Z121S won't start without starting fluid

[RogSto5]

Need help. Runs/mows great once started with starting fluid

 

[85Hokie]

Welcome to the forum.

However - if you want that engine to last any longer ........... STOP using the starting fluid!
IT is very bad for diesels !!!

I would pull the glow plugs ..... and do a compression check on your engine. I think you will find the compression to be somewhat low. Report back what those numbers are.

 

[D2Cat]

Welcome to the forum.

However - if you want that engine to last any longer ........... STOP using the starting fluid!
IT is very bad for diesels !!!

I would pull the glow plugs ..... and do a compression check on your engine. I think you will find the compression to be somewhat low. Report back what those numbers are.

Would that starting fluid be OK for gas engines?

 

[85Hokie]

Would that starting fluid be OK for gas engines?

The problem with starting fluid - which most contain ether is two fold - one it takes away from the lubrication that diesel provides - but at 20+to 1 ratio of compression - is will explode WAY TO early in the cycle, thus creating a lot of strain on the piston/rings/connecting rods. A gas engine will compress at something like 9ish to 1 - thus the ether will ignite much closer to the top dead center timing.

IF you need to use the starting fluid - either, bad glow plugs, or bad compression needs to be looked into being fixed.

 

[wgator]

The problem with starting fluid - which most contain ether is two fold - one it takes away from the lubrication that diesel provides - but at 20+to 1 ratio of compression - is will explode WAY TO early in the cycle, thus creating a lot of strain on the piston/rings/connecting rods. A gas engine will compress at something like 9ish to 1 - thus the ether will ignite much closer to the top dead center timing.

IF you need to use the starting fluid - either, bad glow plugs, or bad compression needs to be looked into being fixed.

I think D2Cat's point is the the Z121S has a 21HP Kohler 747cc 2-cyl gasoline engine: TRACTOR DATA LINK
Edit to OP, is the choke working properly?

 

[85Hokie]

I think D2Cat's point is the the Z121S has a 21HP Kohler 747cc 2-cyl gasoline engine: TRACTOR DATA LINK
Edit to OP, is the choke working properly?

Excellent point - one of those assumptions that was wrong!

 

[NCL4701]

Assuming it has the 21hp Kohler gas engine and it runs fine but won’t start, that sounds like you have some sort of issue with the choke not closing when you’re starting it. I have a 21hp Kohler V-Twin on my Cub ZTR and although may not be exactly the same engine, it needs full choke to start and then no choke at all after running for approximately 0.5 seconds, so I’m pretty confident I could start it on ether with no choke at all. Can’t tell from the TractorData link if it has automatic choke (hate those on small engines) or manual choke. If manual should be pretty easy to check and fix. Just pull the air cleaner and see if the choke control is moving it correctly. If automatic, pull the air cleaner when it’s cold, try starting it, and watch to see if it’s operating correctly.

 

[Russell King]

I had a similar problem on a different older gas engine. If you have been using gasoline with ethanol then you may need to get the carburetor cleaned or just replace it. The ethanol makes this weird gel in the bowl of the carburetor and clogs jets and generally can cause trouble with starting.

You can try the cleaners in the gas first but you will also need to get fresh fuel with zero ethanol to keep your trouble away if that is the problem.

 

[lugbolt]

you have one of a couple possibilities.

One (most common) choke is not choking all the way. Does it stay running after you help it with the kick starter (starting fluid)? If so, your throttle/choke cable could stand to be adjusted.

Second possibility. This is a usual symptom: Kick start it with starting fluid, then as soon as the fluid "shot" runs out, the engine dies. Repeats over and over, will not self-sustain. Assuming the fuel is actually getting TO the carburetor, the possibility exists that the fuel shutoff solenoid is stuck. The solenoid cuts fuel flow through the jet in the carburetor, so it don't backfire when you turn the key off. It also doubles to reduce hydrocarbon emissions, as when you cut spark from the engine, the engine will continue to rotate, which draws in fuel/air through the carb, and exhausts it out of the tailpipe--installation of the solenoid solves those two issues. But it's also another part to go south. The majority of the time, if i saw a solenoid fail it was due to old staled fuel. There were a couple exceptions but not many.

if you ain't getting any fuel to the carburetor, I would be willing to bet that the pickup tube and/or the shutoff valve in the fuel tank is plugged up.

 

[kubotafreak]

Most common issue for gas lawn mowers is the idle jet is clogged. It has some of the smallest ports. They need to be removed off the carb and a wire run through them. There should be a front facing air jet(the one not covered by the choke plate), and a vertical pilot fuel jet(can be seen on top external to the carb). The idle pilot jet has holes on the side as well as a tiny one vertical. These are very delicate and use of the wrong screw driver will damage them. They do not need to be gorilla torqued on either. I bet if you clean both of these well it will start right up.(wire brush bristles work good to poke the jet holes)

It is also common with these two jets to cause engine hunting at idle.

 

[Motion]

It' not the OP's problem, but confusion over it being a gas engine and not a diesel, D2cat is correct, never use starting fluid on a diesel, if you must, use brake cleaner still not preferred but way better than starting fluid. Just my .02