Yesterday while on a nice drive my 68, 427, started running rough and within
a mile quit running. It will try to start but won't stay running. When I
check the voltage at the coil it is a very constant 7.29 volts with the
ignition on but the car not running. Any ideas....seems it should be 12v or
nothing....the 7.29 is unusual. This is why it will try to start but the
7volts isn't enough to make it stay running when you give it a little
gas....the spark requirement is more than the coil and produce with this
voltage. Any ideas???? Thanks for looking and hopefully someone has had a
similiar problem. The timing and dwell is right.
Mike in Morgantown, PA
Sounds like an aging ballast resistor or 'resistive link' in the hot
side of the coil wiring.
I don't have the diagram for that engine but that vintage of cars used a
ballast resistor in series with the coil. Identify this by two wires
going to the 'hot' side of the coil. One comes from the starter
solenoid. ItThat wire provides 12 volts to the coil for a hotter spark
while the engine cranks. The other wire goes to the ballast resistor
and it provides something between 6 and 8 volts after you quit cranking.
The ballast resistors were originally in a white ceramic housing on the
firewall. Sometime around the late '60s and early 70s they saved money
by putting a 'resistive link' in the harness. Might be near fuse block.
THIS IS A FOLLOWUP TO MY ORIGINAL POST. IT TURNED OUT THAT THE CONDENSOR
HAD FAILED. ONCE REPLACED IT WORKS FINE. SEE THE OTHER POST WHICH DESCRIBE
HOW THE SYSTEM WORKS. THE 7.5 VOLTS IS RIGHT FOR THIS SYSTEM.
THANKS TO ALL WHO HELPED.
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.