I have a 96 gmc jimmy 4.3L Vortec, every time it rains it doesn't want to start, it cranks there is fuel because I hear the humming of the fuel pump and press tire value under hood for fuel and fuel comes out. I have changed sparks, wires, cap, rotor, ignition module and coil pack. I had this problem like two weeks ago in the morning but after 10 hours sitting without rain it started up no problem. What can I do?
Rain or Shine Do below and get back with some testing results
Next time it refuses to start don't wait for it to make up its mind-do below immediately to determine if its fuel or spark problem
Get a helper disconnect a sparkplug wire or 2 and ground it to the engine atleast 3/16 away from ground-have helper crank engine over-do you have a snapping blue spark? If so-you have a fuel related problem, Do you hear the fuel pump come On when you turn key on? If not check fuel pump fuse and fuel pump relay if so, check the fuel pressure to rule out the fuel filter/fuel pump/pressure regulator and listen to the injector/s are they pulsing or hook up a noid light. No snapping blue spark continue to troubleshoot the ignition system-power input to the coil/coil packs, coil's resistances, cap and rotor, distributor pick-up coil, ignition control module, cam and crank sensors and computer Note: If it doesn't apply disregard it and keep testing