Lawnmower won't start; now what do I do?

[57]

Nuje: Could also be vapour lock if it happens after the engine gets warm and if it works again properly when cold. It's not anything you did to make the situation better, other than letting the engine get cool.

Sometimes using "better" gas may help, or purchasing gas in the summer when the the gas produced by the refiners has a lower vapour pressure (fewer "light" components).

[Nuje]

Thanks for the suggestions, guys. However, I don't think it's vapor lock, 57, as it's so random. Today was one of the mower's good days - was out there for over an hour throttle pretty much wide open and it ran flawlessly.

My guess all along has been something more along the lines of what mrvanwinkles suggested - just an intermittent ignition/electrical issue. And being that it is so random and intermittent, it's a beach trying to pin it down.

[stampeder]

Nuje, the fact that it started immediately once you removed the air filter is significant. It is possible that the engine is running too rich (too much gas in the mixture) due to a variety of reasons including internal clogging of air passages so when you removed the filter it finally could breath properly. If it is running too lean it would fake stalling on a lot of occasions before just plain quitting, and if it is too rich you will see a bit of blue smoke just before it dies and probably smell some raw gas too. Anything like that happening?

As for the ignition, your mower probably has a simple magneto, and if so there isn't much that could go wrong there.

Finally, is the underside of the mower clear in case build-up is gagging it?

[mrvanwinkles]

Originally Posted by 57

Sometimes using "better" gas may help

YES.

[ although I don't think the gasoline is necessarily the problem in this case ... but ... could not hurt to dump whatever gas is in the thing right now (burn it elsewhere, like dump it into the car / mixed with the rest of the car's good fuel, full tank) and put in fresh PREMIUM gas into the small engines.]

I mentioned it, quite a while ago - in an earlier post in this thread.

I will explain again in more detail WHY.

YES (!) Premium fuel in the small engines - with no added alcohol.

For small engines - today / now adays - they recommend using absolutely the best quality gasoline that you can purchase - in small engines.

Typically that is the PREMIUM gasoline at the pumps - and usually labelled with 91 Octane or something like that.

And with NO added alcohol / no ethanol - just gasoline.
( read at the pump or ask the gas station - does your PREMIUM have any added alcohol ? Or is it just good Gasoline ? )


I purchased, a few years ago, a good self propelled SNAPPER brand lawnmower with a good quality 6.75 HP Briggs and Stratton 4-cycle engine from a specialized equipment seller / small engine shop. (the Briggs "QUANTUM" series of engine - I believe is the good quality one.)

That shop / distributor is really good. They do tune ups, maintenance and service for their customers - right at their shop.

They went to the trouble to MAIL me (and probably all their customers) a hard copy letter - to advise all customers - to use only PREMIUM fuel in all small engines. Apparently the ALCOHOL added to lesser grades of gasoline can cause problems in a small engine's components. Maybe they are talking about the plastics and rubbers in the fuel system as well as the engine itself.

... and in any case - the small engines don't burn large quantities of fuel - so the extra cost is not that much.

... and the small engines, usually only one cylinder, benefit a *HECK* of a lot - performance wise / starting wise - with the best quality fuel.

(your car, a much larger engine, in contrast, has, usually a lot more cylinders, and better engine control systems - and can handle fuel with a little bit "lesser" quality and some alcohol in it. Plus you burn a LOT more fuel in the car. But none-the-less ... some benefit also, in various ways - by putting only PREMIUM in the car. If the extra $$$ is not so important to you.)

[mrvanwinkles]

Originally Posted by Stampeder

Riding mowers can be fitted with light duty snow plow blades for long driveways and sidewalks, so over the winter it is good to dump about 20ml of Gas Line Antifreeze (methyl hydrate) into the gas tank

[ Stampeder earlier post #68 ]

Yes.

If using small engines in winter / or storing with gas over the winter, some (a little) gas line antifreeze - I would think - is a good idea.

Yes ... a little Methyl Hydrate / Pure Methyl Alcohol will work ... will help ...

BUT ... wanted to mention also ...

There is also a PREMIUM type of gas line antifreeze which costs more, but also works better.

(read carefully the small print on the container - to try and confirm what stuff you are actually buying)

It is pure ISOPROPYL alcohol.

