New Onan not working right

[Carl Stouffer]

So, the new, reconditioned Onan is not doing it's job reliably. My son picked up the motorhome to take it on a trip to Colorado Springs last evening
and drove it about 7 miles to Costco to get gas. He shut down the generator while pumping gas and it would not restart until some time after he got
home to his house, another 5 miles.

I had set the timing and adjusted the carburetor and run the generator, under load, for at least a half hour with no issues. I suggested that Mark
re-adjust the carburetor, which he did and said it was running better. It quit again on him later and he decided to replace the fuel pump that came
with it, a 7-9 psi solenoid type, with a new Mr Gasket #425 (2-4 psi). He did that quick this morning before they left and said it was running well.

After a stop at Walmart on the way out of town, they left it running, but it had quit while they were shopping. In Deming NM, it restarted, but
apparently only ran for about 45 minutes before it quit again. I looked up the spark plug number and suggested he check to make sure it has the right
plugs in it, Grasping at straws here.

Any suggestions?
--
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

 

[Carl Stouffer]

Just heard from my son. He said the plugs are Denso W14L. From the GMCMI parts interchange, they should be W16LS. Could that make enough difference
to worry about, or should he be looking elsewhere for the problem?
--
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

 

[a.]

> So, the new, reconditioned Onan is not doing it's job reliably. My son picked up the motorhome to take it on a trip to Colorado Springs last
> evening and drove it about 7 miles to Costco to get gas. He shut down the generator while pumping gas and it would not restart until some time
> after he got home to his house, another 5 miles.
>
> I had set the timing and adjusted the carburetor and run the generator, under load, for at least a half hour with no issues. I suggested that
> Mark re-adjust the carburetor, which he did and said it was running better. It quit again on him later and he decided to replace the fuel pump that
> came with it, a 7-9 psi solenoid type, with a new Mr Gasket #425 (2-4 psi). He did that quick this morning before they left and said it was running
> well.
>
> After a stop at Walmart on the way out of town, they left it running, but it had quit while they were shopping. In Deming NM, it restarted, but
> apparently only ran for about 45 minutes before it quit again. I looked up the spark plug number and suggested he check to make sure it has the
> right plugs in it, Grasping at straws here.
>
> Any suggestions?

Symptoms indicate a failing coil.

 

[mike]

> So, the new, reconditioned Onan is not doing it's job reliably. My son picked up the motorhome to take it on a trip to Colorado Springs last
> evening and drove it about 7 miles to Costco to get gas. He shut down the generator while pumping gas and it would not restart until some time
> after he got home to his house, another 5 miles.
>
> I had set the timing and adjusted the carburetor and run the generator, under load, for at least a half hour with no issues. I suggested that
> Mark re-adjust the carburetor, which he did and said it was running better. It quit again on him later and he decided to replace the fuel pump that
> came with it, a 7-9 psi solenoid type, with a new Mr Gasket #425 (2-4 psi). He did that quick this morning before they left and said it was running
> well.
>
> After a stop at Walmart on the way out of town, they left it running, but it had quit while they were shopping. In Deming NM, it restarted, but
> apparently only ran for about 45 minutes before it quit again. I looked up the spark plug number and suggested he check to make sure it has the
> right plugs in it, Grasping at straws here.
>
> Any suggestions?

Do not use the filter that came with the Mr. Gasket pump. It is known to leak after a short while at the crimp for the two halves and will suck air.

--
Mike K.
'75 PB
Southeast Michigan

 

[Ken H.]

>
> ​...​
>
> Symptoms indicate a failing coil.
> ​...
>

​Could be, but y'all are in the too-easy-to-reach corner where you're
shooting in the dark at you know not what.

When it won't run, check for spark. He'll probably need to purchase an
ignition tester because the spark is so weak it can hardly be detected
visually in sunlight. Grounding one plug wire while checking the other
will help.

If there's spark, the the problem has to be fuel, so check that -- it's not
easy on an Onan, but one can at least loosen a gas line and check for
seepage -- I'm betting that's NOT your problem, now that the
too-high-pressure pump has been replaced.​

​That's about all I can suggest from a distance -- for a generator I
haven't fooled with for 10 years.​

​Good luck,

Ken H.​

 

[jim kanomata1]

Never use pump that exceed 4 psi.
Heat is causing a sit down, replace the oil sender with a lower pressure one.
I'm out at dinner so allow me couple hour to send you specifics

Sent from my iPhone

>
> to

 

[jim kanomata1]

our oil pressure switch is rated at 15 psi,get a 8 psi one.
Contact Jeff Sirum at Alex Sirum for correct thread size and part #.
Should this not solve the problem, it will be a relay problem.

