Hi i am having a fuel pressure problem

This is my hardware
quintum 365lph fuel pump
pump is hard wired
standard fuel lines
standard fuel rail
a1000 aeromotive fpr
id1000s
95octane

car is making 400whp on 17psi
gt3582r

fuel pressure
ignetion on 62psi
idle 56psi
wot 78psi

So my problem
Car starts fine no problem
i drive it for the first 10 min no problem
then when i go full throttle the fuel pressure rises to about 68psi and then drops off to 35psi causing it to go lean

Stuff i have checked
i have removed the standard filter element from the pump hanger
installed a high flow inline filter
installed a new fuel pump,same problem
changed the fpr
drilled a hole in the top off the hanger to look with a endoscope if the fuel level runs low in the fuel tank,it does not run low

what els could i look for

 

if you are losing pressure at full throttle it can only be a few things...

pump, line restriction or clogged in line filter.

typically if you dont have enough fuel, your pressure will be fine at lower rpm's but then will start decreasing as the rpm's go up (cause the duty cycle goes up)

 

Ok
BUt why only after a 10 min drive
It goes full boost 8000rpm every time ,for the first 10 min

If it is one off the above wont it do it from the begining

Thanks

 

Have you logged your battery voltage during WOT?

 

The car had the same problem with the original wiring to the pump
Then i hard wired the pump with a 40amp relay direct from the battery
and it still has the same problem

I have not logged battery voltage during wot,
Brand new battery installed

Thanks will check voltages on wot

 

Voltage to pump is 100%

 

20+ PSI too high.

 

Are you on stock fuel lines?
62psi base pressure seems extremely high. Try to lower it to 43 and it should fix your issue if you are on the stock lines.

 

you have your regulator hooked up to the manifold right? It needs to be boost referenced. Also maybe your base pressure is so high that when your regulator tries to increase it with boost your hitting the bypass in the pump itself. People often modify walbros to increase the bypass pressure in the pumps. Maybe your pump has something similar. Something else to think about, pressure at the pump itself is going to be higher then at the rail.

 

The pump i am using relief valve pressure is above 120psi

 

if i drop the fuel pressure the hole fuel map will be lean?

 

Yah it might need a little bit of tuning.

Unless you specifically test for it, you don't really know what the pressure at the pump is. Its for sure going to be higher then at the regulator though. So it could be that 75-80 psi at the regulator translates to 120 psi at the pump. With the way the pumps flow drops off at higher psi though I would think lowering the pressure would help.

 

You mention problem starts after 10min, but does the system work as designed prior to 10min? Pump cavitation can be an issue if the supply side of the pump is clogged or if fuel temps get too high.

Also, read this thread.
https://www.evolutionm.net/forums/ev...ease-help.html

 

Have you tried swapping out another fuel pump? (Completely different brand). I had a similar issue with the AEM pump, swapped a new walbro 255 in and my issues were solved.

 

what happened with AEM? I don't have a fuel pressure gauge to watch my pump.