Onan issue

There are times when the oil thins out after running and the oil pressure
drops, the standart pressure sensor will shut off.
I'm not sure of that sender we use, but that can be a possibility.
You can fool the sender and see.
These engines are older and as it wears, the oil pressure does drop some
when oil get warm.

> I have had many years of experience with air cooled, valve in block
> engines, and over time I have encountered several instances of expanding
> engine blocks that "used up" all the valve to valve tappet clearance when
> they got hot. This would prevent the valve, or valves, from opening fully
> and no fuel mixture or not enough fuel mixture could enter the cylinder.
> Then the engine acts like it is running out of gas, which it is, but for a
> different reason. One of my John Deere riding mower with a Kohler engine
> did this, and it took me quite a while to figure out what was going on.
> Cure? Grind a bit more clearance off the end of the valve stem. Worked for
> me.
> Jim Hupy
> (Retired Vocational Instructor in Small Engines and Power Mechanics)
> Salem, Oregon
>

>
> > Good point, Sully. Fuel starvation must not be the problem, at least not
> > due to a restriction in the pick-up.
> > --
> > Carl Stouffer
> > '75 ex Palm Beach
> > Tucson, AZ.
> > Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive,
> > Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American
> > Eagles,
> > Solar battery charging. GMCSJ and GMCMI member
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>

--
Jim Kanomata ASE
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
 
I assume the oil pressure switch was bypassed via jumper in earlier
troubleshooting, is that the case Jon?

Sully
bellevue wa

> There are times when the oil thins out after running and the oil pressure
> drops, the standart pressure sensor will shut off.
> I'm not sure of that sender we use, but that can be a possibility.
> You can fool the sender and see.
> These engines are older and as it wears, the oil pressure does drop some
> when oil get warm.
>

>
> > I have had many years of experience with air cooled, valve in block
> > engines, and over time I have encountered several instances of expanding
> > engine blocks that "used up" all the valve to valve tappet clearance when
> > they got hot. This would prevent the valve, or valves, from opening fully
> > and no fuel mixture or not enough fuel mixture could enter the cylinder.
> > Then the engine acts like it is running out of gas, which it is, but for
> a
> > different reason. One of my John Deere riding mower with a Kohler engine
> > did this, and it took me quite a while to figure out what was going on.
> > Cure? Grind a bit more clearance off the end of the valve stem. Worked
> for
> > me.
> > Jim Hupy
> > (Retired Vocational Instructor in Small Engines and Power Mechanics)
> > Salem, Oregon
> >

> >
> > > Good point, Sully. Fuel starvation must not be the problem, at least
> not
> > > due to a restriction in the pick-up.
> > > --
> > > Carl Stouffer
> > > '75 ex Palm Beach
> > > Tucson, AZ.
> > > Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final
> drive,
> > > Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American
> > > Eagles,
> > > Solar battery charging. GMCSJ and GMCMI member
> > > _______________________________________________
> > > GMCnet mailing list
> > > Unsubscribe or Change List Options:
> > >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> >
>
>
> --
> Jim Kanomata ASE
> Applied/GMC, Newark,CA
> jimk
> http://www.gmcrvparts.com
> 1-800-752-7502
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
 
I have not seen that method published .

> I assume the oil pressure switch was bypassed via jumper in earlier
> troubleshooting, is that the case Jon?
>
> Sully
> bellevue wa
>
> On Wed, Sep 15, 2021 at 4:58 PM Jim Kanomata

>
> > There are times when the oil thins out after running and the oil pressure
> > drops, the standart pressure sensor will shut off.
> > I'm not sure of that sender we use, but that can be a possibility.
> > You can fool the sender and see.
> > These engines are older and as it wears, the oil pressure does drop some
> > when oil get warm.
> >

