Lingering Fuel Pump Problems - PLEASE HELP!

[mlochala]

I just replaced the fuel pump in my wife's Mountaineer. I also replaced the fuel filter, air filter and replaced the two sections of flex fuel line between the tank and the hard lines (rails) that go to the engine. I replaced the fuel lines with high pressure hoses and conventional screw type clamps.

(I had to replace the fuel lines because they would not release from the tank spigots. I had to cut them off because there was so much sand build up in the quick release mechanisms.)

However, I am having a problem I can't figure out. When the tank level gets down below 1/2 full, the vehicle is stalling as if it is starving for fuel. It does this after going down a hill or after coming to stop at a stop sign.

I've taken the tank back down about 3 times and checked the float and even carried the new fuel pump back and exchanged it. However, the problem is still there. The vehicle runs fine otherwise.

Please help me as this is about to drive me crazy figuring this out.

 

[swetrid]

Is the bucket/sump still on the bottom of the tank? I have seen this dislodge from the tank and then move around tank disrupt fuel flow.

 

[mlochala]

Thanks for the reply!

Yes, it is still there. It did not appear to be loose in any way.

I know from experience that when these vehicles get low on gas, they are very sensitive to angles that cause the fuel to gather in the front of the tank, but it should not be doing what it is doing now.

To my knowledge, I have not re-installed the tank in any way that would change it's normal angle.

 

[gbissi]

This probably a Gerotor pump, sensitive to hot fuel handling and vapor lock in the gears that make pressure. But, this should not be your issue. Did you repalce the entire pump/sender assembly or just the pump? The fuel pick- up sock has to sit on the bottom of the tank floor. The sock should have a tubular screen that keeps the upper & lower filter halves from collapsing on each other.
Other than that, you need to install a fuel pressure gage from Harbor Freight in the pressure line & monitor pressure. Should be 34 psi, engine running.

Gerry

 

[Turdle]

are you sure the sending unit ( float) arm is not bent, indicating fuel when it is indeed empty?

 

[mlochala]

This probably a Gerotor pump, sensitive to hot fuel handling and vapor lock in the gears that make pressure. But, this should not be your issue. Did you repalce the entire pump/sender assembly or just the pump? The fuel pick- up sock has to sit on the bottom of the tank floor. The sock should have a tubular screen that keeps the upper & lower filter halves from collapsing on each other.
Other than that, you need to install a fuel pressure gage from Harbor Freight in the pressure line & monitor pressure. Should be 34 psi, engine running.

Gerry

It's an Airtex, from Autozone no less, and I only replaced the pump, pick-up sock and filter. I didn't do anything with the sender assembly. When I can, I will get the fuel pressure gauge and try that.

I will say this, as far as performance goes, when this isn't happening, it runs very well. To me, it runs noticeably better than it did before the old one went out, very responsive and with smooth acceleration.

 

[mlochala]

are you sure the sending unit ( float) arm is not bent, indicating fuel when it is indeed empty?

Nope, I've checked that float arm and it is not bent.

Thanks for the replies, guys!

 

[gbissi]

Did you say what year it is? I missed that.

gerry

 

[gbissi]

I see it. 1998.

 

[mlochala]

Aah...figured it out, I think.

Well, last night I dropped the tank on the Mountaineer again to install a new evaporator valve and make another attempt to figure out this issue.

On a hunch, I removed what was left of the old evap valve and peered into the tank with a flashlight. What I discovered was that the fuel pump strainer was bent in a 90 degree angle against the side of the fuel tank.

So, I pulled the fuel pump/sending unit assembly and inspected it. Sure enough, the strainer had a permanent bend and kink in it. Apparently this must have happened when I installed it the first time.

I went back to Autozone where they were nice enough to allow me to exchange that strainer for another one. When I reinstalled fuel pump assembly this time, I turned the unit 90 degrees as I inserted it so that the strainer would not impact the sides of the reserve tank on the inside.

Once I had the assembly completely in there, I turned it to the correct position and replaced the bolts. Peering in again from the evap valve hole, I was pleased to see that the new strainer is laying flat against the bottom of the tank just like it is supposed to.

I haven't had a chance to test it yet, but I'm fairly certain this has been the problem. I'll let you guys know in a day or two if this has been resolved.