Hey guys my blazer has been feeling like its starving for power.

It's rough on the start up but once I give it some gas it will smooth out. I figured this might be the fuel pump. It's obviously pumping because it does run and drive. I pulled the two wire plug near the top of the tank and tested the voltage (one wire to the other) and it reads right around 7.5 volts (with ignition on, engine off). This only confused me more.

I assume it should be 12 volts(?) Could the low voltage cause the loss of power and rough starting/idling until I press the gas?

I did recently swap out the gauges (oil pressure, water temp, and volt) for mechanical gauges. I read somewhere not have the oil and water sensor in could mess with the engine computer but I was having same issues pre-change. I also want to mention at speed it surges occasionally with more power.

1991 s-10 blazer
z engine
rebuilt 400 miles ago- new pistons, rings, valve job, msd coil, headers

All and any input/ideas would greatly be appreciated!
Thanks!

 

you should have 12v at the fuel pump . there are a few poeple that have had issues with the ground wire . i would start there ! its just in front of the rear bumper about in the middle on a crossmember under the tail gate.