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770 Spark

A

Andy Airgood

Member
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. I?ve systematically replaced the spark plugs, points, condenser and coil without improving the situation. My battery is relatively new and I?ve charged the battery to make sure I have a good charge. I?ve tried converting to an electronic ignition but still have the problem so went back to points and condenser so I could see the spark.. I?ve also ran a direct wire from the battery to the coil. Any thoughts on what could be causing my problem?
 
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
 
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.
 
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.
 
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.
Clint
 
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.
 
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
 
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
 
Finally got time to work ion the tractor again. As it turns out I had to reset the timing. I had to rotate the distributor clockwise 1/4? at the base. Any thoughts on what could make the timing change?
 
1/4 turn indicates something slipped or the distributor was installed improperly, I would remove the distributor and make sure the roll pin has not sheared in the drive gear also 1/4 turn would be right if the wires were put in the cap one hole off, rotor tip should point to number one spark plug when the engine is at TDC on the compression stroke. Even with that, the spark should not be weak or erratic. If you reinstalled the Pertronix setup you should have at least 3/4-1 inch strong spark, If you did, make sure you have the Pertronix wired exactly as the instructions show. If you have the engine running now the upper right cap post should be number 1 wire. It seems I am repeating myself but I want to be as clear as possible.
 
IF,You had the distributor out,,maybe,it was reinstalled off? Or perhaps from previous attempts to diagnose?You stated you have swapped and checked everything. it is assumed you still have issues with weak spark,that is not a condition of timing,and are you timing with a good quality light? Or by the fail safe "ear" method?or has it just been that way all along and you just learned it?
 
I am pretty certain I was dealing with two problems. I
disconnected the battery ground with the switch turned off and
noticed a small arc between the ground cable and tractor. I
disconnected the alternator and the short went away and I got
a strong spark. I still couldn?t get the engine to fire. That?s
when I reset the timing and it runs great. I hadn?t done
anything with the distributor such as removing it before finding
the timing needed reset. I have had a similar issue with the
timing once before. It seems like there is an internal issue
with the distributor but I?ve never taken one apart to
understand what it could be.
 
Google the distributor so you have a good idea what the parts look like,and it will more than likely give you R@R instructions,as mEL had stated,the gear may have turned,i do not know him personally,but over the years,i have seen he knows his stuff.bit personally,you will have to pull the distributor to see.
Clint
 
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