Truck Repair: 1979 Ford F-350 Pick Up-Ignition Module Problems, ford f 350, barrel carburetor

Question
My original Ford module lasted for 18 years, and the Big A
replacement lasted for 7 years. Living in the desert of Arizona
while driving on the freeway with outside temperature's of over
105 degrees, the engine starts to fade, like a vapor lock or
starving for fuel.  It usually happens at 50 to 60 mph, and then if
I back off on the throttle a bit it will keep going, but if I give it
too much gas, it will backfire.  The coolant temperature is only
215-220 degrees.  Under the hood temperature is about 195
degrees and the fan clutch has not clicked in.  When I get to
town, I can drive all day at speeds of 30 to 40 mph, and even up
to 50 mph where possible and no problem.   But, then back on
the freeway at the higher speeds, the problem sometimes occurs
again.

I have two electric carter racing pumps and three in line fuel
filters.  I have checked the fuel pumps, and volume and pressure
are okay and so are all of the fuel filters, I have the small Holley
fine ceramic filter at the inside inlet of the carburetor.

I have put on a new needle and seat and power valve.  In 2005, I
replaced the ignition module with a Carquest module and the
problem cleared up, but now 9 months later the same problem
is occurring.  It seems that heat is the big issue and when this
happened two days ago on the freeway, I took some ice cubes
wrapped in foil and covered the module to cool it down but that
did not help.

The repair shops say that it cannot be tested and so I have
bought a new module.  I have all of the Ford manuals and have
tried to check the volts, but this condition is so intermittent that
these tests don't seem to make any sense.  I have never had a
module go back so that the truck will not start; it has always
been an intermittent problem.

The motor has been rebuilt, and the Holley 4 barrel carburetor is
only 8 years old.

Any suggestions on how to test this module or should I just
install the new one I bought and return the defective one.  Is this
a common problem with aftermarket modules from Carquest,
Napa, and AutoZone?  Should I take out the ceramic inlet filter
on the Holley?

Thanks for your help.


Answer
The heat is an issue -- Some ignition modules are very problematic -- I would replace the defective module - and also check the coil -- they are very sensitive to heat -- also an electric fan is a good idea for a vehicle that runs in that type of climate.