Ok here goes. the truck is a 1994 s10 with the 4.3 tbi 4x4. we removed the engine to replace all the seals and gaskets in it. it has sat for 11months since we pulled the motor out. recently we got back at it and put the motor back in. the issue is...there is no imput to the fuel pump relay from the computer to turn the fuel pump on. if i hook a jumper into the relay, the pump runs. if i crank the engine over with the pump jumped no fuel is spraying into the throttle body. so it seems that the fuel side of the computer isnt sending signal to make the truck run. I poured some gas into the throttle body and the truck will run untill it runs out of gas. so the ign side is working. I have checked the 4 grounds on the back of the block. they are good. i just put a new oil pressure senser in it thinking maybe the old one was bad. no luck. so is there a saftey somewhere else in the system that i dont know about? I am having a hard time thinking its the computer, because the truck ran when we started this project. any input would be helpful

 

heres an update, I replaced the computer....no fix..[]

 

Mine did the same thing. I replaced the head gasket, did a valve job. It ran good but had a leak at the freeze plug on the back of the block. I pulled the engine replaced the plug and installed a new clutch. Put the engine back in and now there is no signal from the computer to the fuel pump relay. I've checked every ground and plug thinking maybe a pin was bent. All were good. I pulled the computer and ran a 12v fused 5amp wire to the wire that goes to the fuel relay. The fuel pump ran so the circuit is fine. My question is, is there something outside of the computer that tells the computer to fire the 2 sec pulse to the fuel relay when the ign (key) is turned on?