My son’s truck

[sp53]

My son’s truck is a 97 Ford Ranger with a fuel delivery problem. The pump has 4 wires- black, red, yellow, and green. When I measure voltage at the pump I get 12 volts at the yellow with the key on. When I hook power to the red and black the pump will run. I replaced the ignition; still no joy. My thoughts are to hold the key to the start side and see if I get power on the red post and to perhaps replace the key side of the ignition. I cannot find a fuse but did find a relay and traded one over with corresponding numbers, still nothing. Any ideas?
Thanks steve

 

[AngliaGT]

The pump's in the tank,right?

 

[sp53]

yes

 

[Don_R]

If I remember correctly, there should be a inertia cutout switch under the dash, passenger side I beleive....if this is tripped the pump wont turn on.....