> >
> > > I have had many years of experience with air cooled, valve in block
> > > engines, and over time I have encountered several instances of
> expanding
> > > engine blocks that "used up" all the valve to valve tappet clearance
> when
> > > they got hot. This would prevent the valve, or valves, from opening
> fully
> > > and no fuel mixture or not enough fuel mixture could enter the
> cylinder.
> > > Then the engine acts like it is running out of gas, which it is, but
> for
> > a
> > > different reason. One of my John Deere riding mower with a Kohler
> engine
> > > did this, and it took me quite a while to figure out what was going on.
> > > Cure? Grind a bit more clearance off the end of the valve stem. Worked
> > for
> > > me.
> > > Jim Hupy
> > > (Retired Vocational Instructor in Small Engines and Power
> Mechanics)
> > > Salem, Oregon
> > >
> > > On Wed, Sep 15, 2021, 2:23 PM Carl Stouffer

> > >
> > > > Good point, Sully. Fuel starvation must not be the problem, at least
> > not
> > > > due to a restriction in the pick-up.
> > > > --
> > > > Carl Stouffer
> > > > '75 ex Palm Beach
> > > > Tucson, AZ.
> > > > Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final
> > drive,
> > > > Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American
> > > > Eagles,
> > > > Solar battery charging. GMCSJ and GMCMI member
> > > > _______________________________________________
> > > > GMCnet mailing list
> > > > Unsubscribe or Change List Options:
> > > >
> > > _______________________________________________
> > > GMCnet mailing list
> > > Unsubscribe or Change List Options:
> > >
> >
> >
> > --
> > Jim Kanomata ASE
> > Applied/GMC, Newark,CA
> > jimk
> > http://www.gmcrvparts.com
> > 1-800-752-7502
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>

--
Jim Kanomata ASE
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
 
There is a way iirc to bypass the lop switch in Duane Simmons diagnostic
chart to isolate it from the equation. Cannot remember which pins to jump
however.

Sully
bellevue wa

> I have not seen that method published .
>

>
> > I assume the oil pressure switch was bypassed via jumper in earlier
> > troubleshooting, is that the case Jon?
> >
> > Sully
> > bellevue wa
> >
> > On Wed, Sep 15, 2021 at 4:58 PM Jim Kanomata

> >
> > > There are times when the oil thins out after running and the oil
> pressure
> > > drops, the standart pressure sensor will shut off.
> > > I'm not sure of that sender we use, but that can be a possibility.
> > > You can fool the sender and see.
> > > These engines are older and as it wears, the oil pressure does drop
> some
> > > when oil get warm.
> > >
> > > On Wed, Sep 15, 2021 at 2:56 PM James Hupy

> > >
> > > > I have had many years of experience with air cooled, valve in block
> > > > engines, and over time I have encountered several instances of
> > expanding
> > > > engine blocks that "used up" all the valve to valve tappet clearance
> > when
> > > > they got hot. This would prevent the valve, or valves, from opening
> > fully
> > > > and no fuel mixture or not enough fuel mixture could enter the
> > cylinder.
> > > > Then the engine acts like it is running out of gas, which it is, but
> > for
> > > a
> > > > different reason. One of my John Deere riding mower with a Kohler
> > engine
> > > > did this, and it took me quite a while to figure out what was going
> on.
> > > > Cure? Grind a bit more clearance off the end of the valve stem.
> Worked
> > > for
> > > > me.
> > > > Jim Hupy
> > > > (Retired Vocational Instructor in Small Engines and Power
> > Mechanics)
> > > > Salem, Oregon
> > > >
> > > > On Wed, Sep 15, 2021, 2:23 PM Carl Stouffer

> > > >
> > > > > Good point, Sully. Fuel starvation must not be the problem, at
> least
> > > not
> > > > > due to a restriction in the pick-up.
> > > > > --
> > > > > Carl Stouffer
> > > > > '75 ex Palm Beach
> > > > > Tucson, AZ.
> > > > > Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final
> > > drive,
> > > > > Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear
> American
> > > > > Eagles,
> > > > > Solar battery charging. GMCSJ and GMCMI member
> > > > > _______________________________________________
> > > > > GMCnet mailing list
> > > > > Unsubscribe or Change List Options:
> > > > >
> > > > _______________________________________________
> > > > GMCnet mailing list
> > > > Unsubscribe or Change List Options:
> > > >
> > >
> > >
> > > --
> > > Jim Kanomata ASE
> > > Applied/GMC, Newark,CA
> > > jimk
> > > http://www.gmcrvparts.com
> > > 1-800-752-7502
> > > _______________________________________________
> > > GMCnet mailing list
> > > Unsubscribe or Change List Options:
> > >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> >
>
>
> --
> Jim Kanomata ASE
> Applied/GMC, Newark,CA
> jimk
> http://www.gmcrvparts.com
> 1-800-752-7502
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
 
I was under the impression, if you jumper from pin 9 to pin 5, and start the generator, that you are basically by-passing everthing on the control
board including the LOP. so that is all that we have done.

