55.2-59 Urgent

[Bridgeman57]

Pulling a 91 350 and need to know what wiring I need for the efi system. I have about about her 2 hours of work. Have the fuse box off from the firewall and everything disconnected from under the dash but not sure what part of the harness I need

[joedoh]

Originally Posted by Bridgeman57

Pulling a 91 350 and need to know what wiring I need for the efi system. I have about about her 2 hours of work. Have the fuse box off from the firewall and everything disconnected from under the dash but not sure what part of the harness I need

the tbi harness will run from the motor to the firewall usually on the passenger side, it might have a big right angle looking water director on it. you need all that wiring intact and the computer that hooks up inside, sometimes they are in the passenger kick panel.

follow the big harness from the motor, get everything it hooks to.

[Bridgeman57]

Do I need anything under the drivers side dash???

[1project2many]

So... 91 is a split year where the old square body style trucks were still available alongside the new "GMT400" or C/K trucks. I'm going to guess you're working with the GMT400 trucks.

There are wires that run to the fuse box. They connect at the driver's side bulkhead connector on the driver's side. Pull the connector but don't worry about what's under the dash. You can connect the power wires later. Look for the DRAC, white box under RH side of dash. This adjusts the speed signal so the computer can read it properly. Grab the connector, too.



I'd also think about getting the relays from the RH side of the engine compartment on the firewall, the terminal block on the firewall, the wiring to the transmission and starter, and anything else connected to the engine wiring. You can throw out extra but it's really a pain to try and add what you forgot.

[Bridgeman57]

Yeah I knew I forgot something. The dang DRAC. I didn’t snag anything from under the dash on the drivers side. And stepdad decided to get frustrated and cut a few wires behind the engine so I’ll be dealing with that later. Thanks for the help guys. Always very much appreciated. I’m sure you’ll be hearing from me on how to put it back together lol ����

[burnin oil]

Make sure you have a good wiring diagram for a 91. Tbi is stupid simple but gm changed things slightly every couple of years. Just off the top of my head they changed the EGR around, location of the distributer brown wire for timing, and color codes of wiring. It's simple enough if you know what the plugs go to but can be confusing if you are going by color codes.