattached hose- Starts up and then dies.
If I try to start again immediatly takes a while of cranking before starting.
If I let the pump run a bit before starting; it will start right away then die as it runs out of gas.
I bought a replacement pump but before installing thought I'd see if there is a simple solution that I'm missing.
Any suggestions? Thanks
|
C. Boyd
76 Crestmont
East Tennessee
|
|
|
|
|
|
|
|
| Re: Onan Fuel Pump Mystery [message #176485 is a reply to message #176477] |
Thu, 12 July 2012 14:41 |
gbarrow2
Messages: 765
Registered: February 2004
Location: Lake Almanor, Ca./ Red Bl...
Karma: 3
|
Senior Member |
|
|
Armand,Chuck, Dan,
Can't check pressure since engine won't run. Oil level is ok.
I assume that the low pressure switch opens the elec ignition circuit so there should be no spark if oil is too low. Engine starts but won't stay lit. That's why I suspect fuel problem.
I'll try what Chuck and Dan say- when it cools down out side. Temp is 102 and rising. Got to 107 yesterday. Sposed to be hotter today.
Still open for other suggestions.
Thanks
Gene Barrow
Lake Almanor, Ca.
1976 Palm Beach
|
|
|
|
|
|
|
|
|
|
| Re: [GMCnet] Onan Fuel Pump Mystery [message #176491 is a reply to message #176485] |
Thu, 12 July 2012 15:10 |
Beach Coach
Messages: 50
Registered: December 2011
Karma: 1
|
Member |
|
|
Hi Gene,
First step: - check the fuel tanks for adequate fuel supply.
Second step: - goto http://www.gmcmhphotos.com/photos/facet-pump/p7114.html ,
this will show you how to check & clean the fuel pump properly. Please note
that when you release the clip pin, parts will fly in all directions, so do
this in an enclosed area.
Hugh MacDougall
Antigonish, Nova Scotia
1978 Palm Beach
1977 Transmode
On Thu, Jul 12, 2012 at 4:41 PM, gene barrow <barrowgene@gmail.com> wrote:
>
>
> Armand,Chuck, Dan,
> Can't check pressure since engine won't run. Oil level is ok.
> I assume that the low pressure switch opens the elec ignition circuit so
> there should be no spark if oil is too low. Engine starts but won't stay
> lit. That's why I suspect fuel problem.
>
> I'll try what Chuck and Dan say- when it cools down out side. Temp is 102
> and rising. Got to 107 yesterday. Sposed to be hotter today.
>
> Still open for other suggestions.
> Thanks
> --
> Gene Barrow
> Lake Almanor, Ca.
> 1976 Palm Beach
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
hugh MacDougall
Antigonish, Nova Scotia
1975 Eleganza II
|
|
|
|
| Re: [GMCnet] Onan Fuel Pump Mystery [message #176501 is a reply to message #176491] |
Thu, 12 July 2012 16:01 |
UziYaH
Messages: 282
Registered: July 2007
Location: 10-O-C
Karma: 0
|
Senior Member |
|
|
Had the same problem with my Onan. Fix? There is a little 'button' in the center of the fuel pump that gets stuck.
http://www.gmcmhphotos.com/photos/facet-pump/p7115.html
Simply 'unstuck' the the button by pushing on it and your Onan might run. Mine did.
Howard Nylander
Royale Class of '78'
Greeneville, Tn.
________________________________
From: Beach Coach <palmbeach78@gmail.com>
To: gmclist@temp.gmcnet.org
Sent: Thursday, July 12, 2012 4:10 PM
Subject: Re: [GMCnet] Onan Fuel Pump Mystery
Hi Gene,
First step: - check the fuel tanks for adequate fuel supply.
Second step: - goto http://www.gmcmhphotos.com/photos/facet-pump/p7114.html ,
this will show you how to check & clean the fuel pump properly. Please note
that when you release the clip pin, parts will fly in all directions, so do
this in an enclosed area.
Hugh MacDougall
Antigonish, Nova Scotia
1978 Palm Beach
1977 Transmode
On Thu, Jul 12, 2012 at 4:41 PM, gene barrow <barrowgene@gmail.com> wrote:
>
>
> Armand,Chuck, Dan,
> Can't check pressure since engine won't run. Oil level is ok.
> I assume that the low pressure switch opens the elec ignition circuit so
> there should be no spark if oil is too low. Engine starts but won't stay
> lit. That's why I suspect fuel problem.