> Never use pump that exceed 4 psi.
> Heat is causing a sit down, replace the oil sender with a lower pressure
> one.
> I'm out at dinner so allow me couple hour to send you specifics
>
> Sent from my iPhone
>

> >
> > to
>

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

 

[Ken B]

You have the symptom of vapor lock. What is the temperature there?

I have never had vapor lock on my 455 but my Onan would shut down when temps approached 100 Degrees. The solution was to insulate the gas line
feeding the fuel pump with fire sleeve and reflective aluminum tape. I also covered the fuel pump with reflective tape. It has never failed since
them.

I seriously doubt that a spark plug change will do anything. If you want to check for spark, get an inline spark checker from Harbor Freight (or
your favorite auto parts store) and insert it in line with either plug. Then crank the engine and observe.

https://www.harborfreight.com/in-line-spark-checker-69014.html
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

 

[jim miller]

> I had set the timing and adjusted the carburetor and run the generator, under load, for at least a half hour with no issues. I suggested that Mark
> re-adjust the carburetor, which he did and said it was running better. It quit again on him later and he decided to replace the fuel pump that came
> with it, a 7-9 psi solenoid type, with a new Mr Gasket #425 (2-4 psi). He did that quick this morning before they left and said it was running well.

It is highly unlikely that this is either a carb adjustment or a spark plug type issue; neither would result in a successful 45 minute run followed by a failure.

Have you ruled out the control system by jumpering battery+ to coil+ and then attempting a start/run?

Have you ruled out fuel delivery by removing the fuel hose from the carb and then jumpering battery+ to coil+ to see if fuel comes out the hose with good flow and pressure?

Do you have known good fuel hose between the tank and the Onan’s pump?

Does it have breaker point ignition? Have the points been cleaned or had the condenser replaced?

I agree with others that 7-9 psi of fuel pump pressure is far too much.

Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH

 

[robert mueller]

These are the exact same symptoms the ONAN in Double Trouble demonstrated
until the coil was checked immediately after shutdown.

You can use a coil from a Harley V-twin as they are waste spark as well. If
you know any guys that have a Harley chances are they'll have a coil as one
of the upgrades is to install a single fire ignition system.

Regards,
Rob M.
The Pedantic Mechanic
USAussie - Downunder
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808

-----Original Message-----
From: Gmclist [mailto:gmclist-bounces] On Behalf Of A.
Sent: Friday, June 16, 2017 10:31 AM
To: gmclist
Subject: Re: [GMCnet] New Onan not working right

Symptoms indicate a failing coil.

 

[Carl Stouffer]

>
> > I had set the timing and adjusted the carburetor and run the generator, under load, for at least a half hour with no issues. I suggested
> > that Mark
> > re-adjust the carburetor, which he did and said it was running better. It quit again on him later and he decided to replace the fuel pump
> > that came
> > with it, a 7-9 psi solenoid type, with a new Mr Gasket #425 (2-4 psi). He did that quick this morning before they left and said it was
> > running well.
>
> It is highly unlikely that this is either a carb adjustment or a spark plug type issue; neither would result in a successful 45 minute run
> followed by a failure.
>
> Have you ruled out the control system by jumpering battery+ to coil+ and then attempting a start/run?
>
> He hasn't tried that, but I did tell him to jumper pins 9 & 5 to bypass the low oil shut down switch. We'll see how that works today.
>
> Have you ruled out fuel delivery by removing the fuel hose from the carb and then jumpering battery+ to coil+ to see if fuel comes out the hose
> with good flow and pressure?
>
> Yes, fuel delivery is good
>
> Do you have known good fuel hose between the tank and the Onan's pump?
>
> All fuel lines were replaced in 2010 and inspected during the generator swap. All looked good.
>
> Does it have breaker point ignition? Have the points been cleaned or had the condenser replaced?
>
> It has Onan solid state ignition, timing is set to 21 degrees BTC.
>
> I agree with others that 7-9 psi of fuel pump pressure is far too much.
>
> That pump has been replaced with a new Mr Gasket 42S - 2 - 3.5 PSI
>
> Jim Miller
> 1977 Eleganza
> 1977 Royale
> Hamilton, OH
>
>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

I tend to think Jim K is on the right track and the oil pressure switch is shutting it down when it gets too hot. I did not change the brand new oil
that was in it and so have no idea what weight oil is in it. Could be 0W10 for all I know, so the pressure might be on the low side.

