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Hello, I have a Craftsman w/ 18.5hp Kohler Magnum. After mowing for an hour or so it will sound like its starving for fuel and start cutting out and eventually die and won't start again until it sits awhile. I replaced the fuel filter with a larger diameter than stock, would that harm anything? It was the same size line so I didn't think it would matter. I had this problem last year also with the stock size filter. I would appreciate any ideas, thanks.

Next time it quits pull the plugs and see if you have spark. ignition module may be breaking down when it gets hot. If it has a fuel solenoid on the carb. Make sure it clicks when you turn the key on and off after it quits.

If it ever stops raining here I'll check that out and let you know how it works out. Thanks alot

Most likely won't be this week. I am expecting rain every day until next Tuesday. With up to 5 inches expected this Wednesday.

It finally acted up again yesterday. It's getting spark it will fire for a few moments with the the help of starting fluid. I pulled fuel line from the carb side of the fuel pump and cranked it, nothing came out. Can I assume fuel pump? The filter is new this year. I don't know if this is related to the previous problem or something new. Thanks, Doug

Failed ignition modules can show intermittent spark at the plug. But under the stress of a firing cycle the intermittent spark fails. Keep the engine as cool as possible so excessive heat is not transferred to the ignition module. (fins clear, shrouds intact ,oil level ,etc) IMO

Every Kohler Magnum that I have dealt with, probably 4 or 5, I've had to do several things to in order to keep them running.
a) Replace and rerun the fuel supply line farther away from all heat sources.
b) Remove the cylinder heads and do a decarb of the combustion chamber area, piston tops and valve faces.
c) Readjust the carb high speed adjustment periodically as vibration from the machine changes the adjustment toward a lean condition.
d) Replace the fuel pump assembly.
Other considerations;
The spark plugs have been changed to a different heat range, don't recall what the new plug number is.
Make sure that the fuel tank cap vent is working so as to not cause a vacuum in the fuel tank during machine operation.
Clean the cylinder cooling fins and under the flywheel. You can use HP air to blow out the dust accumulation under the flywheel.
A larger fuel filter isn't always better as it increases the demand on the fuel pump to suck fuel into the filter and push it to the carb.
If you do replace the fuel pump, you will find that it is a universal fit pump. There is an assortment of input and output fittings with the new fuel pump kit.
Do not install these fittings until you are sure of which one goes where and what angle they should be installed at as these fittings are not easily removed and repositioned and damaging the pump and or the fitting is very likely. At pump replacement, I have always needed to replace some fuel lines in order to smoothly connect to the new style pump fittings.
I also suggest using fuel that is higher in octane rating than 87, particularly if the fuel has 10% ethanol.
Just a few thoughts from Mad Mackie in CT:laughing::biggrin::smile:

If the Magnum is anything like the Command(pretty sure they are 98% the same), and the engine is on a Craftsman AYP built machine, you can have fuel starvation caused by the fuel turning to gas in the fuel line. That will happen more on hot days.
A quick check to see if the heated air blown past the cylinder head & cylinder is getting re-cycled back into the blower on the top of the engine and causing mumble mumble mumble - the word for fuel turning to vapor - OH. Vapor lock. Getting old.

I took the hood off, and the thing ran like gangbusters with no problem. I think the fuel had too much 'winter' contents, and was turning to gas in the metal line that ran over the top of the cylinder from the pump to the carb inlet. I had replaced the pump as it died out on the lawn, new filter, drained the tank and removed all water droplets, and it still chugged and ran and chugged. Hood off, and bingo.
Some back in the day would use clothes pins clipped to the fuel line to prevent vapor lock. I don't think they'll help, but I bet some binder clips holding some soup can sheetmetal clipped onto the metal fuel line would act as heat sinks, and transfer some of the heat from the metal line to atmosphere, allowing the fuel to stay liquid.
But. If the pump won't deliver fuel when cool, or cold, then there's another problem. Fuel line disintegration internally while looking perfect externally, fuel filter filled with gunk, outlet plugged with schmutz in the bottom of the tank, or a plugged gas cap vent can all affect delivery volume.
Enuf.
tom

I replaced fuel pump runs great. However I did clean alot of debris from the cylinder head cooling fins under the cowling, may have been a contributing factor. I know that engine was running way to hot I guess there's more to maintenance than lube,oil and filters, oops my bad.

douglasw said:

I replaced fuel pump runs great. However I did clean alot of debris from the cylinder head cooling fins under the cowling, may have been a contributing factor. I know that engine was running way to hot I guess there's more to maintenance than lube,oil and filters, oops my bad.

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A new fuel pump fixed your problem, so wonderful. It is a surprised to me because the Kohler magnum has a mechanical fuel pump and I just don't under stand how heat would affect it. Learned something new. I would more think cleaning out the debris.

tomw0 said:

If the Magnum is anything like the Command(pretty sure they are 98% the same
Enuf.
tom

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It more like 98% different not the same engine at all.

I actually don't think the fuel pump was the original problem because it would always start after it cooled down. However this time it wouldn't and after taking the pump apart I noticed one of the one way valves that are pressed into the housing fell out so it wouldn't create a vacuum. Anyway I already had the new pump so I used it and I'll save the old for a spare. I really think the original problem was the overheating because it was really clogged up under there.

douglasw said:

I actually don't think the fuel pump was the original problem because it would always start after it cooled down. However this time it wouldn't and after taking the pump apart I noticed one of the one way valves that are pressed into the housing fell out so it wouldn't create a vacuum. Anyway I already had the new pump so I used it and I'll save the old for a spare. I really think the original problem was the overheating because it was really clogged up under there.

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Loose one way valves is a very common problem with that style fuel pump and the only way to repair it is a new pump. Makes more for a cold starting problem then hot. Not a wasted repair. :thumbsup: