Briggs dies when warm

[Dale_W]

engine:
model 10D912
type 0144 B1
code 03010654

mounted on a karcher pressure washer:
Model G 1800 LB
Serial 714744 103
part # 1.133-124.0

Originally came to me because it would not pump pressure water. Cleaned and lubed unloader valve, and replaced broken o-rings on hose.
Works just fine.

Customer returns because engine dies. Sure enough, after using for 30 minutes, the engine dies and has no spark.

I order and install new coil. Engine runs fine. For maybe 5 minutes that is. It still has spark, but after the engine warms up, it will die, unless I hit the primer bulb.
Running with the gas cap off has no effect.

Could there be an issue with the diaphragm(?) in this carburetor?

Any other thoughts?

I should add that I installed a new spark plug, RJ19LM.

Thanks,

Dale

[bgsengine]

Had the crossover tube off, or the gas tank/carb removed? Check crossover tube , gaskets, and the carb o-ring. even a simple coil replacement can disturb a slightly loose crossover tube to where it develops and air leak.

[38racing]

Had the crossover tube off, or the gas tank/carb removed? Check crossover tube , gaskets, and the carb o-ring. even a simple coil replacement can disturb a slightly loose crossover tube to where it develops and air leak.

i recall reading something a different cross tube used on some because of interference with the coil.

[Dale_W]

I had not pulled tank or carb, BUT could I have disturbed the crossover tube enough? sure
and the lean symptom that started with the new coil is just too coincidental.
I'll check for leaks and post back in a few days.
thank you.

Dale

[bgsengine]

Yeah those things could be sneaky suckers sometimes. They'd even SEEM tight enough if the tank was bolted up snug, but once you pop the tank and carb off, if you were not aware of the potential issue, it's easy to forget to check that the tube is actually still firmly in place and doesn't wiggle - They can loosen up enough they can shift on the gasket surfaces, but the tension from carb & tank being installed is enough to make them "seem" snugly fitted, and yet they still developed leaks. It was common enough it was one of the first things I'd check before tearing into the carburetor when I suspected a fuel issue (much like yours).

[38racing]

I've had a couple not tight where they bolt to block.

[KE4AVB]

I would be also checking the valve clearances considering this is a 19 year old L head engine.

[Dale_W]

This thing continues to be sneaky.
When running, as it is about to die, I spray starting fluid around the base of the carb, no change.
I spray starting fluid where the carb connects to the crossover tube, no change.

Right, it is an old engine, but I should think lower hours. I will check/adjust the valves and let you know.

Thank you again.
Dale

[bgsengine]

This thing continues to be sneaky.
When running, as it is about to die, I spray starting fluid around the base of the carb, no change.
I spray starting fluid where the carb connects to the crossover tube, no change.

Right, it is an old engine, but I should think lower hours. I will check/adjust the valves and let you know.

Thank you again.
Dale

Have to be careful since you'd be working above the muffler, but tried spraying around the crossover tube gasket when it is about to die?

Also, if it is a plastic crossover, they can develop hairline cracks along the length. Metal crossover tubes had a tendency to loosen where the steel tube is press fit into the aluminum elbow - worth a suspicion when it is possibly heat related (different rates of expansion) if it was me, I'd pop the top , remove coil and pop the tubes off for a close inspection while checking valve clearances.

[Dale_W]

OK, I removed the plastic crossover tube and gave it a thorough inspection under a bright light.
I see no cracks.

On to the valves. The intake was .005, and the exhaust was .004.

Near as I can tell from the manuals the intake should be .006, so that is close. But the exhaust should be .010

Could this be causing the lean condition? Remember, after it warms up, only a shot from the primer will keep it running.