5KW CCK Onan won't stay running

[Childeric]

This is on a 77 Dodge Champion and only has about 110 hours on it, it will start up and run "ok" for about 15 seconds then dies. I took the carb off, had a lot of dirt in the bowl so disassembled, soaked in carb solvent, blew out passages and reassembled, zero change. I can coerce it into running longer by playing with the throttle... it'll slow down and stumble a bit but I can pretty much keep it running by playing with the throttle. The oil was recently changed, quite clean looking, the oil level is just slightly below the mark... is this enough to affect the running? How does this low oil level shut down work? If it was a low oil level would I still be able to trick it into running with the throttle? Could a dirty plug make it run this way? Fwiw, I do need to change my spark plug wires as the boots are not making firm contact with the plug. I have btw, tried running it with a load, doesn't seem to make a difference, thanks.

[redtail]

the low oil shuts off the spark by grounding it sounds like a fuel problem may be a filter or fuel pump , How much fuel is in the tank most generators wont run with less than a 1/4 tank of fuel one i had would stop at half a tank Mike

[JaycoEagle10]

Like Redtail said, and I'll expand upon that.

How old is the fuel? Anything around 1 year(even if sta-bil treated) needs changed out to fresh. You can put used fuel into your vehicle to get deluted with it's fresh fuel to not waste.

You NEED to replace all rubber fuel lines as they've deteriorated over the years. May look brand new on outside, but inside it's falling apart. Remember it's 30+yrs old rubber. Number of hours on the clock means nothing. It's age and environment.

Take the carb back off and go back through it. If you didn't run some stiff wire(s) through the fuel passages you need to do so, as some grit is still caught in one or more passage.

Try this trick. If you can choke off the carb some(small piece of carboard, fingers or pull choke) and it picks up and will run, maybe bad but run, that tells you it's carb problems and needs attention.

Get back to us if it still doesn't work. You might have a manifold gasket problem(these are split manifolds on Onan's), fuel pump diaphragm problem or something that's causing a vacuum leak that needs repaired.

[Childeric]

Take the carb off again... mmmm ;-) Actually I didn't do any poking of wires because I'd read somewhere specifically not do do that, but I guess I "gotta". Tank is basically full of new gas btw, though it does have an aftermarket pump (will see what it is again, exactly) on it... AND the fuel cut off valve has been inop'd, it's still hanging there via the wires, sigh... that was going to be my next question, what to do about that little bit of diy hack-job. Oh, where might I source some good stiff, small gauge wire? Sounds slightly exotic... Thanks

[JaycoEagle10]

Childeric, you might find some small, stiff wire in a hardware store. Take your carb with you, to find the size that will get through the (smallest) of holes. Larger passages, the carb cleaner wand(carb spray) will fit and you can spray a good blast to dislodge any crud. Carb passages can be very small, but critical to be clear of any obstruction to make work properly. DO NOT leave any burs on wire to scratch the interior passages if you cut the wire(too long to use comfortably). Shouldn't need over 6 to 7 inches of wire length at most for these small carbs.

You don't worry about bends. If you go through one hole without the wire going out the other side, you simply stop, to NOT damage the hole and figure where that hole goes to and put wire into hole from other end. This way you won't damage any passage holes, but if there's any debris, the wire will help dislodge.

After the rodding out of holes with wire, I always follow up with a good shot of carb cleaner spray by running the spray wand into hole and blasting while with-drawing the spray wand and then follow up with air blasted into holes. This of course if spray wand fits into hole. I use computer compressed air as it's easy, convenient/on hand and has good pressure.

Before putting carb back together, check all decking surfaces for warpage with a straight-edge. 6" metal mechanics ruler works very well.
If you find any warpage, high spots need to be filed down to bring back all clamping surfaces straight.

I've been doing these tricks to carbs since the early 70's without problems.

You've got me confused about the fuel pump though. It needs to be screwed/bolted down.

Replace that fuel cut off valve when replacing the fuel line with a good 1/4 turn, inline barbed, metal valve, and you'll never need to replace it again. they cost around $14 at a tractor supply.

