129 ?
 

Have a IH 129, the weekly workhorse, that I was using to mow. I ran over a bit of a tree root, a somewhat significant bump, and the engine just died. The engine still turns over but just won't start. Was thinking maybe a safety switch but the switch to engage the blades seems to be working just fine. There is no spark but that might make sense. Any thoughts on how to begin to troubleshoot this? Any general direction would be greatly appreciated. Thanks in advance.

Newbie Rob

Switch to engage the blades? 129 has mechanical Pto. Do you have a later engine transplant in this? You need positive battery volts to positive side of coil during start and run. Negative side will flash test light during start, doyou have that?

Sorry. The brake pedal that engages a switch behind the gas tank ( won't start without your foot on the brake ) and your absolutely right about the pto for the blades.

First, welcome to OCC.

Sounds like an electrical issue. Click on this link for the Wiring Diagram..... 129

With the Key in the On position, do you have 12V from engine block ground to the (+) of the Ignition Coil...???

Actually, they do have a pto safety switch on the driver's right side as well as the foot pedal safety switch, but I doubt that it went out. You do need to pull back on the deck engagement handle to enable that safety switch! Have you pulled back on it and tried starting?

Cub Cadet 123

Using your 12V test light attach the clip to ground, turn the key on and touch the pointed end to the pos side of the coil. It should light up. Turn the key and make the engine turn, it (the test light) should stay on.

Clip on ground, touch pointed end to neg side of coil, turn key to make engine turn. Light should go on and off while engine is turning.

If these requirements are not met, your engine will not run and there is no need to look any further.

So I don't have a light but just used a multimeter

Key on- Ground to (+) side of coil= 12v
Key on- Ground to (-) side of coil = 0v

Key on to start - Ground to (+) side of coil= 12v
Key on to start - Ground to (-) side of coil = 0v

Does this tell me it's the coil then? Thanks for all your help.

Rob

Did you try to clean or replace the points?:bigthink:
That's the most common ignition issue i have with old engines

Sounds to me like the coil is fine
On the tests that you got 0v you should have done. Ignition on, one wire from meter to negative on coil and other wire to positive on battery. You should get 12v then.
If you wanted to test ohms you could do negative on coil to ground

Tells me that everything on the positive side of the ignition circuit is OK.


Test your Ignition Coil per this....... Test

Step #2 - What you see depends on whether the points are open or closed at the particular time you are measuring. If the points are closed, you have a ground coming through the points to the negative side of the coil and will read 0V. If the points are open you will see 12V coming through the coil from the positive side.

Step #4 - What you see will be some positive voltage less than 12V because the voltage is pulsating as the points open and close and the meter can't fluctuate fast enough. A test light would flash on/off at the speed the points open/close.

Steps #1 & 2 - As long as the key is in the on or start position you should always have 12V on the coil positive pole. Off position always 0V.

Incorrect indications on the coil negative pole can be caused by points that are pitted, dirty, shorted, not set correctly, etc. Also your condenser is attached to the negative pole of the coil and to ground on your engine housing. The condenser is a capacitor and is electrically bridged across the points to reduce arcing on the points. If the condenser shorts out it is the same as your points never opening and you will always see 0V on the coil negative pole. On the other hand the condenser can burn out and this will shorten the life of your points.

Test lights are cheap & helpful, pick one up.

With the key on and the points closed the neg side of the coil to ground should show 0 volts, when the points are open, neg side of coil to ground should show 12 volts.

If you do not show 12 volts with the key on and the points open, check to see if something on the neg side of the coil is shorted to ground. Look in the tech section and check the coil as described.

So picked up a circuit tester and and a digital multimeter

With key on and the circuit tester on the + coil to grd, light is on
With key on and start, the circuit tester on the + coil to grd, light is on

With key on and the circuit tester on the - coil to grd, light is off
With key on and start, the circuit tester on the - coil to grd, light is off

using the multimeter set to 200 ohms, and key on, it reads -172 from + coil to grd

using the multimeter set to 20k ohms, and key on, it reads 8.5 from plug wire hole to grd.

Not sure if any of this makes sense. Does this confirm it might be the coil? thanks for any and all suggestions.

For the moment, forget anything about reading ohms.
All that matters, whether with the test light or the meter, is that you see 12V at the pos side of the coil with the key in the run and start position. That is good.

Next, As I tried to explain earlier, what you should see on the negatives side of the coil depends on whether the points are open or closed at that particular time. So, with the key on, measure (or test light) the negative side of the coil and turn the engine by hand far enough that you can see the points open and close and tell us what you measure (or the light does) as they open and close and let us know.

Key on, Points closed, from neg coil to grd, light out

Manually turn engine

Key on, Points open, from neg coil to grd, light out

Coil? Points?

points, clean them, or if you haven't replaced them , replace them. when the points are closed the light should be on, open it should be off.

So the points looked to be in pretty good shape. The contact surfaces didn't appear to be pitted but I still lightly sanded them. With the key on and points closed, neg coil to grd is still unlit. Does this point then to the coil?

That is incorrect!
When points are CLOSED, light is OFF.

Anyways, next step:

Remove both the wire to the points and the condenser wire from the negative pole of the coil. With the key on, what do you see on the negative pole of coil??

If you still have no light, the coil is bad, try another coil.

If you now have a light, first try touching the condenser wire to the negative pole of the coil. If the light goes off, the condenser is shorted. If the light remains on it is probably good.

Next, rotate the motor by hand to a point where you can see that the points are open. Now touch the wire from the points to the negative side of the coil. If the light goes off either your points are shorted or the wire from the negative side of the coil to the points has a bare spot and is touching ground.

you're right. I wrote it backwards, just leave the point cover off, with points closed , flick the points open and closed with your finger. light should blink on and off.

there was no light and the coil was bad,

Sourced locally was very expensive but the growing grass and weeds waits for no man.

Just wanted to say thank you!!! for everyone's advice and direction

Glad to help.