Groundsmaster 52 runs 10 minutes, then dies

[Volvoman]

Tractor is a Toro Groundsmaster 52 with 16HP Briggs L head cast iron engine, 32000 series. Manufactured back in 1980. The problem is, it runs and cuts fine for approximately ten minutes, then dies. I can interrupt the dying by choking the engine and it comes back to life. But, only for a few seconds. Then it dies again. Choking again before it totally shuts down and it comes back to life. This is a rinse and repeat thing until I limp back to the garage with it. Let it sit for an hour or longer, and it starts up, runs fine and cuts grass for another ten minutes. Then the cycle repeats. Does this sound like a coil going bad? Or, due to the fact I can choke it back to running before it completely dies, is it a fuel issue?

I have replaced the fuel filter, cleaned the carburetor, replaced the fuel lines, replaced the fuel pump, and with no change from doing that, have pulled the fuel tank and cleaned it out as well. Still no change. Oh yeah, I replaced the condenser for good measure.

I was of the understanding that a faulty coil would shut the engine down once it was hot, but then would not restart at all until the engine was totally cooled down. Or, will a failing coil cause the engine to die, but allow it to come back to life by quickly choking it as described above? I am leaving the coil replacement as a last resort due to it requiring the entire engine to be pulled from the tractor in order to access it. The ten minutes having to elapse before the problem arises leads me to think it is a heat related issue, most likely the coil. Anybody here had a similar problem with a cast iron horizontal shaft briggs?

Vvm

 

[seville009]

I'm going to suggest what I have seen many others suggest in similar seemingly fuel starved situations - maybe the fuel cap is defective. The next time it starts stalling, remove the fuel cap and see what happens. Hopefully it's that simple.

 

[Xfaxman]

Right the fuel cap may have a vent that is plugged.

If the fuel tank is like the 300 series, the tank will have a vent hose. And that might be plugged.

 

[MossRoad]

If you have to choke it to keep it running, that cuts the air and makes the mixture richer with fuel. Since cutting the air supply makes it run better, that would suggest not enough fuel in the mixture when the choke is off.

Make sense?

That would indicate a fuel starvation problem, as others suggest.

Some causes:
Fuel tank not venting.
Fuel filter restricted.
Fuel lines partially blocked.
Vapor lock.
Fuel pump getting hot.

But you’ve already done most of that.

Simplest test would be next time it hints at acting up, turn off the blades, set the parking brake, and crack the fuel cap open.

 

[Volvoman]

Sorry, I failed to mention that I have already loosened the gas cap to relieve any vacuum condition that may exist. Also, tried 3 different caps without any favorable results. Any thoughts on how a malfunctioning coil would behave?

 

[Volvoman]

Although I have drained the fuel tank twice, the fuel that I put back in was E10 regular. I am assuming there is no water in it, but to double check that, I’ll drain it one more time, then replace with non-oxygenated regular 91 octane, the recommended modern fuel for old engines. It’s a long shot maybe, but other than the coil, I cannot think of any other possible sources of this problem…

 

[Volvoman]

Some new information to add. Wife took the mower out this afternoon to try it again. She reported that after about ten minutes, while mowing, it suddenly did the shut down thing again. She stopped forward movement, while leaving the blades engaged, and found the engine gradually regained full rpm. She moved forward with deck engaged and cutting. A few feet later, same thing. She tried this repeatedly with the same result, but soon became impatient and drove back to the garage and parked it. The difference between what I found a day earlier is she didn’t have to choke it to regain rpms. So, this seems to me to reinforce the notion that this might be a fuel quality issue, or at least a fuel quantity issue. Or, possibly a combination of the two.

If the non-oxygenated fuel doesn’t make for further improvement tomorrow, will be taking the carb off one more time to see if 1) there may be water showing up in the bowl, or 2) if some crud has found it’s way into the carb and messing up the needle valve, or possibly some crud may have gotten into the brass elbow connecting the rubber fuel line to the carb. While a slim chance this has happened to the GM 52, I had exactly this problem a very long time ago in an old Studebaker, when a small pebble, just small enough to find it’s way into the fuel line and lodged in an elbow mounted to the fuel pump. Strange, but true. The chances of something like that happening here is remote to say the least.

 

[Xfaxman]

I have replaced the fuel filter,

Is it clear plastic so you can see the gas?

Any thoughts on how a malfunctioning coil would behave?

Pulling the choke would have no effect.

 

[M59]

I am agreeing with all others that this is a fuel starvation issue and not a faulty coil issue since you can keep the engine limping along by richening up the mix by adding choke. If a faulty coil then richening the mix would not allow engine to continue to run.

Do you have access to the float bowl? I would install a fuel shut off valve in the fuel line to the carb. The next time the engine dies, immediately close the valve and then remove the float bowl. I expect you will find it empty or nearly empty and at least so low the fuel is below the point it can be drawn into the engine.

I believe you have a rubber line that may be collapsing when it gets hot or you are pulling a vacuum in the full tank due to a defective one way valve that lets air into the fuel tank and is not functioning. Some engines use a hose to let air into the fuel tank and a bee or something else crawled in there or made a nest in the hose. Mud dauber?

Also the possibility of vapor lock which creates low fuel in the float bowl.

Installing the fuel shut off valve allows you to verify the low fuel/ no fuel problem so the float bowl doesn't refill before you can examine it.

 

[stuckmotor]

I too, think it's a fuel issue, possibly: wrong filter, filter installed backward, or collapsing fuel line. Just in case though, I'd probably get an inline spark checker handy and check for spark as soon as the engine quits running next time. My spark checker came from Harbor Freight and I love it. They're $3.99 and $4.99.