He was traveling from Tucson to Albuquerque along I-10 and I-25, temps were in the 90s I would guess, so vapor lock is a possibility. I do not know
if the coil was replaced during the refurb that Kerry had done, but it looks new. The control board is a new Onan board and seems to function
correctly under most circumstances. I had exactly the same symptoms on my old Onan that went away with a new fuel pump. That doesn't seem to have
helped this time, so maybe it could be the coil.

Mark said it was not too unbearably hot and his three year old doesn't seem to mind the heat. They will be heading to Colorado Springs today, so it
will be cooler in the higher altitude. They may not really need the generator until the return trip
--
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

 

[john r. lebetski]

Do a very close inch by inch fuel line inspection. The line feeding to the drawer casing, and the "snowmobile" hose feeding from the drawer casing
barb to pump inlet barb. Mine had your symptoms. There was a tiny split crack in the hose before where the clamp was on the barb. Cold it was ok but
would soften with heat and suck air. Onan was fine but got blamed when fuel ine was bad. Used a hosr cutter and cut off 1". Cost of repair $0.
--
John Lebetski
Woodstock, IL
77 Eleganza II

 

[Carl Stouffer]

After further checking and testing, the symptoms do point toward the coil as the problem. I took the known good coil off the old generator, boxed it
up, and sent it up to my son this morning. At least that will allow us to confirm or eliminate the coil as the culprit.

He should get it on Monday or Tuesday and will install it for the trip home. I'll report back.
--
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

 

[jim miller]

> After further checking and testing, the symptoms do point toward the coil as the problem. I took the known good coil off the old generator, boxed it up, and sent it up to my son this morning. At least that will allow us to confirm or eliminate the coil as the culprit.

Regarding coils…

I have used the 166-0820 coil for dozens of hours in my Onan as a replacement for the original coil. The -0820 is about 20 years newer than the one that came with our Onans.

In addition I am experimenting with the 166-0761 coil which has worked in initial tests but I’ve not had the opportunity to test it with prolonged runtime so at this time I cannot declare that it is a viable replacement. This part is even newer than the -0820.

These coils have worked for me in their original Inductive (Kettering) ignition mode as well as with the MSD CDI box that JimK sells.

—Jim

Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH

 

[Carl Stouffer]

>
> > After further checking and testing, the symptoms do point toward the coil as the problem. I took the known good coil off the old generator,
> > boxed it up, and sent it up to my son this morning. At least that will allow us to confirm or eliminate the coil as the culprit.
>
> Regarding coils...
>
> I have used the 166-0820 coil for dozens of hours in my Onan as a replacement for the original coil. The -0820 is about 20 years newer than the
> one that came with our Onans.
>
> In addition I am experimenting with the 166-0761 coil which has worked in initial tests but I've not had the opportunity to test it with prolonged
> runtime so at this time I cannot declare that it is a viable replacement. This part is even newer than the -0820.
>
> These coils have worked for me in their original Inductive (Kettering) ignition mode as well as with the MSD CDI box that JimK sells.
>
> --Jim
>
> Jim Miller
> 1977 Eleganza
> 1977 Royale
> Hamilton, OH
>
>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

Thanks Jim.

I guess if the other coil fixes the problem, I'll replace it in the new generator and put the old one back in the old generator. I would like to keep
the old one in tact so I can sell it as a working unit (if there is a market).
--
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

 

[Carl Stouffer]

Back to this: After swapping out the coil for a known good one, the Onan still would only run for a very short time and then quit. While I had my
son on the phone, I had him pull a spark plug and ground it to the engine while cranking. He said there was a nice fat spark (this unit has the Onan
solid state ignition). He then loosened the carburetor float bowl and found it to be dry. He put the old (too high pressure) fuel pump on and it
fired up. All this in the RV park where he really couldn't mess with it too much.

Back on the road on Friday AM. it would run for a while, quit, and not re-start. He found a split in the fuel line near the pump, fixed that, and
thought that was the problem. The too high pressure pump then overpowered the needle valve and flooded out the carb, so he put the Mr Gasket pump
back on (with a Wix filter). It still would run for a while, maybe 20 - 40 minutes, and shut down.