Looking at Duane's information, it might be a little more complicated then that. this being a dinosaur board currently it does not really have
"pins" wires are soldered direct to board, so jumpering is a little more difficult, but can be done. we can always re-install another old board
too.

but isn't the LOP switch itself just a grounding thing? so if a person disconnects the LOP switch entirely, it should be open circuit and fool it
into thinking the oil pressure is fine?

we are dealing with fresh oil. It is Ed's, but I believe he is running SAE 30 VR1. I know I realy topped off the oil and probably a little over
filled the oil last week, and did not change a thing. I think he sucked some oil out yesterday to meet the top mark and did not effect.

the reason he did that is he went down to the onan dealer and talked to them. He also bought onan coil and condenser, and I think new plug wires.
he talked to a couple tech's. one was an idiot, who told him overfilled oil can cause shut down, then followed that statement up with he needs to
read the codes off the diagnostic light near the switch. Ed had to explain to him that the diagnostic light on onan generators were not around in
the 70's. Probably not the 80's or 90's either? Another Tech came out and seemed to have a better grasp of a 70's onan model. He did not like
the idea of the Harly coil, and there is a relationship with spark plugs, coils and plug gaps that can cause some issues. So now it has a Onan coil
in it, and still seems to be same problem.

I think to add fuel to the fire, I might run over there this weekend and we can take the heads off and do a quick carbon clean up. His is a low
hour onan, but one never knows. That is easy thing to do. I can't imagine that being a problem because of how well and smooth it runs when it is
running. I am still wondering if we are running out of fuel and there is an issue with the new fuel pump.

--
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
 
Let me know via phone as to how it shuts down.
Not worth pulling off the heads yet.
New fuels run very clean so carbon build up is not an issue.

> I was under the impression, if you jumper from pin 9 to pin 5, and start
> the generator, that you are basically by-passing everthing on the control
> board including the LOP. so that is all that we have done.
>
> Looking at Duane's information, it might be a little more complicated then
> that. this being a dinosaur board currently it does not really have
> "pins" wires are soldered direct to board, so jumpering is a little more
> difficult, but can be done. we can always re-install another old board
> too.
>
> but isn't the LOP switch itself just a grounding thing? so if a person
> disconnects the LOP switch entirely, it should be open circuit and fool it
> into thinking the oil pressure is fine?
>
> we are dealing with fresh oil. It is Ed's, but I believe he is running
> SAE 30 VR1. I know I realy topped off the oil and probably a little over
> filled the oil last week, and did not change a thing. I think he sucked
> some oil out yesterday to meet the top mark and did not effect.
>
> the reason he did that is he went down to the onan dealer and talked to
> them. He also bought onan coil and condenser, and I think new plug
> wires.
> he talked to a couple tech's. one was an idiot, who told him overfilled
> oil can cause shut down, then followed that statement up with he needs to
> read the codes off the diagnostic light near the switch. Ed had to
> explain to him that the diagnostic light on onan generators were not around
> in
> the 70's. Probably not the 80's or 90's either? Another Tech came
> out and seemed to have a better grasp of a 70's onan model. He did not like
> the idea of the Harly coil, and there is a relationship with spark plugs,
> coils and plug gaps that can cause some issues. So now it has a Onan coil
> in it, and still seems to be same problem.
>
> I think to add fuel to the fire, I might run over there this weekend and
> we can take the heads off and do a quick carbon clean up. His is a low
> hour onan, but one never knows. That is easy thing to do. I can't
> imagine that being a problem because of how well and smooth it runs when it
> is
> running. I am still wondering if we are running out of fuel and there is
> an issue with the new fuel pump.
>
>
> --
> Jon Roche
> 75 palm beach
> EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
> St. Cloud, MN
> http://lqqkatjon.blogspot.com/
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>

--
Jim Kanomata ASE
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
 
Jon,

Set it up with a remote tank of known clean fuel and suspend it above the
onan. Plumb it directly to the carb inlet upstream of the fuel pump. If you
still have the same problem with this gravity feed system I think you
should be able to rule out fuel supply and fuel pump.
JWID

Sully
Bellevue wa.

