Ignition Coil Ampere Gauge

[Brutus45]

I have a new problem I was hoping someone can help with as I prefer mechanical problems and my electrical knowledge is limited. On my cockshutt 30 when I have the ignition on and hold the starter button down to crank the motor, the motor will keep cranking and not start the engine until I release the button.

I think I am draining power from the coil? Voltage directly from battery is about 14 volts. With the key on, voltage from -side of battery to the + side of ignition coil is about 8.22 volts (seems like a large drop, should I still see 14 volts at this point?). From -side of battery to -side of ignition coil is about .22 volts. I am wondering if I have some wires tied incorrectly to my ampere gauge

 

[rvirgil_KS]

You likely have a weak battery, or excessive resistance in the circuit.

?I think I am draining power from the coil?? You are correct in your thinking

What coil are you using? 6 volt coil, or ?12 volt external resistor required coil? with an external resistor? Or a ?12 volt no external resistor required? coil?

? With the key on, voltage from -side of battery to the + side of ignition coil is about 8.22 volts (seems like a large drop, should I still see 14 volts at this point?). From -side of battery to -side of ignition coil is about .22 volts.?

.22 volts indicates the points are closed. 8.22 volts indicates you may have a ?12 volt , no resistor required coil? (3 ohm primary) and a 1 1/2 ohm resistor in series with the coil. If that is the case get rid of the resistor.

Charge your battery and clean both ends of both battery cables. If cables are corroded replace them. Clean, bright, and tight on all connnections. Get the frame end of the ground cable as close to the starter as possible, do not depend on a rusty sheet metal connection.
 

[Bob]

Is the wire from the ignition switch to the coil a normal stranded copper wire, or a special resistance wire?

I have NO idea what your tractor would have originally had, or someone could have added a special resistance wire.

The were used by a number of automotive or machinery manufacturers as an alternative to a discrete wire-wound ceramic resistor, either of which basically allows a 5 Volt coil to be used on a 12 Volt system.

If such a wire IS present and someone has installed a "true" 12 Volt coil along with it, spark will be weak and it would act as you describe.

If you CAN measure the primary Amps, if all is well, you should "see" between 3 and 4 Amps, lower end gives a weaker spark, much over 4 Amps is tough on points and coils.
 

[oliver90owner]

Connect a wire directly from the battery live to the coil and check the voltage across the coil terminals while the contact breaker points are closed. It should be almost battery voltage. If the voltage across the coil, fed from the normal wire, is only 8.2 volts there is either a ballast resistor in that line or the feed wire is resistive.

The usual use of a 6 volt coil involves bypassing the ballast resistor while cranking, thus feeding the coil with full battery voltage only while cranking.
 

[Brutus45]

What coil are you using? 6 volt coil, or ?12 volt external resistor required coil? with an external resistor? Or a ?12 volt no external resistor required? coil?
I am using a 12 volt internal resistor style coil. I have a 12 volt system

8.22 volts indicates you may have a ?12 volt , no resistor required coil? (3 ohm primary) and a 1 1/2 ohm resistor in series with the coil. If that is the case get rid of the resistor
I do not have a separate resistor in place on this system.

cables and battery terminals are clean, ground is fairly close to the starter and clean, I do think my battery is a bit weak but will crank over the motor to start it. THanks for the feedback, did you take a look at how I have the amp gauge connected? does that look ok?
 

[Brutus45]

Great suggestion. I purchased a whole new wire harness when I was rebuilding my tractor, and specified a 12 volt system. This is something that I can take a look at. I honestly did not know they made a special type of resistance wire. I replaced the coil, so I know it is a 12 volt coil
 

[rvirgil_KS]

Amp gauge is wired correctly. Charge wire from alternator to one side of amp meter and wire from there to supply power to the switches. Other side of ammeter to battery cable side of the start solenoid/switch. If ammeter indicates correctly you are ok. If indication is reversed then reverse ammeter connections. I have seem ammeters that were not consistant in their + and - markings.

What is the resistance of the wire from the "run" post on the switch to the + side of the coil?
 

[Brutus45]

Ok, checked resistance does 81 ohm sound correct?
 

[Brutus45]

Not sure what I did the first time but checked again and getting a reading of 24 ohms
 

[Brutus45]

ok, did another test and here are the results:
A) I disconnected the wire from the + side of the coil and ran a wire direct from the +side of the battery to the +side of the coil. When I test voltage from the -side of the battery to the center of the coil (distributor plug) I get about 15volts. When I set it back up with the ignition wire to the +side of the coil turn the key on and test for voltage to the center of the coil I get about 9 volts. The resistance in the wire I used for the test and the wire that is currently on the ignition switch registered about the same, so thinking not resistance in the wire. Is it possible the white wire going to R1 on the alternator being in contact with the black wire on the amp meter going to the +side of the coil is draining power (See my diagram).
 

[rvirgil_KS]

"When I test voltage from the -side of the battery to the center of the coil (distributor plug)" Voltage readings to center of the coil are irrelevant. This I the high voltage out to the plugs

" Is it possible the white wire going to R1 on the alternator being in contact with the black wire on the amp meter going to the +side of the coil is draining power" No, not likely.

checked again and getting a reading of 24 ohms

If this is the wire from the run side of ignition switch to + side of coil it is way too high. You should have near 0 ohms on that wire.

Sub another wire from switch to coil. What do you get for voltage at Run on switch and at + on coil?
 

[Brian Jasper co. Ia]

You probably have a 12v battery with a bad cell. A 12v battery with one bad cell will still crank a 6v tractor starter well enough, but the voltage will drop enough that a 12v ignition system won't spark under compression.