9n no voltage when coil is installed

[Shimano]

Been having a long drawn out problem with 1940 9n 12volt. Bottom line problem is that there is no spark. Traced back to no voltage to coil. Took off coil and distributor. then checked voltage throughout the electric system. All good 12v. attached the wire to coil without the rest of the distributor. All good 12v. Attached rest of distributor to coil. still not bolted to tractor. All good 12v. then bolted on to the tractor. NO POWER in the whole system.

I have went over Bruces test on the bench 10 times and all checks out. Something must be causing a short. Where should I look?

 

[mhb@ufe]

It has to be shorting out in the distributor as that is the only source to ground. Remove it and check with an ohm meter with the points open. Just overtightening the screws for the condensor wire or point spring can cause them to short through the insulation.

Mark

 

[HCooke]

Isolate the problem by running a hot wire from the non grounded side of the battery straight to the coil. Try and start it. If it starts the problem lies in the wiring, resistor, and switch between the battery and the coil. If still no start the the problem is in the distributor.

 

[Royse]

"NO POWER"? Are you using a test light or a meter?
If that voltage actually drops to zero volts I would expect
there to be some smoke pretty quickly!

If you have a multimeter, measure the resistance from the top of
the coil to ground, wire disconnected and points open. (no power)
It should show an open circuit. If it shows a low resistance
instead, something in the distributor is grounded.

Common to have the plastic insulator broken where the points
connect, or just to have the condenser wire touching the plate.

 

[Shimano]

I will try the suggestions to test. Took the distributor apart last night. cleaned and checked pieces as assembled. didnt find anything. same result. Could it be possible to have a bad ground on the tractor?

 

[R Geiger]

Not if the starter works! Sounds like you are missing something. I would recheck the distributor and do not assume that anything is right. double, triple check everything. something is shorting out in my opinion.

 

[mhb@ufe]

With the distrbutor removed, install the coil to the distributor and turn the key on with the points open and check to see if you are showing power to the base of the distributor. If it does then you need to check for a short.

Mark

 

[souNdguy]

to show -0- volts at the top of the coil when it is installed, means hte coil HAS to be a dead short, and I'd expect smoke.

More likely is upstream. a connection at the resisstor and key swithc.. or the switch itself is bad. showing voltage on a high impeadance meter.. but not enough to power a 3a ignition circuit.