Generators and Motors
[Home] - [HELP] - [Forums] - [Library] - [Photo Gallery] - [Groups] - [Classified Ads] - [Subscribe] - [Links] - [Books] - [Sponsors] -

Go Back   SmokStak > SmokStak® Vintage Electrical Equipment > Generators & Motors General Discussion > Onan Generators
Forgot Password? Join Us!

Notices

Onan Generators Restoring, operating and maintaining vintage Onan generators.

Onan Generators

Onan 7.5 JB-3CR running issue


this thread has 173 replies and has been viewed 4637 times

Reply
 
Thread Tools Display Modes
  #61  
Old 03-20-2017, 11:25:31 PM
mheltunen mheltunen is offline
Registered-I
 
Join Date: Mar 2017
Location: Atlantic Mine, Michigan, USA
Posts: 85
Thanks: 58
Thanked 26 Times in 12 Posts
Default Re: Onan 7.5 JB-3CR running issue

I did wire up a outlet and when I fired it up the first time I plugged in a trouble light and seemed fine. This is where things went south.....😡. I was fiddling with the carb when the set stalled. I restarted it and it ran rough and bounced around a bit (sitting on a pallet). I did not have the screws for the control box in place (I know...dumb) and it jumped up and the bottom of the board grounded out on the frame of the set...light fireworks 😖. After I put it back in place and installed the screws I re fired it and noticed the light was very dim. I then checked the voltage at the outlet and read between 30-40 volts. Yes the reset switch was tripped and I did reset it before starting the second time. Sometimes when you take shortcuts they come back to bite you.
Reply With Quote
Sponsored Links
  #62  
Old 03-21-2017, 05:24:49 AM
squidtrap squidtrap is offline
Subscriber
 
Join Date: Nov 2012
Location: Forked River, New Jersey
Posts: 1,016
Thanks: 1,526
Thanked 484 Times in 336 Posts
Default Re: Onan 7.5 JB-3CR running issue

Fireworks are never good.
Reply With Quote
  #63  
Old 03-21-2017, 07:16:21 AM
Max Thompson Max Thompson is offline
Sponsor
 
Join Date: May 2009
Location: N.W. Missouri, USA
Posts: 5,638
Thanks: 4,841
Thanked 5,131 Times in 2,821 Posts
Default Re: Onan 7.5 JB-3CR running issue

Quote:
Originally Posted by mheltunen View Post
I did wire up a outlet and when I fired it up the first time I plugged in a trouble light and seemed fine.

it jumped up and the bottom of the board grounded out on the frame of the set...light fireworks ��. After I put it back in place and installed the screws I re fired it and noticed the light was very dim.
I have paid for my mistakes more times than I like to admit. Sounds like a new board is in your future.

Are you running it the way it is shown in the pictures in your first post? Just sitting on the oil pan on a pallet? That is a lot of weight on the aluminum pan. You really need to get some vibration isolators under the feet. Even a block of wood with a piece of rubber under the feet would be better than nothing. I once bought a set that had 2" pieces of heavy walled hose about 1 1/2" in diameter under the feet, not perfect, but better than nothing.
Reply With Quote
The Following User Says Thank You to Max Thompson For This Post:
  #64  
Old 03-21-2017, 07:56:25 AM
mheltunen mheltunen is offline
Registered-I
 
Join Date: Mar 2017
Location: Atlantic Mine, Michigan, USA
Posts: 85
Thanks: 58
Thanked 26 Times in 12 Posts
Default Re: Onan 7.5 JB-3CR running issue

I do need some isolators for the feet. Currently for testing I have been running it as shown. It does appear a board is in my future indeed. I may look at having it repaired or perhaps there are some different options available. Looking at Drawing #612-4794 I have some confusion over the AC terminations. I have been able to identify the T leads so that is a help but I'm unsure how the read the schematic. I intend to run it as 120V 60 HZ. Looking at the drawing to me it appears if I want to use it in this configuration I tie T3 and T1 together and T4 and T2 together and run those out to each side of an outlet to achieve this. If this is the case what is used for a ground if any?

