My 95 blazer with a 4.3 started to overheat the other day while my wife was driving it ho
E the other day. When i got home from work i started the truck and it ran fine, so i went to get a thermostat to put in. When i went to move the truck in the garage it wouldn't cycle the fuel pump.

This is what I've done so far:

Checked the fuses and relays and they are good.
Replaced the oil pressure switch.
Replaced the fuel pump and strainer.

After we replaced the pump still nothing. Tested at the test lead and it cycled fine. I know that a lot of the fuel system stuff can be ran through just about anything including the radio so i am wondering if there is something that isn't allowing the pump to cycle, like maybe the temp sensor or something else. Any help would be great thanks.

 

Confused, does the truck run?

 

Does not run. Fuel pump will not cycle fuel when you hit the key.

 

At the fuel pump module connector:
The grey wire must have battery voltage for 2 seconds when the ignition is turned to the RUN position, then drop to zero volts.
The black wire must have less than 5 ohms resistance to ground at all times.

FYI: The oil pressure switch will not stop fuel pump operation. The switch only provides an additional path that allows for increased amperage flow to the fuel pump when the oil pressure is above ~7psi. GM realized it wasn't necessary so 1996 and newer S&T bodies no longer have the circuit.

 

Simplest thing to do first is check the ground wire on the top of the rear cross member attached on the passenger side of the fuel filler neck (unless you have a two door). Mine came loose for no reason one night and it took me forever to figure it out.

 

Have a whole new set of problems. I checked to see if i had spark and i don't have that either. Thought that maybe i cooked the computer when it overheated. But that wasn't the case. Distributor maybe? But why wouldn't the fuel pump work. I also have a constant 8.6 volts at the fuel pump module plug and it doesn't move when i turn the key. Really starting to hate computers on vehicles right about now.

 

Have you had the battery on a charge through all this. Still got 12 on it? What were you using for ground when you got the 8.6?

 

if it's a 2door check the ground bus under rear bumper. it's got 11 wires that run into it w/ a blue cap. pull the cap and check for corrosion. this worked for my fuel pump problem, only after replacing the pump w/ no luck.. checked it. mine was burnt on 1 ide