756 Starting Issues

[Bill VA]

Posted this to RP, posting here for a few more looks.....

A little time today before baling some squares and I pulled the gas 756 out to do a tune-up on it. New plugs, solid core wires, new distributor
cap, dust cover, rotor, condenser and points. Also put on a new ignition coil as the tractor would occasionally just shut-off when warm and all
signs pointed to this.

Old plugs were fouled bad. Old wires were on bad shape too. Points pitted too.

However it started and ran.....

With the new stuff in place, the tractor will not fire.

Couple of questions. Ignition coil - negative side should go to the distributor? Should it be a 6 or 12 volt coil? External resistor is somewhere
in the wiring harness under the dash?

The old coil is an IH coil, p/n 396546-R93. It says on the label 12V with RES, or 6V. The coil I bought (or was given at the parts counter) is a
12V no resistor. What is the correct ignition coil for this tractor?

I've got plenty of gas and air, but no spark as best as I can tell.

Any ideas as to what's wrong? It will be next week before I can look at the tractor again.

i was kind of hoping to put this tractor on my JD348 baler with wagon in tow, didn't work out. Haying is over for us this year, maybe 2018.

Thanks!

 

[old]

Stop guessing and check that you have a good blue/white spark at the center wire of the distributor cap and at all the plug wires that jump a 1/4 inch gap or more. I do not know that tractor as such but I bet it has a 6 volt coil and a resistance wire so you need a 6 volt coil. One way to maybe figure that out is to hot wire it and if you have good spark/ it runs then you know where the problem is. Or put the old coil back on. In all my years I have only had 2 or 3 coils go bad and one when it went was due to the ignition being left on in a 6 volt VW bug with a 12 volt battery and it exploded and sound like a shot gun going off and made one big mess under the hood

 

[Janicholson]

12v no resistor is a true 12v coil designed for 12+ volt operation directly. (it has no resistor in it, it is just woung=d for the higher voltage. Use a 6v coil, or one designed for use with external resistor. Make sure your fastening of the bolt connector on the distributor is not shorted to the case. The use of a test light from ground to the distributor terminal and cranking it should show a flashing test light as the points ground and open. Jim

 

[John T]

Good questions I pretty much agree with the other gents, heres my take

Couple of questions. Ignition coil - negative side should go to the distributor?

If its NEG ground yes the - side of coil goes to distributor

Should it be a 6 or 12 volt coil? External resistor is somewhere in the wiring harness under the dash?

If it has an external series voltage dropping (12 down to 6) ballast resistor in the LV primary ignition circuit and you want to continue that system IT SHOULD BE A 6 VOLT COIL. If its a 12 volt tractor and you don't wish to use any external series ballast IT SHOULD BE A FULL 12 VOLT RATED COIL


The old coil is an IH coil, p/n 396546-R93. It says on the label 12V with RES, or 6V. The coil I bought (or was given at the parts counter) is a 12V no resistor. What is the correct ignition coil for this tractor?

If it uses an external series voltage dropping (12 to 6) ballast resistor A 6 VOLT COIL IS CORRECT If it does NOT use any ballast THEN IT NEEDS A FULL 12 VOLT COIL no resistor required.

I've got plenty of gas and air, but no spark as best as I can tell.

To find the cause of no spark work through my Ignition Troubleshooting Procedure

http://www.ytmag.com/cgi-bin/viewit.cgi?bd=farmall&th=5745

John T
John Ts Ignition Troubleshooting

 

[the tractor vet]

Yep on your tractor it has a wire that is a resistor wire built into the main harness and with ALL I H tractors they use a 6 volt coil , Older I H 12 volt gassers had a external resistor close to the coil the little white thingy that had two wires going to it and the one going to the coil had a second wire coming off the S side of the started solenoid so when ya pushed the button to start it gave a 12 volt hot shot to the coil for fast start. . Now if in a bind for a coil or working with DUMB parts counter help at a big box parts store then you can use a coil off a mid sixty's Mo Par or a Ford Product. as both ran external resistors. Ford had the resistor wire in the main engine harnesss and Mo Par ran the little white two prong resistor mounted on the fire wall , you can also use this one when converting from 6 to 12 and never change coils . Now after you put the correct coil on and you still have no start then get another set of points. I can not tell you how many times i have installed a new set of pionts that they will NOT work . And i got the bad points from our friendly local Case I H store . I always had points cond. cap rotor and plugs wires valve cover gskts on my service truck along with PTo clutch kits seals gskt and a bunch of the tiny little pins for the PTO valves for the 06 and up. After 20 plus years of making house calls shell we say ya learn what ya need to keep on hand and usually everything runs in THREES . when you have a gasser I H ya keep on hand extra plugs and points don't worry about the condenser Cap and rotor depending on hours run with a GOOD cap they last a long time with just light cleaning , junk cap a year. Keep sediment bowl gskts on hand . Each time you change points reset ing timing .