Black Oak 2006 F150 RS3

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.

Here is a attached photo of the fuel pressure around 4700 RPM its extremely low

On another not im chasing a miss on cylinder 1 and 2 but mostly 2 this week I should have the truck to compression test and do a leak down test to see if the head has a valve issue. The truck is old and I'm Trying to help a customer out and get his stage 3 Roush back to its original condition with some improvements. The PCM recorded a total 4miisfires o cylinder 1 & 19 misfires on cylinder 2 in the last few weeks of him driving the barometric pressure was accurate for our location and the Hertz were 155.06 which means the cats are working and doing there job. Now the freeze frame data for the misfires recorded at 105 load. I did pull the plug on cylinder 2 which I just replaced all 8 them a couple months back and gapped to 32 my problem was the plug looked like it was brand new and had no evidence of any combustion evets which is worrisome to me. So this week ill look deeper in bank 1 and see what's going on, The odd thing is the engine has no abnormal top end noise its actually one of the quietest 3 Valves engines I've heard in a log time.

Can the low fuel pressure issue be contributing to my misfire issues at high load usually when a vehicle is missing its constant this is interment. I did ran the power balance test and 2 was alive the other day with a slight miss even at idle which comes and goes.

Again any insight is appreciated thanks again fellow tuners i do appreciate you guys that can help.

One more thing to look at is the Fuel Pump Driver Module. I had intermittent fuel problems on mine until it finally failed. It?s located at the rear frame above the spare tire. Gets corroded easily.

Ya I have to pop the spare down to fully inspect it but when i did have it on the lift I did use a mirror to make sure it didn't have the corrosion issues and looked good but next time I work on the truck ill give it a good look. Hopefully we can upgrade the pump to a dual setup Holley is basically giving away the fuel pumps at the moment and told the customer to capitalize on it while he can.

So finally pulled the spare down this evening and checked out the driver no corrosion on the unit that made it through the case. I cleaned the frame where it sits and installed a couple rubber spacers so it doesn?t sit on the frame and has some room for debris to fall through. I replaced the fuel pump tonight as well with a dual pump unit that I been wanting to do that way at wot it does not have the fuel pressure dip around 3500 like it can?t keep up. Anyone have any issues with miss fire on cylinder 2 & 7? The vct system is actuating as commanded with little error and hovering around zero at idle. I replaced plugs and gapped to .32 I will pull cylinder 2 and 1 and swap them to see if it is the plug since the coil swap changed nothing. Just let me know your inputs getting a smoke machine tomorrow I swear I hear a leak towards the back of the intake took my camera scope and the booster line looks to be on but is oily and swollen it may have a small leak I just don?t see the smoke will show all.

Got the truck to back to normal and running better than ever. Fixed all the misfires and wiring hiccups so far to the truck. Also installed a twin fuel pump assembly and dialed in the FPDM on the truck with a consistent 39.15 psi base pressure with no lean spikes. I still personally think cylinder 2 has some damage on the top ring possibly from the customer running 87 so i took it on a few road test filled it with $50 of 93 and the truck is on point. Now on to the next issue the huge vibration at 45 to 60 mph this is either due to the torque converter, the drive shaft, tire balance, or rear axle only time and proper diag will tell.

SIDE NOTE: The customer did break the flex plate in the last few months as well as broke the universal at the rear axle of his drive shaft. Then dragged the shaft a half mile down the road i went on a road call fixed the drive shaft and sent him on his way. Only problem was the damage at the universal holes in the axle had to file some material to push out the old pieces and install the new one due to a chip. I dumbed down the power some for safety but this guy loves to beat on his truck even when things aren't right and I tell him to take it easy. I shouldnt complain cause it just makes me money but I like it when things last and are properly maintained.