Parts House Adventure

One Friday morning I left the house on my way to Dothan, the big town down the road where I worked for so many years – the Ford dealership parts manager had a brand new 7.3L engine block he needed to dump, either on me or in the scrap iron bin.  I fired up my old pickup and headed up the street.  I’m teaching engine repair next semester and the 7.3L block might be a nice training aid.

The weather was kind of damp and misty, and the old truck tends to skip and carry on in weather like that; it needs a set of wires and a cap, but I’ve been putting that purchase off for years, dreadfully guilty of my own indictments to others about ignoring known concerns.

I bought this truck for $2000 back in the summer of 1996. Since then, I’ve put about 12,000 miles on it. This 80 model F150 has about 80k miles total on it; I almost never drive the old bomb, but it has new tires and I recently replaced the radiator due to a leak. This is the vehicle I leave at the airport when I fly and at the school when I’m on a road trip in one of the college vehicles.  When I start it, I have to let the torque converter fill up before it’ll move. That’s how long it sits between drives.

When I was replacing the radiator, I noticed that all the potting in the ignition module had liquified and trickled out of the box to re-congeal in waxy rivulets on the inner fender.  I don’t know why that happens, but I’ve seen it before.  And with that in mind, I knew that Duraspark module was on its last legs, but I figured I’d take a chance on letting it show me what it had left.  Since I’m the only driver, it was a calculated risk – no danger of my wife or anybody else but myself sitting beside the road due to my lassitude.  I did plan to get a replacement module to toss behind the seat, but never got around to it…

Well, wasn’t even at the end of my street before I realized I had big trouble.  The truck popped and skipped in a peculiar way that I knew wasn’t wet ignition part-related.  The engine stalled.  I restarted it. It stalled again. Only I noticed that it would run if I kept the ignition slightly past the run position, a maneuver that keeps the start circuit to the module hot.  That circuit uses a different part of the ignition controller and it wasn’t uncommon when I was at Ford to find that a car would run on the start side of the module but that the run side had failed. The small gray module-mounted TFI modules work the same way.

As I kept tinkering with it and restarting the truck, I managed to limp on down to AutoZone, which isn’t far from where I live.  The truck was idling okay even in the run position by the time I pulled into the Zone parking lot, but I wasn’t going to chance a 60 mile round trip with that used-up module under the hood, and I knew good and well the module was the problem.

Auto Zone carries a line of ignition parts called “Duralast,” and the parts clerk told me this line of parts used to be WELLS, but I can’t verify that, not even doing internet research.  Maybe it’s WELLS’ second line?  I don’t know.


I bought a peculiar-looking little replacement module and plugged it in right there in front of the store only to have the truck kick back and carry on like it had crossed spark plug wires or something. I checked the cap for moisture and didn’t find any.

Reconnected my old module – the truck started right up.  Reconnected the Never Ever Worked module.  The truck snorted and kicked back.

It was the classic A-B-A swap.

Back inside the store (wearing jeans, boots, and a T-shirt, no ASE patches) I encountered a skeptical parts guy who had probably seen a lot of yo-yos trying to use his parts for troubleshooting.

“We don’t need to just go swapping parts like this.  We can check your old module to make sure it’s bad.”

“Why don’t we check your new one?”  I asked.

We did.  The Wells machine checked all the circuits and illuminated the red ‘fail’ light.

The parts guy looked surprised.  I told him I wasn’t surprised at all.  He got a new one and we checked it on the WELLS ignition module tester.  It passed with all green lights.


Back in the parking lot, I plugged the second new module in with the same results.  Same A-B-A swap. The old module started the truck. The new one acted EXACTLY like the previous new module, green lights notwithstanding.

Leaving the engine running with my old Duraspark module connected, I walked back into the store to find the parts guy.

“Can you come out here for a minute?”  I asked.

“Sure,” he was more than courteous.

The engine was running.  I disconnected the module.  The engine died.  I connected his module.  It wouldn’t start.  I reconnected my original module.  It started.

“Doesn’t that module have to be grounded?”  I groaned.  Okay, here we go.

“No.”  I told him.   “It doesn’t.”  I fingered the harness.  “See this black wire?  That wire comes from a terminal screwed to the body of the distributor and that’s the only ground this module needs.”  The orange and purple wires go to the pickup coil.  The green wire goes to the ignition coil.  The black wire that is grounded in the distributor provides the ground that the module uses to fire the coil.  The red and white wires are the start and run circuits. There is NO external ground necessary on this box”

He was shaking his head, a little shocked that I knew the system that well, but he remained unconvinced.  After all, how much can a guy in faded jeans and a T shirt know anyway?

We retested the module on the WELLS machine.  It passed (again) with flying colors.  The parts guy was still skeptical.  This WELLS diagnoser was his go-no-go tester.  Yet in the last five minutes he had seen one module fail and another one pass on the machine, yet neither module would start the truck.

“I don’t know what this means…” he muttered,  “I mean, I’ve worked on cars for a long time… ahhh… not professionally, you understand, but…”

“Look, I know what it means.” I tried to be gentlemanly.  “It means this machine can’t be trusted.  It doesn’t load the internal module circuits the way the module is loaded when it’s firing an ignition coil.  It can pass a module with all green lights and the module can still fail to work right.  If I had driven twenty miles to get this part instead of being right outside the store I’d be pretty hot. Wouldn’t you be?  The acid test of whether these modules are good or not is out there, not in here, green lights or no green lights.”

“Well, I just need to refund your money, I guess, and let you go somewhere else.  Do you think you can trust the parts at O-Reilly’s or Advance?”  I looked up at the big AutoZone banner for a second or two. At the risk, of sounding like Mitch Schneider, how could I answer that?  Let me count the ways.

“I don’t actually trust any electronic part that doesn’t come from the manufacturer – when I was at the Ford dealer, I don’t know how many times I replaced aftermarket ignition parts to take care of annoying misfires and the like. If I saw an aftermarket ignition part on a car with ignition-related driveability problems I found that replacing it with an OEM was the wisest thing I could do.”

He gave me back my $23 and I drove down to Advance, where I bought a Sorensen ignition module that worked like a brand new one. I went and picked up the 7.3L block.

Oh, and by the way, I just plugged it in and let it lay on the fender.  When I have time to bolt it down, I will.  Until then, it can ride next to it’s failed predecessor.  My old Ford doesn’t complain much.

That’s the F150 ignition module story.

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