Hi everyone. I have a 1975 F-100 longbed with a small block and a C-6, plus Holley 600, and Holley pump, headers ,etc.This engine and trans were transplanted from another Ford vehicle by a previous owner. I am assuming from the C-6 and the ample torque and overall power exhibited that it is a 351w., and perhaps from the early eighties.
The ignition system is electronic, but I do not know which. It might be a duraspark?
It has a distributor cap which looks like an older "points" cap. Inside it has an 8 tooth "rotor" and a fairly small ignition module with a bright metal roughly rectangular magnet assembly with a blue plastic " reluctor? " , and outside vacuum advance which is plugged.
The problem I am having is ignition related. I am usually a logical troubleshooter, but this has me stumped.The truck will shut-off suddenly, just like the key is turned off, once it stops it is very hard to restart. The ignition will not fire while cranking, until you let go of the key. If the ignition is off and I use my remote starter the ignition fires normally, but no start, with the key in the run position there is no spark when using the remote starter. If one ,ahem, grasps a plug wire the spark seems quite ample The non-starting, and shut off is getting worse and more frequent, I am now afraid to leave my driveway. LOL.
I have googled this problem and it seems common, but with variations, to several Ford products. This seems to be the best informed and most sensible forum so I joined .
Perhaps you can point me in the right direction.
Last edited by LimeyRich; 04-27-2011 at 05:53 PM.
Reason: wrong word
Follow the wires leaving the distributor, and you should run into a silver box. This is the ignition module. I would replace it. Even if it's not the problem, it's good to have one under the seat as a spare.
Thank You "Franklin2" and "Number Dummy" ! You hit the nail right on the head, especially Number Dummy's 3 step description of the fail sequence. I am used to GM electronic modules that die all at once or maybe give you one restart when cooled off.
This however reminds me of mid 1970s British electronic ignitions, a slow but fatal decline starting with a shut off and then a 20 minute cool down before running about 50 more minutes, this might keep up for a couple of weeks. Those Brit electronic engineers were always a nerdy twisted lot, they apprenticed under Lucas electric ( the Prince of darkness) ! Apparently some must have gone to work for Fords
Thanks again, you have set me on a more positive path.
Additional info! OK, after a nice afternoon with the local parts houses I couldn't get a Motorcraft ignition module for a '75, and the Ford dealer didn't have it. A few "use any year as long as the plugs fit" answers didn't generate much confidence. Didn't want a Chinese made unit either.
So. I did the HEI mod From "RRiggs of gofastforless.com" Followed his instructions to the "T". Got a nice fat Heatsink and fan working. The truck seems happy with it, I just need to tidy up the wiring next week. We will see how reliable that is.
Last edited by LimeyRich; 04-29-2011 at 08:58 PM.
Reason: New info
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