Ok, long story short...

Gas mileage has dropped considerably over the last year and I've done nothing to the truck that would cause this. Recently the fuel gauge has started goofing up (the full til almost empty kinda stuff). I have a lack of acceleration in higher gears. I also have to turn the truck over twice to get it to start after it's been sitting awhile.

I have also noticed a whine that is coming from the rear of the truck, but it only comes when I give it gas - if I let off, the whine goes away.

The air filter is clean. (It's a K&N)
The MAF is brand new. (less than 500 miles)
The IAC is brand new.
Plugs and wires have ~20k on them.
O2 Sensors have ~20k on them.
Fuel filter has ~20k on it (more info below).

Alright - so after using the wonderful search feature here, I've narrowed it down to a few things (or a combination thereof).

1. The fuel pump.
2. The fuel pressure check valve
3. The fuel filter (more info below)

The whining noise leads me to believe it's the pump going out causing the noise and poor acceleration. I also think that if it's going out, it's possible the check valve is going too...

Now, info on the fuel filter...

A little more than a year ago, I had the filter changed at a local service shop when I had the oil changed... when I got home, I noticed I was leaking fuel... Checked it out, and the fuel lines were not secured to the filter (it's only about 1.5 miles from the shop to the house). While securing the lines, I noticed the filter is directional... I just curious if the idiots that couldn't secure the fuel lines could read to get the direction properly...

Which brings me to the next part...
Does anyone know which way the fuel filter direction is... My Ranger's a 1999 4.0 OHV... the filter currently shows a direction arrow rearward toward the fuel tank. I know in some cases there are multiple fuel lines running between the tank and the rails, but I thought it odd to have a "backwards" direction... Can anyone confirm actual direction on a properly installed fuel filter.

(It would also lead me to believe this is a possible cause for the other problem - causing the fuel pump to labor excessively.)

Any direction from some of the techies here?

 

The arrow on the fuel filter is supposed to be pointing toward the front of the truck.

 

^what he said.
dont forget to check tire pressure also... (this would have nothing to do with the whining noise.. but affects gas mileage)

 

To make it a little more narrow - I've checked everything obvious, including tire pressure...

 

You could also have a fuel pressure regulator problem. But I would start by getting a new fuel filter and installing the correct way. It should be installed arrow facing forward.

 

Milage most likely would'nt have anything to do with this though. For that I'd look at plugs, or maybe dirty intake valves, or maybe a dragging wheel bearing / brake.

Yes the arrow on the filter points in the direction of flow. The larger fuel line is your engine supply one (has the filter in it) and the smaller one is the return line (for what the engine did'nt use)

The other lines are most likely evap related. *and* if plugged or cracked they too can effect milage a little. If they are bad enough they'll store a soft code in your computer but *NOT* throw a CEL. It'll only fire off a CEL if it gets real bad. Scan the computer and see if you have anything related to emissions or evap.

Rich

 

"Gas mileage has dropped considerably over the last year"

Let's start from the beginning....
What do you consider "considerbly"? Did go from 15 to 7 MPG? Or maybe 15 to 12 MPG which is normal for winter gas? So that would lead into was it the last year or just this past winter?
Are you the only driver?
Do you let it idle when it's cold out?
Have you changed route to work? At an old job I would go in early and travel the 2 lane. I almost doubled my gas mileage. I was doin 45 instaed of 75 and all the redlights were on yellow that early in the morning.