Bman2000

Ok so like the title says. I had my dyno time. I made a whopping 335rwhp with the super conservative base tune timing curve. 8psi ect. Disappoint numbers, but i ran into another issue. Currently my rail pressure goes from 40 nice and solid, then i hit about 5300 and the rail pressure just drops to 20psi, and shortly after around 5800 it starts to go lean. So a little more info, the dyno sheet shows a spike in fuel richness starting at the same time rail pressure drops and ending at 5500, where it goes from 11to1 back to 12to1 over 500 rpm then starts leaning out quick.

So i guess at this point i have a few questions, that stuff doesnt make sense to me, how i could lose rail pressure but yet it get rich? even if it is brief. Now i know at this point its fuel pump related but heres where i need more information. I have no clue how to actively test the voltage to the pump? at the pump? Basically i need a way to find out for sure if this brand new ford gt supercar pump is failing. Because they arent cheep. The fuel filters new, as far as i know the lines are clear. The mods to get the pump in were cut factory harness and splice in the new connection, pprv delete with a metered relief hole (it wouldnt stay attached to the basket kept blowing the fuel line) and holes in the bottom of the fuel basket. Im just letting everyone know what ive done, so that maybe i can get an idea of what the heck to do. This car should be making almost 400 and its sucking me dry not working right. Ideas welcome.

Lastly anyone know the cost of a return style swap? cheep version without the cobra tank? Also is there tuning issues with this system being a variable voltage fuel vs constant?

Thanks

cliffyk

I would first suspect the FRPS as I understand that they can be damaged by fuel pressure spikes that occur when high capacity pump(s) are installed. Kenne Bell makes a restriction disc that mounts under the FRPS to dampen such spikes and offer a measure of protection for the sensor.

To check the fuel pump voltage you can test the voltage at the FPDM as shown below, or monitor the duty cycle of the PCM-->FPDM command signal--this will require an oscilloscope...

Bman2000

Wouldnt a damaged frps be a more....broken thing? Like if its damaged i would think it wouldnt work right at all? Id be happy if thats all it was though since its way cheeper and easier than pump stuff. I have had a few spikes when i first did the pprv delete that set off the sel, but only happened twice, hundreds of miles ago, hasnt happened since?

cliffyk

They get confused--not 100% broken...

Bman2000

is there a way to check the frps? since it seems to be working fine normally, other than the massive drop. Or is it one of those, if you suspect it replace it things?