I just bought this truck a couple months ago from a friend who was moving, he had been having a hard time with the tanks, and thought it had bad gas in the back tank, swithching to the front it ran fine.
Its a 96 f150 302, this year has two in tank high pressure pumps, and no recalls on the diverter ( i checked).

I put some heat in the rear tank and filled it from 1/4 to full with premium, it still wouldnt run off the rear tank. From running on the front it would stall 30 seconds after switching.

Acouple times after playing with selector switch, flipping back and forth a couple times, it stayed running, and ran continuously on the rear tank, until I shut it off. Then, when i tried to restart, it wouldn't, and i would have to switch back. Altogether I was only able to use a quater tank from the rear over two months, (maybe 3 times i got it to work). The last time it was running on the rear tank, i hit a medium size bump on the highway and immediately felt it kick off, since then, I have not gotten it to run on the rear tank.
After putting it off for a while, i finally crawled under the truck and tested for voltage at the connection to the pump, I didn't have a pinout/diagram but there seemed to be 12volts on one set and 6 volts on the other, I'm a little suspicious b/c neither of those kicked off within a few seconds of turning on the ignition.
** Does anyone have the pinout/wire colors for the tank connection??
I was thinking it was the selector switch but now im not so sure.
When it was working, I noticed the front pump had the usual high pitchd whine, "ehhhhhh." but the back pump sounded much lower pitched, is this normal, or is this warning of pump/power problems.
okay thats the first half......
Within the last week, the truck has stalled on the highway 3 times,and twice on reg streets. the first time 2 times, i coasted at about 55 for 10 seconds and it started back up, the third time, it was about 20 seconds and i shifted to neutral and restarted before having to come to a complete stop.
The last time it stalled, and wouldnt restart for about ten minutes, it almost drained the battery, but luckily restarted finally.
Im not positive but, it seems like once it stalls, it doesn't ding when i try to restart it, then after a few minutes it will ding, and shortly after it will start. This makes me think ignition switch. But even when it doesn't ding, i can hear the front fuel pump kicking on, but it still doesnt wont to fire, till it dings........

I was about ready to give up and let the dealer try to fix, but they wanted 120 to read the codes, and going up from there.
i dont have a thousand dollars for someone else to guess with.

My thoughts are fuel pump/s, selector switch(easy enought to test/clean) fuel pump relays? ( not sure where they are), ignition switch, and beyond that, a crappy wire that bounces in and out that would either control spark, or fuel injection......

Ah yes and in the last 3 days, i replaced the positive battery terminal because the copper cancer(corrosion) had eaten it up. Unfortunately, it did it again the next day.

Any helpfull sugestions, including wiring locations, pinouts, colors/voltages, relay locations, and magic answers will be appreciated. Any generic answers like check the battery voltage will also be appreciated for you attemps to help.

 

My thoughts are fuel pump/s, selector switch(easy enought to test/clean) fuel pump relays? ( not sure where they are), ignition switch, and beyond that, a crappy wire that bounces in and out that would either control spark, or fuel injection......

I have the same truck and love it no problems. sound like you are on the right track. Did you test your voltage with a test light or a multi meter? If you tested with a light you will not a an acuarat voltage reading, it wil just tell you if you have a circut or not. since it is an intermitan problem it makes it hard to test. waht you could do is run a set test leads of 14 or 16 gage wire from you test point, pump, selector swtich, ect. to the cab of your truck. atcach you multi meter there so as you drive around you can test your voltage, then ussing the OME setting you can test continutiy, (resistance} when you truck stall you should see a change. if You fist test at the pump and you see a flux in the Volts move up the line to the next link. if you see the same change keep moveing closer to the battery. if you dont se the change. you have isolated the bad link . it will be the one next away from the bat. frome where you got a normal reading.
also be sure to check all the the ground staps under the truck that atatch to the frame. any one of them could be a bit rusty or loose and could be in creesing the resistance to the pont that the pumpe wont work. Be sure to test the good tank so you know what a good ont looks like so you will know if the other one is abnormal I'm asuming ther is no problem with the front tank right?? if both are bad look at the selector swith and colser the the battery.
Hope you find the problem Jim

 

I went through the exact thing with a truck I used to have. It's common for these fuel pumps to gradually fail as time goes on. They get worse and worse until the truck won't even run on it anymore.

