My voltage is acting weird. The truck was down for about two weeks waiting on the pump to get resealed. when I got it running again the voltage drops to around 12 when I idle and comes back up to around 14 with throttle. The truck has a voltage regulator and a new alternator. The truck is a 1991.5

 

Did you check your idle speed with the new pump?

 

Yes. It's right about where it was before I pulled the pump

 

How old is the battery?...Mark

 

If the voltage is dropping to 12, it could be that that is the battery voltage, try checking battery with truck off. It should be near 13 volts or so. If it is good, it could be dropping under load and still be bad. Try turning on the headlights with the engine off and see how far it drops, it shouldn't be too much...Mark

 

Just replaced battery today. Double checked it anyway. Battery with engine off is 12.8v. When I turn on the headlights with the engine off it only drops down to 12.6v

 

But, when you start it and idle it, it drops to 12v? I see that it is a 91.5, that is intercooled, right? I would check all the grounds and connections and then hope that JMartin chimes in, he knows a lot more about pcm equipped trucks than I do...Mark

 

Yes it is a 91.5 intercooled with the voltage regulator on the firewall. I've cleaned all the grounds with sand paper and made sure everything was tight.