Ok guys here's the deal.

1986 F150 302 V8 4x4
note: has adjustable fuel regulator

At idle fuel preshure gage reads 35 and ticks about every 5 seconds down to 33.

When i drive the truck with the pedal halfway down its fine.

When i drive the truck with the pedal all the way down and the RPM's get up to the point where its gona shift the truck STALLS, STUMBLES.

Im thinking its a fuel pump problem (the one on the rail).
But i don't have enough expirance with fuel systems to know.

Please help i have sunk about 3500$ in rebuilding this truck and im about to take my rifle and punch a hole in the block. im so god damm frustrated.

Vacum system is fine.

Everything iv'e done on this truck:

Fluids:
„« Engine Oil
„« Coolant
„« Transmission Fluid

Ignition:
„« Wires
„« Plugs
„« Cap
„« Rotor
„« Coil
„« ICU (Idle Control Unit)
„« Throttle Plate Sensor

Electrical:
„« EGR Valve Sensor
„« Coolant Temperature Sensor
„« Coolant Sending Unit
„« Nock Sensor
„« O2 Sensor
„« New Battery
„« New Battery Wires
„« New Starter Motor
„« New Starter Motor Solenoid

Engine:
„« Intake Manifold Honed
„« Two-Step Cam
„« Both Heads Machined and new valves
„« New Water Pump
„« New Timing Chain
„« Smog Pump removed

Fuel:
„« New Fuel Filter (Rail)
„« New Fuel Lines
„« Adjustable Fuel Regulator

 

Could be the pump on the frame but I would suspect the pump in the tank. Sounds like you have decent pressure but when you have a high volume situation it starves out. Have you dead headed the system and checked max pressure?

 

1. If it has the fuel pump in the tank, it could be the pick-up filter on the inlet to the pump.
2. Is the catalytic converter clogged?

 

i have the EXACT same truck with the exact same problem before you go and shoot it and spend money on electric fuel pumps under the truck drivers side inside the frame near the transfer case should be a canister fuel filter with a heavy steel guard 2 bolts remove the guard use lots of wd-40 or some other penetrating oil on the bolts remove the guard use a small oil fliter wrench or a strap wrench and remove the fliter cover have a bucket handy to catch the fuel that will drain out replace the fliter and reinstall the guard. im now in the habbit of doing this every 6 months and like you i did the fuel pressure test and had the same readings and assumed fuel pump when i went to find it i saw the filter and decied to try that first. let me know how it goes i have plenty of other ideas.

 

Ok i forgot some things on my list

New Exhaust system
New Intank Fuel pump

Teh_Brown_Beast
Im gona try your sugestion first. To be honest with you i hope i see a very dirty filter so i can finally fix this problem.

 

WoW, Teh_Brown_Beast!!!!

THAT WAS IT!!!

THANKYOU VERY MUCH!!!!

I really can't belive changing the canister fuel filter fixed the problem!

Teh_Brown_Beast you have solved a problem that four shops with dynos couldn't figure out.

THANKS AGAIN!

 

Great solution. The only thing worse than being at your wit's end is being at your wick's end.