6.0 swap help

[Sdguffey]

I'm putting an lq4 6.0 into a 57 chevy truck. I hooked everything up today and im getting power to the fuel pump but nothing to the starter any ideas?

[pajeff02]

Stock wiring harness? I presume you checked the relay?

[Sdguffey]

Yeah complete harness from the 2001 and i replaced the relay thinking that was the problem. but it wasn't. when you turn the key you can hear the fuel pump kick on but nothing when you turn the key to start

[pajeff02]

If you run a temporary jumper at the relay, will she crank over? Let me know if you need a schematic.

[SMWS6TA]

If it is the original ecm I'm better it's looking for a BCM or VATS if they were not tune out.

[pajeff02]

Yeah, there is an interconnection there. VATS usually kills the fuel pump though if I recall correctly.

[Sdguffey]

Where would you jump it at I guess I will need a diagram if you could thank you

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It's the stock ecm and complete harness from the 2001 truck

[pajeff02]

Locate the starter relay in the underhood electrical panel which I presume you also swapped over. On our cars, the dark green wire is power to the coil in the relay, yellow/black is the ground for the coil which feeds from the BCM (Body Control Module -- this could be your issue), red is power to the switch side of the relay and purple is the other side of the switch to the starter solenoid. To jumper at the relay, you would use a length of wire to momentarily run power to the purple wire to see if the starter engages. Ensure that the vehicle is in park and the ignition is energized.

Turning the key sends power to the relay coil, but the BCM has to also complete the ground circuit as power alone will not pull in the relay contacts. My guess, as noted above, is that the relay coil does not have a ground and that is why it will not engage the starter when you turn the key. You can probe the receptacles with the relay removed to test for power, ground and continuity to the starter solenoid. If it is in fact the ground that is missing from the equation, you can run a makeshift ground to that prong on the relay and the engine should crank over.

[SMWS6TA]

Yeah, there is an interconnection there. VATS usually kills the fuel pump though if I recall correctly.

IIRC it does the starter too. Depends on what year and car.

[pajeff02]

^^ Yes it does. I saw the interconnection to the BCM in the schematics last night. Looks like it would be an easy bypass though as you simply need to hook up a ground wire to the coil side of the relay.