I have a 1995 gmc pickup with the 5.7 vortec everytime it rains the truck will not start I have changed the cap, rotor, wires,coil,ground strap and even the starter but nothing has helped
I will try that thank you very muchRemove the Distributor Cap without changing the physical position of the Distributor Body in the back of the Engine Block. CRC has some Electrical Contact Solvent that should be sprayed around the inside cavity of the Cap and any residual moisture driven out. Next... focus your attention on the RUBBER or PLASTIC Grommet where the small wire bundle feeds into the outer body of the Distributor... you should see a small depression where Rain Water and Ambient Moisture can settle and invade the interior of the Distributor...essentially short-circuiting its operations on "Rain Days".
Get some High Temp RTV and seal around that Grommet after wiping down the area first with a non-oil solvent... the CRC will do nicely there as well. Allow the RTV to cure well for around 15-30 minutes without starting the truck engine to accelerate the Cure Time. You should be able solve the rain water issues in this manner. If you have accidentally moved your distributor body when working back there and now the truck engine is hard starting... we have a post that has ample information needed to set things right. Remember to allow any moisture still present in the cap and body of the distributor to completely dry out before applying the RTV. Good Luck.