Coleman Generator Problem

As per my post in Hurricane Warnings Up, I tried to fix a Coleman 10hp 5000w generator for a lady today. Freezer and sump pump at stake. She hadn't run the machine in 7 years. No man around the house. Her son overfilled it with oil, had to drain a pint out. They had it outside their basement, I took the carb off and ran to the shop to clean it, definite rusty junk in the bowl. Simple carb. Got it back on the machine, fired it up, and it ran great; for a few minutes. Then it sputtered and died. If it sits for a few minutes it will start right up and run smooth as silk -for a few minutes. Then it sputters, runs rough and dies. Have good fuel flow. I'm thinking it's a bad ignition coil, or maybe something to do with the low oil cutoff switch. Any ideas? I had to say goodbye and felt bad, but my shop is down with the brownout and I'm Irened out.

Sounds like float needle partially blocked...restricted fuel flow.

I always run a piece of wire through all the holes in the carb when they sit and I take them apart. That said, it does sound like a fuel delivery problem, not the coil or ignition. Blocked needle would be my first check. If the tank has a suction line, it could be picking up crap on the screen and choke it off after a while. After it sits the crap settles off/repeat? If it has a fuel pump, is the suction line slowly collapsing?

McGiever wrote:Sounds like float needle partially blocked...restricted fuel flow.

Yes, exactly. It is running on the gas in the bowl, but the bowl isn't filling up fast enough. Check the float is not water-logged, and the needle tip is not rotted off.

Do what was suggested above, and make sure the tank is vented.

Make sure the choke is set correctly for running.

Check for cracks in the fuel lines, or vacuum lines, the ethanol isn't the best thing for rubber. Does it have a fuel pump or is it gravity fed ? I cleaned a carb on a husqvarna saw that would only run with the choke on to discover numerous cracks in the fuel line, easy fix as hind sight is 20/20

Just soldered a brass float on a 60's Sears gen set - actually I should say ... I watched someone else do it - too many beers for me today.

Ran great most of the day, then started pissing fuel out the vent. Took a couple tries to figure that one out.

Then it ran great for another half hour then seized solid. Thought those suckers were built good! Oh well .... Another project for another day.

Thanks for all the replies. I checked this top tank (hdpe) gravity fed machine last week, but with the storm coming I was in a hurry. I knew it was running rough. Thought it would keep running. The lady was right there. " Oh, I forgot to ask you to check the generator until there's a hurricane bearing down on a few million people...")
In tank filter, tank was bone dry when I first looked at it last week. Fuel shutoff stop valve out of the tank, 1/4" fuel line with a disc shaped inline screen filter. Fuel line flexible and intact. When I took off the carb today I opened the fuel valve and blew back into the full tank. Fuel poured unrestricted out of the fuel line.
I couldn't do a thorough rebuild with all this craziness. Out of carb cleaner. I had just enough electronics spray to spray up through the main tube and through any idle circuits I could see. Then compressed air, what was left in my compressor! Brownout here today. The Idle jet seats firm into its passage, no adjustments. It might have had a tiny check ball and spring in it, maybe that was jammed. In other words, It had two little perpendicular pick up holes, which I think might have fed gas to vacuum right in the carb throat. I think that would only affect idle, and this generator was set to run fast.
The bottom ,uh metering jet? you know, with a couple holes in it, was also the nut that holds the bowl on. And the center tube part of the body casting, where you usually see a screw-out jet, looked like it had an insert. No slotted jet. Looked like nylon, plastic. Maybe it could be withdrawn with needle nose pliers.

Brass float was intact. Aluminum needle was intact. Sometimes needles seat on a little rubber insert needle seat. Wasn't sure if it was one of those. I've blown those out by mistake with compressed air and lost them more than once...

Anyway, fuel delivery problem sounds like a logical diagnosis. Seems like the running time is right for a bowl of gas, float seemed adjusted parallel to the body. Since I couldn't figure out how this could be a fuel problem, I started thinking about ignition. Thought maybe the coil started fritzing when it got warm, but that doesn't make as much sense as "post bowlful fuel starvation." Maybe the float's hanging up, but then how do you explain the easy restart soon after? It's like the gas seeps back in to fill the bowl. Little float needle has typical wire retainer, maybe that also helps pull the needle down with the float. It looked a little loose.
I choked it right when it was starting to run rough, but if the bowl was dry then that wouldn't give it more gas. Tapped on the float bowl.
I'll call the lady tomorrow and offer to keep working on it.

Thanks everybody for considered diagnosis!

some rocket scientist/bean counter that works for walbro or titilson carburator, decided that the best way to get C.A.R.B. compliant with mixture screw's
isnt to put those plastic limiter gimicks on anymore......people just cut them off and adjust the carb anyway....

what they have done is to make the needle with no slot for a screwdriver, instead if you look there is a flat spot on one side and it taked a special tool to adjust it. the have also cast the carb body to stand taller than the installed height of the needle to avoid the needlenosed pliers...

so we take a little dremel with a little cut off wheel and slice right down thru the excess carb body down to the needle and cut a shallow slot in the needle so a small screwdriver can access and turn it.

I have found they set the main needle too lean and after the first tank of gas and break in the machine needs a 1/4 turn out more gas.

i found this common on chainsaws from sears as well as other small engine.....

so, you might have some mung stuck in there somewhere..... a new can of carb medic and the light of day might be your answer!! dont spray it in your eyes...

I have found they set the main needle too lean and after the first tank of gas and break in the machine needs a 1/4 turn out more gas.

I found the same thing this morning when "loaded" our generator. I know that the fuel system is squeaky clean, but it still required a little choke to run smooth under load. I will be adding a little fuel to the main circuit as you suggested.

markviii wrote:

I have found they set the main needle too lean and after the first tank of gas and break in the machine needs a 1/4 turn out more gas.

I found the same thing this morning when "loaded" our generator. I know that the fuel system is squeaky clean, but it still required a little choke to run smooth under load. I will be adding a little fuel to the main circuit as you suggested.

You may need a higher octane fuel now. These 10% ethanol mixtures are playing havoc with the small engines. Befre you adjust the needles, try High-test.
I believe all new Stihls require it, and have it listed in their Owners Manuals now.

It has 93 octane in it already.

Poconoeagle wrote:what they have done is to make the needle with no slot for a screwdriver, instead if you look there is a flat spot on one side and it taked a special tool to adjust it. the have also cast the carb body to stand taller than the installed height of the needle to avoid the needlenosed pliers...

so we take a little dremel with a little cut off wheel and slice right down thru the excess carb body down to the needle and cut a shallow slot in the needle so a small screwdriver can access and turn it.

I have found they set the main needle too lean and after the first tank of gas and break in the machine needs a 1/4 turn out more gas.

Yeah, when I looked into the tube, all I saw was a tan plastic disc wtf. done a lot of Dremel work and got Gumout carb cleaner in the eyes lots of times.

I was on my back under a Cadillac once changing the fuel filter, for my lady. Gas ran out of the fuel line and into my EAR The pain was unbearable. I ran down to the house taking the Lord's name in vain. My girlfriend said, "Why don't you try praying TO God instead of cursing." By then I had taken a garden hose to my ear. The pain went away after I flushed my ear hahahhaha.

Haven't heard from the generator lady, got our own problems here. The basement is safe, the water table has mostly receded. No full power yet, no water...

still no power in the newfoundland compound. both generators there doing a great job but it sure is cheaper to pay the electric company for the juice instead of the a rabbs for the gaz.....

the ear thing.....ouch!! also nice is the old stinky gear oil down the arm past the elbow into the arm pit...... smells for a week