This 1977 Ford F-150 has gradually built up a "won't start after sitting for over a week" problem. Once it does start, it keeps starting perfectly all day -- and its on-road performance shows no signs of trouble; it runs great; no stalling, no roughness.
Its emissions seem fineβ¦
2018 - HC 90 loaded, 171 idle / Cmox 0.09 loaded, 0.84 idle.
Though it's a 1977, it has only 126K miles on it; I bought it used in 1987. I've driven it sparingly since 1991, but I start & run the engine regularly to keep it in good shape. The last time it started was in early December 2018; I've tried various remedies (checking ground, etc.) since, with no luck. The battery is new, from January this year.
The last time major work was done on this truck was the late 1990s (carburetor overhaul, maybe other items); as far as I know, the ignition module is the same one as when I bought it in 1987; the plug-in connectors look very weathered on the outsides.
Suggestions will be appreciated!