Re: h not starting

Posted by John T on October 12, 2005 at 20:48:35 from (66.244.90.98):

In Reply to: h not starting posted by 46 baler on October 12, 2005 at 19:50:41:

Baler, Okay, if the coil wire is producing a spark when held about 1/8 inch away from the tractors steel somewhere, but NOT at the plugs, thats sounds like its EITHER the wrong distributor cap,,,,,,or the caps not mounted correct in time to the distributor (but they usually have locators??) or a bad cap (but its new???),,,,,,,,,or a bad rotor,,,,,,,,or bad plug wires or bad plugs BUT MOST OF THATS NEW RIGHT???

When you say no spark at plugs, you sure they are good and grounded?? Try for spark just from the bare plug wire ends ?? (see below)

Hows the ignition switch (it may be resistive, that happens) and is there near battery voltage on the coil?? (see below)

The battery has to maintain and supply sufficient voltage at around a 5 amp draw, measure its voltage and the voltage on the coil, but if when on a chager theres no improvement, that dont sound like the problem.

See if the plug wire bare ends spark to frame the way the coil wire does?? If NONE of the plug wires are firing but the coil is firing, Im back to the wrong cap, or its bad (check top center carbon), or not mounted in time, or the rotor button is bad???

TAKE A GOOD LOOK AT THE ROTOR TIP AND THE CARBON BRUSH IN THE CAPS CENTER to be sure theres good electrical contact and no chips or cracks etc.??????????????????????

To check cap location/timing:::::::::

Remove the cap but mark or be aware of where its inner terminals are and then closely observe that if each time the points break open the rotor tip is lined up with where one of the caps inner towers would be located????????? Each time the points open the coil fires and its the distributor cap and rotor tips job to direct that spark to the inner cap terminal to fire thta plug wire. Does that all seem correct on your cap n rotor????????????

NOW REGARDING A WEAK SPARK::::::::::::::

If the coil wire is held about 1/8 inch from tractor steel, when it fires it ought to be a blue and NOT a faint thin wimpy yellow spark. Whats yours look like????????? If its weak wimpy yellow, check the points gap. If the condensor were dead shorted there wouldnt be any spark at all, but if theres no condensor in the circuit at all, she still sparks but indeed its weaker.

MAKE SURE THE CONDENSOR IS WIRED TO THE POINTS TERMINAL AND ITS THE CORRECT RATED CONDENSOR. If its too big, a weaker or no spark, if its too little, the points burn up quickly.

Finally you didnt mention the coil as new??? It could be faulty, how old is it??? Is it the correct voltage coil to match what voltage youre running at????????????? 6 volts on a 12 volt coil would make for a weak spark. Is this 6 or 12 volts?????? What voltage is the coil??? Is there an external ballast resistor in use????

You have to figure out if its a cap or rotor or cap timing problem (Coil fires but NO fire to any plug wires) ORRRRRRRR a weak spark problem (like coil spark is wimpy yellow). If its a weak spark, check points gap and condensor wiring and insure the correct voltage on the coil.

OTHER CAUSES OF WEAK SPARK

YOU COULD HAVE LOW VOLTAGE TO THE COIL CAUSED BY A BAD/RESISTIVE IGNITION SWITCH. To check that, try to hot wire direct to the coil from the battery or any other good hot voltage point. If the sparks strong hot wired BUT NOT via the switch, it may be a bad resistive switch contact. Use a voltmeter and measure the voltage on the coils high input (from switch not to distributor) terminal with ignition on and points closed. It should be near battery voltage unless its a 12 volt system and a 6 volt coil and external ballast.

For now my best guesses are a bad/resistive ingition switch,,,,,,,,then a bad or unconnected condensor,,,,,,,,,then mis gapped points,,,,,,,,,,then a bad/weak coil or its not operating at the correct voltage,,,,,,,,,,then the cap n rotor n timing issues if the coils fire is good but NOT the plug wires.

Good Luck n God Bless, let us all know, check that ignition switch and points gap and condensor fer sure

John T, retired electrical engineer

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