Starter will turn motor only one rev.

[Kruzer]

Thanks for all the quick replies. Let me run down and try to better describe the situation.

It is a riding lawn mower. I was cutting grass that was about 4 inches tall so no strain I would believe.

I tried with the plug out..the same. The plug was dry and the top of the piston was dry. I would assume if my rings were shot i would lose compression and have blow by. With the plug out i feel/hear air pushing out the hole. I threw in a new plug too.

Regarding jammed belts. nothing there. I can turn the motor by hand, turning the fan. Also no smell of rubber when it happen. I cut almost 200 feet before this happen.

Regarding the starter. The flywheel and drive are new. I replaced them last year. The drive fully engages. When I first started it up, it did with no problems. I pulled the starter away from the motor and tried it. It worked fine.

Regarding Battery. I'm sure I drained the battery with many attempts but i used a jumper pack then after hooked up to my truck. It would make one rev. i would have to help it by hand make another.

Regarding mice. I've had my battles with them and know their tactics. I saw no signs of them this time. The mower has it's own shed. After the last time they attacked, I surrounded the mower with traps, poisons to where the stupidest mouse knows to avoid it. I will check the muffler but even if there is internal damage such as valves, shouldn't the motor still give me more then one rev when trying to start?

Regarding Iplayfarmer question about speed of the rev., with a good battery on it, I would say normal. It's hard to really say though because it only makes one rev then stops.

Thank you for the suggestions. I'm sure when I bring what I bought home Tuesday, it's going to fire right up

I still would like to get this fixed. The thing has worked it's axle off over the years and hate to give up on it.

 

[Iplayfarmer]

I was going to say it was your decompression mechanism and to check your valve clearances, but if doesn't crank any faster with the spark plug removed, it shoots that theory.

Just for educational purposes, drain some of the oil out to get it back to normal and then try it. That would at least tell you (and us) if the cranking issue has something to do with the excess oil.

The slow cranking could be the starter. Just because is spins freely on the bench doesn't always mean that it will spin as well when under load. A good mechanic should be able to test it under load for you. A good, honest mechanic probably wouldn't even charge you for it. Sounds like a fun Saturday morning for you

 

[TedLaRue]

Kruzer,

You didn't answer my question about whether you could turn the crank by hand for two or more turns. If you can't, then perhaps either the intake or exhaust valve is stuck in the closed position.

Here's the scenario: One of the valves is dragging on its valve guide either because it's bent or because it's lacking lubrication. When you were mowing, the engine had enough power to keep running for a while in spite of the friction until the valve finally seized. If it seized in the closed or almost closed position, then the engine could turn about one revolution before the lobe on the cam tried to open that valve. At that point, the starter would be unable to rotate the engine.

The easiest way to check that would be to remove the valve cover and see if you can move both valves by hand by pressing hard to compress the valve spring. You could even use a hammer and drift pin (my favorite drift pin is a ratchet extension or a bolt) to give a good rap to the rocker arm above the valve stem. If the valve won't move, or if it goes in but the spring doesn't bring it back, then you know the valve has seized.

If you do have a frozen valve, the repair would involve removing the head and reaming the valve guide and then driving a bushing in. The valve should also be replaced. I don't think that would be very expensive, especially if you removed the head and took it to the repair shop (but you'll need a torque wrench and the torque specs and a new head gasket to put it back together).

You'll have to figure out why it seized and remedy that problem, too. I don't know how the valves in a small engine get lubricated unless it's just from fumes from the crankcase.

 

[JohnBarlow]

"the flywheel was replaced last year" - if the starter motor turns the engine to the same spot then a problem with the ring gear in that spot would do it. Maybe one of the bolts (or something else) is loose and gets in the way of the starter motor gear at a specific point onthe ring gear ?

To check, try the starter motor, let it jamb, then pull the starter motor out and look for an obstruction (or go through a full rotation and look through an inspection hole ?)

How many hours has the new flywheel done (ie: is it so new that it might be the probem) ?

 

[Bedlam]

Is it possible a bolt has come loose and is hitting the underside of the flywheel?

 

[Kruzer]

Sorry about the late reply. I have a horse farm and been taken in some new borders but do appreciate the help

To answer Ted, I can turn the motor by hand as many turns as I want. The starter only turns the motor 1 time. If I assist it will turn it again.

To answer John, I don't feel anything jamming or hitting when I spin it by hand.

After rereading Ted's write up, I'm going to check for that. plus the other suggestions I read.

 

[john_bud]

Sounds like a dud battery. Jump it with a 12v car battery and see if that fixes it.

 

[TedLaRue]

Kruzer,

Since you can turn it several times by hand, I don't think you have a stuck valve, so don't bother checking that.

You said earlier that you jumped the battery with your truck battery with no luck. But still, John_bud could be right about your battery being bad. When you used your truck battery, did you just jump it to your mower battery, or did you remove the mower battery from the circuit? I would hook jumpers directly from the truck battery to the battery cables on the mower without any connection to the mower battery. If it cranks properly, it's your battery that's bad.

But if that makes no difference, then I'd try carefully jumping directly from the truck battery to the starter (bypassing the solenoid). If it cranks properly, you either have a bad connection somewhere (see Bedlam's previous post) or a bad solenoid.

But if it still cranks only one turn, you either have a weak starter motor or some obstruction in the teeth on flywheel (see JohnBarlow's previous post). You said the starter motor ran fine with no load, but it could still have shorted coils which reduce its power.

The only one of these suggestions that might explain why your mower died to begin with is the bad battery. If one or more cells have shorted, it might cause the ignition system to work incorrectly (especially if it's got a solid state ignition module) causing the motor to die. And then the bad battery would also prevent it from cranking properly.

 

[Soundguy]

Ditto waht Ted said.

If it was jumped with t he bad battery in the system.. the dead battery would draw down the power, and then add to that loss, the jumper cables themselves...

I'd *safely* jump from donor battery to starter, and see what I got.

That will let you know if it is a battery, cable/ground issue.. or just a shot starter.. etc.

soundguy

 

[jinman]

I have a single-cylinder 16 hp Briggs that does something similar when it is hot. It comes up on compression and the starter really struggles to get it "over the top" of the cycle. I think the starter is getting weak or the spark timing is slightly off. Even so, once it makes it past the first revolution through the compression cycle, it normally kicks off an starts.

Did you say that the starter would only turn the engine over once even while the spark plug was out? If so, I'd think your starter is dragging. When you removed it from the engine and tested it with no load, there was probably not enough drag to be detected. My guess is that the motor bearings in the starter are worn just enough to cause drag when the starter is loaded. I think that it's time for a replacement starter.