The solution, of course, is to buy a new fuel pump. The bad news is that they go for about $140 a pop.

I had wanted to keep my truck for a while, so I bought both pumps for it and replaced them both at once. Rather than dropping two gas tanks, I went the other route: Took the bed off. My buddy and I both agreed that it was way easier than dropping gas tanks. And I had a bedliner and cap that had to come off, too.

I think it took us an afternoon to do it. Truck ran like a champ after that.

If your truck is real rusty, though, that might not work as well for you. Your Mileage May Vary!

 

truck died on the freeway, had to have it towed in. Really didn't want to mess with it, but knew it was the fuel system and suspected the pump. Needed the truck the next day for work so with no time to diagnose and fix had shop do it OUCH!!! Pump was $270, total was $602.

Sounds like your on the right track. Do you here the rear pump running when you turn the key on? Some times the fuel canister (another fuel filter) located under the bed inside the rail will clog. two bolts, use a bucket to catch fuel spill and replace the filter. It looks like a small oil filter. Might do the trick.

 

You can get a pump from autozone for about 120 bucks. I'd check the fuel pressure, but most likely the rear pump is failing.

 

Thanks for all the help and suggestions,
I spent several hours over the last few days trying to isolate it down.
The truck has stalled twice more on the front pump, leaving me waiting on the side of the freeway, it started again after about ten minutes. Very strange.

Okay, pulled the connector off the back pump and took readings, my book doesn't really have wire diagrams, at least no good ones. It looks like i have 12 volts and 6volts to the rear pump, it doesn't ever kick on now. The last time I heard was about two weeks ago and it sounded much lower pitch, almost groany.

I pulled the dash off and tested and cleaned the selector switch, it seems to be working fine. Ohmed out for both wires to the correct pins when flipped back and forth. The back fuel gauge has always worked, so Im not very suprised.

Checked the fuses in the cab, ok, checked the relay in the power distribution box in the engine compartment. There is only one relay for both pumps aparently. unless there is another set hiding in the cab.... It works fine for both tanks, I could hear it clicking with both front and rear selected.

Followed the fuel lines, and there is no tank selector valve/diverter on this year, it just has T's for the front tank to merge into the lines.

I was running out of time, so was not able to pull the connector to the front pump to look for differences, I think I will try that as last step before replacing rear pump. I'm pretty sure the back one is dead.

The front pump.... not so sure, even after stalling on highway, I can hear the front pump kick on with ignition, but it still wont fire up. Next time i will have to check for spark.
Unfortunately the last two times it has died has been on the freeway, so there is a ton of noise, and Im def. not crawling under it on a narrow shoulder. Maybe i'll get lucky and it will break down somewhere quiet and peacefull next time . . .

If anyone has the DVD or shop manual, i could really use the meter readings at the rear pump connection (4pins), and maybe the resistance across the pump side connections too.

I think Im going to buy a service disk/manual. If a can get one for cheap.

 

Replaced battery, hasnt died on highway since, got wiring schematic from library, alldata .. . .
now just have to fix back tank

 

Sorry to dredge up such an old thread, but I was referencing it for someone and noticed I never posted my fixes. That doesn't help anyone searching.

The rear fuel pump was bad, changed it out, and it works fine now. The front pump has a leaky shuttle valve, so I have to use it first, before switching to the rear.
The fuel filter, was only a problem to change, didn't fix anything.

The stalling came back and eventually got worse, I started another thread on it I think. I used a spark tester to isolate the ignition system. Eventually I tracked it down to an intermittant PIP sensor in the distributor. I changed just the sensor for $20, and it has not stalled once the road since.