Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

I have a strange problem with my Honda GX390, 13HP engine.  I replaced the carb. with a working one it did not help.  The engine seems to run fine in low RPM.  Once I open the throttle it dies.  No problem to restart.  Maybe there is an air leak but I can't figure it out where can it happen other than the carb.  The gasket between the carb. and engine is in good condition.  What else can I try?

Thanks

Bob

I'm glad you made some headway on figuring it out. First things first, the oil level is OK, correct?

I had a Generac engine with a low-oil switch that had failed. It would start, run 5-10 seconds until the control board enabled the low-oil shutoff, then it would die as the control board killed the ignition. I took the switch off and found that the switch would electrically open/close (I think to ground; it only had 1 wire) if you pushed  inside the switch with a screwdriver. So the switch was free to move, etc. But it would not detect oil pressure, you had to actually push on it with something solid to make it register "pressure". I had a few guesses as to why, but never tried to cut it open. Replaced the bad switch, and it's run fine since.

But I'm admittedly unsure of why your switch would see *lower* pressure as you raise the throttle. I'm assuming that the oil level isn't low, and that the engine is on a level surface. If it has an oil filter, could you try replacing that? Maybe there's some kind of restriction in it? I'm sure someone with more experience can help shed some light on this. But I might not just leap to replacing the switch, based on the symptoms. Unless someone can explain why the switch would perceive lower pressure at high throttle, when I'd assume it should be higher.

The GX390 just has a standard oil slinger type lubrication.  It's not a pressure system.  As the rpm increases so does the agitation of the oil in the crankcase.  If the level is low it can
cause the switch to activate. Had the same thing happen on my Honda powered generator one time.  If the crankcase is showing full.  Try bypassing the little metal box the crankcase switch plugs into.
Or you can disconnect the switch all together and just check the oil every once in a while the way it was done for decades.

I don't have an oil filter.  The oil level is not all the way to the dip stick hole but it registers enough on the dip stick.  I will fill it all the way tonight and see if that makes any difference.

I have a generator uses Tecumseh 10HP engine.  The oil level switch has an intermittent problem also.  It shuts off after running for a few minutes when the oil gets hot.  I took it out and it looked exactly like my aquarium water level sensor.   It senses the level not the oil pressure.  I ran the generator with the oil level switch disconnected.   The Honda switch is only $6 here.  Pretty cheap.  http://www.smallengineequipmentparts.com/brand/16131/272/277 . The Walbro carb kit is so much cheaper too comparing to my local shop.  I will buy parts from them in the future.

jrtrebor, thanks for the clarification. For whatever reason, I was assuming this was a pressurized oil setup. For clarity, my Generac engine *is* a pressurized setup, has an oil filter, etc. So I was dealing with a different type of switch. Sorry for the confusion.

bcjm, double check the manual before you go adding a lot of oil. If it has a dipstick with markings, then go by that, of course. But different engines get filled to different points. My Generac has no dipstick, and gets filled until it's about to run out of the oil fill location. But other engines are very different (if I filled my Tecumseh until it came out the fill hole, I would have a very big problem on my hands). Too much oil can be Very Bad, just like too little. I'd just hate to hear of something happening to the engine due to accidentally overfilling it "all the way".

I believe Honda engines oil level suppose to filled all the way up.   I will double check.

bcjm wrote:
I know that on my GX390 the oil level is supposed to be right up to  (bottom edge of the oil fill hole)

jrtrebor, do you mind reply the PM I send? thanks.

bcjm wrote:
Sorry, I sometimes miss those.