When the ingnition switch is in the RUN position there should be 12 volts
applied from the ignition switch to the ballast resistor. The other end of
the ballast resistor goes to the + lead on the coil. The - lead on the coil
goes to the ungrounded side of the points and condensor (mounted on the side
of the dizzy).
When the points open or close the current through the coil is interupted and
then restarted. This causes a magnet field change, which creates the high
voltage required to fire your plugs.
When the points are closed the - coil lead should have about 0 volts to
ground. When the points are open there should be several volts on the -
lead. DO NOT PUT YOUR VOLTMETER ON THAT LEAD WHEN CHANGING THE POINTS FROM
OPEN TO CLOSED OR VISA-VERSA. You could blow the meter up.
If you have a quarter volt or more across the closed points there is a
grounding problem in the distributor caused by points that are either not
well grounded or making proper contact, which will reduce or eliminate your
spark. If you are measuring voltage at the - lead on the coil the lead to
the dizzy could be open.
That is for the RUN position of the ignition switch.
For the START position the voltage is applied directly to the + lead of the
coil from the ignition switch. That is so that the starting voltage on the
plugs will be higher during the high load period for the battery. If the
ignition switch is not applying voltage directly to the + coil lead you will
have no ignition spark during the starting process.
How are you looking for fire? You should put a timing light pickup on the
high voltage lead connected to the coil, not one of the spark plug wires.
That way the timing light will flash anytime there is a voltage spike on the
wire.
Tom
69 2000 "Mr. Hyde"
Portland, OR
-----Original Message-----
From: owner-datsun-roadsters@autox.team.net
[mailto:owner-datsun-roadsters@autox.team.net]On Behalf Of
ambradley@attbi.com
Sent: Monday, May 12, 2003 8:36 PM
To: datsun-roadsters@autox.team.net
Subject: more spark questions
OK, I've replaced points, condenser, cap, rotor, wires, and plugs. I am
getting no spark. I have 12 volts going to the condenser, 8 volts going to
the points. When open, the non-charged side of the points is grounded, I
checked with a continuity tester. I have 12 volts to the coil, continuity
through the ballast resistor. It does not fire with the key in the start
position; I don't have an easy way to test the ON position to see if it
fires
then. The coil tested fine at the local AutoZone, though I will buy a new
coil tomorrow.
My question is, what triggers the coil to fire? What should I see (be able
to
test), and where? Should I show 12 volts between the + and - on the coil,
or
only when the points are open, or only when the points are closed? I assume
something changes in the + and/or - leads to the coil, otherwise, what would
trigger it to fire?
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