You were right telling the guy with the Fiat Spyder that he might have a grounding problem, but there’s a specific ground he should check. The fuel pump (in the gas tank) is grounded to the left taillight. He probably needs to sand off the new paint so that the ground is metal to metal.
Wanna guess how I know?
Steve
ExFiatOwner
I had a 1980 Fiat 2000 Spyder with Bosch FI for 15 yrs… The ignition switch contacts are like old points, there’s no wiping action to clear corrosion and burning residue. If the car sat for a few days in high humidity (like Houston…) it was a crap shoot what would work, not start, not run for long, miss, etc… I found the contacts hot and burnt on the back of the ignition switch. Voltage drop was 2-4 volts! I bypassed the FI circuit on the ign switch with a 20amp relay and the car ran well for the 13 years!!