Thanks
Reply With Quote
  #65  
Old 03-21-2017, 09:56:44 AM
mheltunen mheltunen is offline
Registered-I
 
Join Date: Mar 2017
Location: Atlantic Mine, Michigan, USA
Posts: 85
Thanks: 58
Thanked 26 Times in 12 Posts
Default Re: Onan 7.5 JB-3CR running issue

To address my voltage regulator issue I'm considering trying a SX460 as a cost effective solution until I get all the bugs worked out and the fine tuning to the set? Any thoughts on these? Easy install or do they require a lot of custom wiring?
Reply With Quote
  #66  
Old 03-22-2017, 05:34:48 AM
squidtrap squidtrap is offline
Subscriber
 
Join Date: Nov 2012
Location: Forked River, New Jersey
Posts: 1,016
Thanks: 1,526
Thanked 484 Times in 336 Posts
Default Re: Onan 7.5 JB-3CR running issue

The wiring should b correct 1+3 tied together for hot and 2+4 together to gen frame for ground, then out to form the neutral.

Just get confirmation on that, its early and eyes play games on me now. Ed.
Reply With Quote
The Following User Says Thank You to squidtrap For This Post:
  #67  
Old 03-22-2017, 08:34:48 AM
Jim McIntyre's Avatar
Jim McIntyre Jim McIntyre is online now
Subscriber
 
Join Date: Nov 2004
Location: Mooresville, Indiana, USA
Posts: 3,755
Thanks: 605
Thanked 1,959 Times in 1,157 Posts
Default Re: Onan 7.5 JB-3CR running issue

Quote:
Originally Posted by mheltunen View Post
To address my voltage regulator issue I'm considering trying a SX460 as a cost effective solution until I get all the bugs worked out and the fine tuning to the set? Any thoughts on these? Easy install or do they require a lot of custom wiring?

Check here:

https://www.smokstak.com/forum/showthread.php?t=139868
Reply With Quote
The Following 3 Users Say Thank You to Jim McIntyre For This Post:
  #68  
Old 03-22-2017, 01:32:53 PM
yellowlister yellowlister is offline
Subscriber
 
Join Date: Feb 2010
Location: Granada Hills, California
Posts: 3,728
Thanks: 1,629
Thanked 1,786 Times in 1,177 Posts
Default Re: Onan 7.5 JB-3CR running issue

This is the centrifugal switch I have from a jc. I don't have any covers left..
Attached Thumbnails
Click image for larger version

Name:	20170321_231226.jpg
Views:	44
Size:	92.3 KB
ID:	278183  
Reply With Quote
The Following User Says Thank You to yellowlister For This Post:
  #69  
Old 03-22-2017, 02:24:47 PM
mheltunen mheltunen is offline
Registered-I
 
Join Date: Mar 2017
Location: Atlantic Mine, Michigan, USA
Posts: 85
Thanks: 58
Thanked 26 Times in 12 Posts
Default Re: Onan 7.5 JB-3CR running issue

Update.. I finally have the jb running but much fine tuning and parts will be needed. I have confirmed that the AC side is operational by jumping the f1/f2 leads so I feel a bit better moving forward. I will need a new coil and wires a centrifugal switch and cover, a voltage regulator and isolation feet. I sure appreciate all of the help from everyone and I suspect more may follow.

Thanks,
Mark
Reply With Quote
The Following User Says Thank You to mheltunen For This Post:
  #70  
Old 03-22-2017, 02:47:28 PM
len k len k is offline
Registered-III
 
Join Date: Jun 2012
Location: Manchester, New Hampshire
Posts: 13,678
Thanks: 345
Thanked 4,936 Times in 3,588 Posts
Default Re: Onan 7.5 JB-3CR running issue

Clean the terminals on coil. My brass ones were mucky and it didn't spark till I cleaned them.

Look on ebay for coil, For alternate coil ideas using modern car/motorcycle coils see my thread
https://www.smokstak.com/forum/showthread.php?t=167037
Reply With Quote
The Following User Says Thank You to len k For This Post:
  #71  
Old 03-22-2017, 05:35:59 PM
mheltunen mheltunen is offline
Registered-I
 
Join Date: Mar 2017
Location: Atlantic Mine, Michigan, USA
Posts: 85
Thanks: 58
Thanked 26 Times in 12 Posts
Default Re: Onan 7.5 JB-3CR running issue

I followed your advice and cleaned them well but still no change.

