Music City Rod Shop

The following are some basic steps to take when troubleshooting a Point Style Distributor. Of course, the first thing that should be checked is the condition of the cap and rotor, looking for carbon tracking or corrosion on the terminals or where the plug wires connect. Also check the spark plug wires with an Ohmmeter to insure they have the proper resistance.

If there is no trigger signal to the coil

If the box powers up but does not fire the coil and the white wire is being used as the trigger source, the following tests should be done:

1. Remove the cap, turn the motor over and look at the points to see if they are opening and closing. If they are, see if they are sparking. On a dual point distributor, one set will open with no spark and the other will spark when it opens. If the spark is a big fat one, then the condenser is bad and needs to be replaced.
2. If no spark is visible, check to see if the points or wires are shorting to ground either at the points or at the primary terminal screw going through the housing. Also check where the contact spring connects to the main frame of the points and make sure the insulator is not melted.
3. If all of this looks good then look to see if there is anything else connected to the coil (-) terminal. If so, remove it and see if the motor fires.
4. Last but not least, there could be a problem with the coil itself or the coil wire going back to the cap. To check the coil, use the following test procedure. NOTE: This test should only be done on "stock type" coils. DO NOT try this test with "CD Only" coils, such as the Mallory 28880 or ACCEL 140019 and 140010.
5. • Disconnect the distributor from the coil (-) terminal, taking it out of the loop and allowing the test to be done properly.
   • Disconnect the wires coming from the CD box (if so equipped) connected to the coil (+ and -) terminals and connect the ignition switch 12 volts wire to the coil (+) terminal of the coil.
   • Connect a 24" piece of wire to the coil (-) of the coil.
   • Pull the coil wire out of the distributor cap and get it to where you can jump a spark to ground with it.
   • Turn the ignition to the "ON" position.
   • Rapidly tap the 24" wire to ground. This will fire the coil. You should get a 1/4” to 3/8” spark out of the high voltage coil wire to ground. If you do then the coil and coil wire are good and working.
   • If no spark to ground, change out the coil wire and do the test again. If still no spark, the coil is bad and needs to be replaced.

If the points burn up or the condenser fails frequently

1. Check and make sure that everything is well grounded to the engine block. Condenser failure is often a grounding problem. Make sure all grounding surfaces are clean of free of paint, grease, or oil.
2. If the condenser needs changing, make sure that the bracket is also changed at the same time. The brackets are basically a one-shot use part. They are designed to scratch through the rust preventative coating on the condenser when it is installed. In problem applications, scuffing off this coating will guarantee a good ground.
3. Make sure that the heads are grounded to the block. With all of the coatings and sealers that are used on gaskets and bolts, especially on race applications, the cylinder heads can be poorly grounded. A simple ground strap between the block and each head can make a big difference.
4. A simple ground strap from the distributor body to the block, not the intake manifold can also solve a problem. The strap can be connected to a screw that attaches the vacuum advance chamber or the condenser bracket. Care must be taken that the screw is replaced with a slightly longer one to allow for the thickness of a spade or ring terminal. Make sure that the screw doesn’t come in contact with anything that is revolving inside like the advance weights when they are fully advanced. The point plate also moves and must be free of anything that could bind it. The screw must be flush with the inside of the bowl. Another option would be to put a clamp on the lower shank area of the housing. The distributor clamp is not a reliable ground.
5. Make sure that the block is also grounded to the frame.

Mechanical issues affection distributors

If the timing is sporadic when checked with a timing light

1. First check for excessive wear in the gears. Grab the rotor and turn it back and forth. If it has excessive play, check for wear on both the camshaft and the distributor.
2. If the gears appear normal, use a socket and a breaker bar to gently rotate the crankshaft back and forth. The key here is to see how far the crank rotates before the rotor moves. Anything beyond a few degrees indicates a worn timing chain/gear assembly that needs to be replaced.
3. Check the advance. The simple way to evaluate the advance is simply grab the rotor and turn it. This will activate the mechanical advance and give some indication if there is a problem in the distributor. If you can turn it one way against the springs and it snaps back to the original position when it is released, it is fine.
4. • If it binds, the advance is suspect and needs to be checked.
   • If it turns but does not come back to the rest position, the springs have probably either come off or are broken.

If the points are continually out of adjustment

1. Check the upper end of the shaft for excessive side to side movement. Lateral movement will cause the points to require constant adjustment. The only solution is to replace or rebuild the distributor.
2. Confirm that the point set is not designed for racing only with excessive spring tension. This increases rubbing block wear even with properly lubricated.