Onan generator- off topic!

I have an Onan 4000 that came out of a 2001 Minnie. Back in 2017, when we were running away from hurricane Irma, we went to Alabama. On the way back, we boondocked at a couple of Walmarts. The generator had never worked since we got the camper, but we needed power, and tried to get it running. Long story short, it ended up catching on fire. Fan shroud is toast, but ended up finding a new one.



















Carb isn't worth fixing, so I ordered a cheap one on ebay, to get it running. Biggest challenge will be the wiring. It originally had an electric fuel pump, but that won't be needed as it will be stationary, and have a top-mounted fuel tank. I'll try my best to keep this updated as I work on in it.

I've fixed a lot of old Onan's on sailboats back in the late '70's- early '80's but never an underslung one like that.
Back then they were transitioning to Subaru Robin engines, which seemed much more reliable but hard to find parts for here in the states.
I did know a few ex-pat Brits down in the islands, but parts were slow to get, and Japanese dealers were non-existent.

Good luck!
I'm following to see where this leads ...

Jim, I have two Onans and a Kohler. The Onans are a 305 CCK and a 4.0 CCK, both actually rated at 4.0 KW. The Kohler is a 6.5 KW.

The 305 CCK is a recoil start engine and actually isn't too bad to start, it just doesn't pull fast. Once started I have run our 30 ft 5th wheel on it including the AC for an entire weekend twice. The first time I didn't have a big fuel tank, so it sat in Darth's bed at Oceana NAS in Virginia Beach and we took turns going out and filling 5 gal cans. Second time I had a 30 gal marine fuel tank that had been in a Winnebago for travelling up the Alcan highway, owner traded me a tune up and carburetor repair on his Onan genset for the tank.

4.0 CCK was removed from a motorhome being scrapped and given to me, it can be battery started and has reverse flow cooling. It is nice to use but really needs a proper mounting frame. The Kohler came out of a big sailboat a co-worker's family owned. Both of these use what is called "stator cranking" where the generator acts as a direct drive starter.

I'm going to get a new plug for it tomorrow. I'll have to build a whole new fuel system for it. I'm doing away with the electric pump (mainly because I hate them and don't trust them). The fuel tank will be mounted overhead (gravity feed). The whole thing will be mounted in a movable wooden frame/stand. I'll be using the F250's old rear tank. 19 gallons should run that thing for a while...

I really wish I could take the engine out and use it in a mower or something fun. It's rated at 9.5 hp, and I've heard that these Onans are pretty tough. I'm impressed with the construction so far. Of note is the cast aluminum valve cover, instead of the usual cheap stamped steel. But, I need this generator, so in it will stay.

Every ICE on the road in the last 38 years has electric fuel pumps. They can be very reliable
(I don't understand the hatred?)

I'm curious too. Usually there is a backstory to 'hatred'

I've been through so many on the F250 that I just don't trust them anymore. I also sell them, and see how many come back, and how many originals fail. I know they are a solid technology, but I still don't like them. I'm just like that. Might not make sense, but that's how it is.

Quite a backstory. Chasing a working electric fuel pump is part of how I got my job at the parts store. Every fuel pump I put in the rear tank on the truck failed (or had a wrong resistance range-but that's another story) except a Holley. I still got so disgusted with them that I went to a mechanical pump.

Personally I'm not that worried about OEM in-tank high pressure electric fuel pumps.  I think they've proven their value.  Aftermarket replacement in-tank electric fuel pumps are a little more questionable.  It seems that there is a fair amount of junk out there, but I'm sure there are good ones as well.

But for a carbed Onan generator you can't use an OEM in-tank high pressure electric fuel pump.  I'm not aware of any OEM in-line low pressure electric fuel pumps (I'm well aware that there may be some I'm not aware of).  And my experience with aftermarket in-line low pressure electric fuel pumps had led me to try to avoid them whenever possible as well.

You just spelled it out EXACTLY. If I can avoid an electric anything I will.

Looks like electric fuel pumps got you where you are

I think a large part of the problem in the history of electric fuel pumps is vapor lock

- high pressure in-tank pumps completely solve the problem of vapor lock by pressurizing the fuel ahead of the pump so much that vapor lock is impossible. In addition, being in-tank means little to no fuel to be vapor locked from suction

- low pressure pumps in-tank are still subject to vapor lock due to the relatively lower fuel pressures ahead of them in the engine bay.

- low pressure pumps away from tank are a big risk.. the long suction part is definitely a big risk for creating vacuum which is when vapor lock occurs, and the low pressure ahead is also not helpful in the engine bay heat.

So far I've had success with frame mounted low-pressure fuel pumps... fancy or cheap ones.. as long as a few best practices have been followed to avoid vapor lock. (proximity to tank, mounting angle). They are cheap and easily replaceable on the road.

Cheap and easily replaceable, yes. But I'd always be waiting for it to go out. Why don't we just mount the fuel tank on the hood and let it gravity feed to the carb. No pump needed!

I can understand your frame of mind. I have been soo bit by something I am never going to try it again. Like a Toyota in my case  which I'm sure 99% of the people think I'm crazy but I don't care that's just what I think.
 

Heh. I've had some fun with a Toyota before...

I have a Hudderite aunt who lives in northern Idaho.
She seems to get by just fine without electricity!  💡

viven44 wrote

....  So far I've had success with frame mounted low-pressure fuel pumps... fancy or cheap ones.. as long as a few best practices have been followed to avoid vapor lock. (proximity to tank, mounting angle). They are cheap and easily replaceable on the road.

That's what I had on my Bronco.  But "cheap and easily replaceable on the road" is faint praise when you're stranded on the side of a freeway in afternoon rush hour on a rainy day the second time a low-pressure in-line electric fuel pump failed (at least it wasn't raining the first time it stranded me in afternoon rush hour).

Now I have a mechanical fuel pump.  I know they can fail too.  But all three times I had one fail (and all on Chevy 350s, for what that's worth...) I could still limp it at least off the freeway if not all the way home.  And those three times were all with fuel pumps that had over 100,000 miles on them.  Neither of the electrics that failed on me had even 20K.

But I'll repeat, I don't feel the same about the OEM in-tank high pressure pumps.  I'll stick with fuel injection on my "real" cars!

That is true. I haven't crossed that bridge so I don't know what it will take when faced what that crisis.

I have nothing against mechanical pumps. The vehicles I had with a mechanical pump, they were really easy to maintain and service. No wiring to deal with, etc... as simple as it gets.. Based on what I read on the possible failure modes, I did worry about diaphragm rupture and fuel getting into the crankcase... that did worry me a bit.

When mine failed it didn't leak, it just wore the fulcrum right out of the pot metal trunnion.

I was in a drive through and popped the hood, got out, took the air cleaner lid off and filled the primary bowl through the vent with a 60cc syringe.

That's enough to idle for a couple of minutes, but only enough to make it to a parking spot.
I was set up now, so I positioned my truck so it was easy to tow.
Then I called my buddy Theo.  😉

How many miles did you have on it?