Onan Start prime switch

[Luke D]

In the outside switch on the Onan 4000kw gas generator I now have a new issue. If you press prime it takes a few seconds for the light to come on an fuel pump to start. Then if you press start it fires right up, but dies. If you push and hold start switch gen runs fine. Not sure if switch can go bad or where I’m loosing power once running.
The generator has new control board, carb, filter and pump. Motorhome tank over half full on gas. Up til today was running and functioning fine. Only issue prior was a loose growing coming off fuel solenoid. It was surging and by accident I noticed loose black wire. Tighten and ran awesome. Now today this. Guess my Onan generator hates me. Has 363 hours on it.
Any thoughts.

[pneumatics]

There is another fault somewhere. Low oil switch, something. Holding Start when it is running just overrides everything since the starter is most likely still engaged. Is there lights blinking after it shuts off? Should be. These are error codes.

How old is the installation? I had a similar problem with a unit where pin holes and cracks developed in the fuel line back to tank and it allowed air to be pulled in when the pump was running. Older hose will do that.

[16ACE27]

Originally Posted by Luke D

In the outside switch on the Onan 4000kw gas generator I now have a new issue. If you press prime it takes a few seconds for the light to come on an fuel pump to start. Then if you press start it fires right up, but dies. If you push and hold start switch gen runs fine. Not sure if switch can go bad or where I’m loosing power once running.
The generator has new control board, carb, filter and pump. Motorhome tank over half full on gas. Up til today was running and functioning fine. Only issue prior was a loose growing coming off fuel solenoid. It was surging and by accident I noticed loose black wire. Tighten and ran awesome. Now today this. Guess my Onan generator hates me. Has 363 hours on it.
Any thoughts.

That's a lot of parts from the parts cannon in one day.

Once you release the start button it is up to the sensing circuit to insure the generator is running correctly. It will shut down the engine if it senses improper voltage or frequency and you should have a flashing error code that you can look up to see WHY the generator shut down.

[16ACE27]

Originally Posted by 16ACE27

That's a lot of parts from the parts cannon in one day.

Once you release the start button it is up to the sensing circuit to insure the generator is running correctly. It will shut down the engine if it senses improper voltage or frequency and you should have a flashing error code that you can look up to see WHY the generator shut down.

EDIT: I'm slow today; pneumatics beat me to it.

[Luke D]

Originally Posted by 16ACE27

That's a lot of parts from the parts cannon in one day.



Once you release the start button it is up to the sensing circuit to insure the generator is running correctly. It will shut down the engine if it senses improper voltage or frequency and you should have a flashing error code that you can look up to see WHY the generator shut down.

No codes, not sure of sensor errors . Oil level good. Besides Onan 4000kw is a pancake motor design. Like a lawn motor engine. No oil sensor or filter on this model design. Only time any flashing is when you hold down start switch making it run. Then it constantly flashes. No stop or counting possible.
Sucks

[Luke D]

Originally Posted by pneumatics

There is another fault somewhere. Low oil switch, something. Holding Start when it is running just overrides everything since the starter is most likely still engaged. Is there lights blinking after it shuts off? Should be. These are error codes.



How old is the installation? I had a similar problem with a unit where pin holes and cracks developed in the fuel line back to tank and it allowed air to be pulled in when the pump was running. Older hose will do that.

Unit is five yeArs old 363 hours. No error codes. Checked oil but level fine. Besides Onan 4000KW is a pancake design, no oil sensor. Basically a lawn mower engine. Only time red light flashes is you hold start button down making it run. Then it flashes fast and constant. In prime position it lights and you heat pump. Gives no codes.

[Luke D]

Originally Posted by Luke D

Unit is five yeArs old 363 hours. No error codes. Checked oil but level fine. Besides Onan 4000KW is a pancake design, no oil sensor. Basically a lawn mower engine. Only time red light flashes is you hold start button down making it run. Then it flashes fast and constant. In prime position it lights and you heat pump. Gives no codes.