]I have also considered trying one of these : https://www.denniskirk.com/2001766.s...d=154651372798. Thoughts ?
Reply With Quote
  #72  
Old 04-06-2017, 02:50:11 PM
mheltunen mheltunen is offline
Registered-I
 
Join Date: Mar 2017
Location: Atlantic Mine, Michigan, USA
Posts: 85
Thanks: 58
Thanked 26 Times in 12 Posts
Default Re: Onan 7.5 JB-3CR running issue

Update: I installed a "new" centrifugal switch and with a borrowed coil it indeed runs. My next step is to look at an aftermarket or used oem coil if one can be located without dropping huge $$ on it. based on my pictures and information from earlier posts does anyone have and suggestions for an aftermarket coil? I have heard of some making a older twin harley coil work as well. I am also for now looking at installing an sx460 voltage regulator as a cost effective fix and possibly upgrading that later. I have heard that a resistor needs to be added to drop the field resistance down a bit. to do this from my understanding is you need to measure the resistance between F1 and F2 then add the appropriate resistor to meet the new boards recommendations. Where is this resistor to be added? In series i assume but on which wire? The f1 or the f2 or does it not matter? I am also looking for a door panel (the one that goes in front of the carburetor) as well i anyone has one laying around. Again all help is appreciated.
Attached Thumbnails
Click image for larger version

Name:	image1.jpg
Views:	43
Size:	89.6 KB
ID:	279429   Click image for larger version

Name:	image2.jpg
Views:	40
Size:	105.3 KB
ID:	279430  
Reply With Quote
  #73  
Old 04-06-2017, 03:06:31 PM
mheltunen mheltunen is offline
Registered-I
 
Join Date: Mar 2017
Location: Atlantic Mine, Michigan, USA
Posts: 85
Thanks: 58
Thanked 26 Times in 12 Posts
Default Re: Onan 7.5 JB-3CR running issue

I was able to confirm by both measuring resistance and the "paper clip" trick that my factory coil is shot...kaput... The coil is a 166C346
Reply With Quote
  #74  
Old 04-18-2017, 07:42:38 AM
mheltunen mheltunen is offline
Registered-I
 
Join Date: Mar 2017
Location: Atlantic Mine, Michigan, USA
Posts: 85
Thanks: 58
Thanked 26 Times in 12 Posts
Default Re: Onan 7.5 JB-3CR running issue

I switched over to a sx460. The original voltage regulator needs some work done but thats a bit over my head (or interest level). In the past some guys have said they like to work on the boards. If anyone has any interest in this one PM me.
Attached Thumbnails
Click image for larger version

Name:	IMG_2417.jpg
Views:	35
Size:	85.0 KB
ID:	280330   Click image for larger version

Name:	IMG_2418.jpg
Views:	36
Size:	97.5 KB
ID:	280331   Click image for larger version

Name:	IMG_2419.jpg
Views:	32
Size:	72.7 KB
ID:	280332  
Reply With Quote
The Following 2 Users Say Thank You to mheltunen For This Post:
  #75  
Old 04-18-2017, 01:13:40 PM
mheltunen mheltunen is offline
Registered-I
 
Join Date: Mar 2017
Location: Atlantic Mine, Michigan, USA
Posts: 85
Thanks: 58
Thanked 26 Times in 12 Posts
Default Re: Onan 7.5 JB-3CR running issue

Spoken for ����
Reply With Quote
  #76  
Old 04-21-2017, 10:00:13 AM
mheltunen mheltunen is offline
Registered-I
 
Join Date: Mar 2017
Location: Atlantic Mine, Michigan, USA
Posts: 85
Thanks: 58
Thanked 26 Times in 12 Posts
Default Re: Onan 7.5 JB-3CR running issue

Update. New sx460 volatage regulator installed. New coil (12v and removed resistor) , centrifugal switch. Had it running good. Today I went to start and will only stay running if start switch is held. (Starts very well). I'm suspecting relay k12 as the culprit but Not sure at this point. I ran into this same problem intermittently before but now I can't keep set running. Any thoughts?
Reply With Quote
  #77  
Old 04-21-2017, 11:21:22 AM
nothingbutdarts nothingbutdarts is offline
Sponsor
 