>
> I'll try what Chuck and Dan say- when it cools down out side. Temp is 102
> and rising. Got to 107 yesterday. Sposed to be hotter today.
>
> Still open for other suggestions.
> Thanks
> --
> Gene Barrow
> Lake Almanor, Ca.
> 1976 Palm Beach
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Howard Nylander
Royale Class of "78" "Rocinate"
E-10-o-C
|
|
|
|
| Re: [GMCnet] Onan Fuel Pump Mystery [message #176505 is a reply to message #176486] |
Thu, 12 July 2012 16:58 |
gbarrow2
Messages: 765
Registered: February 2004
Location: Lake Almanor, Ca./ Red Bl...
Karma: 3
|
Senior Member |
|
|
Couldn't get a jumper from terminal 12 to ground so I located the oil pressure switch and jumpped the wire to ground. Onan started and promptly died just as before.
So back to square 1.5. will try cleaning carb before replacing fuel pump. Waiting for cooler temp. Only 106 so far.
Gene Barrow
Lake Almanor, Ca.
1976 Palm Beach
|
|
|
|
| Re: [GMCnet] Onan Fuel Pump Mystery [message #176513 is a reply to message #176505] |
Thu, 12 July 2012 18:11 |
armandminnie
Messages: 864
Registered: May 2009
Location: Marana, AZ
Karma: 2
|
Senior Member |
|
|
| gbarrow wrote on Thu, 12 July 2012 14:58 |
Couldn't get a jumper from terminal 12 to ground so I located the oil pressure switch and jumpped the wire to ground. Onan started and promptly died just as before.
So back to square 1.5. will try cleaning carb before replacing fuel pump. Waiting for cooler temp. Only 106 so far.
|
Gene,my reading of the procedure is that shorting pin 12 to ground is testing that the board will stop the generator if it gets the low pressure signal which is pin 12 is grounded. To test whether that is your problem you need to pull the connector off of pin 12 or take one of the wires off of the switch so it cannot ground pin 12.
Armand Minnie
Marana, AZ
'76 Eleganza II TZE166V103202
visit my gmc blog
click here to visit gmcws.org
|
|
|
|
| Re: [GMCnet] Onan Fuel Pump Mystery [message #176519 is a reply to message #176513] |
Thu, 12 July 2012 18:43 |
gbarrow2
Messages: 765
Registered: February 2004
Location: Lake Almanor, Ca./ Red Bl...
Karma: 3
|
Senior Member |
|
|
Armand,
I've tried it both ways with the same result. When I discovered that I couldn't get a jumper on pin #12 I took off the shroud to find the pressure switch.
I removed the wire and started the Onan and then it died. Reconnected the wire and Replaced the shroud. Then I read Emrey's post again. Realized that his instructions said to ground the wire. So back out to remove the shroud again and ground the wire.
Same result as before; engine starts and then dies in less than a minute.
So unless some one has another suggestion; I'm going to clean the carb as Chuck recommends. After the temp drops down from 108.
I have near full fuel tanks- full oil in Onan- replaced board with Dinosaur board several years ago- removed filter cap from bottom of fuel pump and depressed the ball in the check valve as suggested by Howard.
Don't want to replace the pump till I'm convinced that's the problem.
Can my board be bad again? How can it be checked?
Thanks
Gene Barrow
Lake Almanor, Ca.
1976 Palm Beach
|
|
|
|
|
|
| Re: Onan Fuel Pump Mystery [message #176527 is a reply to message #176485] |
Thu, 12 July 2012 19:42 |
 |
mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
|
Senior Member |
|
|
| gbarrow wrote on Thu, 12 July 2012 12:41 |
...
Can't check pressure since engine won't run. Oil level is ok.
I assume that the low pressure switch opens the elec ignition circuit so there should be no spark if oil is too low. Engine starts but won't stay lit. That's why I suspect fuel problem.
...
|
If the board is jumpered and it still will not stay running, it is _NOT_ the low oil pressure circuits... they have been DISABLED with the jumper. (OBTW, to check JUST the Oil switch, just disconnect pin 12, but do NOT ground it. The switch grounds pin 12 when it senses no pressure.)
If the engine is NOT running and you run the pump, the pump should run until it pressurizes the lines, then slow to a stop. (Sound familiar?) If the pump does this but will not supply enough fuel for sustained running, I would suspect a problem upstream of the pump. Cracked fuel lines (sucking air) or maybe .... low on fuel.
Try running the generator from a fuel can. (Better yet, a outboard boat tank.)
