Mustang TFI

[TC Chris]

Tonight's project: installing a remote, heat-sinked location for the Mustang's "TFI" (thick-film ignition) module. The TFI is a known failure point for Fords of that era. Ford saved a couple pennies per car by locating it on the distributor, on top of the engine, a place where its subjected to high heat. And guess what high heat does to the TFI? They designed it to survive the warranty period. My first one failed in about 1995. The engine just stopped as I was driving. Well, last fall, last drive before storage for the winter, the engine stopped as I was driving. That time it restarted but it doesn't do much for confidence in the reliability of the vehicle. I ordered a relocation kit from Jason McCully. So tonight I was out drilling holes in my Mustang to mount the heat sink. Ouch. My 1960s vehicles have enough room under-hood to set up housekeeping or stretch out for a nap, but by 1986 things were getting crowded.

Next is to rotate the distributor to get access to the screws for the old TFI. The video says to mark it before rotating and then set it back to the mark. Seems like maybe it would be wise to check the timing. I've never timed the Mustang. It's electronic and stable. I have a couple good old timing lights from breaker point days, but wonder if they'll handle the higher ignition voltage of newer vehicles? Any experience, good or bad, with that?

I'll need to consult the shop manual for timing conditions. No vacuum advance line to plug on this one, and no mechanical centrifugal advance to worry about. Any experience with timing EEC-IV Fords?

Chris Campbell

[electra225]

My experience with Ford TFI and also the older Thunderbolt ignition has generally been good. The TFI that mounts on the distributor is probably the better of the two systems as far as reliability is concerned. Secondary ignition condition, plugs, plug wires, distributor cap and rotor are critical for long life and reliability in that system. The GM HEI system and the newer C3-I systems were almost bulletproof. I found it critical to use genuine Motorcraft igniton modules in the TFI systems. Not only do the aftermarket modules fail more often, they can also mess up other systems, such as injector "on times". If we were investigating a weird or intermittent driveability issue in a Ford with TFI and found an aftermarket ignition module, that was our first avenue of investigation. I kept a known-good Motorcraft TFI module in my tool box for substitution testing in such cases.

[TC Chris]

Apparently the good Motorcraft modules are unobtanium now. The current ones are not reliable, and the aftermarket brands are superior.

The problem was just poor design, putting the modules in a location where excessive heat kills them. There was a big lawsuit and that's where they discovered that Ford knew the devices would fail--shortly after warranty ended. It was a purely cost-related design decision.

Chris Campbell

[electra225]

The 5 litre Mustang guys ran high energy aftermarket ignition systems back in the day, I believe made by Mallory. I had one in the shop that had punched through the insulation of the stock plug wires. They had to run spendy wires made to handle the high voltage.

[TC Chris]

The night before last, I installed the last step on the TFI relocation project--the dummy TFI on the distributor, with wires from it running to the new TFI on the heat sink. It took 3 hours in heat & humidity. Lots of @#%**$!!!. The online video makes it look like a half-hour job, but that must have been on a truck engine. On the Mustang, there's plumbing and brackets in the way. Couldn't even hold a Sharpie right for the distributor timing mark--took 3 ties. No room for the hands to hold the device and turn the tiny Allen wrench. When I was done I was too tired to drive, and besides, I did not want a disappointment. Last night I went sailing after work and then came home, rolled the Magnavox out of the way, and turned the key.

After 8 months in storage, it started on the first crank. Not a single miss. It always missed for 5 or 10 seconds after storage. I didn't even get the clutch chatter that usually showed up on the first two or three engagements. Drove around town, stop and go, and the 7 miles down the highway and back. No problems.

If you've got a Ford with the notorious TFI, I endorse the McCully Racing Motors kit and the Accell aftermarket TFI module.

Chris Campbell

[electra225]

Congrats on a successful retrofit. The distributors with breaker points benefit from the installation of an Ignitor to replace the points. I've heard you can't buy dependable breaker points currently. Nobody is putting any R&D money into a technology that essentially went obsolete over 50 years ago. Next up will be carburetor rebuild kits....

[19&41]

It's wonderful not having to deal with that TFI crappiedaux any more. Whoever started the instruction to use dielectric grease on the module instead of thermal heat sink compound to mount the module had to hate mankind.

[TC Chris]

The kit came with dab of gray thermal grease and instructions to treat it carefully because it's so expensive to replace. I kept getting my finger in it as I was unboxing/exploring. The Accell TFI came with a tiny packet of white grease that I have saved for future use. Hope it won't be needed but I will carry the old module in the car, just in case, along with the Allen wrench for the new screws ( no special tool required). I'll get a photo of the big new heat sink soon.

Chris Campbell

[19&41]

The white grease contains finely ground epsom salts. It' best to apply it with a razor blade to get a thin layer. Some make the mistake of applying a thick layer on it. It is only to fill the minute imperfections in the metal's surface to provide effective heat transfer. Now, if one was to mount the module to the distributor's housing, it would seem that the heat transfer would be from both the housing with the engine's heat and the modules' internally generated heat. Add this little fact into the mix: All of the more recent modules were assembled using lead free solder that softens and melts at a much lower temperature. Conventional mounting is a failure waiting to happen.