Good morning everyone just wanted to touch on a subject about returnless fuel systems and there limits.
I?m working on a Roush truck for a while now trying to get it mechanically sound since when the customer brought it to me the truck was in ruff shape. The truck has new high flow cats, +6 lower ring, 60lb FRPP injectors, new coils, plugs, exhaust system due to the factory system rotting out basically. Beside those few things the truck is pretty much stock or as it came from roush big 108mm maf system and M112 blower with IC. Also just replaced the Intercooler pump due to it being failed and urging the customer to buy the part due to the increase boost level and heat it can produce. Now the fuel is dialed in the timing is good but I?m having issues with the returnless fuel system at 100% load or over, truck usually will max out a 1.54 to 1.64 air load depending on the conditions of the drive and environment.
As I watch the log I notice vct operation is online no out of whack phasers or vct commands, the maf is reading good with no weird dips or out of sorts data, but one thing I do notice is on a wot tip in the fuel pump will fall below the specified 39 base psi it?s suppose to be at down to 28 psi or even 25 psi at times.
I have played with the FPDM voltage tables a little but nothing seems to correct this issue as far as calibration goes. I have since replaced the fuel filter which was probably honestly the original from the truck it was horrible and full of grit. I haven?t put my mechanical gauge on the rails yet to check actual fuel pressure incase the sensor is going bad which I will do this week when I have the truck a few day to diag a miss on 1 & 2.
Do you guys think I?m maxing out the fuel pump or the fuel pump is so old that it?s just not able to supply the fuel to the truck anymore?
I mean cursing and up to 80% load the truck is perfect or as good as I?d expect for what it is but the wot tip in is just not right and every time I go back and look at logs it?s always the fuel pressure dropping to low a lot of times triggering a P0191 code (fuel rail pressure range performance) any input would be appreciated or tests I can try to see if I can fix it in the calibration.
Attached is a photo of what happens through out a pull.