My brother had a mechanic check out his '96 S-10 truck due to starting problems and found out it was the fuel pump. He took off the bed, replaced the fuel pump and put the bed back on but didn't tighten the bolts. It started up fine, so he tightened the bed up, tried starting it up again and now it won't start. He says the fuel pump isn't engaging and he can hear a clicking coming from the engine - this may just be the starter though.

Any ideas?