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

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

Notices

Onan Generators Restoring, operating and maintaining vintage Onan generators.

Onan Generators

Onan 4.0 BFA-1r16004c - Stops when I release START switch


this thread has 16 replies and has been viewed 801 times

Reply
 
Thread Tools Display Modes
  #11  
Old 08-23-2017, 12:01:30 PM
len k len k is offline
Registered-III
 
Join Date: Jun 2012
Location: Manchester, New Hampshire
Posts: 16,065
Thanks: 445
Thanked 5,824 Times in 4,229 Posts
Default Re: Onan 4.0 BFA-1r16004c - Stops when I release START switch

In general Onan used 2 relays to power the spark coil and fuel pump. Looking at schematic it's K2 and K3.

One relay K2 would power them while holding start switch to start engine.
The other K3 would continue powering them after you released start switch, if oil pressure was up.

Possible a relay contact is dirty, these were open relays, not sealed

Odd but from schematic looks like this gen does check to see engine is turning. It uses back EMF from starter windings to power K3

Last edited by len k; 08-23-2017 at 12:21:05 PM.
Reply With Quote
The Following User Says Thank You to len k For This Post:
Sponsored Links
  #12  
Old 08-25-2017, 04:35:40 PM
ErikTande ErikTande is offline
Registered
 
Join Date: Jun 2017
Location: Denver, Colorado, USA
Posts: 11
Thanks: 2
Thanked 7 Times in 2 Posts
Default Re: Onan 4.0 BFA-1r16004c - Stops when I release START switch

Quote:
Originally Posted by Billy J Shafer View Post
The serial number will be some thing like B84355676.

First of all stop holding the start button and running the AC. You stand a good chance of burning up the system. The run relay can be bought at any auto parts store. Just a Bosch relay. The control resistor is back by the cooling fan if it is open it will cause your problem. Also look in the bottom of the control box for loose screws. That control box had a bad habit of screws coming loose and falling into the bottom. Shorting out the relays

Go to the twinslan section of this site. Down load the service manual.
Oh come on, you don't really think I'm holding the start butting and running the AC do you? : P

I make the wife do that. ; )


Onan Dan said it could be that the generator isn't making power, I was just pointing out that it does.

Combined with the fact that sometimes the start button does NOTHING it all, what could it be other than the start button? The relay? My point is, why not order both so I have backups on hand?

Could it be anything other than those 2?

Thanks again!
Reply With Quote
The Following 2 Users Say Thank You to ErikTande For This Post:
  #13  
Old 08-26-2017, 05:11:27 PM
gnucklehead gnucklehead is offline
Subscriber
 
Join Date: Dec 2011
Location: Williamsport, Pennsylvania
Posts: 1,610
Thanks: 1,118
Thanked 869 Times in 585 Posts
Default Re: Onan 4.0 BFA-1r16004c - Stops when I release START switch

1. Resistor R1 may be open
2. Run Ignition Relay K3
3. Low Oil Level
4. S3 Low Oil Pressure Switch may be defective

Or a bad connection or broken wire can cause the same symptom.

BFA (Spec C) Operator's manual (965-0122) has a controls troubleshooting guide
http://www.twinslan.net/~n0nas/manua...0(04-1981).pdf
Reply With Quote
The Following 2 Users Say Thank You to gnucklehead For This Post:
  #14  
Old 08-26-2017, 06:21:36 PM
Onan Dan's Avatar
Onan Dan Onan Dan is offline
Subscriber
 
Join Date: Oct 2012
Location: Waynesburg, Pennsylvania
Posts: 3,792
Thanks: 8,566
Thanked 2,878 Times in 1,434 Posts
Default Re: Onan 4.0 BFA-1r16004c - Stops when I release START switch

My Uncles 4.0BFA acted the same way it would turn over and run long as one held the start switch it was the start run relay in control box I had a used pair of relays and replaced them both and took care of the issue.
Reply With Quote
The Following User Says Thank You to Onan Dan For This Post:
  #15  
Old 09-12-2017, 12:28:06 AM
ErikTande ErikTande is offline
Registered
 
Join Date: Jun 2017
Location: Denver, Colorado, USA
Posts: 11
Thanks: 2
Thanked 7 Times in 2 Posts
Default Re: Onan 4.0 BFA-1r16004c - Stops when I release START switch

I did a little more troubleshooting (very little) and in the first post I mentioned that sometimes when I press the start switch I get nothing at all. Well now it's not sometimes, it's all the time. Switch does nothing, neither the switch on the generator or the remote start switch in the cab. Knowing that, it's probably not the switch that's the problem, right? Oil level is fine.

So it could be the run relay. (just a bosch relay?) I have one laying around so I'll try swap that first.

From there it could be the resistor or the S3 Low Oil Pressure Switch, right?

Thanks!

Oh, and I took the motorhome racing at Bandimere speedway. Any guesses what it ran?


Reply With Quote
  #16  
Old 09-12-2017, 07:08:51 AM
KPack KPack is offline
Subscriber
 
Join Date: Feb 2016
Location: Bryan, Texas
Posts: 546
Thanks: 1,751
Thanked 426 Times in 219 Posts
Default Re: Onan 4.0 BFA-1r16004c - Stops when I release START switch

I've got a parts unit here if you need something. No guess on the mh
Reply With Quote
The Following 4 Users Say Thank You to KPack For This Post:
  #17  
Old 09-12-2017, 11:59:09 AM
len k len k is offline
Registered-III
 
Join Date: Jun 2012
Location: Manchester, New Hampshire
Posts: 16,065
Thanks: 445
Thanked 5,824 Times in 4,229 Posts
Default Re: Onan 4.0 BFA-1r16004c - Stops when I release START switch

AS a test I'ld disconnect remote start/stop switch from gen , at the gen. That way your only testing gen, not RV wiring. Shorts in RV wiring can cause problems.
Reply With Quote
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 7.5JB dies after you release start switch jfikes01 Onan Generators 29 08-04-2016 05:24:01 PM
Onan 6.5- cuts off when release the start switch Eacosta71 Onan Generators 20 08-21-2015 01:48:59 PM
Onan MDJF stops released start switch Centrifugal Switch Problem Chuck711 Onan Generators 10 01-29-2015 03:22:11 PM
Onan 4k start/stop light doesnt work and stops running when release start switch JoshD Onan Generators 12 09-06-2014 07:51:40 AM
Onan stops when I let off the start switch shadetree13 Onan Generators 15 10-21-2011 06:56:52 PM


Use "Ctrl" mouse wheel to change screen size.
All times are GMT -4. The time now is 03:57:30 AM.

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