I was wondering if the PCM or ECM has any control on the LP(flowrate, off/on etc.). More specificly does it control a FASS if you replace the LP with the FASS?

 

The ECM controls the lift pump. I don't have any experience with the FASS, but I would suspect the stock lift pump would be out of the picture at the point of FASS install.

 

I understand the stock LP would be out because the FASS replaces it. WHat I need to know is does it actually control the rate of the LP. If so I would suspect that it would control the FASS as well since they supply it with a harness that hooks into the original harness.

 

I bet the harness is used to trick the ECM in to thinking the LP is still there, no other reason. I think the ECM wouldn't be able to provide enough power to run the FASS, the FASS probably get it's voltage from the battery via some kinda of relay?

 

Mike D,

Thank you for responding but I actually think you misunderstood what I was getting at. I'm not talking about powering the LP or FASS. I'm trying to find out if the ECM or PCM actually controls the flow rate or tells the LP how much or how little fuel to supply like it does with the IP.

 

I guess I was confussed. I would say no, any excess fuel is returned to the tank from the IP bypass.

 

There is a "low flow" function from the ECM that tells the stock pump to run less than full pressure for a couple of seconds on start up. Other than that it's WOT all the time.

The FASS is powered by the battery using the ECM to trigger a 12 volt relay. It's either on or off.