3.4 swap into 91 Trooper

[CNCguy]

Still chronic clutch problems. I'm going to have to pull the tranny again to clean the clutch up, I wasn't as careful as I should have been last time around, think I contaminated it. The worse problem is the hydraulics. Seems my new slave cylinder started leaking after a few weeks of driving. Can't get my clutch to stop dragging. I bled it on a couple occasions and that seemed to help at first, but not anymore.

Just a thought but did you install a new pilot bushing? Is the 3.4 bushing the same size as the stock bushing? I have seen pilot bushings cause problems that appear to be clutch release issues. Too tight and friction will keep the shaft spinning when the clutch is disengaged. Too loose and the input shaft can sag causing the clutch disk to drag between the flywheel and pressure plate.

[Canyonero]

Well, there are two problems. The clutch slips if you dump it or shift too hard. The 2.8L with an old clutch would spin the tires no problem and chirp the tires into 2nd gear. I'm thinking that is just because I was careless handling the clutch when I was installing it.

I'm fairly certain the other problem is hydraulic. The clutch had been working fine for a few weeks when I first got the Trooper on the road again. The slave cylinder is the only part of the hydraulics I've messed with. I had replaced it when troubleshooting my improper clutch disk installation.

The engine was from an auto, so I did have to install a pilot bushing (came with the clutch kit). Everything fit fine and was working fine for a while...

[Canyonero]

Clutch is fine now. Doesn't seem to be slipping anymore, nor is it dragging. I replaced my slave cyl again - no more leaking, also got the floor mat out from under the pedal. That extra little travel makes a difference!

So, here are some wires that might be useful to future Trooper swappers, in no particular order:

Black/Yellow - 12v Switched (on and start), formerly used for the ignition coil, now a convenient source of switched power for the new ECU.
White/Red - Alternator
Black/Pink - "Main" Fuel Pump Relay signal from ECU
Blue/Black - Oil Pressure Switch (closed circuit w/ pressure, "backup" fuel pump relay and dash relay for heater fan and ?)
Yellow/White - Oil Pressure Switch (open circuit w/ pressure, idiot light off and ?)
Black/Red - Tachometer (Adapted to use ECU signal with MSD-8920 Magnetic Pickup Tach Adapter)
Yellow/Black - Coolant Temp Gauge (use sensor in head from Trooper 2.8L, sensor in LIM goes to ECU)
Orange/Blue - Oil Pressure Gauge

My standalone harness has the fuel pump relay built in, but I think I'm going to remove that wiring and just feed into the original Trooper wiring. The Trooper uses two fuel pump relays; the "main" one is triggered by the ECU (Black/Pink) and the other "backup" relay is triggered by the oil pressure switch (Blue/Black).

The OEM tach (Black/Red) won't work without an adapter such as the MSD-8920. It buzzes, so you'll probably want to put it out in the engine bay. (keep in mind you'll also need switched power for the adapter).

[Canyonero]

Here is my cluttered engine bay as of this afternoon. I will be very happy when the wiring is cleaned up.

What are the proper wire colors for the heated O2 sensors? I just used black and red, that's what I had on hand.

I'm thinking of using red wire loom when I tidy all this up. Would that be too much red?

[cardana24]

What are all of those red wires for? Did you have to do much extra wiring even with the custom harness you bought?

[Canyonero]

I was in a hurry to get my heated O2 sensors installed (had to run power to them). Red and black was all I had on hand to do the temporary wiring.

I'm actually going to take some wiring out of the custom harness too. It has a fuel pump relay built into it which I'm going to remove in favor of the chassis wiring.

I found a place where you can order specific color combinations of wire, Allied Wire and Cable. (is there somewhere better? please share.)

http://www.awcwire.com/ProductSpec.aspx?id=Type-SXL

Once I figure out how I'm going to wire everything permanent, I'll order in some spools of the proper colors.

