Community Forums

sjholt · 06-12-2016, 08:39 PM

Does anyone know what fittings I need to change my LP genny from hi pressure liquid to vapor?

I have a 96 Monaco Windsor.

Skip H

Skip426 · 06-12-2016, 09:10 PM

What brand of gen set do you have?
I thought they all ran on vapor,

or at least I should say every gas engine I converted to propane ran on vapor.

johnhicks · 06-12-2016, 09:16 PM

I'm curious about this too; my Onan runs on liquid. Of course a call to Cummins/Onan would provide the answer if only I could remember to call.

Skip426 · 06-12-2016, 09:26 PM

JMHO: If the gen set is set up to run on liquid , it'll take more than a few fittings to switch it to run on vapor. Must have it's own vaporizer and regulator some where.

Skip426 · 06-12-2016, 10:51 PM

I downloaded an Onan gen set handbook ; it's to big to re-post here in the forums; anyway , page 19 in the Q&A section .

Q. How is LP fuel supplied to the generator .
Last line in the answer, states.

Cummins Onan generators use vapor with drawl.

What the text doesn't say is if the vapor is at tank pressure ( 125 PSI ) or taken off after the regulator.

Gentlemen , liquid propane can cause frostbite to exposed skin in less than a second , do not attempt to modify a propane system unless you know exactly what you're doing. Many areas won't allow you to purchase propane fittings without a gas fitters license.

johnhicks · 06-13-2016, 01:14 PM

My rig has two outlets, one labeled "vapor" which runs the house propane and one labeled "liquid" which goes to the generator.

sjholt · 06-13-2016, 05:01 PM

Gees fellows,
If you don't know the answer- why say anything and I need Internet police like- well you know.
I know there is someone who converted there LP generator from liquid to vapor to prevent oil from getting into the carb evaporator and gumming up the works and stopping the generator as it is doing now..
I'll be changing this in a couple of days- by myself- and breaking all kinds of rules so If I don't post back- you'll know I blew up the motorhome!

bill06447 · 06-13-2016, 07:10 PM

Most LP engines draw from the liquid side and the vaporizer/regulator assembly turns it to, well, vapor. The oil (actually tar is the technical name) needs to be drained off periodically as part of the routine maintenance. Even after only 100 hours of use you'd be surprised at the amount that comes out of the drain on the vaporizer. Sometimes I have to remove the carburetor diaphragm and wipe that down as well.

Pa Miller · 06-13-2016, 07:15 PM

I thought they were already vapor... my 1995 Monaco is vapor from the factory.

ahicks · 06-13-2016, 07:17 PM

Never heard of a conversion like this (genset running on vapor). Would be interested in details when/if you find them.

Gary RVRoamer · 06-14-2016, 10:01 AM

As can be seen from the responses, there are both types in use, vapor and liquid. Onans have used vapor for a long time, maybe forever. Some other brands use liquid. To make the conversion, you have to change components on the generator end as well as the plumbing into the tank. Basically it's a different type of "carburetor", though that's not the proper tech term for an LP gas engine. One handles liquid LP and evaporates it to mix with air, while the other is basically just a vapor mixer. Both have to manage pressure into the engine intake, though.

While propane is obviously dangerous in that it is flammable and under pressure, it is not really difficult to work with and I think sjholt will have no great difficulty with his project.

ahicks · 06-14-2016, 12:33 PM

Skip, as my somewhat limited propane Onan experience was pretty much opposite yours, I dug in and looked. Not hard, but I did find this.

Onan Generator Kits

If we had the OP's model number we could see what he has for sure, and what his options are. -Al