Andy’s 1995 CCLB 7.4L TBI to Vortec Swap

[andy396]

After getting the chassis all blasted and painted I could finally start making real progress. Dropped the engine and transmission in, exhaust hooked up and fuel tank in. In the process of redoing the chassis I discovered a couple cracks in the frame. One on the rear upper shock mount and one from a factory cold weld on the upper left a-arm mount. Everywhere else looked good. Welded them back up and moved on.

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[andy396]

While working one day on the exhaust I had this guy come into the garage and keep me company. He didn’t even seem to mind all the noises I was making. He probably hung out for a couple hours.

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[andy396]

At this point I started hooking up all the wiring for the power train. I used everything from the 2000 L29 except the front to rear harness. The new fuel pump came with a new connector so I cut off the '95 and installed the new connector. Up front at the firewall the connector just needed some pins moved around (if I remember correctly). So with the chassis wiring installed I focused on the dash. The dash in the '95 was cracked pretty badly so I was lucky and found one out of a '95 6.2L diesel in a junk yard in perfect shape. I transferred everything out of the '00 dash into the good one. There are some differences, aside from the '00 having the big hump on passenger side for the airbag on the light duty trucks, which creates some extra wire in the '95, there's also a difference in the metal support bracket on the driver's side.

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I'm not sure exactly why it's different other than it has a place for the daytime running lights module.

 

[Supercharged111]

So how did the duck taste?

 

[PlayingWithTBI]

Smoked duck goes great with Whoppatoolie, tastes like spotted owl.

 

[andy396]

So how did the duck taste?

lol! Don't know. I let him keep his freedom. Haven't seen him or any of his friends since.

 

[andy396]

Back to the dash, I transferred the bracket over to the new dash. This of course involved drilling out the rivets and re-riveting it back in. Even though the replacement dash was in great shape, it was a touch faded. I opted go ahead and give it a fresh coat of color. I first sprayed a coat of SEM Sand Free wet one wet adhesion promoter specifically for ABS and PVC plastics. I then immediately followed that with SEM 15043 Shadow Blue. This was my first time using this combination. The color and sheen are a perfect match! Thank you SEM for not forgetting about us guys who like our old blue interiors.

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I also did some reinforcing around the three attachement points up near the windshield. I bent some thin sheet metal around where the mount is and epoxied it in place. I've seen this as a failure point in many of these dashes where the screw hole just gets busted out. My hope is this helps to spread the stress out some.

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This is the area I'm talking about. I wrapped the sheet metal around all three sides, and epoxied it on the back side.

 

[andy396]

At this point, I've set the body and bed back on the frame. The bolts won't go in until the very end in case I find out that I've screwed something up and need to pull something back out of the chassis.

Now comes the tricky part. I'm trying to reuse the interior cab wiring from the '95. I've got two extra doors with power windows, an overhead console, and a rear window defroster that the '00 parts truck never had. I've got to figure out if I can marry that with the '00 dash wiring. Specifically, it's the cab cross over harness I'm reusing.

This brings us to about a couple months ago where I started this post asking for help.

https://www.gmt400.com/threads/what-is-this-connector.44642/page-2#post-1043733

If you don't feel like going down that trail, I'll summarize it for you here.

For whatever reason they felt like moving stuff around. The cab clearance lights and the electrochromatic mirror got their own connector instead of plugging into the convenience center. I think this is because they ran out of space after adding a wire that energizes in reverse in order to turn off the mirror dimming when you put it in reverse. Whatever! Can't say that was ever an issue for me. I kept the '95 mirror (for now) and everything else is now moved back into the convenience center like it was in '95. I kept the '00 connector in tact. I just spliced into the wires with the pins I stole out of the '95 diesel parts dash.

 

[andy396]

Thinking I've got the wiring all figured out I decide it's time to hook the battery up and test some things out. As I go to connect the terminal the horn starts blaring. Try the power locks, nothing. Turn the key to on, try the power windows, again nothing. At some point in this series of tests the ABS unit spins over as well. Plug in the headlight switch, no interior lights with the door open, no HVAC blower, no radio. At this point the list of things that work in the cab is probably shorter than the list that doesn't.

I'm feeling pretty overwhelmed and deflated.

I'm back to this forum asking for help.

https://www.gmt400.com/threads/who’s-crazy-idea-was-this-1995-1996-cc-wiring-diagram.45023/#post-1051740

I try comparing the wiring diagrams from '95 to '98. I've never really tried to understand GM wiring diagrams before. I don't know about you, but I struggle. I kind of got it now, but that's after weeks of staring at them. Feeling like I am going to have to abandon the idea of using the '95 cab wiring I start hunting for alternatives. The closest thing I can find is a '99 Suburban not too far from me. I connect with the guy and he is kind enough to let me have the cab crossover harness out of his Suburban in exchange for my time in helping him disassemble some of the dash parts. He also let me have the PCM/ABS mounting bracket that I learned is not the same as the ABS/Washer Fluid bottle in '95 (they're really close looking which is why I didn't save the '00 bracket). It's like they tried to make it the same, but somehow screwed up when it came time to build the '96's. Anyway, he was a great guy and I was very thankful. My thought in getting the Suburban harness is I'd have enough to be able to build my own '00 crew cab pickup harness between everything I had. The biggest discovery I had when removing the Suburban harness was that there was a ground lug over on the passenger side that my '95 didn't have! I landed that ground terminal on an insufficient ground when I installed the '00 dash! When I got home I moved that terminal over to a solid grounding point on the cab and more things started to work, particularity the blower, HVAC, radio sound. I still had no illumination on the radio itself.

More staring at the wiring diagrams and more probing wires between the '95 dash and the '00 dash. What I needed to make the windows and locks work was another ground. Once I connected the ground coming from the door wiring to the instrument panel ground all the power door stuff started working.

Down to just the interior lights not working when the door jamb switch activates (but they do work with the over ride on the dimmer), the horn still going, and the radio not illuminating I decide it's time to see if the engine will run.

Turn the key, it cranks.....and cranks....and cranks....nothing.

 

[andy396]

I'm beyond deflated at this point. What could I have missed? Put the timing light on #1 and don't see any spark. I walk away...

One other issue I had this whole time is I couldn't communicate with the PCM. I wonder if I fried the PCM as part of this fiasco?

Back to craigslist looking for a PCM. Find a college kid very nearby parting out a '99 Denali Suburban. So I pick up that PCM as well as the temp sensing mirror in addition to the 120mph speedo for Kennythewelder. Get home, plug in the PCM, still no communication.