Join Date: Apr 2014
Location: Bailey, Colorado, USA
Posts: 1,886
Thanks: 4,220
Thanked 763 Times in 534 Posts
Default Re: Onan 7.5 JB-3CR running issue

The centrifugal switch is what triggers the relay, check wiring and the contacts in the switch.
Reply With Quote
  #78  
Old 04-21-2017, 11:25:41 AM
len k len k is offline
Registered-III
 
Join Date: Jun 2012
Location: Manchester, New Hampshire
Posts: 13,678
Thanks: 345
Thanked 4,936 Times in 3,588 Posts
Default Re: Onan 7.5 JB-3CR running issue

Put probe of a 12V ice pick test light on wire between centrifugal switch (S1) and R11, put ground of test light on neg of battery. Should light when centrifugal switch closes, if switch and wiring are good. If not then use the test light to check that +12V is present on other wire of centrifugal switch.

I have a JB , I've found I have to hold start switch till engine comes up enough in rpm. Makes a difference if engine is having a hard firing and getting up to speed. Switch closes at ~ 900 rpm, normal engine speed is 1800. I have the same spec AA gen as you do.
.

Last edited by len k; 04-21-2017 at 11:48:38 AM. Reason: lable centrifugal switch as S1
Reply With Quote
  #79  
Old 04-21-2017, 11:46:46 AM
mheltunen mheltunen is offline
Registered-I
 
Join Date: Mar 2017
Location: Atlantic Mine, Michigan, USA
Posts: 85
Thanks: 58
Thanked 26 Times in 12 Posts
Default Re: Onan 7.5 JB-3CR running issue

By manually closing the centrifugal switch It indeed pulls the relay in. In fact its when the switch closes (makes contact) it seems to lose ignition power (spark). I will have to check this weekend or monday with a test light to confirm the below tests. I have the set at work now and I have a good meter there but test light is in the garage. It sure sounds like a basic wiring issue, just trying to find it is the problem. When i had the set running in the past it sometimes would exhibit the same symptoms but after repeated attempts it would eventually start.
Reply With Quote
  #80  
Old 04-21-2017, 11:56:47 AM
len k len k is offline
Registered-III
 
Join Date: Jun 2012
Location: Manchester, New Hampshire
Posts: 13,678
Thanks: 345
Thanked 4,936 Times in 3,588 Posts
Default Re: Onan 7.5 JB-3CR running issue

Quote:
Originally Posted by mheltunen View Post
By manually closing the centrifugal switch It indeed pulls the relay in. In fact its when the switch closes (makes contact) it seems to lose ignition power (spark).
When centrifugal switch pulls in it powers coil of relay K12.
When K12 pulls in it BOTH kills power to coil of relay K11 AND supplies +12V to spark coil.
( when energized K11's contacts were supplying spark coil with +12V)

Sounds like the contacts of relay K21 that supply power to spark coil are dirty or corroded. Use test light to check for +12V at relay on wire from K12 contacts to spark coil. If poor light, clean relay contacts with some fine sandpaper, ~180-360 grit depending on corrosion
Reply With Quote
The Following User Says Thank You to len k For This Post:
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

F o r u m Jump

Similar Threads Chosen at Random
Thread Thread Starter F o r u m Replies Last Post
Onan KY Microlite 4000 Running Issue bills02jeep Onan Generators 14 12-10-2016 12:32:44 PM
small associated running issue (help!) Chris Steffen Antique Gas Engine Discussion 8 12-25-2012 01:57:23 PM
Onan Model 4.0 DKC-3CR/1A Serial # E860820953 Running issue KWA915 Onan Generators 1 07-02-2012 10:29:47 PM
Maytag 92 running issue Lvolling Maytag Engine Collectibles 3 05-29-2011 01:34:09 AM
Onan DJC12 start/run, stay running issue dougvnbalto Onan Generators 2 10-29-2010 08:59:03 PM


Use "Ctrl" mouse wheel to change screen size.
All times are GMT -4. The time now is 08:42:54 PM.

Smokstak and Enginads site search!


All use is subject to our TERMS OF SERVICE
SMOKSTAK® is a Registered Trade Mark - A Community of Antique Engine Enthusiasts
Copyright © 2000 - 2016 by Harry Matthews P.O. Box 5612 - Sarasota, FL 34277