| Onan fuel pump suction spec [message #184961] |
Tue, 18 September 2012 10:16  |
kwharland
Messages: 246
Registered: November 2005
Location: Central Florida
Karma: 0
|
Senior Member |
|
|
I've developed a problem that appears to be related to the Onan fuel pump. What is the desired suction on the inlet side? Mine's barely reading 1" of vacuum which seems weak to me.
1978 Eleganza II
|
|
|
|
| Re: Onan fuel pump suction spec [message #184965 is a reply to message #184961] |
Tue, 18 September 2012 10:51  |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
|
Senior Member |
|
|
| kwharland wrote on Tue, 18 September 2012 08:16 |
I've developed a problem that appears to be related to the Onan fuel pump. What is the desired suction on the inlet side? Mine's barely reading 1" of vacuum which seems weak to me.
|
I have never seen a fuel pump rated at the intake only the output PSI.
Roy Keen
Minden,NV
76 X Glenbrook
|
|
|
|
| Re: Onan fuel pump suction spec [message #184966 is a reply to message #184961] |
Tue, 18 September 2012 10:54 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
|
Senior Member |
|
|
It's not uncomon to have a bad hose that leaks air and the most likely place to leak is at the gas tank connection.
Roy Keen
Minden,NV
76 X Glenbrook
|
|
|
|
| Re: Onan fuel pump suction spec [message #184987 is a reply to message #184965] |
Tue, 18 September 2012 13:23 |
kwharland
Messages: 246
Registered: November 2005
Location: Central Florida
Karma: 0
|
Senior Member |
|
|
After thinking about this for a bit, I decided I need to re-test using a known supply of fuel plus having the pump vertical. I haven't looked inside yet, but often check valves in smaller systems work using gravity only and I may have defeated that with my first test.
And Roy is correct, most ratings are output but if it's not gravity fed and it can't create enough suction to pull fuel to the pump, it's not going to have any output...which is the symptom I'm dealing with.
And it's my feeling a leaky hose from the fuel tank would show up as just that...a leak! I'm not inclined to replace hoses considering the difficulty of that task until I'm more certain of my problem.
1978 Eleganza II
|
|
|
|
| Re: [GMCnet] Onan fuel pump suction spec [message #184996 is a reply to message #184987] |
Tue, 18 September 2012 14:41 |
Jim Miller
Messages: 501
Registered: March 2008
Karma: 10
|
Senior Member |
|
|
On Sep 18, 2012, at 2:23 PM, Ken Harland wrote:
> After thinking about this for a bit, I decided I need to re-test using a known supply of fuel plus having the pump vertical. I haven't looked inside yet, but often check valves in smaller systems work using gravity only and I may have defeated that with my first test.
Old gasoline that has turned to varnish will cause the check valve in the pump to stick open or closed. I've had that happen once or twice; a gentle tap on the side of the case seems to loosen it back up.
I do not think there are any mounting orientation requirements on the cylindrical Facet pumps. I have one of them mounted horizontally on a jet engine test stand and it has no problem keeping the turbine fed with Jet-A at 30 GPH.
--Jim Miller
1977 Eleganza II
1977 Royale
Hamilton, OH
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Jim Miller
1977 Eleganza II
1977 Royale
Hamilton, OH
|
|
|
|
|
|
| Re: [GMCnet] Onan fuel pump suction spec [message #185058 is a reply to message #185018] |
Tue, 18 September 2012 22:37 |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
|
Senior Member |
|
|
| kwharland wrote on Tue, 18 September 2012 17:33 |
Problem solved, lower check valve had a piece of debris keeping it from closing. Cleaned entire pump and filter screen and all is well.
|
If you tested the suction after the repair, what was it???
Curious minds want to know.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
|
|
|
|
| Re: [GMCnet] Onan fuel pump suction spec [message #185085 is a reply to message #185058] |
Wed, 19 September 2012 11:33 |
kwharland
Messages: 246
Registered: November 2005
Location: Central Florida
Karma: 0
|
Senior Member |
|
|
Interestingly enough, suction after cleaning was still the same. And considering the design of the pump, a suction test is really a poor test but I was grasping at straws at the time.. The pumps use fairly loose clearances in the piston and without fluid in that gap, suction will always be minimal. It's pumping at 3-4 psi now which is more than adequate for the generator.
1978 Eleganza II
|
|
|
|
| Re: Onan fuel pump suction spec [message #185092 is a reply to message #184987] |
Wed, 19 September 2012 12:28 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
|
Senior Member |
|
|
| kwharland wrote on Tue, 18 September 2012 11:23 |
After thinking about this for a bit, I decided I need to re-test using a known supply of fuel plus having the pump vertical. I haven't looked inside yet, but often check valves in smaller systems work using gravity only and I may have defeated that with my first test.
And Roy is correct, most ratings are output but if it's not gravity fed and it can't create enough suction to pull fuel to the pump, it's not going to have any output...which is the symptom I'm dealing with.
And it's my feeling a leaky hose from the fuel tank would show up as just that...a leak! I'm not inclined to replace hoses considering the difficulty of that task until I'm more certain of my problem.
|
Glad to hear you fixed it. Fuel hose problems on the suction side (tank to pump) don't always drip on the ground sometimes they just leak a small amount of air into the hose.
Roy Keen
Minden,NV
76 X Glenbrook
|
|
|
|
GMCforum
Search
Help
Register
Login
Home
