No Power to Fuel Pump
September 11th, 2016, 3:26 PM
#1
No Power to Fuel Pump
So my wife's burb had intermittent starting problems. Told her to leave it parked until I can figure out what it was. Figured it was the fuel pump. Would crank a few times before it would start. Replaced with a tyc pump. Truck ran fine for 2 weeks after. She left work one day. Said it gave the infamous device stabilitrak and traction control. Then stalled. Would not kick back on. Well after cursing tyc and their pump. I dropped the tank again to check the connections. Nothing. No power while off. While In run. While cranking. Checked the relay. Relay ok. Checked the fuse. Fuse ok. Checked the power box under the relay. No power. Why would there be no power. PCM???
September 12th, 2016, 6:45 AM
#2
CF Active Member
The fuel pump fuse is after the relay (relay needs to be energized for fuse to have power). The relay is controlled by the ECM (Engine Control Module). Check for power at the fuse while cranking. If you have power at the fuse, look for bad wiring / connectors going to the tank.
September 12th, 2016, 10:33 AM
#4
CF Active Member
If there is no power at the relay, you should not have any power at the fuse. If that is the case, you have a problem with the fuse block. Look at the back of the fuse block for burnt / loose connections.
If you have power at the fuse, you made a mistake checking for power at the relay.
Power flow -------->
BATTERY ---> MEGA Fuse (175A) ---> Pump Relay ---> Pump Fuse(20A) ---> wire harness to pump.
September 12th, 2016, 1:50 PM
#5
No burn marks. The only thing that I can tell is that there is no power to the fuel pump relay. What is the circuit prior to the relay. Could a bad cps cut power to it. It's either that or the pcm. I'd rather be sure. Than throw parts at it. But at this point a $30 cps is cheaper than the stealership.
September 12th, 2016, 2:56 PM
#6
CF Active Member
No burn marks. The only thing that I can tell is that there is no power to the fuel pump relay. What is the circuit prior to the relay. Could a bad cps cut power to it. It's either that or the pcm. I'd rather be sure. Than throw parts at it. But at this point a $30 cps is cheaper than the stealership.
cps?? Not sure what you're referring to.
The only thing prior to the relay is the MEGA fuse. Nothing works without the MEGA fuse being good.
Closing the relay is done by the ECM (Engine Control Module). A bad ECM or the wiring between the ECM and the relay would keep the relay from closing.
Checking for power at the fuse will rule out the ECM and relay circuits. (Power at the fuse = relay and ECM circuits are OK)
The A/C CMPRSR and the FOG LAMP relay would be a good check of your testing equipment/methods. They're powered from the same circuit as the pump relay. At least ONE of the relay terminals should have power ALL the time.
The following users liked this post:
Jamiengeorgia1 (November 27th, 2021)