i have a 91 chevy s10 blazer with the 4.3 v6. my problem started as a fuel pump working intermediately. so i replaced it and the truck ran fine for a week. when i turn the key the fuel pump wasn't engaging. the wire for the gauge has power but not the fuel pump. so i bypassed the wire and ran a wire straight from the panel to a toggle switch to the fuel pump. Now i got gas to the throttle body but its not spraying into the intake. i need to know the steps to troubleshoot this problem. i was told i cant run a toggle because the fuel pump relay works with the computer. i

 

Thats right, you should not hard wire due to the in-line realys work with the ECU and the PCM for engine management. If with the factory wires it was not working then I would find the fuel pump relays and replace those first. That could be the route of you problem there.

 

Does your check engine light come on? I would start by checking fuses, and fuseable links.

 

ok the fuel pump relays are bolted to the firewall by master cylinder. i believe my short is between the fuel pump relay and the pump. but tracing it down seems very tedious. i have changed the relay to the pump already im just not which one of the two is to the actual pump. i checked for power at the harness with the key turned and onerelay was hot and one wasn't. so im getting the gas to the tbi just nothing spraying out. how should i go about this problem. im an apprentice electrician thats just learning but willing to learn i've done all my own repairs for the most part by being told what was wrong and being able to fix. thanks

 

i need to get the schematics for the fuel pump relay and pump and that would help. is there a way i could bypass somethings or rewire myself leaving the factory wires in. when i turn the key the pump isn't turning on but i have power at the harness where it plugs in to the pump. pulled the tank and replaced the fuel pump and ran a better ground to the frame. nothing so i took out the tank and checked the pump and it was working. check power again and the wire to the pump isn't hot but the wire to the fuel gauge was. so i thought i put in switch and just turn the pump on and off. did that and i was getting fuel to the tbi. just nothing spraying out to start the truck. so father in law says try a new computer but i can't bypass the relay and thats why the computer isn't getting a signal....right? so im stuck need schematics for 1991 chevy s10blazer 4x4

 

I'm thinking that you need to look further into the non-spray, and not the electrical issue. If your fully connected to the relays behind the glove box, and not getting a fuel pump whine, the ECM may believe that you have enough pressure to start. Thus not always sending a signal to the pump harness. I would make sure you don't have a clog in the filter, or with a leak-down test checking to see if the fuel that is in the TBI is leaking possibly into the upper plenum. I had a similar problem, and after a new pump found my FPR to be leaking and dissapating the 60psi needed to start. However this is only a home-schooled mechanics opinion, so trust the evidence.

 

so the relays are located behind the glove box by the computer.