1989 to 1985 Blazer engine swap

[Cspenc]

Hey all,
I am new to the CK5 forum. My son and I are converting a 1989 K5 Blazer all engine and Transmission into a 1985 K5 Blazer. All the engine and computer and tranny are installed. My problem is that the 1989 is fuel injected and the 1985 was Carbureted. The fuse block through the fire wall is slightly different. What I need is a color diagram to match the 2 main harnesses together to make the 1989 engine and tranny all work together without pulling the whole factory harness out of the 1989 headlights to Tail lights. I do not believe this is necessary to make the newer engine and transmission run properly. And all the proper engine management equipment. I think there has to be a relatively easy way to make this conversion work. Looked online and couldn't find a color wiring diagram for both trucks. I Know guys take these fuel injected motors and install them in Jeeps and make them work . I would think making a Chevy to Chevy swap should be fairly uncomplicated. I realize there is a couple more wires needed to run the fuel pump and such. Any help would be greatly appreciated.
Spenc

 

[kennyw]

My opinion is it would be easier to swap the complete harness from the donor rig. Either that or you need to pull the donor harness apart to get all the extra parts that don't come with the '85. That in itself is almost as big of a job as swapping the harness.

 

[dyeager535]

Kenny is right. The fuse panels aren't wired the same on the inside of the cab. You'd have to rewire the cab side of the fuse panel, and have you ever taken one of those apart? Possible, but a mess. You'd have to disassemble another panel to get the proper fuse terminal ends anyway.

Everything disconnects on the harness, unplug the one, plug the other one in. The physical size and shape of the panel is the same, I don't know as there are any differences outside of the connectors on the firewall (and injection related wiring/fuses) between the '85 and '89.

I converted an '85 diesel harness to injection, but had to use an exorbitant amount of extra wiring to power it off the various accessory terminals across the top of the fuse panel, run an auxilliary fuse panel to properly fuse each lead for the injection (injector 1, injector 2, fuel pump, ECM for four right there) which are key-position dependent.

You COULD add a later GM car/truck fuse/relay center underhood if you want, and had plans for other electrical modifications (electric fans, running lights, etc), but even that is a fair bit of work if you are just trying to convert the '85 to the stock '89 stuff.

Yes, a hassle to swap the entire harness, but it will work right and you won't have any issue. Well, I assume the headlights might cause a bit of wiring work, but better to deal with those than the ECM/fuel pump/injector controls that the '89 harness is wired for.

If the taillight wiring is one solid run from the fuse panel terminals to the connector, I'd probably be tempted to add in a couple of weatherpack connectors, because that wiring IS a pain to run if the body is on the frame. I just can't remember if there is a connector before it hits the frame or not...I don't remember one.

 

[Stomis]

The guys are right. You're better off swapping the harness because of extra connections. Think about fuel pump wiring too. Its the other end of the truck...

 

[Cspenc]

Got the wiring figured out

Thanks guys.
We made the entire harness swap. Everything seems to work ok. Have a few problems we are working through but minor issues. Thanks for the input to get the 85 Blazer back on the road....
Cspenc

 

[dyeager535]

Nice! Too bad GM didn't start injecting these things far sooner so you didn't have to go through this!