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Re: ls swap and dual tanks
I have dual tanks on my 85 and recently replaced all the wiring for the fuel system. I also converted to 87 tanks and new sending units with GM pumps. I don't have an LS ecm but I do have Edelbrock PF-4 efi. I would assume both our ecm's output a ground trigger signal to a relay to power the pumps.
Th easiest, reliable way I found was to make a simple circuit separate from the factory harness that only powers/switches the fuel pumps. The factory sending units remain unchanged and use the OEM selector switch, 6 port valve and gauge.
It requires a toggle switch and two relays. The switch also doubles as a hidden anti-theft device as well. It also allows an easy way to manually pump your tanks dry for maintenance /repair. Using the output of the ecm also retains the safety features. If there is no oil pressure or RPM signal it cuts the pump signal.
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