Wiring LS1 swap fuel pump to harness in 1972 C10 using MU2101 pump in Boyd’s tank

It’s going to be a while before I wire and plumb my own Boyd’s fuel tank and pump in my 1972 C10 so hopefully this will answer some basic questions I’ve been getting until I can do an in depth video of doing all the wiring and plumbing in my own truck.

[curtrobinsongarage]

It’s going to be a while before I actually wire my own C10 so hopefully this will answer the wiring questions till I can do a much more in depth video on my own truck.

[deankay]

Great information Curt. Star washers help cut in metal cleaned by small thumb sized wire wheels to simple 36grit. Dielectric grease with keep moisture and water off this frame fastener providing a low resistance to ground for years. Choose the wire size be length & published fuel pump amperage, but solder and shrink tube any slices. The “LS” swap requires the PCM reprogrammed and provides 2 grounds for electric fans, but ground (Yours May Vary) but internal quad-drivers ground the relays coil to engage pump prior to crank and 5Vdc oil pressure gauge to PCM shuts off fuel with loss of pressure. A fuse/relay block would have a 10 amp fuse to the relays coil and jumps to the fuel pumps switched contacts on 30 to 87-NO. So one fuse protects relay and pump. A “B+” fuel terminal is empty so during diagnostics, a fused jumper wire and energize the pump during pressure test, amp draw test and total amps to fuel pump test. Amp clamps today are cheaper, accurate and have direct readout on the face. This excellent investment will allow you to choose wire size based upon length as 12 AWG may work great over 16’ if running 7.5-9.0 amps. If pump or component use more, check with published charts for size, length and amperage used. Just remember “In-Rush” current to fan motors, fuel pump motors or conventional incandescent light bulbs. Like a cranking motor/Starter, when cold, copper has low resistance pulls 90-130 amps but less than second drop to a continuous 80-90amps at the starter. People ask how many amps does the fuel pump draw? I tell them to install a fused jumper wire at the relay and check it. 7.5-9.0 amps is common depending on the size & brand of fuel pump.
A digital multi meter maybe equipped with a “Min-Max” feature and safely handle 15 amps, most are 10 amps. No amp clamp required if circuit operates within this range. The “Min-Max” feature records the high reading, only if circuit is off. While running, they allow for amperage reading for continuous amperage. Choosing fuse size, relay and wire size becomes easy at this point.
Great information for discussion at the internally regulated Corvette filter is popular for these swaps! My 2003 Tahoe 5.3L runs at 53 PSI and the pump draws 7.2 amps. If a turbo, supercharger are added, they may need higher fuel pressure or volume.
I just hope folks doing "LS" swaps realize the PCM provide ground to fan relays and other. As crank circuit should run thru reverse, neutral, park circuit switches correctly!
Thanks Curt! Best of luck with the build, I am enjoying it. So should a 100, 000 others!