JD70 No Spark...help!

cam.man67

Member
Hi everybody! First time poster, long time lurker on here. Hoping you can help me with my most recent acquisition:

blogger-image-701046729.jpg


This is my pap's 70, and since he passed away before I was born, it's the only piece of machinery I have of his. I rescued it last summer after it sitting idle for 15 years. In 3 days I had it running, and drove around as I cleaned it up and refurbished bits and pieces over the past winter.

Most recently, however, I'm stumped. I let it sit for about 3 weeks while I was taking off first-cut hay...when I got back to it last week, no spark whatsoever! :( It had new points, condenser, cap, and coil on it when I got it running last year. I have 12v coming from the ignition switch to the coil, and it drops to 7v when cranking. There's no power going from the distributor tot he coil, however. With that in mind I replaced rotor, points, and condenser yet again, but this time I still have no spark. What am I missing? I want to bring it back in service to run a hay rake in about 3 weeks, so I've got to get it running ASAP.

Any help you can give me is much appreciated!
 
If you have no power from coil primary to distributor....either the primary side of the coil is "open", or your points aren't closing.
My $.02 worth.
 
Agree with [b:654c4848f0]Old Popper[/b:654c4848f0].

"[b:654c4848f0][i:654c4848f0]I have 12v coming from the ignition switch to the coil,[/i:654c4848f0][/b:654c4848f0]"

Take a look at the photo below.

a193793.jpg" width="650"


Turn the ignition switch ON.

With power coming to the coil, next test for power to the points.

Take a look at the photo.

a193794.jpg" width="650"




"[b:654c4848f0][i:654c4848f0]I replaced rotor, points, and condenser yet again,"[/i:654c4848f0][/b:654c4848f0]

Make sure the tractor is in neutral, both brakes are locked, and the gas is tuned OFF.

Presuming that the condenser is good, remove the No. 2 spark plug and test for spark.

Lay the spark plug against a good "grounding" spot on the tractor.

Turn on the ignition and crank the motor over.

If there is no spark, then change the spark plug.

If there is still no spark, test the spark plug wire.

Test the No. 1 spark plug as described above.

Hope this helps.
 
1) You state...." I have 12v coming from the ignition switch to the coil, and it drops to 7v when cranking"

That's a lot of voltage drop and low voltage to the coil. Depending on the battery and starter condition and cables and connections and TEMPERATURE I might understand coil voltage dropping down to 9 or 10+ or so volts when cranking, BUT 7 VOLTS IS VERY LOW. I would use a jumper wire to by pass the ignition switch and hot wire 12 volts direct to the coil and read coil cranking voltage then and see if it fires, you may have a faulty resistive ignition switch or a bad starter of bad cables or ground or a weak battery. I take it that 70 DOES NOT use a 6 volt coil and have a voltage dropping (12 to 6) ignition ballast resistor and a ballast by pass while cranking system????????????????


2) You state: "There's no power going from the distributor tot he coil"

NOTE: When the points are closed THERE SHOULD BE NEAR ZERO VOLTS on the coils output to distributor terminal.


Here's part of my Ignition Troubleshooting Test Procedure

Place a test lamp on the coils output to distributor terminal, turn her on, and as the engine cranks over slowly it should flash ON (points open) and OFF (points closed). If it never comes ON the points may not be opening (are they gapped correct) or the condenser is bad/shorted, or theres a short from coil to distributor such as where the wire passes thru the distributors side or the points or points wiring is shorted. If it never goes OFF, points aren't closing fully (check that and their gap) or are bad or the wires open from coil or inside distributor to points.

If you take the time to work through my Ignition Troubleshooting Procedure linked below, it can help find the cause of no spark. No sense in re inventing the wheel each time this is asked LOOK AT MY FULL TEST PROCEDURE

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

John T
John Ts Ignition Troubleshooting Procedure
 
Thanks for the thoughts, guys! I have tested for power at the points, but no dice. The points are closing and are gapped to .022. So I've got all that down.;)

(quoted from post at 11:51:15 06/16/15)
That's a lot of voltage drop and low voltage to the coil. Depending on the battery and starter condition and cables and connections and TEMPERATURE I might understand coil voltage dropping down to 9 or 10+ or so volts when cranking, BUT 7 VOLTS IS VERY LOW. I would use a jumper wire to by pass the ignition switch and hot wire 12 volts direct to the coil and read coil cranking voltage then and see if it fires, you may have a faulty resistive ignition switch or a bad starter of bad cables or ground or a weak battery. I take it that 70 DOES NOT use a 6 volt coil and have a voltage dropping (12 to 6) ignition ballast resistor and a ballast by pass while cranking system????????????????

Correct, it's a 12v system, and no, there's no ballast resistor. I will have to try jumper ing it directly to a hot. Thanks for that suggestion!


(quoted from post at 11:51:15 06/16/15)
NOTE: When the points are closed THERE SHOULD BE NEAR ZERO VOLTS on the coils output to distributor terminal.


Here's part of my Ignition Troubleshooting Test Procedure

Place a test lamp on the coils output to distributor terminal, turn her on, and as the engine cranks over slowly it should flash ON (points open) and OFF (points closed). If it never comes ON the points may not be opening (are they gapped correct) or the condenser is bad/shorted, or theres a short from coil to distributor such as where the wire passes thru the distributors side or the points or points wiring is shorted. If it never goes OFF, points aren't closing fully (check that and their gap) or are bad or the wires open from coil or inside distributor to points.

im starting to suspect the wire between the coil and dist may be shorting...no light as the engine turns, though I've verified the points both open and close. The condenser *shouldnt* be bad, and I've made sure it's not shorting.
 
If there isn't a wire short from coil to distributor to points terminal, with points open and ignition on there should be full battery voltage (with respect to frame ground) on the coils output (to distributor) terminal and on the points wiring terminal. If not, disconnect the condensors lead on the points to insure it not shorted.

Another test, remove the coil wire from the coils output (to distributor) terminal,,,,,,,,Place an ohm meter on the Rx1 scale or a continuity tester on that now removed wire end with other end to frame ground,,,,,,,,,with points closed there should be continuity (near 0 ohms) to frame ground but with points open there should be an open circuit (approaching infinity ohms) to frame ground. If theres continuity (low ohms) to ground even when points are open, points or condenser or a wire is shorted or the pass thru boot insulator is shorted.

I have seen the wire from coil to points shorted where the little rubber insulator boot passes through the distributor on its way to the points,,,,,,,,,,,I have seen points that are shorted,,,,,,,,,,I have seen brand new condensors out of the box that are shorted.

Shes never gonna fire until a test lamp on the coils output with ignition ON flashes ON when points are open but OFF when they are closed as engine is slowly cranked over.

If theres no wire on the coils output to distributor terminal and you put a meter there or a test light and turn ignition on so theres is voltage on the coils input............there must be the same voltage on the coils small output terminal or else the coils LV primary winding is bad/open.

John T
Ignition Troubleshooting Procedure
 
(reply to post at 04:56:03 06/17/15)
If theres no wire on the coils output to distributor terminal and you put a meter there or a test light and turn ignition on so theres is voltage on the coils input............there must be the same voltage on the coils small output terminal or else the coils LV primary winding is bad/open.

Ah...well, I'll be danged. That's it then. No voltage on the output side even when disconnected. Thanks so much for the advice!
 

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