Hear pump

[16ACE27]

Originally Posted by Luke D

No codes, not sure of sensor errors . Oil level good. Besides Onan 4000kw is a pancake motor design. Like a lawn motor engine. No oil sensor or filter on this model design. Only time any flashing is when you hold down start switch making it run. Then it constantly flashes. No stop or counting possible.
Sucks

Can't be a pancake with a single cylinder.
It doesn't have an oil filter but it does have an oil level sensor.

Have you looked at the manual?

Did you ever get it running when you had generator problems almost a year ago?

https://www.thorforums.com/forums/f1...tor-21581.html

If you haven't already done so go to https://www.thormotorcoach.com/owner-resource/ and create an account with your VIN. You will then have access to all manuals, schematics, diagrams, videos, etc that apply to your coach.

Here's a picture of the first page of the troubleshooting section that likely applies to your generator:

[Luke D]

Originally Posted by 16ACE27

Can't be a pancake with a single cylinder.
It doesn't have an oil filter but it does have an oil level sensor.

Have you looked at the manual?

Did you ever get it running when you had generator problems almost a year ago?

https://www.thorforums.com/forums/f1...tor-21581.html

If you haven't already done so go to https://www.thormotorcoach.com/owner-resource/ and create an account with your VIN. You will then have access to all manuals, schematics, diagrams, videos, etc that apply to your coach.

Here's a picture of the first page of the troubleshooting section that likely applies to your generator:

Yes have complete manual and schematic. That an a call to Onan is how I know 4000KW micro quiet is basically a lawn mower design. It has a slinger in the pan which splashes oil as it runs. No oil level sensor. Now it senses overheat, voltage, and shorts. If low on oil or over full it can over heat and stops. Even schematics show no oil sensor. Heck 4000 doesn’t even have a filter.
Oh well

[16ACE27]

Originally Posted by Luke D

Yes have complete manual and schematic. That an a call to Onan is how I know 4000KW micro quiet is basically a lawn mower design. It has a slinger in the pan which splashes oil as it runs. No oil level sensor. Now it senses overheat, voltage, and shorts. If low on oil or over full it can over heat and stops. Even schematics show no oil sensor. Heck 4000 doesn’t even have a filter.
Oh well

Now your 4000 may not have a oil level switch, but the A-F series did:



as do most single cylinder "lawn mower" engines made in the last 20 years.

However, you still have the Generator field, voltage, and frequency (speed) sensors that can shut the engine down and as far as I know, all the RV 4K generators do have a shutdown error indicating system; but maybe yours isn't working. You said you replaced the "controller"? How long ago was that? And did this generator ever run correctly after last year's problems?

[Luke D]

Originally Posted by 16ACE27

Now your 4000 may not have a oil level switch, but the A-F series did:







as do most single cylinder "lawn mower" engines made in the last 20 years.



However, you still have the Generator field, voltage, and frequency (speed) sensors that can shut the engine down and as far as I know, all the RV 4K generators do have a shutdown error indicating system; but maybe yours isn't working. You said you replaced the "controller"? How long ago was that? And did this generator ever run correctly after last year's problems?

First off thank you soo much for the assistance. Controller was replaced in November, a long with Carb, fuel pump and gas filter. Has ran fine since until today. I exercise it every two weeks as it is parked . I always turn on the use switch and put a load on it for an hour or more. This is a new problem. Maybe a wire has failed. Slip rings look fine. Guess I’ll have to check schematics and trouble shoot. Something is stopping it from running. Yet no codes displayed. Maybe a wire is grounding out or a bad new controller already. Fun fun fun
Thanks again

[OldWEB]

I just checked my service manual and it indicates the Spec K does not have a oil lvl sw. Hmmm... news to ME.

But I found this in my manual:
GENSET RUNS BUT STOPS WHEN SWITCH IS RELEASED – NO FAULT CODE
Logic: Fault codes are based on time lapse between events
Possible Cause: Not holding start switch long enough to cause fault
Diagnosis and Repair:
1. Check and record last fault code.
2. Start genset and hold switch until control shuts down and displays fault code (approximately 30 seconds):
troubleshoot fault code and reference last fault code recorded above if necessary.

