5.7 intermitant start when key is released?

[Johnc3211]

My 1993 250 EC is giving me fits. I dock it at a marina on Lake Erie. I rebuilt the carb (Weber AFB) and put in new plugs this spring. I replaced the ignition switch a couple years ago because old switch was hard to get key in. Ocasionally over the last 2 years when you try to start -nothing, no click no crank, try again and it works fine. Twice in the last 3 weekends hard to start crank and crank, but when I let up on switch it started. Haven't been to lake to check voltages or conections on wires. Also when I was putting new plugs in I plugged a wire onto a sending unit on the back of the motor, now I get a buzzer when key is on and engine is not running. I have noticed oil pressure when cranking in the past, but didn't think to look lately. When it runs , it runs great, no problem. Sound familiar to anyone? Thanks

 

[Fill Ess]

I've had that problem when the start switch itself was going bad, but I had the setup where the on/off with the key was down in the cabin, and the start switch was on the dash. Another time the dash switch was fine, but the plug/harness on the back of the switch was loose. I also had a sometimes no crank/no start when the shift lever wasn't exactly in neutral.