Mallory Ignition 23, 25, 27 User Manual

Mallory Distributors Manual

Standard And Vacuum Advance

Single And Dual Point

TROUBLESHOOTING GUIDE FOR
A POINT STYLE DISTRIBUTOR

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.

1. Disconnect the distributor from the coil (-)
terminal, taking it out of the loop and
allowing the test to be done properly.

2. 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.

3. Connect a 24" piece of wire to the coil (-) of
the coil.

4. Pull the coil wire out of the distributor cap
and get it to where you can jump a spark to
ground with it.

5. Turn the ignition to the "ON" position.

6. 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.

7. 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

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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
EFFECTING DISTRIBUTORS

IF THE TIMING IS ALL OVER THE PLACE 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.

1. If it binds, the advance is suspect and
needs to be checked.

2. 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.

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