ls swap and dual tanks - The 1947 - Present Chevrolet & GMC Truck Message Board Network

rodstored-72 · 06-05-2022, 11:14 PM

All, I have question and think this is the right place for it. I have a 2013 4.8 LS with original trans., ecm, and wire harness. It is in a 1986 C10 2wd with factory dual tanks. I have replaced the tanks with ’87 tanks, ’87 dash switch (ac delco) and a 87 tank valve and 6 wire harness (pollack). I am wanting to know if anyone has experience in a similar setup? Also I was wondering if anyone has heard about or experienced a issue with the ECM fuel pump signal and switching the tanks? I am wondering if there might be a “delay” or “reset” to get the ECM to signal the power for the fuel pump power?

thanks

SunSoaked · 06-06-2022, 12:12 PM

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.

rodstored-72 · 06-07-2022, 11:14 AM

sunsoaked
Thanks for the info. it appears to be "operating" correctly (I think)... I am just getting everything buttoned up to actually start and run to begin tuning. I have noticed that when I turn everything off for like 10 seconds, switch tanks at the dash switch and then turn key to the "key on" position that I don't hear the valve switch or the pump turn on?? I am wondering if the ECM "thinks that the pump is already primed, so it does not send a pump signal? I believe that I have things wired correctly....

06-05-2022, 11:14 PM	#1
rodstored-72 chevy truck fan Join Date: Mar 2005 Location: Gilbert, arizona 85298 Posts: 1,984	ls swap and dual tanks All, I have question and think this is the right place for it. I have a 2013 4.8 LS with original trans., ecm, and wire harness. It is in a 1986 C10 2wd with factory dual tanks. I have replaced the tanks with ’87 tanks, ’87 dash switch (ac delco) and a 87 tank valve and 6 wire harness (pollack). I am wanting to know if anyone has experience in a similar setup? Also I was wondering if anyone has heard about or experienced a issue with the ECM fuel pump signal and switching the tanks? I am wondering if there might be a “delay” or “reset” to get the ECM to signal the power for the fuel pump power? thanks

06-06-2022, 12:12 PM	#2
SunSoaked Registered User Join Date: Dec 2011 Location: Yuma Arizona Posts: 1,526	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.

06-07-2022, 11:14 AM	#3
rodstored-72 chevy truck fan Join Date: Mar 2005 Location: Gilbert, arizona 85298 Posts: 1,984	Re: ls swap and dual tanks sunsoaked Thanks for the info. it appears to be "operating" correctly (I think)... I am just getting everything buttoned up to actually start and run to begin tuning. I have noticed that when I turn everything off for like 10 seconds, switch tanks at the dash switch and then turn key to the "key on" position that I don't hear the valve switch or the pump turn on?? I am wondering if the ECM "thinks that the pump is already primed, so it does not send a pump signal? I believe that I have things wired correctly....



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