WHY? (What I heard / read) :

Isopropyl alcohol type of "Premium gas line antifreeze" works really well because this type of alcohol LOVES water. It seeks out water and combines with it really well. It also LOVES gasoline - and combines really well with that too. ( a fair bit better than Methyl Hydrate / Methyl Alcohol )

So what the Isopropyl alcohol does - it takes any water it finds in your fuel system and gets it to mix really well both with itself and also with the gasoline in solution - making a nice "homogeneous" fuel mix.

When you run the engine - you burn that mix - and you take the WATER *OUT* of the system that way.

Water / condensation and gasoline alone don't mix so well - so you're left with some straight water (heavier than gas) accumulating at the low points (bottom of the tank or carburetor) of the fuel system.

There ... when it gets cold enough - the water that separated from the GAS will FREEZE - and cause you problems.


Side point:

The other Tip - when it gets cold - try to keep the gas tank near full.

Cold climates where the temperature varies up and down alot - night and day - the source of water in the system is usually condensation from the AIR part of the tank .

More fuel = less space for air = less air = less source of air for condensation (water vapour from that air)


Careful - small engines hold small amounts of Gas in the tank. So read the instructions carefully and use and measure out only the small amount you need.

[Nuje]

I'm starting to think that it is as simple as bad gas. The container I was using sat half-empty over the winter, so I'm guessing I got some condensation (water) in with the gas.
Thanks for pointing me to the painfully obvious (amazing how often I'll start looking for the complicated problem when so often it's the simple one); we'll see if the new gas continues to run without issue.

[Danster]

When I start a new season with my small engines, I usually add a few drops of octane booster with my gas in case it went a tiny bit stale in the winter or any storage time. It seems to work since I don't have any problems with my equipment. "knocks on wood"

[Blackloz]

Originally Posted by Coop

I gave up on a gas mower last year and bought a Black&Decker 36V rechargeable. So far it's handled everything I've thrown at it.

That is the exact same thing I did. I got tired of all the yanking on the pull cord the fuel & Oil ect,ect.

[stampeder]

Here on the Wet Coast a small engine left sitting outdoors all winter really requires an oil change too each spring due to condensation that can form in the crankcase. A typical 5W30 weight oil will do fine or you can get single-weight dedicated small engine oil from most big box stores for strictly warm weather use.

[mrvanwinkles]

Originally Posted by Nuje

I'm starting to think that it is as simple as bad gas.

O.K. - possibly the problem was just the "GAS".

But don't make that assumption so quickly.

Intermittent problems like that can fool you easily.

The newer, better GAS probably helped the situation - generally - for sure.

But hard to prove, I think, right now, at this point - that just the GAS was the whole problem in the first place.

( if the lawnmower fails again - you'll probably be cursing it up and down - but have patience - I suspect it may fail again - given the sort of problem and failure method / symptoms - that you have described )

So keep going with it. Monitor and see how it runs.

Intermittent problems like that ... keep running er' till eventually she fails completely - or alot more often.

i.e. the intermittent problem becomes constant, or much more often - then you can troubleshoot and actually *FIND* the BAD component / or Bad system to narrow down the search.

[ Otherwise - it's hit and miss guessing - and changing parts at expense and waste of time and labour and patience ]

Keep running er' now - and see how it goes. Monitor.

[sandwich]

Edit - I have to do some more troubleshooting.

[ta guy]

I don't know if anyone has noticed but the gas nowadays is pure crap. It used to be that gas would last in a jug for the winter,but now at the end of winter any gas I had left in a jug is rotten(really stinks). Any gas left in my ride on mower is rotten and it will not start either until I fill it with premium gas.I've noticed too with regular gas the mower runs ok but has a little skip in it,with premium it runs smooth.

[jshel101]

I personally haven't had any of these problems with gas. I usually leave my gas in the jug all winter, and some in my lawn mower. In the spring I have no problems with what you are experiancing with the gas. So far I have not had any problems starting my mower because of leaving the gas all winter.

[stampeder]

ta guy, are you seeing that from all the gasoline vendors in your area or just from one in particular? Skunky gas will almost always still ignite if it's been sitting just one winter, but it might mean a few more pulls on the starter rope.

jshel101, you are in probably the best location in Canada other than Edmonton for fresh, good quality gas that will keep.

[jshel101]

, yes, only a few hours from the source.