Honda GX390 wont stay running

[aczlan]

Looking at a friends pressure washer which has a 13 HP GX390 engine on it. Seems to have good spark but it will only start and run for ~1 minute and then it shuts off like someone hit the kill switch.
Carb looks OK, tip cleaner fits into all the orifices. Tried disconnecting the kill switch and the oil pressure switch but no change.
Plug is black and sooty but every time I pull it, it's dry and has decent spark.

Any thoughts?

Aaron Z

 

[aczlan]

Also, when I pull the drain on the bowl fuel drains out until I put it back in, so there appears to be a decent supply of fuel to the bowl.

Aaron Z

 

[BukitCase]

Yeah, just went thru that with a GX340 engine on my pressure washer - the thing acted like a fuel problem. It would start and run OK at idle, but under load it would run maybe 15-20 seconds and die - if I was quick enough, choking it would SOMETIMES keep it from dying.

Checked the in-tank fuel filter, looked NEW. Pulled float bowl, flushed out everything with the nastiest carb cleaner I could find, no fuel restrictions, etc -

I had bought a replacement plug previously, pulled and checked the old one, looked real sooty but had spark.

Was gonna replace the in-tank filter anyway, but since that is a major PITA, figured I'd try just replacing the dirty plug first (easier and quicker :=) -

Been running fine ever since, strong and solid at ANY pressure up to its 3300 psi max.

Hope you get as good results; BTW, no more "congressional gas" for ANY of my small engines, 2-cycle or 4 -

Ethanol-free gas stations in the U.S. and Canada

... Steve

 

[aczlan]

Yeah, just went thru that with a GX340 engine on my pressure washer - the thing acted like a fuel problem. It would start and run OK at idle, but under load it would run maybe 15-20 seconds and die - if I was quick enough, choking it would SOMETIMES keep it from dying.
Checked the in-tank fuel filter, looked NEW. Pulled float bowl, flushed out everything with the nastiest carb cleaner I could find, no fuel restrictions, etc -
I had bought a replacement plug previously, pulled and checked the old one, looked real sooty but had spark.
Was gonna replace the in-tank filter anyway, but since that is a major PITA, figured I'd try just replacing the dirty plug first (easier and quicker :=) -
Been running fine ever since, strong and solid at ANY pressure up to its 3300 psi max.

I'll try that first. When it dies, it shuts right off (no sputtering) and not even a snort of ether down the intake will keep it running.

Aaron Z

 

[BukitCase]

Your case might be a bit different then - sounds more like maybe the kill switch wires may be touching something they shouldn't ? My DR lawn vac/mulcher did that to me, kill wire was buried behind the motor cooling fins and would intermittently rub. That one took a while... Steve

 

[aczlan]

Your case might be a bit different then - sounds more like maybe the kill switch wires may be touching something they shouldn't ? My DR lawn vac/mulcher did that to me, kill wire was buried behind the motor cooling fins and would intermittently rub. That one took a while... Steve

If it is on the "kill wires" it is isn't outside and ALWAYS kills it within a minute of running...
I'll start with the cheapest option (plug) as it looks like it could stand replacement.

Aaron Z

 

[crazyal]

Did you check the oil level? I think most Honda's have a low oil level kill switch. Even if the oil level is OK I would remove it just to eliminate it.

 

[aczlan]

Did you check the oil level? I think most Honda's have a low oil level kill switch. Even if the oil level is OK I would remove it just to eliminate it.

Oil level looks fine, the first thing I tried was disconnecting the oil pressure kill switch and the manual kill switch.

Aaron Z

 

[BukitCase]

Aaron, does the engine die the same way whether it's idling or revved up under full load? Mine would idle til the cows came home, but only lasted about 20 seconds under full load. That's what kept me looking for a fuel problem.

"Monday morning quarterbacking" being the wonderful thing it is, when I look back I suspect that the plug was just not able to fire under more stringent conditions - no other idea as to why it'd run @ idle.

Just curious whether you can vary the "on time" of the motor by varying load conditions... Steve

 

[aczlan]

Aaron, does the engine die the same way whether it's idling or revved up under full load? Mine would idle til the cows came home, but only lasted about 20 seconds under full load. That's what kept me looking for a fuel problem.
"Monday morning quarterbacking" being the wonderful thing it is, when I look back I suspect that the plug was just not able to fire under more stringent conditions - no other idea as to why it'd run @ idle.
Just curious whether you can vary the "on time" of the motor by varying load conditions... Steve

Seems to run about the same time +/-20 seconds no matter what the throttle or choke position.

Aaron Z