I have put this off and just used the rear tank . Thought for some dumb reason I would try to figure out if its the pump or ground . I have searched and read many of the past posts until I just confused myself even more .

Front pump does not come on when key on . Gauge does work . from the side of the tank there are 4 wires going into it . Which I understand to be :
pump - pump + sender + sender -

with key on I have

no voltage on pump -
voltage on pump +
voltage on sender +
no voltage on sender -




un hooking the 4 pin connector that goes from the harness to the front tank ( u shape with the flat part being top ) key on -switch on front tank .

At the 12 o' clock position voltage
3 voltage
6 no voltage
9 no voltage
the voltage at the 3 o'clock does not light up the light as much as the 12 o'clock does . There is no voltage at the front harness as I would assume would be correct when the switch is on the rear tank and key turned on .

If both tanks share ground and one works would't that eliminate a ground problem from the spot where the two tank harneses meet and go forward . Where does this ground go ?
On rare occasions I was able to switch back to the front and drive 4-5 miles before it would start stumbling and switch back to the rear .

thank you

 

I didn't get this formated the way I wanted so tried to edit it to make it easier to read .

Thanks

 

Check and see if the (-) on both the sender and the pump have continuity with ground. If they do, then a ground is not your problem. It could very well be a bad pump. I ended up puling the bed off to replace mine, 6 bolts in the bed, 6 bolts on the filler necks (3 each), 2 hose clamps holding the filler necks on, one plug on the drive-side frame rail (tail lights), and it lifts right off. I had one helper and my wife to help keep the whole thing stable as we moved it.

 

I'm a little dense so hope you don't mind a couple more qustions !

Ground the black meter probe to the frame and check each - with the red meter probe looking / listening for continuity with the key on ?

should I do this at both the female harness plug in the loom and then also the wires going into the tank with everything connected ?

Thanks for your help

 

Switch the meter to the continuity setting; touch red lead to black lead to test and make sure you are in the right mode, most meters beep, however some will just show the resistance on the screen. If thats the case, just look for the screen to change really, mine normally shows "1" then switches to 000's when they are touched together. Once you know you're in the right setting, touch one lead (red or black) to the frame (clean metal spot). Touch the other lead to the (-) of the pump and sender. The screen should change\meter should beep, etc. If it doesn't that is most likely your problem. The key does not need to be on to perform this test, the pump is grounded at all times, it only recieves the 12 signal when the key is on.

 

I ran this test tonight . I first checked those wires at the plug from the loom on the truck and then plugged it back together and tested the wires right where they go into the tank . I did get a beep on both tests and on both wires .

thank you

 

I am wondering I have a hum under neath my 4.9l six F150 it has two tanks, the hum seems to becoming from around the front fuel tank it stillhums when i shut the truck off is it probably a bad pump relay the engine has a problem idiling can these be from a bad pump thanks cuda47130@yahoo.com