Starter won't turn

[Old Murray]

Greetings everyone.

I have a Murray riding mower model# 425007x92 that is about 8 years old and it has a B&S 17.0 HP I/C OHC.

The problem I'm having is that the starter will not turnover at all. I installed a new battery yesterday and I'm getting 12.5 volts on battery side pole of the solenoid (3 poles) but only 6.2 volts on the starter side pole and 6.2 volts on the ignition switch pole when I turn the key. When I remove the wire from the starter and turn the ignition I get 12.5 volts on all 3 poles and at the end of the wire that attaches to the starter. The oil is clean and the level is good and the flywheel turns freely so I'm pretty sure the motor is okay.

I have read that compression could be the problem. Last year it wouldn't start but the motor would turnover about half a turn. I learned on here that it needed a valve adjustment so I did that, but the mower is kinda old so they may need adjusting again. The question I have about compression, though, is can a motor maintain compression all winter long? I realize that if the valves aren't adjusted right the compression can't escape through the valve, but over a period of a few months it wouldn't eventually leak out? (The mower has not been started this year. The engine has not turned over once this year...)

Another obvious potential problem is a bad starter or ground. Since nothing would work no matter what I did I pecked on the starter with a small hammer, but it didn't help. The electrical print shows a ground coming from the starter so I looked for it but didn't see it. I may have missed it because it was getting dark but I was wondering if it is grounded to the motor? If so, is the motor grounded to the frame by being bolted to it or is there another place I should look for the motor ground? Also, is there a way to check the starter using a multi-meter?

I have asked a lot of questions, some of which might be elementary, but I am trying to learn so any help would be greatly appreciated!

 

[bertsmobile1]

First thing remove spark plug and turn engine over by hand then try the starter motor.
if it works OK without a plug and nothing came out of the cylinder ( fuel/ oil etc )
the look at your valve clearances and check for stuck valves.

Second test
Get some jumper leads.
Jump from the - on the battery to a good earth on the mower like the oil drain bolt.
Try to start the mower.
If it works OK you have a bad earth strap.
The starter earths out via the mounting bolts so make sure they are tight.
If you can see a bit of rust/ corrosion around them then take them out and clean them up and the bit where the starter touches the engine.

Third test ,
run a jumper from the + dise of the battery to the hot side of the solenoid.
try starter
If it works you have a bad connection or wire from the battery.

Fourth test
Run a jumper from the switched terminal on the solenoid to the + input wire on the sarter motor.
Starter works then that wire is dirty / broken / corroded.

Still no joy then run a jumper from the + on the starter motor to the + on the battery.
Do it this way because you might get a big spark.
Starter motor turns properly then the solenoid is duff.
Starter motor does not turn then the starter is duff.

Most usual problem is crud building up on the brushes shorting them out or wearing them out.
The whole brush section is a drop in replacement part.

 

[Old Murray]

Thanks for the quick reply. I did try running a wire straight from the battery to the starter but it still would not turn. I will try the other tests tomorrow and I will get back on here to let you know what I found.

 

[ILENGINE]

If you tapped on the starter very hard with a hammer there is a good chance that you broke the magnets and will now need to replace the starter. four things come to mind. Bad battery which isn't holding the load, bad connections between the solenoid and the battery, bad ground connections or shorted starter.

If the engine had been cranks multiple times over with the valves misadjusted will cause overloading of the starter and eventual starter failure, which is what you may have.

 

[Tinkerer200]

This model of engine very seldom needs the valves adjusted and then usually right after some one did a valve job and flubbed it. It is the OHV engines which you see refereed to as needing valve adjustment.

Difficulty cranking is however a common complaint with this engine. I have a list of the most common causes IF you would like it. Address below, put in proper format and remind me, engine model number and what you want.

Walt Conner
wconner5 at frontier dot com

 

[Old Murray]

First, thanks to everyone who replied. I appreciate the help.

Second, I found the problem. I removed the old starter to make sure the grounding surfaces on the motor and the backside of the starter were clean, which they were. I used my multi-meter to check for continuity from the motor block where the starter was mounted to the frame and it was good. Resistance was .2 ohms. I inspected the starter and it looked old, but nothing looked obviously wrong. I tried to turn the starter drive, but it wouldn't move. I wasn't sure if you could turn those by hand so I took it to a place nearby that rebuilds starters, alternators and other various electrical components. They happened to have a rebuilt starter like mine and I could easily turn the starter drive on it by hand so then it became pretty obvious my old starter was bad. I traded in my old one and bought the rebuilt one for $50, took it home and installed it and the mower fired right up. I wish now, though, I had taken the old starter apart so maybe I could have seen something wrong internally because it might have been knowledge I could have used in the future. As it is, the mower is ready to go. It's raining now, though, and the forecast is calling for more rain everyday this week so it might be a few days before I can Git-R-Done.

Thanks, again, for the help and hopefully this thread helps someone else in the future.

 

[Rivets]

As a tech who has rebuilt more starters than I want to remember, I'll bet your problem was as stated earlier, broken magnets caused by hitting the starter with a metal object. The magnetic material used in small engine starters is as brittle as glass. Does not take much of a hit to crack them.