> I was under the impression, if you jumper from pin 9 to pin 5, and start
> the generator, that you are basically by-passing everthing on the control
> board including the LOP. so that is all that we have done.
>
> Looking at Duane's information, it might be a little more complicated then
> that. this being a dinosaur board currently it does not really have
> "pins" wires are soldered direct to board, so jumpering is a little more
> difficult, but can be done. we can always re-install another old board
> too.
>
> but isn't the LOP switch itself just a grounding thing? so if a person
> disconnects the LOP switch entirely, it should be open circuit and fool it
> into thinking the oil pressure is fine?
>
> we are dealing with fresh oil. It is Ed's, but I believe he is running
> SAE 30 VR1. I know I realy topped off the oil and probably a little over
> filled the oil last week, and did not change a thing. I think he sucked
> some oil out yesterday to meet the top mark and did not effect.
>
> the reason he did that is he went down to the onan dealer and talked to
> them. He also bought onan coil and condenser, and I think new plug
> wires.
> he talked to a couple tech's. one was an idiot, who told him overfilled
> oil can cause shut down, then followed that statement up with he needs to
> read the codes off the diagnostic light near the switch. Ed had to
> explain to him that the diagnostic light on onan generators were not around
> in
> the 70's. Probably not the 80's or 90's either? Another Tech came
> out and seemed to have a better grasp of a 70's onan model. He did not like
> the idea of the Harly coil, and there is a relationship with spark plugs,
> coils and plug gaps that can cause some issues. So now it has a Onan coil
> in it, and still seems to be same problem.
>
> I think to add fuel to the fire, I might run over there this weekend and
> we can take the heads off and do a quick carbon clean up. His is a low
> hour onan, but one never knows. That is easy thing to do. I can't
> imagine that being a problem because of how well and smooth it runs when it
> is
> running. I am still wondering if we are running out of fuel and there is
> an issue with the new fuel pump.
>
>
> --
> Jon Roche
> 75 palm beach
> EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
> St. Cloud, MN
> http://lqqkatjon.blogspot.com/
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
 
1. Like Sully, I previously suggested suspending a temp tank above the Onan and connecting it
direct to the carb. I hope that is what you did. Run it until it quits. Then see if there is gas in the float bowl. The higher you suspend the
tank the more fuel pressure you will have at the carb.

2. The LOP switch grounds when there is no oil pressure. Simply unplug it and then ONAN will run. I would not run it for long that way in case you
have a real oil pressure problem.
Run it connected and when it starts to fail disconnect the wire. You could also make to a couple of short, 12" or so, jumpers and run them to the
outside of the Onan. Hook one them to the disconnected switch wire and the other to the switch terminal. The other ends of those 2 jumpers can be
connected together outside of the ONAN where you can easily get to them and disconnect them when it starts to fail.

3. I doubt the above will be necessary since you already tried pin 5 jumpered to pin 9 and that eliminates the LOP circuit operation.

In the end you need to diagnose and decide for sure if you are shooting a fuel or an electrical problem. Otherwise 50% of the time you are spinning
your wheels in the wrong part of the Onan.

Good Luck. This sounds like one mean bug.

Ken B.

> Jon,
>
> Set it up with a remote tank of known clean fuel and suspend it above the
> onan. Plumb it directly to the carb inlet upstream of the fuel pump. If you
> still have the same problem with this gravity feed system I think you
> should be able to rule out fuel supply and fuel pump.
> JWID
>
> Sully
> Bellevue wa.
>

>
> > I was under the impression, if you jumper from pin 9 to pin 5, and start
> > the generator, that you are basically by-passing everthing on the control
> > board including the LOP. so that is all that we have done.

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