I experienced a new-to-me form of failure a week or so before Christmas, and thought I’d share the details, since even a pretty detailed Google hunt failed to turn up any other account of this problem.
The vehicle is a 1996 Ford Econoline with a 300 I-6. After driving around perfectly for an hour, it suddenly lost most of its power mid-drive, running smoothly but unable to exceed about 10mph. Manual shifting of the C6 proved we still had both first and second, and it still started acceptably (if weak), with no sign of engine shakes or cylinder misfires. A quick roadside diagnosis showed no new codes, nothing out of the ordinary in the OBD II data stream, and a look at the distributor indicated it was still tight and hadn’t shifted from the previous owner’s paint mark (which was correct, I’d checked timing in November after purchasing it).
After a tow home, I began diagnosis. After eliminating some of the other basics, I got the timing light out, and found it was running with a base timing of about 20* ATDC. Loosening the distributor hold down and twisting in about 30* more timing immediately removed the symptoms. Then, it was time to find the cause.
With a loose hold down bolt ruled out, the usual suspects would be the timing set, the distributor gear at the cam, or the shear pin that holds the gear to the distributor shaft. A dead timing set or stripped distributor gear usually mean no start, not timing slipped. I suspected the shear pin might have went, with the gear just tight enough on the shaft to have “stuck” after losing some timing.
I pulled the cap and rotor, and everything looked normal at first glance. Here’s a shot after having pulled the distributor.
However, once I grasped the shutter wheel and gave it a bit of light torque, I immediately felt a “notchy” click, and was able to rotate it. The possibility of a magic “half-stripped” distributor gear went briefly through my head, but it didn’t take long to realize the distributor shaft wasn’t turning at all. In fact, the shutter wheel popped right off in my hand.
At that point, it was obvious what had happened, though I still can’t point to why.
I pulled the distributor, verified the gear and shear pin were in fact fine, and popped in a NAPA reman, which was the only thing I could get locally that day. The failed unit was a Richporter Technologies, and the NAPA is a reman Motorcraft.
I still have no clue why the original distributor was replaced by the previous owner – I’ve never had an original actually fail, and this engine has pretty low mileage for a 300. I’m guessing his mechanic swapped it in when they were trying to hunt down a SPOUT circuit error, which I suspect is part of why I got this van so cheap. That was something simple I fixed five minutes after we bought it – a slightly loose terminal at the back of the SPOUT connector. Haven’t had a single real issue with it other than the SPOUT issue and the newly failed aftermarket distributor.