After driving through the night to beat the heat, they arrived home at about 2:30 AM. Mark got up and exchanged the possibly defective Mr Gasket pump
for a new one which I will install. This is sounding more and more like a vapor lock condition and I will install the new fuel pump back on the frame
away from the heat of the generator per Ken B's suggestion. I will try to insulate the line as well. Maybe that will do the trick.

Any other suggestions?
--
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

 

[Carl Stouffer]

> Back to this: After swapping out the coil for a known good one, the Onan still would only run for a very short time and then quit. While I had
> my son on the phone, I had him pull a spark plug and ground it to the engine while cranking. He said there was a nice fat spark (this unit has the
> Onan solid state ignition). He then loosened the carburetor float bowl and found it to be dry. He put the old (too high pressure) fuel pump on and
> it fired up. All this in the RV park where he really couldn't mess with it too much.
>
> Back on the road on Friday AM. it would run for a while, quit, and not re-start. He found a split in the fuel line near the pump, fixed that, and
> thought that was the problem. The too high pressure pump then overpowered the needle valve and flooded out the carb, so he put the Mr Gasket pump
> back on (with a Wix filter). It still would run for a while, maybe 20 - 40 minutes, and shut down.
>
> After driving through the night to beat the heat, they arrived home at about 2:30 AM. Mark got up and exchanged the possibly defective Mr Gasket
> pump for a new one which I will install. This is sounding more and more like a vapor lock condition and I will install the new fuel pump back on
> the frame away from the heat of the generator per Ken B's suggestion. I will try to insulate the line as well. Maybe that will do the trick.
>
> Any other suggestions?

Oh, forgot to mention that the behavior was unchanged by jumpering from 5 to 9 or even from bat + to the coil.

--
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

 

[jim miller]

> Back on the road on Friday AM. it would run for a while, quit, and not re-start. He found a split in the fuel line near the pump, fixed that, and
> thought that was the problem. The too high pressure pump then overpowered the needle valve and flooded out the carb, so he put the Mr Gasket pump
> back on (with a Wix filter). It still would run for a while, maybe 20 - 40 minutes, and shut down.
>
> Any other suggestions?

Possible remaining causes:

1. Control board flakes out when exposed to excessive heat soak.
2. Flywheel alternator fails due to extended vibration or heat soak.
3. O/P switch indicates an incorrect LOP condition either due to decreased oil viscosity (and correspondingly low pressure) OR the switch gets flaky when the crankcase gets hot after a long run.

Troubleshooting approach is the as that which should always be followed…process of elimination.

Bypass control board, LOP switch and flywheel alternator by jumpering +12V to ignition coil +; you should hear the fuel solenoid click and the fuel pump running. Start the engine, see if it runs for an hour or two without failing. If so, follow control board troubleshooting procedure that has been published by others.

If the unit still craps out after 20-40 minutes then disconnect from the vehicle fuel system and run a hose from the Onan’s fuel pump inlet to a can of gas sitting on the ground and then repeat your runtime test.

—Jim

Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH

 

[jim miller]

> Oh, forgot to mention that the behavior was unchanged by jumpering from 5 to 9 or even from bat + to the coil.

That’s good info. Your message above crossed the ether with my previous one which suggested that very same test. At this point you’ve ruled out the control system - so now try running the Onan from a fuel can sitting on the ground beside the coach and see how long it will run.

—Jim

Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH

 

[Carl Stouffer]

>
> > Oh, forgot to mention that the behavior was unchanged by jumpering from 5 to 9 or even from bat + to the coil.
>
> That's good info. Your message above crossed the ether with my previous one which suggested that very same test. At this point you've ruled out
> the control system - so now try running the Onan from a fuel can sitting on the ground beside the coach and see how long it will run.
>
> --Jim
>
> Jim Miller
> 1977 Eleganza
> 1977 Royale
> Hamilton, OH
>
>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

Thanks Jim. I'll give that a try. What do you think about the remote mounting of the fuel pump idea? I guess I'll have to see if the gas can idea
makes any difference first. The funny thing is that the old generator ran for hours on end, while driving under the same conditions. The only issue
I ever had with it was fuel pump related, and it acted very similar to what this one is doing. A new fuel pump completely cured that problem. I
suppose the brand new Mr Gasket 42S pump was bad right from the get go.
--
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