I am glad to hear you are using pin 5, NOT pin 11, for your voltage to apply to pin 9... it is protected by a fuse and could save a board from damage. But yes, I prefer jumping 6 to 9. These are near the bottom of the board and keep the start/stop switches active.
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
|
|
|
|
| Re: Onan Fuel Pump Mystery [message #176551 is a reply to message #176527] |
Thu, 12 July 2012 22:07 |
gbarrow2
Messages: 765
Registered: February 2004
Location: Lake Almanor, Ca./ Red Bl...
Karma: 3
|
Senior Member |
|
|
Mike,
Thanks for the response; but I've done that. Using seperate gas can and a short hose. Starts but will not run.
Pump runs fast at first and then slows but never stops- like the house water pump.
Does that sound like the pump is not supplying enough pressure?
Gene Barrow
Lake Almanor, Ca.
1976 Palm Beach
|
|
|
|
|
|
| Re: [GMCnet] Onan Fuel Pump Mystery [message #176567 is a reply to message #176553] |
Fri, 13 July 2012 01:07 |
|
mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
|
Senior Member |
|
|
Just read somewhere, "Most "carburetor problems" are electrical."
IE: Carbs are fairly reliable, electrical parts are less so.
Anyway, in the days before alcohol laced gas this was VERY true... nowdays... not as much, but still something to think about.
| Robert Mueller wrote on Thu, 12 July 2012 20:12 |
Mine did the EXACT same thing and it was the coil.
-----Original Message-----
From: Marcel Bourgon
Had a similar problem with my Onan last year. Would run for 15 - 20 minutes and would die. Simple fix is replace the fuel pump.
|
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
|
|
|
|
| Re: Onan Fuel Pump Mystery [message #176570 is a reply to message #176551] |
Fri, 13 July 2012 01:23 |
|
mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
|
Senior Member |
|
|
| gbarrow wrote on Thu, 12 July 2012 20:07 |
Mike,
Thanks for the response; but I've done that. Using seperate gas can and a short hose. Starts but will not run.
Pump runs fast at first and then slows but never stops- like the house water pump.
Does that sound like the pump is not supplying enough pressure?
|
Sounds like the pump isn't building enough pressure to stall the pump. If this is "enough" pressure... I do not know. I know a good system will pump to "a stall."
To determine if a problem is fuel related or ignition related I use a trick with starting fluid. (Keep in mind, many do not like using starting fluid, but I only use a small squirt.)
I disconnect the crankcase breather tube, just before the carb. Fire up the generator. As your problem appears and the engine starts to die, squirt a small shot of starter fluid into carb through the breather tube connection. If the engine runs a little longer, your problem is fuel related. (Carb or fuel pump.) If it just dies, you have a problem in your ignition system.
Cuts your problems in half.
I have seen both points and coil cause similar problems.
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
|
|
|
|
| Re: [GMCnet] Onan Fuel Pump Mystery [message #176572 is a reply to message #176567] |
Fri, 13 July 2012 04:49 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
|
Senior Member |
|
|
Take that pump off of the Onan. Remove the bottom nut/cap and remove the filter. Look inside and you should see the plunger and then and then ha round ball bigger than a pencil eraser. Remove the clip and then the ball. Clean the ball and everything else that you can see. That ball is the check valve that operates when the pump is running. If it is not perfectly clean it will leak a bit and even though it will pump up some pressure it will not have the volume to keep the generator running. I'm think you are getting just enough volume to start it but not enough to keep it running.
We use that same pump as a boost pump on carburetor air plane engines. Since it says aircraft on it the price of a replacement pump is several times normal. For that reason we always fix (clean) them rather than replace them.
If ou have some really stubborn deposits, Hoppies #9 gun solvent works good to remove them. Hoppies is what we use to clean aircraft fuel injectors.
The trick of spraying starting fluid or gas or carb cleaner after starting in to the carb throat to keep it running works well to tell if you are fighting a fuel starvation. There is a chance it could be an ignition problem. Keep in mind that that is a wasted spark ignition and the plugs are wires in series. So one bad plug or wire will affect BOTH cylinders. You might pull the plugs, clean them and check the gaps are set exactly to spec. I believe that the gap is.016 but look it up for sure.
To check the wires take an ohmeter and read resistance between both spark plug connectors. I forget what it is but it definitely should not be an open circuit. IF I remember correctly it is around 4,000 ohms. The correct figure is in the Onan manual.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
|
|
|
|
GMCforum
Search
Help
Register
Login
Home
