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JC 15kw parts needed

Max Thompson

Sponsor
Last Subscription Date
09/03/2019
http://www.skilledcrafting.com/onanfiles/

You will find your parts manual at the above linked site. The complete model & serial numbers will help us a lot, include the spec. letters at the end of the model number. If you can find the part number in the manual, you may get faster help.

That being said, J series carbs and parts for them are getting scarce. If all you need is the heater ribbon that goes inside the spring, several other Onans used the same part.
 

suntreemcanic

Registered
I have a 15.0 JC propane generator. It has the three in one carburetor. The choke is blocked off from functioning. My generator starts right up at 0 degrees. That is one great things of using propane as it starts real easy in cold weather. I see you are from Florida, if you are having starting issues you have another problem because propane does not require a choke.
 

EICBob

Subscriber
Age
62
Last Subscription Date
06/15/2020
Need carburetor auto choke thermal
heater for 15kw ojc! Cold start issues with propane! Help!
Hi Bcboyer100....
I would like to add my 2 cents as well, I am troubleshooting a cold start issue on one of my Onans, this unit was designed solely for gaseous fuels and there is no choke assembly at all.
I would second Ben’s suggestions to verify proper operation of the gaseous regulators and fuel lines.
Check for proper ignition system operation too. A weak spark will make cold starting harder.

-BobC
 

Bcboyer100

Registered
Hi Bcboyer100....
I would like to add my 2 cents as well, I am troubleshooting a cold start issue on one of my Onans, this unit was designed solely for gaseous fuels and there is no choke assembly at all.
I would second Ben’s suggestions to verify proper operation of the gaseous regulators and fuel lines.
Check for proper ignition system operation too. A weak spark will make cold starting harder.

-BobC
I thought about this last night realized that I had 4 probable resolutions: 1. Low compression
2. Bad butterfly bushing (leaky shaft issues in the carb) 3. Demand regulator adjustment or 4. Safety solenoid not opening on propane input!
Eliminated number 1 2 and 4!
Tried to start while adjust the demand regulator and got it to start every time. I also adjusted the propane secondary regulator to 11 inches of input to keep the engine running without “coughing.” Then fine tuned the main carburetor jet for smooth running engine! It did like a little lean adjustment!
Again thanks for the input and I do plan to reset the plugs to 5 thousands less gap as suggested!
 

Bcboyer100

Registered
I thought about this last night realized that I had 4 probable resolutions: 1. Low compression
2. Bad butterfly bushing (leaky shaft issues in the carb) 3. Demand regulator adjustment or 4. Safety solenoid not opening on propane input!
Eliminated number 1 2 and 4!
Tried to start while adjust the demand regulator and got it to start every time. I also adjusted the propane secondary regulator to 11 inches of input to keep the engine running without “coughing.” Then fine tuned the main carburetor jet for smooth running engine! It did like a little lean adjustment!
Again thanks for the input and I do plan to reset the plugs to 5 thousands less gap as suggested!
Well I spoke to soon! I installed a inch gauge on the input to the Garretson demand regulator and watched as I started the engine! Noticed no pressure on the gauge . I had installed a gas shutoff valve between the second stage regulator and the Garretson for safety. This valve receives its 12v from terminal #4 which ultimately gets its voltage from the charging winding during run. That voltage comes up slowly as the engine gets started. I need a connection location that will give me 12v at startup and run but will go to O volts when engine quits? Apparently this shutoff relay needs more instant current to pull than that solenoid circuit can muster during slow startup? Can’t use the start solenoid because I need it to stay on for run!
Any suggestions?
 

Wayne 440

Registered
Without your complete model number I cannot refer to a diagram for your machine. There is a specified place for a fuel valve to connect; I suggest that you consult the appropriate wiring diagram for your JC and go from there.
 
Last edited:

VelocityDave

Subscriber
Last Subscription Date
06/23/2019
Terminal #4 is the proper place for power. It receives power while cranking from the battery and then switches over to gen power after engine starts. If you don’t have power on terminal #4 while cranking look at your wiring diagram and follow wire 4 back to K11 start solenoid. This is where it gets battery 12 volts to crank. After cranking K12 switches wire 4 over to 12 volt after battery charging circuit. You have a relay or wire connection problem. TB12-4 is the correct place to get your power. Is the valve that you installed pulling so much load that it is pulling the voltage down? Again TB12- wire #4 is the correct wire for powering everything that has to do with the engine running.

David
 

BigBlockChev

Subscriber
Last Subscription Date
07/06/2019
Clean the points on the centrifugal switch , they might be dirty. If you are still experiencing a low voltage on terminal #4 after starting maybe use that terminal to operate a relay to activate the fuel solenoid. Cheers Dan
 

Bcboyer100

Registered
Terminal #4 is the proper place for power. It receives power while cranking from the battery and then switches over to gen power after engine starts. If you don’t have power on terminal #4 while cranking look at your wiring diagram and follow wire 4 back to K11 start solenoid. This is where it gets battery 12 volts to crank. After cranking K12 switches wire 4 over to 12 volt after battery charging circuit. You have a relay or wire connection problem. TB12-4 is the correct place to get your power. Is the valve that you installed pulling so much load that it is pulling the voltage down? Again TB12- wire #4 is the correct wire for powering everything that has to do with the engine running.

David
Thanks David
I have been getting a pretty good education on this problem in general and have seen found my issue! Decided to install a safety gas solenoid and unfortunately it take a solid 12v plus or minus 5%! While cranking I’m not getting a full 12v due to the drag of the starter. Therefore I Am not opening the safety gas solenoid! The fix is: 1. Install a higher ccs battery to overcome the “old” starter amp load or
2. Have the starter rebuilt!
Question : is there an alternative starter for the 15kw or is there someone out there that rebuilds the original unit?
Thank in advance!
 

VelocityDave

Subscriber
Last Subscription Date
06/23/2019
Bcboyer100 nothingbutdarts has some good information above as always. If your starter is bad it will only get worse. Repair it before damage is beyond repair. It might just need a good clean and lube. That being said Onan made these generators (J line) for a long time. They (all diesels included) run everything off of terminal #4 12 volts. IGN coil, fuel pump,choke,gas valve, fuel solenoid I’m sure I probably missed a few things.
Don’t procrastinate (a$$ around) on the starter. It will bite you at the worst of times.

David
 
Last edited:

BigBlockChev

Subscriber
Last Subscription Date
07/06/2019
Thanks David
I have been getting a pretty good education on this problem in general and have seen found my issue! Decided to install a safety gas solenoid and unfortunately it take a solid 12v plus or minus 5%! While cranking I’m not getting a full 12v due to the drag of the starter. Therefore I Am not opening the safety gas solenoid! The fix is: 1. Install a higher ccs battery to overcome the “old” starter amp load or
2. Have the starter rebuilt!
Question : is there an alternative starter for the 15kw or is there someone out there that rebuilds the original unit?
Thank in advance!
There is an alternative Mitsubishi starter available but it is kind of pricy like $300+ if you can find one. Pretty much all J series require a BFB (big fricken battery) I'm partial to type 31s also 2ga or bigger cables are a good idea. Any old-time auto electric shop can rebuild the existing starter. If your solenoid is that fussy try a relay to operate it , might work and it is cheap and easy, most solenoids are not that sensitive. Cheers Dan
 

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