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Working on a Kohler twin. No ID tag on it, but I think it's around 20/25hp. It starts up n,e fi but only runs about 15 seconds and quits. can restart immediately. Fuel pump working and getting spark to the plugs. Could it be a faulty fuel solenoid?

Yes it could be or faulty wiring going to it....
I despise those things... I've taken the guts out of them and installed a simple cutoff petcock inline to manually shut fuel off when not running.

Chevychopper said:

Yes it could be or faulty wiring going to it....
I despise those things... I've taken the guts out of them and installed a simple cutoff petcock inline to manually shut fuel off when not running.

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Do you realize those fuel solenoid do nothing but block the main jet / noozle in do nothing to stop fuel flowing into the carburetor? It seems all the laymen and nearly every U-tuber out there thinks they are a fuel shut device that stop fuel from flowing completely; they don't and never was intended to do that, they just stop majority of fuel/air mix from entering the cylinder during shutdown so fresh can clear out the cylinder.

StarTech said:

Do you realize those fuel solenoid do nothing but block the main jet / noozle in do nothing to stop fuel flowing into the carburetor? It seems all the laymen and nearly every U-tuber out there thinks they are a fuel shut device that stop fuel from flowing completely; they don't and never was intended to do that, they just stop majority of fuel/air mix from entering the cylinder during shutdown so fresh can clear out the cylinder.

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EPA feel-good ruling for OPE carbs. Of course, without it, that occasional shutdown backfire can be fun!

Unless you have to pickup a hot muffler like I did when my IH PU backfired going down the road and blew off the muffler years ago.

StarTech said:

Do you realize those fuel solenoid do nothing but block the main jet / noozle in do nothing to stop fuel flowing into the carburetor? It seems all the laymen and nearly every U-tuber out there thinks they are a fuel shut device that stop fuel from flowing completely; they don't and never was intended to do that, they just stop majority of fuel/air mix from entering the cylinder during shutdown so fresh can clear out the cylinder.

Click to expand...

That's all great until the day you try and start your engine and realize the fuel solenoid has stuck in the open position ... And now you have a engine block/crankcase full of gas to deal with ..

Chevychopper said:

That's all great until the day you try and start your engine and realize the fuel solenoid has stuck in the open position ... And now you have a engine block/crankcase full of gas to deal with ..

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Yet again you don't understand how these fuel solenoids work. They DO NOT stop fuel flow from a leaky float needle seat.They have never been designed to do that and probably will never be design to totally block fuel flow as it is impossible to do so as long as a float valve system is used.

Thanks for the replies, but I didn't need a dissertation on how a fuel solenoid works.

gregjo1948 said:

Thanks for the replies, but I didn't need a dissertation on how a fuel solenoid works.

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It wasn't aim at you but @Chevycopper that was pushing disinformation or just showing his lack of knowledge about these.

But normally when one of these fail you will not even be able to start the engine. Now loose terminals on the wiring harness can cause intermittent problems with them. I have the best mechanics get sideline by loose connections. The ones that work until hit a bump especially. Even a nearly clogged fuel filter or faulty spark plug can minick the problem you are having. It takes pateince and experience to troubleshoot these kinds of problems.

gregjo1948 said:

Thanks for the replies, but I didn't need a dissertation on how a fuel solenoid works.

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Well that is good but obviously some others do need to understand what they read on face ache & saw on Boob Tube was garbage .
For you, we have to work out if it is electric or fuel
For diagnosis purposes I have a red flashing spark tester , a variety of old solenoids with the plungers removed & a can of carb cleaner, plus pf course over 300 spark plugs
For us we really need to know what the Kohler is fitted to
This is because some brands use an ignition relay to kill the spark while others use the key
Some like Toro, Scag & Spartan use a control module hidden in the hour meter and when they go bad you can get these symptoms
FWIW
I fit the spark tester and just watch to see if it stops flashing before the engine starts to slow down indicating a wiring / magneto fault .
If this happens the next step is to remove the kill wires from the magneto to work out if it is wiring or magneto .
Magnetos can not be fixed .
NExt step is to remove the air filter and shoot short shots of carb cleaner down the carb throat
Note the use of the word SHORT .
If I can keep the engine running like this for a minute ( or at least longer than it was running by itself ) then that points to a fuel problem so the substitute solenoid goes in.

When that is done I catch the contents of the float bowl checking for debris & in particular water.

Depending upon the actual carb fitted, having a float bowl 1/2 full of water can cause this because on some the idle circuit draws fuel from the top of the float bowl so get fuel while the main jet sucks fuel from the bottom and thus gets water .

When none of these make any difference then the spark plug or HT lead & cap become prime suspect .

But as I already mentioned this will depend upon what your engine is in.

StarTech said:

It wasn't aim at you but @Chevycopper that was pushing disinformation or just showing his lack of knowledge about these.

But normally when one of these fail you will not even be able to start the engine. Now loose terminals on the wiring harness can cause intermittent problems with them. I have the best mechanics get sideline by loose connections. The ones that work until hit a bump especially. Even a nearly clogged fuel filter or faulty spark plug can minick the problem you are having. It takes pateince and experience to troubleshoot these kinds of problems.

Click to expand...

I have a great deal of experience, but I might be a little short on patience.

StarTech said:

Yet again you don't understand how these fuel solenoids work. They DO NOT stop fuel flow from a leaky float needle seat.They have never been designed to do that and probably will never be design to totally block fuel flow as it is impossible to do so as long as a float valve system is used.

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It works for me, that's all that matters... I shut the fuel off let it run for 30 seconds to a full minute then shut off engine...
If it's the needle valve or solenoid letting fuel by.. it can't if there's no fuel there to flow by.. now how's that wrong?
The engine cranks and runs perfect and does not flood... I just want the assurance when it sits for x amount of time it won't be flooded one way or the other...
It's called insurance
Carbs worked for decades without electric fuel solenoids ... Now it's a must to have one operating functionally or you're a YouTuber wannabe mechanic..
Just because I don't conform to your information doesn't mean it's wrong... It's just not to your spec..

You do you and I'll do me