Engine/Transmission (1994 - 1998) raising fuel pressure on p-pump?

[Cummnzpowr]

i have a friend with a 98' 215 truck... . who not only is {stock} but gets 9 mpg empty {4x4,ext cab,auto}. He asked me to ask about raising fuel pressure on these pumps?... can anyone answer me this? will this give him better milage as well?:{

 

[Missouri Mule]

Cummnzpowr,

Yes increasing fuel pressure or amount of fuel going into high pressure lines usually increases mileage.



But first has your friend check all other posibilities as to why is mileage is so low.



I think there is a big problem with fuel system, turbo and other related components, fuel guage is reading wrong or odometer/speedometer is way off.



You/friend can turn afc screw up a few notches to increase amount of fuel in relation with boost.

Boost guage, EGT gauge and fuel pressure guage are a must for finding where is engine/fueling/boost are at, they can be installed or use hand held ones.



Check for fuel leaks from fuel tank to injectors, air leaks from turbo to intake manifold.

Do fuel pressure test to see if transfer pump is up to par, overflow valve is working and no blockage in fuel filter/ fuel heater, prefilter/ fuel lines 9 mpg is way to low for being empty.

 

[Cooker]

What it is fuel pressure at now?



Before raising the pressure, you should get a baseline to see where he is at. If your pressures are within specs, I see no need to raise it, and you should start looking else where for the reason for low MPG's.



I don't think raising the fuel pressure over stock on a stock or mildly BOMBed engine, that it will increase MPG's. I ran 45psi (at idle) of fuel pressure for over 10k miles and after dropping it down to spec (I think mine it 25psi at idle now) I noticed no change in MPG's. On a heavily modified engine, this may not apply.



-Ryan