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Case Tractors Discussion Forum

770 Spark

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Andy Airgood

11-06-2019 18:13:34

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Every now and then I get a very weak spark an inconsistent spark or no spark at all on my 770 spark plugs. It appears to affect all plugs vs. a single plug. Iíve systematically replaced the spark plugs, points, condenser and coil without improving the situation. My battery is relatively new and Iíve charged the battery to make sure I have a good charge. Iíve tried converting to an electronic ignition but still have the problem so went back to points and condenser so I could see the spark.. Iíve also ran a direct wire from the battery to the coil. Any thoughts on what could be causing my problem?

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11-09-2019 07:10:16

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 Re: 770 Spark in reply to Andy Airgood, 11-06-2019 18:13:34  
Besides what others have stated please check the insulator on the breaker points plate.Had two friends that had the same problem.The insulator would ground out but not totally and make the tractor run bad.Part number A44287 andA24774.You

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11-07-2019 08:15:53

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 Re: 770 Spark in reply to Andy Airgood, 11-06-2019 18:13:34  
Hot wire it and see if the problem goes away. If it does then the problem is from the distributor back to the battery and could be a bad connection or bad switch or a wire that might be rubbing some place and shorting out.

If the hot wore does not fix it then it is in the distributor. And it could be the wire going from the coil to the points or the insulator in the side of the distributor. Or even the cap or rotor could be bad. Also if it happens when it is wet out the cap could be cracked. A way to check if it is a crack cap is fire it up and put your hand on the cap. If you jump 10 feet whn you put your hand on the cap it is bad

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11-07-2019 07:18:40

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 Re: 770 Spark in reply to Andy Airgood, 11-06-2019 18:13:34  
Sounds like an eratic connection somewhere in the electrical circuit. Have you checked out ALL of the positive and ground circuitry? Is the plate that holds the points and condenser grounded good to the distributor housing?

Sometime dumb questions have to be asked and checked out. LOL For example, Is the distributor housing grounded good to the engine?

You ran a wire direct from the battery----. Did you connect direct to the battery post or to the battery cable clamp? Are the battery clamps clean? Is all the battery's ground circuit okay.

Do the head lights flicker? Nuff dumb questions. Hope you find the problem.

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11-07-2019 06:37:22

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 Re: 770 Spark in reply to Andy Airgood, 11-06-2019 18:13:34  
Had similar problems,the advance plate would loose ground,inside the distributor.and at the risk of criticism,i agree with,mel.the electronic is superior,except on old Harley's,but that,is a different affair,,,,,,,,,, ,lol.


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11-07-2019 04:47:27

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 Re: 770 Spark in reply to Andy Airgood, 11-06-2019 18:13:34  
Does it have copper wires or resistance ? It looks like you have covered all the bases as far as substituting parts. Put a copper core wire in the coil and look at the spark before it goes to the cap and rotor. Condensers have been a problem of late in one of the most popular tune up kits line. I would also check charging voltage to make sure the Ign circuit is getting enough voltage. Also, personally I would reinstall the electronic ign system, my experience is they throw a much stronger spark and returning it to stock did nothing to correct your problem. Also make sure you install the electronic system according to the directions with a resistor wired in as the schematic shows if you are running the most popular (Pertronix) kit. Some on here don't care for the electronic system but I have had excellent success and serve the local Case tractor pulling community so I have more experience than most with them.

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John Saeli

11-07-2019 05:37:03

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 Re: 770 Spark in reply to mEl, 11-07-2019 04:47:27  
I won't sell the #$%&*'n electronic kits because of past experience our customers had and I had to eat them. Anyways, do the Pertronix kits say to use resistor plug wires? Seems I heard that.

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Case Nutty 1660

11-07-2019 04:47:26

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 Re: 770 Spark in reply to Andy Airgood, 11-06-2019 18:13:34  
a bad connection (rust) between the breaker plate and distributor will cause this,, seen it be on the outside of the distributor shaft that is in the block also cnt

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11-06-2019 20:53:19

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 Re: 770 Spark in reply to Andy Airgood, 11-06-2019 18:13:34  
We had trouble with the rotor on a 870 gas. Everything is made so cheap that the rotor was shorting thru the bakelite material it was made of.

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