Briggs & Stratton 15.5 hp dies after it has run for about 1/2 hour

[Silviasil]

This is on an MTD Yard Machine Riding mower. Mdl 760. B&S Engine is 282H07-0334-E1 with a Nikki carburetor. It dies after the engine gets good and warmed up. It is still getting spark as the engine is winding down so I believe it is fuel related. It has the fuel shutoff solenoid screwed into the bowel of the carburetor. I suspect this solenoid.
Question: Is it normal for this solenoid body to get uncomfortably hot to the touch. I suspect that it is failing.
I had similar dying last summer and narrowed it to really fine “grit” down around the plunger and plunger spring that would not let the plunger fully retract. I cleaned it up and has worked fine until now. Thanks in advance for suggestions.
It appeared clean this time but I could barely hear it click until I cleaned all electrical connections and now I can even hear it click with my ear muffs on!

 

[Silviasil]

Solenoid part number is 596038. Resistance cold is about 42 ohms. Will try to get a reading when it is hot and when the mower has died

 

[Auto Doc's]

42 Ohms sounds like too much resistance to me.

I gave up fighting those pesky solenoids. I just cut the top of the pintle off and install a simple inline fuel shutoff. No more issues.

You have to be diligent and remember to cut the fuel off after using the rider and then cut it back on when it is time to use again.

Don't be alarmed if an occasional flame shoots out of the exhaust when the key is shut off. Shut the key off at low idle. That is why the solenoid is called an "after fire" solenoid. It shuts carburetor fuel flow down, so the engine momentum does not draw in fuel during shut down.

 

[sgkent]

make sure the fuel cap is not on so tight that the tank is acting non-vented. Also get a spark tester to see if you have spark when it dies.

 

[Tiger Small Engine]

42 Ohms sounds like too much resistance to me.

I gave up fighting those pesky solenoids. I just cut the top of the pintle off and install a simple inline fuel shutoff. No more issues.

You have to be diligent and remember to cut the fuel off after using the rider and then cut it back on when it is time to use again.

Don't be alarmed if an occasional flame shoots out of the exhaust when the key is shut off. Shut the key off at low idle. That is why the solenoid is called an "after fire" solenoid. It shuts carburetor fuel flow down, so the engine momentum does not draw in fuel during shut down.

Auto Doc’s- The anti-afterfire solenoid on carburetor has nothing to do with keeping fuel from hydro locking engine. That is the needle and seat’s job. You say to use fuel shut off valve diligently. You of all people should know this.

 

[Silviasil]

make sure the fuel cap is not on so tight that the tank is acting non-vented. Also get a spark tester to see if you have spark when it dies.

Good point on the gas cap . I was able to easily blow through it. And fuel flows freely through the disconnected fuel line downstream of fuel filter. As for the spark….I did connect an automotive timing light to spark plug wire and it continues to flash as the rpm’s drop while engine dies.
Now this mower has all kinds of safety interlocks on it. I am not sure if the interlocks shuts off the spark or if it shuts off the electric to the “suspect” solenoid.
There has been times when I can cycle the ignition key to off then back to run quickly and the engine will continue running but sometimes only briefly.
I guess I will install a shutoff valve in the fuel line and somehow temporarily keep the solenoid from shutting off the flow of fuel.

 

[Silviasil]

42 Ohms sounds like too much resistance to me.

I gave up fighting those pesky solenoids. I just cut the top of the pintle off and install a simple inline fuel shutoff. No more issues.

You have to be diligent and remember to cut the fuel off after using the rider and then cut it back on when it is time to use again.

Don't be alarmed if an occasional flame shoots out of the exhaust when the key is shut off. Shut the key off at low idle. That is why the solenoid is called an "after fire" solenoid. It shuts carburetor fuel flow down, so the engine momentum does not draw in fuel during shut down.

I guess I could with the solenoid unscrewed turn the ignition key to run for many minutes to let the solenoid heat up and see if the electromagnetic force becomes weaker over time. I would hate to disable it permanently in case the problem is somewhere else. I have also suspected the ignition module because some times I can turn the ignition switch off and on, off and on and mower will continue running for a while. I am not sure of internal workings of that module.

 

[Auto Doc's]

Auto Doc’s- The anti-afterfire solenoid on carburetor has nothing to do with keeping fuel from hydro locking engine. That is the needle and seat’s job. You say to use fuel shut off valve diligently. You of all people should know this.

Hello TSE,

I made no mention of hydro locking; I know the float and needle usually cause that problem.

But what takes place if the pintle is stuck in the open position and the float or needle is weak?

It's just as well that you mention it though. There are lots of people who visit this site that do not quite understand what takes place inside of a typical carburetor like this.

Myself, I got fed up with the solenoids hanging up closed and failing with my older riders. No hydro locking issues involved, just pesky no- starts on a regular basis. Cleaning the solenoid pintles or replacing them got to be aggravating. Most aftermarket new solenoids have different electrical pin fits that also introduces connection issues.

The final straw for one of those solenoids was on my Generac 15KW portable generator.... It's no fun fighting a no-start when the utility company or weather shuts the power down and snow & freezing rain coming down.

I use non-Ethanol fuel or mid-grade regular with a little stabilizer, but moisture still gets in from humidity when machines sit for days or weeks at a time. That moisture collects in fuel tank and in the bottom of the fuel bowl. That eventually creates light rust on the solenoid pintle and spring preventing them from working correctly.

 

[slomo]

It dies after the engine gets good and warmed up.

Typically this is either a lack of fuel delivery or a weak ignition coil. Bugs and trash in the fuel tank clogging the tank outlet for example. Fuel line interior degraded causing restrictions. Weak coils can have low rpm spark then fade at mid to high revs. Won't see this without a gap type ignition tester. The inline Christmas light types will not show this.