Greetings Ford Six Fans,
Made great progress on the Ranchero while watching the HOUSTON ASTROS (my hometown team) win the world series!
It seems that the inability to start was caused by:
* Bad ignition switch wiring (replaced the connector and wiring)
* Corroded terminal on coil wire (replaced the coil wire with an excellent MSD specialty coil wire)
* A loose connection from the battery to the MSD 6-AL (large red wire)
This last one was strange:
I have a terminal block below my battery; I like this better than having several connections hanging off of my + battery terminal. The loose connection was the one from the + battery terminal to the terminal block. With the engine off and the alternator supplying no power, the loose connection was supplying all the power to gauge lights, tachometer, oxygen sensor, stereo, etc., and all of these things seemed to work continuously. Can only surmise that, because the MSD operates at the millisecond level, even a very slightly loose connection can cause it to misfire. Cleaned the copper lug and wing nut with a wire brush and tightened the connection, and she started immediately! Of course, at that point I had already replaced the ignition switch wiring and the coil wire. The magnetic pickup and coil were also replaced in the process; let's consider that a tune-up. When I started troubleshooting, did not realize that the ignition setup in the Ranchero was two years old (although, with only 2,000-3,000 miles).
Back to the issue that caused me to originally create this post - after replacing the ignition switch wiring, replacing the coil wire and fixing the loose connection, the Ranchero started very easily and idled well, but wouldn't rev without backfiring. This time I realized that this only happened if the vacuum advance cannister was connected to vacuum. I disconnected the cannister and was then able to rev the engine without the backfire. The Ranchero will now start very easily and idles well, but doesn't rev as easily as before, and runs very lean (15.5 - 18) at part throttle acceleration and cruise. Was able to drive it around the block, but I'm worried about the lean condition, and it's not running as well as it should.
I did re-check the initial timing (was probably at 24 degrees, backed it down to 20), set the idle mixture (idles at 12.5 - 14.5 now), and set the idle speed. If driven very conservatively, building RPMs gradually, the Ranchero runs well enough to drive it a few miles, maybe to a car show or cruise-in. The accelerator pump on the carburetor is definitely working - I can see the jet of gas when I work the throttle. The main circuit/jets must be working or I wouldn't be able to rev the engine up to 3,000 RPM.
Since the engine backfires if attempting to rev with the vacuum cannister connected, there must be some issue with the distributor. I did verify that the vacuum advance cannister moves if vacuum is applied (tested this with a Mighty Vac). Holding a timing light on the engine while revving it, the timing does generally advance, so the mechanical advance must be working, at least to some degree. The timing isn't "going crazy" (moving all over the place) as I was told it would if the polarity was reversed on the magnetic pickup.
Thanks,
Bob