What Will Keep the Fuel Pump Relay From Switching?

Question

The pump runs when I jump position 30 and 87 where the relay is located.I switched relays for the fule pump and ASD.The fuses all look good also.What will keep the pcm from driving the relays.
This is on a 2000 Jeep grand cherokee laredo

Answer 1

The pcm does not control the fuel pump relay. The relay is controlled by fuel pressure. When the pressure reaches it's set psi it opens the relay. Your pump should ron for a very short time when you turn on the ignition and stop until you start the engine.