Bench test the pump (grey/power- black/ground) pump functions. Test the harness at the pump plug (grey/black) 12v with key on. Plug pump into harness no action. Pulling my hair out here any suggestions? With further testing, the 86 post at 5he relay is showing varying voltage from max full voltage down to 7 volts and bouncing around.
When key is turned on - pump relay should click on then click back off in 3 seconds ..
When key is momentarily turned to START position then released - should hear relay click OFF .. I'm assuming you know voltage is only supplied to pump for 3 seconds - UNLESS engine is cranking..
Voltage testing using a volt meter can be very deceiving - many times meter will show battery voltage but in reality that is not a reliable test for CURRENT.. Test for battery power whith pump wiring connected to pump module. .. Keep in mind there is also voltage present for fuel sending unit .. Make sure no fuses have blown!
The link posted below is for 03 Suburban - note relay pin identification .. Additionally - security (anti thief) system is designed to deactivate injector pulse - not fuel pump..
https://mechanics.stackexchange.com/questions/22815/03-chevy-suburban-fuel-pump-failure
Good luck!
Hello, it would be best to review the fuel system operation of the vehicle. You may learn that certain inputs are required in order to activate the fuel pump. This could be related to vehicle anti-theft protection for example. Determining how the fuel pump gets power would be step one; use of a proper diagnostic tool and shop manual direction is needed.
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A wiring schematic and diagnostic flow chart would certainly simplify this procedure?
The link posted below is for 03 Suburban - note relay pin identification .. Additionally - security (anti thief) system is designed to deactivate injector pulse - not fuel pump.. https://mechanics.stackexchange.com/questions/22815/03-chevy-suburban-fuel-pump-failure Good luck!