1. Home
  2. General Ford Forum
  3. 99 Ranger 4.0 - Fuel Pressure problem

99 Ranger 4.0 - Fuel Pressure problem

Having problem with my 99 Ranger 4.0, rough idle, rough starting. Bought it last summer with 105,000 miles on it with unknown service past Problem is sporadic sometimes idle is good and other times it's so rough that the truck dies while backing out the drive (usually it's the worse when the engine is cold). I have replaced MAF, idle control valve, plugs, plug wires and the ignition coil; all with really no effect expect after replacing the MAF, the truck has much more power but idle is sporadic with roughness.

In thinking back about the idle problem and having poor gas mileage, I started thinking more on line of fuel issues; I bought a fuel pressure tester and checked it. To my shock the fuel pressure is 65 lbs at idle, as I understand according to my Chilton's book the pressure should be more like

30 lbs at idle. Would I be correct to replace the fuel pressure regulator? to my understanding the regulator on the 99 is a non-returning regulator so a plugged return line wouldn't be the issue.

Any thoughts on this?

Reply to
Just me...
Loading thread data ...

throttle position sensor.

Reply to
Doc

His TPS doesn't have a damn thing to do with fuel pressure. He's on the right track with the fuel pressure regulator. Bob

Reply to
Bob

The fuel pressure regulator is what you need assuming you have made sure the vacuum hose is properly connected. If it does not respond to vacuum at the regulator, then the regulator is bad. Around 35-38 is normal at idle. It can go lower or higher depending on vacuum. I have played with a hand pump and watched the vary between 20 and 45 psi. 65 is WAY too high

Reply to
lugnut

You guy's are missing the boat. The fuel system on this vehicle does not have a external mounted regulator and return line; i.e. a returnless fuel system. There are no vacuum lines on the regulator. The fuel pressure specifications are 56-72 psi. The basic engine needs to be checked, ( compression test hot and cold ) before any electronic diagnosis is attempted. It also needs to be questioned of the actual idle quality, does it truly idle rough or is the idle quality the same as the same year vehicle?

Reply to
Thomas Moats

Reply to
Bob

Reply to
Thomas Moats

Reply to
Bob

Reply to
Thomas Moats

I have checked the cylinder compression and all is well; After more research, there is a common issue of bad intake gaskets with the Ford 4.0's.

I plan to replace the upper & lower intake gaskets this coming weekend and go from there....

Yes the fuel pressure is in the right range, the Chiltons book does not describe the proper pressure and is wrong (at least the one I have) so my fuel pressure is not out of range as first suspected.

Reply to
Just me...

I think I'll just tuck my toolbox between my legs and disappear into the woodwork.

Reply to
lugnut

Why? You were just not aware that there was some evolution.

Reply to
Thomas Moats

Things like that make me more aware of my oldfartitis syndrome. Hell, I've even gotten to like my CV almost as well as my F150. I've lowered my dream car sights from a Porsche Carrarra TT to an '05 Stang GT-R but, Raquel Welch is still looking pretty good.

Reply to
lugnut

And ya know? She still does.

Reply to
Thomas Moats

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.