Horrible MPG... 2-3 MPG... Help!
 

Hi all,

I've got a pretty nice 1996 Ford F150 XL with the 4.9L I-6, E4OD automatic, 3.55 rear end, and have a really big problem with it.

Somehow it's getting only 2-3 MPG. Yes, you read it right -- two to three miles per gallon.

The situation is that we just got this truck running. It had been a front end collision, and we replaced everything before running it, spark plugs, cap and rotor, coolant, oil and filter, air filter, transmission fluid, etc. (All that we haven't changed is the plug wires and O2 sensors.)

The check engine light is on, and the catalytic converter was removed by the previous owner. I don't see or smell any gas leaks anywhere. The engine seems to run fine other than a minor miss at idle.

Any suggestions at all?

Many thanks in advance!

Are you using fuel from both tanks and then filling both tanks as well? It sounds like a crossflow problem where one tank will pump to both the engine and the other tank.

^^ X2 ^^

If it were getting only 2 - 3 MPG, you would smell fuel or notice the black cloud following you... :-X04

Ok, here's what happened. It ran out of gas on me while out driving, and I filled up with 2.5 gallons, and set off for the closest town to fill up, and it ran out again after only 6.6 miles of driving! Thankfully it ran out in front of a friend's house, and got it filled up enough to make it to the gas station. I'm filling the front tank. I did notice it shows that the back tank is 3/4 full, after previously showing 1/4 full before I started driving it.

I'm wondering if this is my problem? gas tank trouble - Ford F Series Zone - F150 F250 F350 Super Duty Ranger Tech

The truck doesn't smoke or act like it's running rich at all.

Install an AFR gauge and monitor the AFR's. I'd also figure out what the check engine light is on for. Could be a bad maf/map sensor too

Sounds like your rear tank check valve is allowing fuel to run into it... Our 96 does the same thing quite the bummer... Hope your rear tank works! I belive one way to check this is install a fuel pressure regulator and make sure when you shut the truck off it holds a decent amount of fuel pressure... Hope I helpted a little bit!
DOnnie

That's where your problem is then... drop the rear tank and change the fuel delivery module.

Thanks so much for all the help! I'll try running it on the rear tank and see if the front tank starts filling, or if everything will be OK.

If you have the crossflow, it will never be "ok" without performing the repair.

Which is built into the fuel pump assembly on the later year's..

If your switch is on the FRONT tank and it's filling the REAR tank, the REAR pump is bad.

If your switch is on the REAR tank and it's filling the FRONT tank, the FRONT pump is bad.

My friend has a '96 F-150 with the same issue. He's just been using the bad pump tank for now so it doesn't overfill the other tank.

Update...

Ran it on the rear tank, and it's now filling into the front tank as well. Arghh. So, where do I go from here? It's filling up whatever tank is not selected. Do I need to replace both fuel pumps, or just one? I would like to have the front tank operational.

I suppose I could keep driving it, and switching back and forth every 50 miles, but I really don't want to have to do that.

Your help is greatly appreciated!

Thats not good... Replace one fuel pump and run on the good one till you save for another??? BUMMER