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How-to relocate the TFI module on older Ford EFI V8s

Posted in How To: Electrical on August 16, 2017
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Having the engine on my ’91 Bronco suddenly die while rolling along the interstate at 70 mph with big rigs and cars all around is one of the most unnerving situations I’ve been in, on or off-road. When all power is instantly lost, braking and steering become a big problem. Fortunately, I managed to glide safely to the shoulder—heart pounding.

The sudden die-on-the-road scenario wasn’t the first time this happened to my FSB, nor is it rare among those of us who run Ford engines with the ignition control modules mounted on the distributor. It’s a common malady.

So common that back in 2002, Ford lost a class-action lawsuit that affected 300 models and some 23 million vehicles built between 1983 and 1995. The reason: The placement of the thick film ignition (TFI) module placed too close to the engine block, causing the heat-sensitive module to suddenly fail when it gets above 257 degrees. Our ’84-’91 Broncos are on that list because the TFI is mounted on the distributor—one of the hottest places on an engine.

McCully Racing Motor’s TFI Relocation Kit comes with a 3-foot shielded wiring harness, heat sink, drilling template, and self-tapping screws with aluminum standoffs. We also opted to replace the stock TFI with a Dyna Module from Performance Distributors to go along with their 5.0L billet distributor already in our ’91.

When the TFI cools down, the engine can often be restarted, which makes diagnosing the sudden engine stalling issue problematic. At other times, the TFI has to be replaced because the heat killed it, or damaged it enough that the stalling issue becomes more frequent. Either way, the location of the module on the dizzy is bad news.

The solution, of course, is to relocate the module to a cooler location. One way to do this is getting a remote-mounted TFI and matching distributor from a newer model year at a salvage yard and rewiring the engine harness to accommodate the newer setup.

Another method is to build your own heat sink setup. (Some FSB owners have attached their TFIs to XBOX 360 GPU heat sinks and made their own extension harnesses between the stock distributor and the TFI’s new mounting location.) Both methods work, but are time consuming and a pain to do for the average Joe.

We found a simple, cost-effective answer to relocate the problematic TFI is to use the kit McCully Racing Motors offers. It’s $55 (plus $10/shipping) and looks factory when installed. The kit consists of a well-designed-and-shielded extension wiring harness, heat sink, instructions, and mounting hardware. It took us less than 30 minutes to make the swap.

The photos show how easy it was for us to relocate the TFI module on our 5.0L (we used a high-dwell Dyna Module from Performance Distributors) to the driver-side inner- fender wall of the engine bay. Now our TFI is as cool as can be, and it should live a long, trouble-free life—even in the heat of the summer.

McCully’s heat sink is already prepped with Arctic Silver, a special thermal adhesive that is formulated to conduct heat, not electricity. This helps transmit the heat generated by the module to the heat sink.
We mounted the TFI to the back of the heat sink using the screws supplied with the McCully kit. Don’t over tighten.
The McCully wiring harness has three color-coded wires. Make sure they are connected to the same terminals just as if the TFI were it plugged directly into the distributor. This is best done with the distributor out of the block as the connectors purposely fit very tight to both the TFI and the dizzy.
The self-tapping screws have standoff spacers to keep the TFI from touching the sheetmetal and to provide maximum airflow around the module and heat sink.
We used the provided template to mark and predrill the four holes where the self-tappers hold the heat sink/TFI to the inner fender of our ’91 Bronco. This is the coolest location in the engine bay.
We untapped the factory wiring harness, pulled out the TFI/SPOUT wire so it would plug into the TFI at the new location. This also required splicing in a 2-foot length of 14-gallon wire to extend the coil lead so it’d allow the TFI/SPOUT to reach the new heat sink.
Our finished installation looks like factory and provides maximum cooling for the heat-sensitive Ford TFI ignition control module. We tidied up the install with new split loom and plastic zip ties.

Sources

McCully Racing Motors
267-254-6687
www.mccullyracingmotors.com

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