Fuel pump problems. Need diagnostic assistance.

[Zaphod9er]

Losing power at the relay. Pin 5 will have power upon starting. But once it starts. It's flakes out, loses power on pin 5 to the pump, pump shuts off, car leans out and dies. What could be causing the fuel pump relay to shut off aside from a bad ecm?? It's a new relay.

Thanks

2013 rspec 5.0

 

[Gunkk]

All of this is from my 2012 manual which I presume is the same for your '13.

Looks like the fuel pump relay is designed for pull down operation. In which case it will be off when either a) all control lines are zero volts (key off), or b) all control lines are 12 volts. It will only turn on when the control power side is 12v (pin 5 and 6 connector K) and the ground side (pin 38 connector A) is pulled down to ground, allow current to flow and close the relay.

Check voltage to pin A38 (ground for the control side of the fuel pump relay). Pin A38 should be low (pulled down to <1V) when pump relay is energized (pump is operating) normally.




Pin 5 on connector K controls the power to the control side of the fuel pump relay, should be 12V when pump is on (when mains relay is on). A problem either K5 or K6 (say if they are low or 0V instead of 12V when fuel pump is on) might cause your issue.

 

[Zaphod9er]

All of this is from my 2012 manual which I presume is the same for your '13.

Looks like the fuel pump relay is designed for pull down operation. In which case it will be off when either a) all control lines are zero volts (key off), or b) all control lines are 12 volts. It will only turn on when the control power side is 12v (pin 5 and 6 connector K) and the ground side (pin 38 connector A) is pulled down to ground, allow current to flow and close the relay.

Check voltage to pin A38 (ground for the control side of the fuel pump relay). Pin A38 should be low (pulled down to <1V) when pump relay is energized (pump is operating) normally.

View attachment 58904
View attachment 58905

Pin 5 on connector K controls the power to the control side of the fuel pump relay, should be 12V when pump is on (when mains relay is on). A problem either K5 or K6 (say if they are low or 0V instead of 12V when fuel pump is on) might cause your issue.

View attachment 58906

View attachment 58903

I finally got around to having time to test the ecu outputs. A38 has 59mv-80mv. K5 has 12.5v and k6 had no voltage. I used a t-pin, volt meter and an alligator clip, and referenced known voltage befor and after testing to validate my meter and leads. So if k5 isn't outputting, does that mean bad ECU? Or possible problem elsewhere?

 

[Zaphod9er]

Correct me if I'm wrong, but according to the wiring diagram, I should be able to check and have continuity from the output side of the main relay, to k5 which seem to be working. Then test continuity from main relay output to k6 and fail, thus confirming the lack of voltage to the ecu.

 

[Zaphod9er]

Just tested continuity from pin 87 at the relay to k5 and k6, both read .3ohms which tells me continuity is good from relay to ecm. Maybe my t-pin wasn't making connection?? If I had continuity, I should have been able to see the 12v right?

 

[Gunkk]

Correct me if I'm wrong, but according to the wiring diagram, I should be able to check and have continuity from the output side of the main relay, to k5 which seem to be working. Then test continuity from main relay output to k6 and fail, thus confirming the lack of voltage to the ecu.

Yeah K5 and K6 should be the same voltage, so you likely have an open wiring fault on the K6 leg. All this presumes that the wiring diagram is correct.