I just replaced the factory lift pump with the Carter Black from Summit. I installed it with the 3/8 line and stock banjo on the fuel filter. The electric quage is connected to a tapped banjo bolt on the pump followed by a 30" stainless 1/8 inch line. This is what it reads, At Startup it fairly slowy climbs to 12 psi. At 60 mph it is around 7-9 psi. Floored it is at 5-6 psi. After it is warm it will Idle at 9-10 psi. Could this be a dirty fuel filter? Bad qauge? Normal? Fuel filter was changed about 6500 miles ago. I though it would peg 15 psi. Any thoughts?

 

Hmm, I don't know which model the stock LP is but I know Carter made that one too.

 

Is the Carter pump a #4601HP? If not, it could be a lower pressure internally regulated unit which would be the wrong pump for this application.

 

Yeah Its the 4601hp. I changed the fuel filter today and it went up to 14 psi And floored went to 9 as the lowest I drove it for about an hour total. Now on the way home it just dropped back to 9 psi <edit>. I can floor it and touch 3 again. What do I do?

 

You get a new lift pump, that's what you do! Or a FASS, or RASP, or Air Dog.

 

Also see this thread........

https://www.dieseltruckresource.com/...threadid=74469

 

That thread may be it. I left my lights on yesterday and drained them both. But why would it work fine and then out of nowhere not? Does the ecm vary voltage to the LP? Could I use a relay to just give it full power? It would be easy. I will check the voltages of both batteries tommorow at work and post the results then... At work. ha I hope this is it.

 

I will also check the voltage at the LP.