Craftsman GT5000 Engine Cuts Out, Struggles, Then is Okay

[Rhino35]

Hi All,

My second problem (besides the choke cable sticking in another post) is the 25 HP Kohler engine in my (mother-in-law's) 2004 Craftsman GT5000 intermittently, but frequently during mowing, cuts out, then resurges back to operating RPM. It does this intermittently in all modes of operation except when stationary. Feels very random, although it especially will do it going downhill and after turning left. Something about the motion is either affecting an electrical connection, or causing brief fuel starvation. Turn, count two potatoes, it cuts out, struggles to regain RPM, almost dies sometimes (not always), then roars back up to operating RPM until it happens again. Might be a minute or two, might be 10 seconds.

I suspected the seat safety cutout switch. That definitely works and if you lift off the seat it will kill the engine, but experimenting with partially lifting my weight off the seat did not cause the engine problem. Still, can't rule it out - some minor G force induced loss of continuity could be the culprit.

I'm really thinking fuel starvation. The fuel filter is brand new and contains the normal amount inside it - so if a blockage I think it is between it and the carburetor. I'm vaguely familiar with carburetors - they have jets and floats, and can experience blockages from debris. My mother in law says it happened last summer too. On the way up to resuming operating RPM the exhaust belches some black smoke - unburned fuel?

I'd take it to a mower repair store but right now the turnaround time is many weeks. One place has 300 mowers lined up to repair. So if I can remedy this I'll try. New OEM plugs, clean air filter, new fuel filter, new oil filter and oil. Runs great except for this quirk.

Thanks for any thoughts and advice. It's a nice mower except for the choke problem and this surging. And maybe an oil leak, but I'll leave that for another post if it persists. My neighbor and I just did the cleanup/other stuff I mentioned above.

Rhino 35

 

[Roadworthy]

Fuel starvation could be the problem. There is a fuel shutoff solenoid in the carburetor. On some machines if it overheats it shuts off the fuel. They can be somewhat temperature sensitive.

 

[RalphVa]

Time for a slug of Seafoam. It has saves me carb work so many times. Now have nothing with carbs: all battery power.

 

[Rhino35]

Fuel starvation could be the problem. There is a fuel shutoff solenoid in the carburetor. On some machines if it overheats it shuts off the fuel. They can be somewhat temperature sensitive.

Thanks for reply. I didn't know there was such a thing as a fuel solenoid in the carburetor that could do that. Is it there intended to prevent overheating of air cooled engines? The two times I've mowed with the mower after our "tune up" effort - fresh oil and clean filters - the engine ran great when stationary. Started right up - only a little rough back at full idle on the throttle so it liked a bit of throttle to purr. The outside temperatures were not hot - about 60 degrees both days.

Is it worth trying to get at this solenoid and replace it? Is a full carb rebuild/service, even replacement, a smarter option?

 

[Rhino35]

Time for a slug of Seafoam. It has saves me carb work so many times. Now have nothing with carbs: all battery power.

Hi Ralph - thanks for the suggestion. Yes, I'm making the transition to battery powered tools too.

Hadn't heard of Seafoam. This link says it is great stuff. Telling is the number of 5 star reviews. Usually the ratio of great to poor is more even for just about every product I've seen.

https://seafoamworks.com/product/sea-foam-motor-treatment-oil-fuel-additive/

So you're thinking I've got gunk in the carb and it needs internal cleaning with this solvent type product. My mother in law kept the mower in an unheated barn all winter - she always does - and she didn't add any Stabilize product. I see that Seafoam also acts as a gasoline stabilizer. I've read the unleaded gas can cause a varnish type build up in carbs. I also know someone with various mowers and chain saws who never adds anything over winter and says he never has a problem.

I'm thinking the effect of gravity and centripetal force in turns is briefly sloshing fuel away from an "intake" area. A buildup of varnish might exacerbate that effect. It can't hurt to try a slug of this stuff - and she is paying for it *grin* - so I'll get some. Can't hurt.

 

[tomplum]

A directional hiccup / change can indicate water in the float bowl. Being a Kohler, when then drop a coil you lose half your engine power and they feel real anemic. Then they can pop back into running full steam after they chug out the excess fuel.

 

[Rhino35]

A directional hiccup / change can indicate water in the float bowl. Being a Kohler, when then drop a coil you lose half your engine power and they feel real anemic. Then they can pop back into running full steam after they chug out the excess fuel.

Thanks Tomplum - that certainly sounds like what is causing this interruption in smooth running with motion.

There is a half bowl right behind where the air filter canister screws onto the engine. You can't see it in this photo, but there was liquid in this half bowl when we took it off in my garage. I assumed it was fuel. This is choke in run position. With the choke in cold start position a valve rotates into position and block vertically - flat against the brass colored part and in front of the two screws. Is this float bowl you are thinking of? I was thinking (back 45 years to high school auto shop!) that the carburetor float was an internal receptacle that on a car you looked down into. Lol, I'm so ignorant! But I'm learning!

 

[tomplum]

That's an anti spit cup. So don't spit in it,(protects the filter) but you would have to pull the the 2 10MM nuts and 2 8MM headed machine screws (most have) to remove the tin. Then you will see the bowl. It isn't horribly abnormal to see a touch of residual fuel in these, but it shouldn't build or continue to run out. Most carbs will slide off when you undo the fuel line, solenoid wire connector- but carefully unhook the linkages via the plastic clips and watch over them or they will be gone. Remember that breather hose on reinstallation.

 

[jaxs]

Have you tried feathering the choke when engine falters? That can help deciding between fuel and fire. I've more experience with briggs but suspect Koler has similar components for fuel delivery ,not interchangeable but similar in function (many cars trucks and tractors did before fuel injection). In addition to high speed jet,it's common to have a brass tube with various size intake holes submerged in bowl and leading to air venturi. As rpm induced vacuum increases at ventura,additional fuel is sucked through holes in tube. On a Briggs (before introduction of ^*@#$% Niki carb) it's a piece of cake to remove upper shell and clear passages with spray cleaner and torch tip files. Enter Seafoam which has a good reputation for clearing/maintaining small passages. I suggest. Pull fuel hose as near carb as convenient and let fuel flow into a container until tank is emptied. Watch for intermittent flow volume so as to eliminate restricted filter or line. Measure out 1 quart fuel and add at least 1 oz (which the normal amount per gallon) or up to 12 oz ( 6 oz in 1 pint). Put treated fuel in tank and run engine under normal load if possible 4 to 5 minutes. If symptoms disappeared, add fuel treated 1 oz per gallon then return to normal duty. If symptoms are still present after 5 minute run time,alow to soak 10 minutes to overnight then run for 5 minutes. Repeat 2 or 3 times if necessary. If problem persists and engine runs well enough to do it;s job,run at least 3 gallons fuel treated 4 oz per gallon before tearing into system. I'm a tit-wad and don't treat every tank if engine runs well but always when storing more than a month and always first tank of the season.
If the jury is still out deciding between fuel and fire,try this to help decide where to go next. There's a lemon size device that fits between plug wire and plug that flashes orange (easier to see in daylight) each time cylinder fires. I recently saw them at Auto-Zone but should be easy to find. An old school timing light will also work. It's pretty easy to see variations in rythem as coil fails at lower rpms.
Althoug I still try it sometimes,I've never found that shouting nor cussing help at all.

 

[mag410]

Mine was doing the same thing. Turned out the rubber seal of the gas cap had deteriorated and a piece had passed into the fuel line and was obstructing the entrance to the fuel filter.