Chevy LS3 V8 - fuel pump power

[anonymous-user]

Hi - I have an LS3 that I've had in a previous installation. I've installed it into a new car and I fired it us yesterday. All seemed good so I turned it off, went inside for the camera and tried to restart. And... starter motor is fine but not firing. I've checked things through and found that the output to the fuel pump is not getting power. I've checked the relays and fuses and all seems good, its just that the relay that supplies the pump isn't being energised. My guess is that the ECU isn't activating the fuel pump for some reason, possibly a bad sensor somewhere. I've checked the OBD2 connection and it indicates full fuel pressure. My question is this: how is the ECU working out the fuel pressure? There don't appear to be any fuel sensors so how does it derive the pressure?

I'm not assuming anyone has intimate knowledge of the LS3 but how in general does fuel pressure get monitored when there doesn't seem to be a specific pressure sensor.

Any thoughts?

Tech info: Its an e-rod package, here are the installation instructions: https://www.chevrolet.com/content/dam/chevrolet/na...

[stevieturbo]

fatbutt said:

Hi - I have an LS3 that I've had in a previous installation. I've installed it into a new car and I fired it us yesterday. All seemed good so I turned it off, went inside for the camera and tried to restart. And... starter motor is fine but not firing. I've checked things through and found that the output to the fuel pump is not getting power. I've checked the relays and fuses and all seems good, its just that the relay that supplies the pump isn't being energised. My guess is that the ECU isn't activating the fuel pump for some reason, possibly a bad sensor somewhere. I've checked the OBD2 connection and it indicates full fuel pressure. My question is this: how is the ECU working out the fuel pressure? There don't appear to be any fuel sensors so how does it derive the pressure?

I'm not assuming anyone has intimate knowledge of the LS3 but how in general does fuel pressure get monitored when there doesn't seem to be a specific pressure sensor.

Any thoughts?

Tech info: Its an e-rod package, here are the installation instructions: https://www.chevrolet.com/content/dam/chevrolet/na...

No, it wont be a bad sensor and we need more details. And no OBD will not indicate full fuel pressure, as the OEM setup does not have a fuel pressure sensor. But I'll guess you're using some generic OBD reader...which all too often give wrong info, so treat it as of limited use here.

So it's simple.

Does the fuel pump relay energise/prime on key on ? Does it receive a signal to prime ?

If yes, then is the relay working, or any fuses relating to it and the pump are ok ?

if yes....does this same signal exist during cranking, as well as 12v power in the relevant places for everything else to work ?
Do you have an rpm signal during cranking ?