Electrical help

[Figo40]

I have a strange problem and it’s driving me crazy.
My tractor will not turn over. Everything is new cables, starter,starter switch, coil, resistor. It has been converted to 12v negative ground. Bench tested the starter and it spins fine. If I pull the starter off and reinstall I get one little bump then nothing. I can ground to the starter with jumper cables and touch the positive cable directly to the starter post and get nothing. I show almost 14 volts at the starter with everything hooked up.
HELP!

[staninlowerAL]

Best guess is the starter is not grounding to the frame. Try a secondary ground with your jumper cables directly from the starter case to the battery ground post. Also it take a lot less amps to spin the starter on a "bench test" than it does when installed and under a load. Have you checked the condition of the brushes?

[Scrivet]

........and touch the positive cable directly to the starter post and get nothing. I show almost 14 volts at the starter with everything hooked up.
HELP!

If this is a starter mounted lever switch, it is normal to get voltage at the post the cable is attached to. Voltage doesn't get to the starter until you pull the lever (starter rod). The lever basically drives a wedge between the head of the bolt that the cable attaches to and the nub sticking up out of the starter under the switch. All four surfaces (nub, both angles of the moveable lever, and bolt head) have to be electrically clean and making contact when you pull the lever. The moveable part also needs insulated from the sides of the switch which can twist from the spring pressure, there are sort of triangular shaped pieces of insulating material that go on each side.

[Eugene]

Everything Stan said. Take the battery to the auto parts store and have it checked.

14 volts tells you the battery is fully charged, But it does not tell you the number of amps available. As a guess it will take between 100 to 150 amps to spin the engine over.

[Figo40]

Using jumper Cables from my truck directly to the nub on the starter ground wire this from the battery to the lower starter mounting bolt of wire brushed all the contacting services between the frame and the starter still only get one little bump but only after I remove and reinstall the starter

[Jim Becker]

Maybe the starter drive is jamming at the ring gear? Depends on how big the little bump is. After your one little bump, try turning the engine by hand a little bit (with hand crank or by pulling the fan) and see if you get another little bump.

[Figo40]

Nope not jamming.

[staninlowerAL]

I recently had this problem on another piece of equipment. The problem was the brushes were worn to the point they would not make sufficient contact with the starter armature to allow the required current flow. Replaced the brushes, cleaned the armature and the problem disappeared.

[inairam]

Did you just paint or install a new battery box? Is you ground cable on the sheet metal of the batter box ? If so try a different ground location.

I use the flat braided cable and bolt it to the bottom bolts on the battery box.

[Figo40]

Brand new starter, brand new everything, the ground cable goes to the lower starter mounting bolt.

[Waif]

Brand new starter, brand new everything, the ground cable goes to the lower starter mounting bolt.

Seems to me ,positive cable should go to starter on a Neg. ground system ,and Neg. to chassis..But ,I don't run a 12v Neg ground systems on my Cubs either...

[Waif]

As Scrivet mentioned earlier , look over your starter switch. The (if you have it ) connection is at the starter switch.
Most cub starters have a switch on top the power cable goes to.

With power going to the switch ,then the switch closed by operator lever , the starter where it touches the frame becomes your ground. Thus allowing power to flow through your starter.

A starter with a cable attached to it's mounting bolt don't seem right ,if it is one of the two bolts that attaches the starter to the frame.

[Scrivet]

.......A starter with a cable attached to it's mounting bolt don't seem right......

Not the normal location for a battery ground cable to be attached. Mainly because of the required extra cable length, but electrically cleaner as that reduces the number of electrical connections.

...... the starter where it touches the frame becomes your ground. Thus allowing power to flow through your starter......

As I understand it the positive cable is going to the starter switch on top of the starter.
The negative cable is going to the lower of the two mounting bolts that attach the starter to the bell housing, which is ground.

As long as the engine is not "locked" up (rusted, hydrolock from leaking coolant or rain down the exhaust, seized fan hub, clutch stuck, transmission in two gears, etc.) then I have to say Stan's idea of the starter brushes seem the most likely cause at this point. Do you have access to a known working starter to try? Would tell you real quick if it was the starter or not.

[Crimson Tim]

I think it’s time for pictures...

I ground (-) cable to a starter mounting bolt would be ok, provided the starter cable (+) went to the switch.

I would disassemble the switch on top of the starter and troubleshoot both directions from there, either upstream into the wiring or downstream into the starter.

Are the cables all new, too? Maybe a sketchy connector if new or corroded spot if old (even hidden by insulation) someplace that isn’t letting much amperage pass?

Did you say the starter was new, too? From a reputable source? This is its first installation, right? so you have not yet ever seen it work?

[staninlowerAL]

Brand new starter........

Given the quality of parts available these days, "new" does not always mean that it is without problems. May be time to verify that the starter is working properly. In your initial post you said it spins fine when not mounted on the tractor. It takes a lot less amps to spin it without a load.