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Weak spark
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- 5+ Years
- Posts: 33
- Joined: Fri Feb 01, 2019 7:19 am
- Zip Code: 16201
- Tractors Owned: International 184
Weak spark
I’m trying to finish up my auction find 154 but I’m having trouble getting it to run. I am able to get it to fire occasionally but it won’t stay running and just misses and sputters when it does. I put new plugs, wires, cap, rotor and points in it and adjusted the points to 0.020 gap, but still the spark is so weak I almost have to turn the lights off to see it. I have a strong 12v to the coil, but I suspect the coil might be bad. Is there a way to check it?
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- Team Cub Mentor
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Re: Weak spark
No good way to test the coil.
Coil wire about 1/4" from engine block. Ignition on, snap the ignition points open and closed while observing the spark. Weak spark, probably the coil.
Faulting condenser will also cause a weak spark. Significant spark across the points, condenser faulting.
Edit. The in tractor tests can indicate that the coil is functioning. If in doubt, test with a known good coil.
Coil wire about 1/4" from engine block. Ignition on, snap the ignition points open and closed while observing the spark. Weak spark, probably the coil.
Faulting condenser will also cause a weak spark. Significant spark across the points, condenser faulting.
Edit. The in tractor tests can indicate that the coil is functioning. If in doubt, test with a known good coil.
I have an excuse. CRS.
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- 5+ Years
- Posts: 33
- Joined: Fri Feb 01, 2019 7:19 am
- Zip Code: 16201
- Tractors Owned: International 184
Re: Weak spark
Eugene wrote:No good way to test the coil.
Coil wire about 1/4" from engine block. Ignition on, snap the ignition points open and closed while observing the spark. Weak spark, probably the coil.
Faulting condenser will also cause a weak spark. Significant spark across the points, condenser faulting.
Edit. The in tractor tests can indicate that the coil is functioning. If in doubt, test with a known good coil.
That's what I suspected. I'll have to pull the coil off of my 184 and test it. I replaced the condenser along with the points so I don't think that's the problem. Thanks.
- SONNY
- 10+ Years
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- Zip Code: 61722
Re: Weak spark
Use the right coil with resistor!! -- either internal or external! IF you have an external one on it now, better check it!-- I had 2 of them shoot craps this past year. If yours is internal, in the coil, it probably is fried. New condenser dont mean good one either! sub good known parts on a trial basis to narrow down the problem. You may find the wires are part of the problem too. Might want to check them.
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Re: Weak spark
What’s the voltage and amperage at the coil?
I’m not sure about the cubs wiring systems but with coils and points there was a bypass wire bypassing the resistor with full 12 volts for starting. With the built in resistance in the coil we have a full 12 volts starting and less amperage running. Since she starts them dies the low side of the coil maybe kaput. Put a jumper wire from the battery to the + side of the coil to see if it stays running. The ign coils have a primary and secondary system.
I’m not sure about the cubs wiring systems but with coils and points there was a bypass wire bypassing the resistor with full 12 volts for starting. With the built in resistance in the coil we have a full 12 volts starting and less amperage running. Since she starts them dies the low side of the coil maybe kaput. Put a jumper wire from the battery to the + side of the coil to see if it stays running. The ign coils have a primary and secondary system.
I'm technically misunderstood at times i guess its been this way my whole life so why should it change now.
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Re: Weak spark
Not on Farmall Cubs.BigBill wrote:I’m not sure about the cubs wiring systems but with coils and points there was a bypass wire bypassing the resistor with full 12 volts for starting. With the built in resistance in the coil we have a full 12 volts starting and less amperage running.
I have an excuse. CRS.
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- 5+ Years
- Posts: 254
- Joined: Tue Jul 29, 2014 4:16 pm
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- Tractors Owned: IH 184
- Location: Farmersville ohio
Re: Weak spark
The coil for a numbered cub is a 3 ohm coil. Usually referred to as a "12 volt" or "internally resisted" coil. Measure across the two screw terminals and you should get approximately 3 ohms. If you measure approx 1.5 ohms you will need a 1.5 ohm ballast resistor.
Some cars and tractors use a 1.5 ohm coil with a ballast resistor and are wired so that the resistor is bypassed when cranking. On cars this was usually done with a 5 wire starting relay. I have a system where i add a lawn tractor starting relay and a 1.5 ohm coil and a ballast resistor and can install a "hot start" resistor bypass system on a 184 without needing to get to the wiring under the dash. The amp draw for a 3 ohm coil is approx 4 amps at 12 volts. With engine running and charging at around 14.5 volts approx 5 amps.
Some cars and tractors use a 1.5 ohm coil with a ballast resistor and are wired so that the resistor is bypassed when cranking. On cars this was usually done with a 5 wire starting relay. I have a system where i add a lawn tractor starting relay and a 1.5 ohm coil and a ballast resistor and can install a "hot start" resistor bypass system on a 184 without needing to get to the wiring under the dash. The amp draw for a 3 ohm coil is approx 4 amps at 12 volts. With engine running and charging at around 14.5 volts approx 5 amps.
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- 5+ Years
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- Joined: Fri Feb 01, 2019 7:19 am
- Zip Code: 16201
- Tractors Owned: International 184
Re: Weak spark
So, I swapped the coil from my running 184 and immediately had a nice hot, bright spark! I had previously checked to make sure I had a good 12+ volts to the coil, and it had 12.7. I had already taken off all of the connections and cleaned them too. The coil was definitely the problem. I ordered a new one with internal resistor, should be here in a few days. Good news is the tractor fired right up after that and ran good. Motor seems solid, no smoke or bad noises. I had previously got it to fire briefly right after I got it home but it didn't run long enough to really evaluate the engine. Now I need to finish the carb rebuild (I cleaned it out but it still needs new gaskets) and tune it up. Compression checked out at 125-130psi on every cylinder, so I think it should run great after everything is set up good.
Great info here, thanks! I'm going to test the old coil just for the curiosity of it.
Larry B wrote:The coil for a numbered cub is a 3 ohm coil. Usually referred to as a "12 volt" or "internally resisted" coil. Measure across the two screw terminals and you should get approximately 3 ohms. If you measure approx 1.5 ohms you will need a 1.5 ohm ballast resistor.
Some cars and tractors use a 1.5 ohm coil with a ballast resistor and are wired so that the resistor is bypassed when cranking. On cars this was usually done with a 5 wire starting relay. I have a system where i add a lawn tractor starting relay and a 1.5 ohm coil and a ballast resistor and can install a "hot start" resistor bypass system on a 184 without needing to get to the wiring under the dash. The amp draw for a 3 ohm coil is approx 4 amps at 12 volts. With engine running and charging at around 14.5 volts approx 5 amps.
Great info here, thanks! I'm going to test the old coil just for the curiosity of it.
- Don McCombs
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Re: Weak spark
Good oil pressure?
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- 5+ Years
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- Joined: Fri Feb 01, 2019 7:19 am
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- Tractors Owned: International 184
Re: Weak spark
Don McCombs wrote:Good oil pressure?
I haven't put a gauge on it but the light goes out as soon as you start cranking the motor over, so there's enough pressure for that.
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