Fuel Octane and Hard Starting

[F56JCW]

Hi all, I posted last year surrounding my Honda GCV160 and am curious to hear your thoughts & experience with different fuel.

Essentially, my GCV160 is still hard to start. It’s nearly a year old and has done barely any hours, the oil is even still clear! I’ve just got in from about 20 pulls of the cord and nothing, nada. Plug is wet through and working, but it’s going nowhere.

I’ve been running it on 99 octane fuel, I’m not sure what this equates to in the US RON system, but it’s the highest we can get in the U.K. reason I’ve been running it on that is due to it having 0% ethanol content, meaning I can store some for a period of time without worrying it’ll go off as quickly.

Now obviously, higher octane fuels resist detonation more than lower octane, is this my issue?!

 

[ILENGINE]

I would say the octane is not the issue. The wet plug is the issue. Either no spark or none ignitable fuel, ie, bad gas or water

 

[F56JCW]

I would say the octane is not the issue. The wet plug is the issue. Either no spark or none ignitable fuel, ie, bad gas or water

Thanks for the reply, plug is sparking as that was the first thing I checked. The same fuel was fine in the summer, but again just difficult to start from cold. Regardless, I’ve drained the tank and going to try with some different fuel another day

 

[Scrubcadet10]

Thanks for the reply, plug is sparking as that was the first thing I checked. The same fuel was fine in the summer, but again just difficult to start from cold. Regardless, I’ve drained the tank and going to try with some different fuel another day

take what fuel you're using now and pour it in a clear glass jar. let it sit for a few minutes, make sure you don't see any phase separation of water on the bottom and fuel on top. even a little bit.

 

[7394]

Home made test kit.. Not rocket science.

 

[Bertrrr]

I ran across one similar to this once - found 2 things going on , one was it was a bit low on oil so the oil level sensor would come into play after it would fire off and shut it down, the other thing was the fuel cap was not vented. Give it a shot of starting fluid and see how it reacts.

 

[Tbone0106]

Had a similar situation once. A customer reported the same symptoms with his Cub LT1050. It turned out his kids had "topped off" the fuel tank with a garden hose and a bottle of energy drink.

That spark plug was wet too.

 

[bertsmobile1]

Physics 101
ONLY GASSES can BURN
So it is the room temperature volatiles ( often also called aromatics ) that determine if the engine will start or the fuel droplets will deposit on the spark plug.
Nothing to do with Octane ration.
Next problem
Modern fuels ( which are not petrol ) conduct electricity at combustion pressures
So if the plug is damp then the spark will run to ground down the side of the plug when you try to start it so no spark = no bang.
On top of that
Modern plugs do not have glaze on the insulator so once wet they stay wet till BURNED OFF and even worse, attempts to clean with a wire brush will leave metal traces on the insulator for the spark to travel down .

 

[Hammermechanicman]

Modern plugs do not have glaze on the insulator so once wet they stay wet till BURNED OFF and even worse, attempts to clean with a wire brush will leave metal traces on the insulator for the spark to travel down .

Yeah the wire brush thing is bad. Have had cust equip come in where they did a tune up and wire brushed the plug and now it doesn't work. A sand blast cleaner is better and i use one to clean the plugs on my IH184 tractor that is a bit if an oil burner and i don't run it hard enough to keep the plugs clean even using D21 (hot) plugs. On most OPE not worth trying to clean a plug when they cost so little.

 

[Oddjob]

Here are two thoughts from an amateur. First:Have you run over something, like a stump? If so, you may have a timing issue. I have seen motors where the flywheel has moved but not completely sheared the woodruff key. Second thought: I had that same engine and the plug was sparking, so explored all other possibilities including rebuilding the carb. A good friend, who was as far from mechanically inclined as they come, kept telling me to replace the plug. Eventually I did. And that is how I discovered that a plug can spark but not good enough.