John deere 2013 Gator - backfires under load

[RobRightmyer]

Hi,

Our gator is idling fine but under acceleration it backfires and sputters.

I pulled out the air cleaner and I get better results but not nearly perfect. Put a new carb in and idle is now from good to great.

I've got new air cleaner and fuel filter on order and will put new plugs in today but the old plugs are less than a year old.

It only has 500 hours on it.

Can anyone think of anything else I should look at? I wondered about coil. Maybe a new coil is in order as well.

Thanks,
Rob

 

[David G]

Yes, weak spark can do this.

 

[MJMJ]

Curious about this as well. Happened to my sons 4 wheeler. Had great spark. It progressed to the point that it won't start at all now and has me stumped. New carb as well.

 

[JIM MN]

What engine do you have in it?? It is two cylinder.. Ignition timing?? Engine, is it 4-stroke?? Then maybe check engine valve adjustment.. Too tight.. Or a valve sticking at full RPM and warmed-up..

 

[Roger in Iowa]

Do you ever get it up to speed? If not, sounds like you are lean on the high mixture.

 

[wore out]

(quoted from post at 09:16:24 11/19/20) Curious about this as well. Happened to my sons 4 wheeler. Had great spark. It progressed to the point that it won't start at all now and has me stumped. New carb as well.

Have you checked for a clogged exhaust?

 

[Lee B]

I'll suggest the fuel pump needs some attention. It's adequate for idle and moderate engine loads but runs short on you when you need maximum flow. I found this to be the case on a riding lawn mower once, the "pressure" spring inside the crankcase pulse driven fuel pump was so strong that the only time it pumped fuel was when the stretched sides of the diaphragm would move, the too strong spring was never being collapsed by the vacuum pulse coming from the crankcase. How these units ever were sold without high volumes of complaints and buy backs I'll never understand, but when I set out to find a suitable weaker spring and replaced it - it was cured of the missing top end full throttle power lag and backfiring and dying that it did. It would restart with some difficulty, but could only idle for several minutes especially the warmer it and the fuel got. As soon as you applied throttle or engaged the blades again, it died. Eventually the battery would run down so far it would no longer re-start until cold and with the battery removed/replaced for recharging. Extremely exasperating for a thousand dollars spent on a riding mower.

Manufacturer didn't catch it and couldn't care less apparently. Nothing wrong with the pulse signal other than it was a two cylinder engine which by default would have a less powerful pulsing or more accurately stated a more complex signal to operate the fuel pump with. This is not in any book, the specs are wrong for this system which I once did find at 1 PSI fuel pressure. That number was pulled from a rather stinky place as the too strong spring couldn't deliver even that much pressure if it did operate as per the design - it was not moving at all, just the slightest fluttering of the sides of the stretched diaphragm is what was pumping the fuel and that was woefully inadequate for the full 17 horses.

 

[MJMJ]

(quoted from post at 14:40:18 11/19/20)

(quoted from post at 09:16:24 11/19/20) Curious about this as well. Happened to my sons 4 wheeler. Had great spark. It progressed to the point that it won't start at all now and has me stumped. New carb as well.

Have you checked for a clogged exhaust?

No, but I will. I left some details out, I didn't want to hijack this thread. But I'm 95% certain it's an electrical problem.

 

[RobRightmyer]

(quoted from post at 04:24:33 11/19/20) Hi,

Our gator is idling fine but under acceleration it backfires and sputters.

I pulled out the air cleaner and I get better results but not nearly perfect. Put a new carb in and idle is now from good to great.

I've got new air cleaner and fuel filter on order and will put new plugs in today but the old plugs are less than a year old.

It only has 500 hours on it.

Can anyone think of anything else I should look at? I wondered about coil. Maybe a new coil is in order as well.

Thanks,
Rob

After a new carb and new plugs all is running great. I think that leaves out the fuel pump. I have a new air cleaner and fuel filter on order.

Thanks for all the great ideas.