I've noticed the past few days(been warmer) that when I get to where I'm going after a decently long trip(30-45min) that the fuel pump seems to be stuck in high mode.

I did not go over about 5lbs of boost from the time I left my house to my destination to test it. When I first started out the pump was in low mode.

Has anyone had any problems with their fuel pump relay or know of anything that could be the culprit?

 

Man I've been asking the question all last week. I think you answered it though - warmer temps outside. This is what I think is going on:
The fuel pressure sol opens to allow boost pressure keep the fuel pressure reg closed to maintain fuel psi. The solenoid is also opened electrically to allow vacuume air assist pressure regualator opening - loss of fuel pressure ( eliminates inline boiling).

I suspect that maybe the warmer temps are somehow triggering the system to open the regulator valve more which in turn makes the fuel pump run more to make up for the fuel coming back to the tank ( through the opening reg vlv)

Or maybe our pumps need replacing, a new one will tell the truth.

 

I would think it to be the relay more than the pump, I think that the relay that controls high pressure/low pressure is getting warm and failing, allowing the pump to run in high mode.

 

slightly Possible.

I took the seat out to monitor better. Sometimes it runs normally - high at wot only. Then it like goes into a whole different mode - high at like 2 psi boost, different operation but consistant.

Bottom line is the pump is getting full voltage through the relay and the relay is controlled by the ecu. So possibly something the ecu is monitoring is malfunctioning

 

are you still running the stock ecu? Just for reference I'm running the AEM.

 

Stock ECU.

There are 3 FP relays, the 1st 2 work or else the pump will never run at all. The #3 FP relay is energized by the ECM (in your case too I guess) under low - mid loads to open it's contacts, now voltage has to go through the FP resistor - low speed. At WOT the ECM deenergizes the #3 relay closing it's contacts giving the FP full power.

If your #3 relay was bad, the pump would likely run full blast all the time (mine isn't doing that).

FYI the #3 relay is located on pass side eng comp fire wall inbd adjacent to the brake line manifld assy, the FP resistor is right below.

I think we have different problems, mine is something to do with fuel supply, regulation, or monitoring (hope not - ecu). Yours sounds like that relay if it's on high constantly

 

Most people have the AEM EMS either always use the high voltage or it sets to use it at 2500 RPMs or so. Yours may be set up in a huge combinations, there is no way to tell unless you post up a map and have someone look it.

 

Using me as an example, I dont use any of the stock wiring or relays. I used my own relay and have the EMS turn it on and off and the pump is hardwired straight from the battery. I dont care about it running at high voltage all the time. Doesnt hurt anything except for heating the fuel slightly more but unless your racing it shouldnt matter.... unless you have a large external pump which you dont.

 

Would this mean you have a stock FP regulator and FP solenoid laying around that you may want to sell by chance?

 

Mine seems to get stuck in "high" mode after some driving as well. Stock ecu here.

 

Bottom line, the fuel pump runs in "high" via ECU. I know how it happens - ecu removes ground for FP relay 3 providing full dcv to pump instead of 8 vdc through resister.

I just need to know what determines the ECU to do it and for what conditions. Is it fuel pressure in respect to MAF Hz?

 

Sure

I dont know about the stock regulator... I think I know where it is. The solenoid I know where is for sure. Send me a PM and we can work it out.

 

After a "spirited" drive up a curvy mtn road sun. I noticed mine going full blast. It did it for awhile even after the car was off for 20min. I had to drive an hour home and it got quiet again.