Fuel System Issues

95 XJ, 4.0L, AX15

At the end of the summer I installed a fuel cell I made from a old hydraulic tank. I washed it out with water and then left it in the sun to try. I attached the factory fuel pump assembly. It has a vented cap and internal baffles.

The problem started a little after the install.

I can drive around for a minute or two, but when I get into the throttle it will choke and sputter and I can hear the fuel pump cycling up and down and see the fuel hose pulsing. The jeep can barely move if it doesn't just die on the spot. If I turn off the key and let it sit for a minute then start it again, it all repeats.

The fuel filter is brand new, I've switched the fuel pump and the fuel pressure regulator with spares to no avail. I inspected the fuel lines for pinches and I also wired the fuel pump straight from the battery to see if the power source was goofy.

The next thing I was going to do is switch the computer with a spare I have for the same year and drivetrain. Also I might try eliminating the fuel filter to see if I just got a bad one.

Thanks for any thoughts.

Almost sounds like the fuel pump is sucking air. Does the problem arise if you just leave it parked and don't drive around or with more fuel in the tank? If not, I'm betting your new tank isn't ideally shaped.

The tank is a large cube, shaped 12"widex30" longx20" tall. The fuel pump is located halfway up side in the middle of the long side. It has baffle inside that is located 1" up from the bottom and about 10" tall.

Sounds to me like it can't equalize pressure--i.e., the tank can't suck air in to replace the fuel pumped out.

I thought that was the problem so I tried driving it with the cap off of the fuel tank, to no avail. I'm debating on drilling another vent hole just to make sure there isn't some other restriction I'm not picking up on.

And the fuel pressure readings during all that are....???

Is longway on tank side to side or longway to the jeep ??


Good Luck,
Orange

Sounds like the baffled area where the fuel pump sits has too small of holes in the bottom to allow the fuel level to equalize. The fuel pump is sucking up fuel faster than it can refill the baffle. Try directing the fuel return line (if that is a return type system) into the baffle where the pump is located.

Sorry, no fuel pressure gauge available.

Picture of tank orientation...looks like I was alittle off on my dimension estimation

http://hphotos-snc3.fbcdn.net/hs635.snc3/31879_10150203596490343_755350342_12761377_373016_n.jpg

http://sphotos.ak.fbcdn.net/hphotos...203596510343_755350342_12761378_2218197_n.jpg

And the return line is directed right next to where the pickup is, just like the factory setup since it is still the same pickup assembly from the OEM tank.

Then run the pump output into a container for a timed run for say 1/2 gallon fuel pumped and figure gallons per minute or hour.

--Make special note that flow rate is steady.--

----Observe All Safety precautions.----

If "sag" last a while, check if fuel gauge reading drops at same time.