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Onan Generators

Onan 7.5 JB 3CR/2442T Added to the Fleet


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  #71  
Old 04-14-2018, 08:07:01 PM
nothingbutdarts nothingbutdarts is offline
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Default Re: Onan 7.5 JB 3CR/2442T Added to the Fleet

Thanks for the updates and hope the wife gets better very soon!

I go in Friday for thumb surgery, 8 weeks off work coming after, YEA BUDDY!
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  #72  
Old 04-15-2018, 06:23:00 AM
EICBob EICBob is offline
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Default Re: Onan 7.5 JB 3CR/2442T Added to the Fleet

Thank you Darts...
Her surgery was on her thumb joint. Arthritis repair, she will be outta work for a few weeks in a “soft” for 3 to 4 weeks then in a hard cast for another 4 weeks.
Fun times.....

I have the same issue in my thumb joint as well. Had an injection a month ago to relieve some of the pain and was told that if the pain and stiffness returned/got worse then I will need to decide on surgery too. (Oh joy)

-Bob
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  #73  
Old 04-24-2018, 04:36:50 PM
EICBob EICBob is offline
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Default Re: Onan 7.5 JB 3CR/2442T Added to the Fleet

Next update...
More parts have arrived for this "rebuild", thanks to some very helpful Stakers and their willingness to sell their parts.
Now all I need is some time.
The wife is on the mend, but being one handed has made for some interesting times.
We were at a funeral in NY over the weekend and went out to dinner with her family, I had to assist her by cutting her dinner. (Flash back)
Hopefully this coming weekend I will be able to swap in some of the replacement parts and see if at the very least this beasty will fire up and run.

Cheers!

-Bob
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  #74  
Old 04-29-2018, 01:47:05 PM
EICBob EICBob is offline
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Default Re: Onan 7.5 JB 3CR/2442T Added to the Fleet

On a dreary Sunday I was able to spend some time with my JB and worked on getting it to start.
I swapped out the open frame relay, K12, with a clean, non mouse attacked one from some of the parts I purchased from a few fellow STAK members.
I removed the additional “Ford” style relay that was added and returned the wiring to its original state.
I will be replacing the chewed wires as soon as I can, so some were just taped today to avoid shorts, sparks etc.
Put everything back together and hit the start switch....nothing
No click, no crank, no love at all. I followed all the wires used in the cranking circuit and cleaned and tightened all the connections. Still nothing.
I took apart K13, cleaned the contact points and verified the coil was not open and bench tested the coil, with 12vdc, and it tested OK and operated as it should. Put it back in and still nothing....
Now here is where things get a tad bit strange, using my 12vdc test light, I followed the voltage path through the various components and found no surprises. When I touched the factory splice at R12, (see attached picture), I heard a relay click, not sure which relay it was.
I tried the start switch and we had crankage!
(Scratching head now)
I have spark and was able to fire the engine on a tiny dribble of gasoline into the carb.
She sounds good!
Now I am not sure why probing connections with a test light would “cure” a no crank condition.

While on the control box rewire/repair, this JB’s start solenoid K11, only has one small terminal and my other JB with the propane option has a solenoid with 2 small terminals. (See attached)
I want to make this unit run on propane, so do I need to change the solenoid or can I just run the necessary 12volts to the propane shutoff solenoid from the feed to the choke heater?
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  #75  
Old 04-29-2018, 03:01:32 PM
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Default Re: Onan 7.5 JB 3CR/2442T Added to the Fleet

You need to STAY with the start relay the set was designed for. Even though the "Ford" style frame relays look the same externally, there is SEVERAL different internals and the way they are wired. Some are grounded base and others are not. You can't go to the auto parts store and just buy one off of the shelf. Cars used different configurations of them too. If you remove the start relay, you should see an Onan part number stamped on it. Cross that to your spec. of your set.
The propane lock off needs to have BATTERY voltage, NOT the choke voltage. Some of the electric chokes on Onans run on higher voltage that is obtained before the charge resistor. The choke also needs to be full open at all times when running vapor fuel.
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  #76  
Old 04-29-2018, 03:15:19 PM
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Default Re: Onan 7.5 JB 3CR/2442T Added to the Fleet

Thanks Motor..
I found the Onan choke hold open wire and placed it through the hole in the choke shaft.
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Old 04-29-2018, 03:20:38 PM
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Default Re: Onan 7.5 JB 3CR/2442T Added to the Fleet

Because you had mouse pee contamination, it is important to clean ALL connections and especially GROUNDS for the low voltage side of your set. if your test light was grounded and the point that you touched made a relay click, to ME, that is pointing to a bad GROUND somewhere. I looked up the start solenoid that seemed for your set and it is a single small terminal solenoid.
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Old 04-29-2018, 04:49:34 PM
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Default Re: Onan 7.5 JB 3CR/2442T Added to the Fleet

Thank you for looking up the solenoid Motor, I appreciate it.
I agree with your suspicion of a bad/weak ground. I do remeber back in my car repair days, grounds were the biggest issue we faced when dealing with wiring issues!
I should have realized that (senior moment)
I have machine tool wire coming along with a new start/stop switch. When they arrive most every wire and terminal in the control box will be replaced.
Will clean out the black crud remnants too. My original plan was to make sure the engine would start and run before committing to a total rewire.
Now on to the rewire and ordering the gaseous shutoff valve and demand regulator.

I recall a thread discussing after market gaseous shutoff solenoids as the Onan ones are pricey and getting scarce.

-Bob
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  #79  
Old 04-29-2018, 06:28:03 PM
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Default Re: Onan 7.5 JB 3CR/2442T Added to the Fleet

Here is an IMPCO on ebay: https://www.ebay.com/itm/3-4-IMPCO-O...Ba017-&vxp=mtr

Here is the EATON one that Onan used: https://www.ebay.com/itm/ONAN-307-03...haae6G&vxp=mtr
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  #80  
Old 05-26-2018, 05:02:19 PM
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Default Re: Onan 7.5 JB 3CR/2442T Added to the Fleet

It has been way too long since I have had any Green therapy!
Due to cruddy weather today, I was able to devote a couple of hours on this 7.5 control box rewire. I replaced the start/stop switch with a new one, replaced the chewed C1 wiring harness from the control box to the choke heater assembly. I know that when I set this up to run on Propane I will not need the choke heater for operation but figured that while I was repairing the wiring might just as well fix that harness too
Replaced the open frame relay with a good replacement relay from a donor control box I picked up from another generous STAK member.
A few more wires to repair/heat shrink insulate and It will be ready to try and start!

To all that have served, all that continue to serve and to all that will come to serve in the future.....
Especially to everyone who are no longer are with us...

THANK YOU!!

Happy Memorial Day!

-Bob
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