Runs Great then Quits

Q: Runs Great then Quits

My problem is my 1968 – 350 runs great in the garage but stops on me under power or extended road work. It can go for days without shutting down and then when I think the problems solved, wham! The motor will sometimes start right back up (sometimes rolling in neutral) or I may have to wait five to twenty minutes. This has been happening for six weeks. I have tested or replaced the following.

1. Fuel pump, flex lines, Carb. Note: No residue in carb fuel line filter

2. Complete tune-up with points, condenser, rotor, cap, wires & coil.

Note: Dwell & timing stay perfect. Anyone out there with an idea.

A: It sounds like you’ve been guessing instead of diagnosing. The next time it quits and stays dead, check for fuel and ignition. If fuel, it may be vapor locking in the steel line, or a fuel pump that’s weak. Could also be a problem with the tank, maybe there’s not enough venting, causing the tank to have a vacuum in it preventing the fuel pressure from being maintained. Ignition is likely to be a bit easier to troubleshoot, unless it’s something weird like a loose wire in the ignition circuit or such.

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