Ford 4.0L Fuel Pressure Help

thede04 · Nov 30, 2009

My 99 ranger has a 4.0L OHV engine and people are telling me my 64psi of fuel pressure is way to high...others are sayin its perfect...my buddy has a 2000 with the same pressure (same engine)...and my book tells me it needs to be 35...also there is no pressure change when i disconnect the vacuum from the pressure regulator..(there is vacuum in that hose)..also the book says something bout blowing back in the fuel return line...There is NO return line...WHATS WRONG HERE...can someone help me????

Ranger44 · Nov 30, 2009

On your 99' returnless system(95'-00' on OHV 4.0), 60 psi is normal.

30-35 psi is normal on 90-94 return systems.

What are you trying to diagnose anyhow? Any particular reason for checking the pressure?

Ranger44 · Nov 30, 2009

Btw, returnless means no return line. The pump on EEC-V is controlled by the PCM. The PCM turns the pump on/off as pressure and fuel is needed.

On a return system (EEC-IV), the fuel is at a much lower pressure. It's cycled through your fuel rail once about every 40min (the entire contents). This increases evaporative emissions, so that's why the 1st mentioned method is used.

thede04 · Nov 30, 2009

Thanks... i had just looked in my shop manual for it...and it said 35psi so i just checked it for the heck of it...and it read 64psi so just made me wonder whats goin on.......also maybe someone knows what i could try next to get more mileage out of it hwy is only bout 15.5 mpg....replaced air filter, fuel filter, spark plugs and wires still same mileage...the truck has 168,000 miles...or does anyone know what mileage its suppose to get??

BlackBII · Nov 30, 2009

15mpg and 4.0 doesnt sound too off.. (my 4.0 gets about 18)

If you drive it like a grandma, you should be able to squeak in at 20mpg.

You have a lift/bigger tires at all?

thede04 · Nov 30, 2009

no lift just its got 265 75 16 tires on it...i thought it should get 20 but ....o well..thanks guys

dangerranger4.0-94 · Mar 15, 2014

I'm having similar problems but my FPR isn't opening up. And I'm getting 7.5mpg. I've replaced it twice and still won't open. I checked my vacuum and it's getting plenty of vacuum. I'm stumped on what the problem is.

Ford 4.0L Fuel Pressure Help

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