The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post

DM72C20 · 09-14-2021, 01:29 PM

After an unintentional summer hiatus, work is going again on the truck!

The gas tank is all welded, pressure tested, wired and mostly plumbed. Everything seems to fit nicely including the fill which involves an S bend tube, a rubber 90 and some straight hose. Might pick up an installation tool for the nylon fuel lines and fittings. I've ordered parts from FMSI since they are local for that stuff.

Wiring cleanup has been in progress too. Everything should be set to the gas tank and fuel pump. Underhood stuff is close. Gauge swap to the S10 speedo is mostly done. Still more work to do at the dash. I still don't quite get how the ignition 'talks' to the PCM yet...

There's an instrument panel connector with some vague sounding wires that remain, along with a VSS wire. I added in a VSS wire to the X1 connector but a bit uncertain about that.

I'm quite confused about the alternator after reading the other day that it needs a GCBM and BCM to have the ability to change voltage output based on load. I don't have either module, however that function sounds nice compared to its default at 13.8V. Keeping the alternator stock is appealing from a parts availability standpoint. I've read a thread about changing out the regulator on the back, but that isn't stock anymore... There was some other thread about a PWM signal generator device... Any suggestions would be helpful.

09-14-2021, 01:29 PM	#38
DM72C20 Registered User Join Date: Sep 2019 Location: Toronto, Ontario Posts: 46	Re: 72 C20 LS Swap/Build After an unintentional summer hiatus, work is going again on the truck! The gas tank is all welded, pressure tested, wired and mostly plumbed. Everything seems to fit nicely including the fill which involves an S bend tube, a rubber 90 and some straight hose. Might pick up an installation tool for the nylon fuel lines and fittings. I've ordered parts from FMSI since they are local for that stuff. Wiring cleanup has been in progress too. Everything should be set to the gas tank and fuel pump. Underhood stuff is close. Gauge swap to the S10 speedo is mostly done. Still more work to do at the dash. I still don't quite get how the ignition 'talks' to the PCM yet... There's an instrument panel connector with some vague sounding wires that remain, along with a VSS wire. I added in a VSS wire to the X1 connector but a bit uncertain about that. I'm quite confused about the alternator after reading the other day that it needs a GCBM and BCM to have the ability to change voltage output based on load. I don't have either module, however that function sounds nice compared to its default at 13.8V. Keeping the alternator stock is appealing from a parts availability standpoint. I've read a thread about changing out the regulator on the back, but that isn't stock anymore... There was some other thread about a PWM signal generator device... Any suggestions would be helpful.