[Luke D]

Originally Posted by Luke D

First off thank you soo much for the assistance. Controller was replaced in November, a long with Carb, fuel pump and gas filter. Has ran fine since until today. I exercise it every two weeks as it is parked . I always turn on the use switch and put a load on it for an hour or more. This is a new problem. Maybe a wire has failed. Slip rings look fine. Guess I’ll have to check schematics and trouble shoot. Something is stopping it from running. Yet no codes displayed. Maybe a wire is grounding out or a bad new controller already. Fun fun fun
Thanks again

I’ll give your latest find a try tomorrow and let you know. I’ll see thud I can get codes

[Luke D]

Originally Posted by OldWEB

I just checked my service manual and it indicates the Spec K does not have a oil lvl sw. Hmmm... news to ME.

But I found this in my manual:
GENSET RUNS BUT STOPS WHEN SWITCH IS RELEASED – NO FAULT CODE
Logic: Fault codes are based on time lapse between events
Possible Cause: Not holding start switch long enough to cause fault
Diagnosis and Repair:
1. Check and record last fault code.
2. Start genset and hold switch until control shuts down and displays fault code (approximately 30 seconds):
troubleshoot fault code and reference last fault code recorded above if necessary.

Well here’s the latest.... spent the day tearing down. Removed control board, start prime switch. I checked all wiring for continuity. Ohm out all I could using Flygt systems manual. Could not find any issue. Note their manual does say that the units using control board 327-1413 is a bear. No real test data for it. Two puzzling issues noted. Even when holding switch to make run for 30 or more seconds no codes????? Manual talks of 5 amp control fuse for control box . No where to be found. Probably inside sealed control board or not on this model 4 KYFA26100P. No real clue on oil switch if used. Chart says if it has one it is near oil fill. None there. Hate to have to pull unit. Guess I’ll set up a repair appointment. Very disappointed in this genders constant problems. Maybe a new one is in the cards but I don’t trust Onan. Only 364 hours.

[OldWEB]

Originally Posted by Luke D

Well here’s the latest.... <snip> No real clue on oil switch if used. Chart says if it has one it is near oil fill. None there. Hate to have to pull unit. Guess I’ll set up a repair appointment. Very disappointed in this genders constant problems. Maybe a new one is in the cards but I don’t trust Onan. Only 364 hours.

Oil switch will be inside the oil pan if you have one, you will have to find the wires. See Ace's above post.

[Luke D]

Originally Posted by OldWEB

Oil switch will be inside the oil pan if you have one, you will have to find the wires. See Ace's above post.

Located pin which normally grounds through oil switch.? No wire connected. Grounded still nothing. Talked to Onan here in Tampa. Alex in service said due to so many issues and failures the sensor was eliminated in 2013 on all 4000KW micro quiet units in the KY series. Looked up my serial number and shows non installed from factory. The KB series had inside the pan until 2014. Alex thoughts were gen not producing power thus run position failure. Board must see 120 and 12 volts. Possible control board failure. Well that’s warranted. Less than 6 months old. Also only Elite models had 5 amp contracts fuse. Also told me to test pins on start/ Prime switch. Switch could be stayed open. Oh well I’ll leave that to my repair guy at Boondockers Repair. Alex says Onan is usually very reliable. Okay lol

[Seabee]

Just for future reference, where/who is Boondockers Repair near Tampa? Thanks.

[Luke D]

Originally Posted by Seabee

Just for future reference, where/who is Boondockers Repair near Tampa? Thanks.

They are first class. Always come to you. Nothing they cannot do. Fast and courteous. Put Lazy days, camping world an all others to shame. Best and fair price on any job. Boondockers RV Repair Service 813 460 8565. Check out their website five star reviews.

[racochran]

I had that problem and was cause by those pesky mice nested in Gen! They eat threw insulation and wire to gen brushes. No voltage no start unless held switch down. Repaired that taking mostly a lot of labor now runs fine.

[Luke D]

Originally Posted by racochran

I had that problem and was cause by those pesky mice nested in Gen! They eat threw insulation and wire to gen brushes. No voltage no start unless held switch down. Repaired that taking mostly a lot of labor now runs fine.

Well could be ..,, The generator is coming out. I’ll let you know. All I know is in two years of ownership all has been fine except for the Onan generator. Its been well maintained so maybe critters did some damage. As far as reliable goes I give Onan a goose egg