This motor is in my zero turn. I have a surging problem that goes away when I use premium fuel. As I understand it, surging is caused by an intake leak of some sort. So why does it go away with the premium fuel. I've tried spraying carb cleaner around the intake and carburetor running low octane fuel with no noticeable affects. If I ad octan booster or run 92 octane, it smooths out. Any ideas what is going on here?
I know I can keep running 92 but I'm curious as to why this is happening.
It may be ethanol in the fuel. I've read it causes issues with small engines, due to moisture collection, and deteriorating plastic parts. Is the 92 ethanol free? Just a thought. A local fuel supplier is touting ethanol free gas for the small stuff.
In reply to Dirtydog (Forum Supporter) :
92 does have ethanol. One station in town does have ethanol free but I haven't used it. Mower is 4 years old. Did small engine manufacturers make ethanol friendly components at that time ? Do they now?
Surging can be caused by almost anything. If it's running lean, rich, poor spark, nearly anything. Something happens to drop the RPMs, the governor opens the throttle, the RPMs rise, the governor closes the throttle.... rinse, repeat.
I highly doubt it has anything to do with Ethanol unless there is some other problem like a partly gunked-up jet in the carb. Higher concentrations of ethanol will cause it to run ever so slightly lean, but unless you're already on the lean side due to some other problem, it shouldn't cause any issues.
The ZT being only 4 years old is most certainly is fine with ethanol in the fuel.
I really wish people would stop talking about how awful ethanol fuel is. People go out and spend insane money on ethanol-free fuel, then they put Stabilizer in it.... which contains ethanol. They have trouble with condensation and water in their fuel so they go by gas-dry... which has ethanol in it.
Ethanol isn't the problem.
It is a massive waste of everyone's money though.
ddavidv said:It is a massive waste of everyone's money though.
At one point I heard that it took 1.2 gallons (estimated) to get 1 gallon of gasohol to market! No clue if that is still the case, and no source of info I would trust today.
In reply to Curtis73 (Forum Supporter) :
I understand what you're saying. Heck, I run 87 with 10% ethanol in my 1950 Ferguson T-20, with no issues. When winterizing my small equipment, I throw the old gas in my Jeep XJ. But the question seemed to center on fuel. Just a shot to start somewhere. Rusty, apparently is trying to knock things off the list.
I have to remove the engine to replace the pan gasket that is leaking so while it's out of the ZT I want to fix whatever is causing the surge if I can find it.
In reply to rustybugkiller :
As you try to knock things off the list, ethanol is not one of them. Old gas can block jets/passageways in the carb; can happen with or without. Ethanol CAN also effect tuning, (air/fuel difference), and the smaller the engine, the more pronounced the difference. But that is about the last place I'd be looking in this case.
dirty carb. Would've first guess
There can be a discussion on gas type differences and +\-'s, but that would be off topic
Curtis's first post would be my first choice of starting places.
I really didn't consider ethanol as an issue. Two other Briggs don't have an issue with the same fuel.
Sounds like cleaning the carb (rebuild kit) is a good idea as well as normal maintenance items
I've "mostly" gotten away without a kit.... small engines that are not antiques rarity need hard parts- just be careful with gaskets! A lot have o rings these days, anyway. Just do a full disassemble and soak the jets ( spray some liquid from the carb spay into the lid of the can!) and spray through the passages. (Make sure all parts go back where they came from; very important step!)
Clean the carb, pay particular attention to possible buildup in the jet(s). If you really want to cover your bases in the first pass, throw a new sparkplug at it too. While reassembling, check gaskets and sealing on all parts from carb to head. Consider a light schmear of RTV.
See where that gets you and come back if it doesnt fix it.
my experience has been that surging on a small engine is typically a dirty carb or contaminate fuel.
A quick check would be to just drain the carb and see if the surge goes away with lower octane after you do that.
You may have some water sitting in the bottom of the bowl and the additives in the 92 octane may help disperse it better than the 87.
Or you might be at a point where the specific gravity of the fuel blends is just different enough to effect the fuel level in the bowl or burn characteristics and the 92 is less effected by the dirty carb:
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