electrical wiring has a lot more resistance when very cold and very hot. so a marginal ground will be ok when the weather is temperate and a problem in very cold or hot weather.

check and clean battery connection, ground to chassis and engine to chassis connections. sometimes an auxiliary ground strap from the neg on the battery to a starter bolt will cure a problem like yours when all else fails.

if the ground is good then see above post.

good luck

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.