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Discussion Starter #1 (Edited)
Howdy. Working on a 2001 Tundra Access Cab 2WD with 4.7 engine and 145,000 miles. Truck began to hesitate and performance slowly degenerated over a month's time. Finally, it quit altogether and woukd crank but not start. It appearsto be a fuel pump circuit problem because, when pump is connected to voltage wires coming from fuel pump relay, the new fuel pump does not operate and no fuel makes it to the engine.

Here it what we have tried:
-new fuel filter
-new fuel pump relay
-new fuel pump (when submerged in fuel and 12 volts applied, old pump is shot but new pump appears to work fine.)
-direct wired the pump, submerged in fuel, to a 12v battery, and the truck started fine and runs well.

Here are the current symptons:
-there is nowhere near 12 volts going to the new fuel pump when ignition switch is turned to "on". Reading is less than 1 volt.

We are figuring that we must have a short somewhere along the wire harness after it leaves the fuse box and heads toward the rear of the vehicle. We can easily access the back portion of the wire harness and it does not seem compromised. It is very difficult to reach (or inspect) the wire harness after it goes through the firewall and before it appears underneath near the truck frame.

Before we start really tearing things apart more than we already have, does anyone have any ideas about what else the problem might be other than compromised wiring from the fuel pump relay to where we can measure the voltage available to the pump?

How often might you buy a fuel pump relay replacement and have the new one not operate properly?

Is there any way to easily test the voltage at the fuel pump relay and along the wiring harness as it makes its way to the fuel pump?

Thanks for any positive input you may be able to provide.
 

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Discussion Starter #2
Really? There is no one out there with any suggestions? Have I posted incorrectly? Or perhaps in an incorrect forum? Please advise...
 

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having this same issue buddy haven’t dug too much into it yet but my relay box only sending 2-4 volts to fuel pump but if I jump the middle pin on the 3rd row of the 5 pin relay to the positive battery cable it has 12 volts concluding my wiring to the fuel pump is working I’ll post a solution to my issue as soon as I can thanks
 
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