97 chev express 2500 -- 5.7 , Will run only when fuel pump jumper wire is connected. Replaced pump, relay, all fuses are good and been manually removed and checked, ecm replaced & flashed, power good to the orange, no burnt wires under fuse box, all look good, communication error to the scanner & no readings. All dash lights light up , fuel guage pegs when red jumper wire connected otherwist no reading of fuel level in tank. help

replace the relay, jumper wire wont work, there is a small set of points inside the relay, there probably burnt, or stuck open

Engine cranking, did you check for spark at the plugs, also, check fuel injector pulse. Any applicable trouble codes?
When you first turn on the key, no crank, can you hear the pump run for a couple seconds?
If only a fuel issue, jump the relay to see if pump will run. Unplug relay, use jumper wire between terminals 30 and 87, the pump should run, don't need to use your key. As you can see, terminal 30 is hot all the time. Also, check that fuse.
Let us know what you find?

is there any check engine light on?

) Unplug the main relay and then turn the key from off to ON(II).

2) Use a jumper wire or paperclip to jump terminal 1 to terminal 7 in the main relay plug. Does the fuel pump run?

3) Now use the jumper wire or paperclip to jump terminal 5 to terminal 7 in the main relay plug. Does the fuel pump run?

There is a break in the wire that supplies power to the fuse box.
You need to trace this power wire from the fuse box to find the break in this wire and fix this wire,.
Ii would help you is you have a wiring diagram of your vehicle as the wires are color coded.

Should be a green-yellow wire from the relay to the pump. The pump is grounded thru a black wire in the harness.
The wire from the relay should be hot when the relay is engaged by the computer or if you jumper it.

check all ur fuses for continuity first, then u can also try to swap out ur fuel pump relay with another relay that looks jus like it, be sure to use a relay like for ur horn or ac relay something that wont affect necessary or direct engine circuits like for ex. an ecm fuse or bcm fuse. if fuses r good an swappin relays wont work, next is to trace bak from fuel pump ur wires an possibly keep back probing to see if u have a broken wire from relay box to pump . good luck hope this was helpful . in ur fusebox ur fuelpump fuse should b labeled or easily found in fuse box legend, most likely on bak of fusebox cover....

loose connection in the wiring somewhere.

Did you check the fuel inertia switch in the passenger side kick panel ?

The fuel pump is powered :
the fuse to the fuel pump relay.
The fuel pump relay to the fuel inertia switch
The fuel inertia switch to the fuel pump itself.

At the fuel inertia switch in the kick panel, power from the relay is the Dark Green w/ Yellow stripe wire and the pink w/ black stripe wire is the power. from the fuel inertia switch to the fuel pump.

If you jumper the fuel pump relay, you should hear it run. If not pull the fuel pump relay, and check the pins in the relay socket, pin 30 should be the power from the fuse.



If you have power at pin #30, jumper the relay socket as shown with the red line above, and check the dark green w/ yellow stripe wire at the fuel inertia switch for power.
Press the button on the top of the fuel inertia switch, and check for power leaving the fuel inertia switch on the pink w/ black stripe wire.

This is tests good, check for power at the fuel pump, same pink w/ black stripe wire.
Fuel inertia switch info is in the owners manual, If you did not get an owners manual with your truck ( purchased used ), you can download one from Ford :
https://www.fleet.ford.com/maintenance/owners_manuals/default.asp

that red wire is a test lead to jumper the fuel pump to test it.if ecmb fuse keeps blowing my guess is your ecm has a short in it,in that case it can be purchased at oreillys