OT - Small engine problem...

[A.K. Boomer]

Further analogy of the diaphragm type pump (again if you have one)

these pumps get weaker and weaker by nature - they start out very supple, then as with most all other rubber components get crystalized,

so with something that's pretty old you can bet this effect has taken place, it results in "micro pumping" as there still some flexibility but not much - so if the check valves are still operable you will get small pulsations in fact just fractions of what once was, but once it catches can be enough to keep the engine running at higher RPM's because they all "add up"...

again if your system is gravity fed please disregard - but keep it in mind for other engines that use this system....

[SteveF]

The first thing i would do is check all the fuel lines. Thanks to that wonderful ethanol i get around 5 years before the fuel lines have degraded enough that they either leak fuel out or leak air in.

[RMinMN]

You must have missed this in Al's reply: "When it was put up for storage over the winter, I remove as much fuel as possible from the tank then run the machine until it burn out all of the fuel and shuts down."

You missed this in his later reply.

"When it was put up for storage over the winter, I remove as much fuel as possible from the tank then run the machine until it burn out all of the fuel and shuts down. I put some of that "ethanol free" VP racing stuff that I get from the local NAPA place, and again start the engine up and run it on that stuff for a few minutes so that the carb pretty much has only that left in it."

His carburetor is not empty for the winter.

[tom_d]

Since the machine started up on ether and then ran fine, I never got as far as checking the spark plug or much else really. It's probably due to have a plug change anyhow so I plan to pick one up before I get back to working on this.

Another suggestion:

In addition to the plug, it wouldn't hurt to examine the rest of the ignition system. A weak spark from a combination of bad points and an old plug might become a strong enough spark when the engine is spinning at idle speed to keep it running satisfactorily. It's just too weak to fire on gas alone when at cranking speeds, but that ether is hot enough to get things going.

[Bob Engelhardt]

You missed this in his later reply.

...

I did! I'm claiming brain fart.

[Bob Engelhardt]

Al: somewhere in all these replies is the answer to your problem. Your problem now is to figure out which one it is. I suspect that it would be easier to solve the original problem.

[I make chips]

Gas that's older than a couple months doesn't like to light off in a carbureted small engine. Dump it in the car and get a new batch for the small engines.

[alanganes]

Al: somewhere in all these replies is the answer to your problem. Your problem now is to figure out which one it is. I suspect that it would be easier to solve the original problem.

HA! You are not wrong, Bob! That gave me a good laugh.

Though I have to say I always learn something (usually several) from these sorts of discussions and there is always plenty of food for thought.

So I did get to spend some time on this earlier today. I did the following:

New spark plug. The old one looked generally OK, but they are cheap and the swap is easy so why not. Double checked for spark with the plug out of the head, got what looked to be decent fat spark.

AKB: this is a full gravity feed fuel setup. Fuel goes from the bottom of the tank through a shutoff and the maybe 3" straight down to the fitting on the carb so no pulse pump. Good info in any event.

But I did pull the hose off and fully drain out the tank and flushed some new clean fuel thorugh. I had some time constraints (and general laziness) so did not remove the carb, but took the bowl off in place as it was easy to access. It actually looked pretty clean in there. I blew through or ran a small wire through the passages I could get to from there and then reconnected the fuel line. I ran some fuel though it to confirm that it's getting to the bowl and that the float shuts it off. All good.

Visually verified the function of the choke and throttle plate.

I blew all of the dust and junk out of the air filters, this thing kicks up a lot of debris when it runs. I forgot to get a new filter but will do that. In any case, what is there is reasonably clean for now.

Once I got it back together it took a fair amount of pulling to get it started which I attribute to having blown out any traces of fuel and having to get everything flowing again. Once it did start, it ran great. I throttled it down and let it run at a low idle for a while, which it did well. I let it sit for a while and it started up much more like its old self.

The real test will be a true cold start after it has sat idle for a day or two. But I am feeling pretty confidant that it's sorted out. This is likely one of those "accumulation of small factors" kind of problems where you don't necessarily find a single smoking gun cause. At least I hope so! I'll be using this at one of my kids places later this week so we'll see for sure then I guess.

As for the ether I have only one diesel, a small Kubota tractor and Kubota recommends against using ether. So I would never use it on that. That machine is still very low hours so it starts easily even in pretty lot temps, so there is no need for magic starting juice. On my gas engines I use it only as a diagnostic tool as an easier alternative to spritzing gasoline. It at least tells me that I have enough compression and spark to make something happen.

Thanks to everyone for taking the time to chime in. Like I said, I always learn things reading through this stuff and appreciate the education. I'll report back the final verdict in a few days if I can resist the urge to try it every time I walk by the thing.

[Bob Engelhardt]

...
This is likely one of those "accumulation of small factors" kind of problems where you don't necessarily find a single smoking gun cause.
...

Yeah, but leaves you wondering whether that's the case, or if there really was single problem that's going to come back and bite you on the ass.

[Robg]

On my snowblower I had a problem with the primer bulb which didn’t prime. To make a long story short, I finally got a replacement bulb and when I went to install it I found the rubber tube to it was split thus causing a vacuum leak. Put the new one in anyway and cut off the damaged tube area, reconnected it and all was fine.
Also on a lawnmower that started fine cold but not so much hot & all seemed otherwise fine. So I decided to pull the spark plug. It looked ok so I opened the gap .005” to .010”. This forces the ignition system to generate a stronger spark to jump the wider gap and provides a larger spark envelop for the air fuel mixture. No more problems.
Hope this helps.

[alanganes]

So just to make a final report, I am declaring a victory over the poor starting problem.

I had let it sit for a few days then gave it a try. It started with a couple of pulls. This is typical as the wheel that does the shredding takes a pull or two to get spinning for a good start. I let it sit for well over a week and and just this afternoon gave it one good pull with the choke on, then another at a bit less than half choke and it fired right up. Shredded up a bunch of stuff without a hint of an issue, it idled smoothly at low throttle and ran back up easily. So I'm calling it good.

I can't be certain what (if anything) was the magic bullet, but if I had to pick something I would say that putting in fresh fuel along with the new sparkplug are my favorites.

Thanks to everyone who chimed in, all the input was most helpful.

[no704]

Late to the party! But when I have a suspected fuel issue, dump all the gas and fill with “TruFuel”

[alanganes]

Late to the party! But when I have a suspected fuel issue, dump all the gas and fill with “TruFuel”

Better late than never!

And yes, that is exactly what I did as well. That stuff is pricey but quite useful and generally worth it.
Thanks!