[JaycoEagle10]

I just thought, when you said wires to fuel cutoff.

Is these wires connected to a valve/solenoid at bottom of carb bowl?

If so, you need to repair these immediately, as it's the fuel cut off solenoid valve when you shut off engine to keep excess gas pressure of fuel pump/gas tank from over flowing carb when not running. At least that's the job of it.

I don't know what you have without seeing pictures of this DIY fix, so you might need to have a lawn mower shop to look at it.

Onan's are expensive, so last thing you need to do is a rebuild due to busted rod from thinned oil from fuel cutoff solenoid not working properly.

[Childeric]

Originally Posted by JaycoEagle10

I just thought, when you said wires to fuel cutoff.

Is these wires connected to a valve/solenoid at bottom of carb bowl?

If so, you need to repair these immediately, as it's the fuel cut off solenoid valve when you shut off engine to keep excess gas pressure of fuel pump/gas tank from over flowing carb when not running. At least that's the job of it.

I don't know what you have without seeing pictures of this DIY fix, so you might need to have a lawn mower shop to look at it.

Onan's are expensive, so last thing you need to do is a rebuild due to busted rod from thinned oil from fuel cutoff solenoid not working properly.

Jayco, yes it's the fuel cutoff valve that has been dc'd, haven't checked out where the wires are going, just into the loom I believe, fuel pump is secured. I think I still have stainless wire used for wrapping motorcycle hand grips, I will try that. But man I soaked that carb for three days in Berryman carb solvent then blew it out using 140lbs of compressed air and that was with the right rubber nozzle on it to make a seal, can't imagine how clogged up it must be for that not to have worked. I will give the wire a go but I may end up taking it to a lawnmower repair place I know of. Well, in the name of keeping things simple, I might just wire a switch to manually cut off the fuel pump and let it starve out to shut it down, instead of using the valve.

[redtail]

i would go to the nearest welding supply and get a tip cleaner for a torch start with the smallest wire and work up dont twist just in and out when they stop going through they are clean Mike

[twinboat]

I clean carb passages with strands of copper wire. I strip back 10 or 8 gauge, stranded, electrical wire and pick out a piece.

[Childeric]

Yeah I was thinking of a welding tip cleaner, think there's even one in one of my grandfathers old tool boxes... might be a bit short though? Copper soft and safe but maybe too soft? I think I'll just go buy a sweet 63 Travco instead Seriously, will try both of those ideas, thanks.

[bsinmich]

Another good possibility is the rubber gas line to the Generator. That old it has probably gotten brittle from age and heat and when the Onan is sucking fuel it is getting more air than fuel. Follow it all the way back to the tank. A way of testing is to have a quart container with a short hose in it. If it runs then you know the line is bad.

[Childeric]

The indicated hole is completely blocked. Before I go crazy trying to unplug it, any chance it's supposed to be a blind hole? Thanks.

[JaycoEagle10]

Originally Posted by Childeric

The indicated hole is completely blocked. Before I go crazy trying to unplug it, any chance it's supposed to be a blind hole? Thanks.

NO. That is plugged by crud. Clean it out.

Any hole on the "interior" of a carburetor is there for a reason and is to be open to allow either gas or air at the correct interval of engine speed and carb butterfly opening.

You just found at least some of your problem. Now clean out ALL passages(just to be sure---again) and please replace that rubber fuel hose with new and install a inline fuel filter. I would install between the fuel pump and carb.

Then install a good inline fuel cutoff valve before the pump, so's you can shut off the fuel when working on the pump, carb, or replacing the filter.

I installed this combo setup immediately when I purchased a used commercial mower last year that is powered by an Onan Performer 20.

Trust me, when a mower cost more than $10K in 1990 as new, it's worth it to keep out of a shop for repairs. It's a Kut Kwick, but not like you see today that cost more than $40,000.

[Childeric]

Well, I was going to make a little joke and ask you if you are sure... but ;-) Ok, will do, already installed 2 fuel filters but will replace the hose(s) and valve, do whatever it takes to unplug the passage and report back. Thanks much, Jayco.