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Things to know about your Onan generator

maillemaker
Explorer
Explorer
So I have a 4BGE Speg G Onan generator in my 1990 Winnebago Warrior. I've been struggling for about a year to get it running again. First it was a split fuel line back at the tank. Then it would run, but shut down. Replaced the ignition control module with a used one, ran for a while and then shut down again.

I thought I would share some thoughts on these things, now that I know my way around them like the back of my hand.

The mechanical side of these things is pretty bullet proof. That is, the engine is pretty well made, at least the older ones. With a couple of exceptions.

When they switched these generators from points ignition to electronic ignition, they installed a plastic rotor (looks like a propeller) deep inside the genset, between the motor and generator halves. If rodents build a nest inside your generator, and you try to fire up the generator, this rotor can easily get snapped off by the nest debris. This did not happen to me, fortunately, but it is a common problem with these gensets. Unfortunately in order to replace this rotor you have to split the generator in half to replace it.

There are only 6 electrical parts that make the generator go:

Coil
Ignition Control Module
Starter
Voltage Regulator
Control Board
Starter Solenoid

The coil you can now buy aftermarket replacements for far less than what some sell them for - $45 vs. $145. I used this one:

https://www.amazon.com/gp/product/B07BFXC9V4

The OEM starter has a fragile plastic keeper system that forces the starter gear to disengage. These last about 5 years and disintegrate. There are now aftermarket starters that have simplified this assembly and use all metal parts. They are also much cheaper than OEM versions ($35 vs. $133). I used this one:

https://www.dbelectrical.com/products/starter-onan-191-1630-191-1667-191-2132-1975-on.html

Unfortunately the Ignition Control Module is Onan-specific. I bought it here for $103:

http://www.partsfortechs.com/asapcart/1660821-ignition-control-onan-p-350.html

The Voltage Regulator and Control Board you can buy from Flight Systems:

https://www.flightsystems.com/

You can also send your VR and CB to them and they will test them for $35 each. These parts are expensive - $200+ each. And, if you have to buy new ones from them, they will waive the test fee.

The good news is all of these parts are relatively easy to replace - especially if you remove the genset from the RV. There is a trick with the Ignition Control Module - you have to turn the motor over by hand until the short cooling fit lines up with the ICM - otherwise you can't remove it from the genset housing.

Except for the VR and CB, you can replace all the rest of the components for a couple of hundred bucks if you do it yourself. Instead of farting around testing and trying (which ultimately fragged my starter, which is why I had to replace it also) I would have been better off, once I identified I had a spark problem (using a spark tester) if I had just replaced all of those components from the get-go.

To keep your generator running, it is IMPERATIVE that you run it monthly. I run mine for half an hour under load.

I used to think this was just an optional thing. You know "exercise" the generator. Right. But it is critical for a couple of important reasons.

First of all, you must keep the slip rings clean. You should measure the resistance between the two brushes - if you get more than 80 ohms you need to clean your slip rings. Flight Systems makes a "slip stick" that will help you polish them clean - it's about $20. I used it on mine and went from 80 ohms down to 20. By running your generator often, it will self-polish those rings.

Why is this important? High resistance on the slip rings will destroy the voltage regulator. That's about $250 to replace. So, exercise your genset monthly and keep those slip rings clean or you will be spending a lot of money!

The second thing is you must keep fresh gas running through the carburetor. Especially with today's ethanol gas. One of the big killers of RV generators and performance is gummed-up carbs. Onan doesn't even recommend rebuilding these anymore - they recommend replacement. That's $300+. Run your genset under load every month for half an hour and the heat and vibration and fresh gas will keep the internals nice and clean.

Steve
1990 Winnebago Warrior. "She may not look like much but she's got it where it counts!"

9 REPLIES 9

Dusty_R
Explorer
Explorer
maillemaker wrote:
Dusty, that's a great point - that is one electrical item I forgot - the fuel pump.

My generator does not have a solenoid in the gas line, but the fuel pump itself is of course electrical, so one could easily install a switch to turn off the fuel pump.

Steve


My memory failed me. I met fuel pump.

Thanks Steve,
Dusty

maillemaker
Explorer
Explorer
Dusty, that's a great point - that is one electrical item I forgot - the fuel pump.

My generator does not have a solenoid in the gas line, but the fuel pump itself is of course electrical, so one could easily install a switch to turn off the fuel pump.

Steve
1990 Winnebago Warrior. "She may not look like much but she's got it where it counts!"

Dusty_R
Explorer
Explorer
We had a 2003 Itasca with an Onan generator. It had a solenoid in the gas line going to the carburetor, most if not all generators do.
I added a switch to the line powering the solenoid. When I knew that I would not be using the generator for a while, I would turn the power to the solenoid off and let the generator run out of gas, leaving no gas in the carburetor to gum up.

Our 2015 Itasca Onan has a drain on the carburetor. But I wonder if when draining it if the gas drains out of the jets?

Dusty

Chris_Bryant
Explorer
Explorer
The magneto is in the new Micro* single cylinder models, not what we are talking about. Fwiw, before electronic ignition, they used points w/ condenser.
-- Chris Bryant

jplante4
Explorer II
Explorer II
Wolfe wrote:
I was told mine needs a magneto, is that part of one of the parts that you listed?
it has been running great but now just turns over won't start.
Coil
Ignition Control Module
Starter
Voltage Regulator
Control Board
Starter Solenoid


The magneto was used before the switch to electronic ignition.
Jerry & Jeanne
1996 Safari Sahara 3530 - 'White Tiger'
CAT 3126/Allison 6 speed/Magnum Chassis
2014 Equinox AWD / Blue Ox

Wolfe
Explorer
Explorer
I was told mine needs a magneto, is that part of one of the parts that you listed?
it has been running great but now just turns over won't start.
Coil
Ignition Control Module
Starter
Voltage Regulator
Control Board
Starter Solenoid

leadknee
Explorer
Explorer
Great information
Steve an Barb
2015 Itasca Solei 340hp cummins
2012 ford fiesta tow

Chris_Bryant
Explorer
Explorer
Excellent write up- I'll just add Flight Systems has a very good troubleshooting guide at https://www.flightsystems.com/troubleshooting/.
For a rough running unit, I will hook up a portable gas tank with super treated gas- Sea Foam or B-12.

Your links, clickable:
Coil:
https://www.amazon.com/gp/product/B07BFXC9V4

Starter gear:
https://www.dbelectrical.com/products/starter-onan-191-1630-191-1667-191-2132-1975-on.html

Ignition module:
http://www.partsfortechs.com/asapcart/1660821-ignition-control-onan-p-350.html (Parts for Techs has great prices on Onan parts)

Flight Systems Voltage Regulator:
https://www.flightsystems.com/
.

(Edit to fix links).
-- Chris Bryant

agesilaus
Explorer III
Explorer III
I don't have one but that seems to be excellent info
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