[Canyonero]

More progress this weekend. I stripped out all the original ECU wiring, and it wasn't as hard as I thought it'd be. Of all the wires running to the ECU location, I was left with eight that I might want to use, all originating from the blue connector behind the glove box, and one from an under-hood connector. I took a few pictures in the progress, I'll upload them later. A1, B1, etc are the pin numbers on the original Trooper ECU connector. There are some duplicate colors so be careful. I pulled my VSS wire in half because I misidentified another yellow wire. Ooops.

A1 - Black/Pink - Fuel Pump Relay
A2 - Green/Black - A/C Controls (?)
A3 - Green/Blue - A/C Controls (?)
A5 - Blue/Pink - Check Engine Light
A6 - Black/White - 12v Switched (from main relay, green connector under hood)
A10 - Yellow - Vehicle Speed Sensor
B1 - White - 12v Constant
B2 - Black/Orange - Fuel Pump Status
C9 - White/Black - Starting/Charging System (?)

The 'standalone' wiring harness I had made has a relay built in for the fuel pump and oil pressure switch, neither are needed. If you're having a harness made, you can omit those and maybe save a little money. What you do want is a tail to connect the fuel pump relay and the fuel pump status to the ECU. Wire those into the A1 and B2 wires, and use the original oil pressure switch and wiring. So, I am now using the original fuel pump circuit and I can strip the relay and oil pressure switch wiring out of the standalone harness.

I identified one of the modules under the hood that I assumed was something for A/C or CC. But it was actually the Electronic Spark Control, which I then removed. The other green connector there that I had disconnected was from the main relay which fed the aforementioned spark control (Black/Blue) and also the ECU (A6 - Black/White). I will probably re-use this for the new ECU (currently using the former Ignition Coil circuit).

I found that the cruise control is completely standalone. I had moved the vacuum actuator when I was fishing wires through the firewall and just forgot to plug it back in. It is the pedal-pull style and gets the vehicle speed from the speedometer, so it really doesn't matter what has been done in the engine bay, as long as it still has vacuum.

The original ECU had the A2 and A3 wires to the "A/C Controls System". Not sure what those are yet, or what will be needed to get my A/C back. Other than the compressor I omitted of course. Anyone know?

Also don't know the significance of the C9 wire to the "Starting and Charging System". The truck starts and charges so I guess it can't be that important, but still something I'd like to know.

[KellyTTE]

Also don't know the significance of the C9 wire to the "Starting and Charging System". The truck starts and charges so I guess it can't be that important, but still something I'd like to know.

On GMs (not as sure about Zoo's), there is a 12v keyed power with a resistor that 'excites' the alternator and tells it to charge. Its possible that its something similar.

[Canyonero]

There are two wires on the diagram B10 (Red/Black) and C9 (White/Black). I don't know where the Red/Black goes, maybe I'll poke around this afternoon and see what I can find. I have a spare Trooper here too with the original everything. The only wire to the alternator (White/Red) is still connected to the Trooper chassis wiring, and I've verified that it doesn't charge when unplugged (Ooops!). Where that White/Red wire goes, I don't know. Not either ECU, I know that. Hopefully I'll have an answer to some of these questions this afternoon and some more pictures. Attached is the diagram I've been using. I also have the Haynes diagrams with everything but this one has been much more useful for ECU related wiring.

[Canyonero]

Cut the fuse block off my standalone harness and pulled more slack into the cab (square fuse block wouldn't fit through the round hole). Stripped out the oil switch connector and the fuel pump relay. Cut back the 12v constant wires to connect to the original ECU power source. Still have to re-loom the engine bay side, but priority now is to clean up the interior wiring.

[Canyonero]

Well, priorities changed. After some bloodied knuckles trying to work the harness through the dash, I got frustrated and yanked the harness out. Partially unloomed it in my living room and wired power for the HO2S proper-like. Laid it out in the engine bay and started relooming so that it could be tucked out of the way. Here it is, partially completed. The engine bay is looking MUCH better. Still have work to do though.

[Canyonero]

Well, count my Bosch O2 sensors as another $100 wasted. I ordered a pair of proper AC -Delco sensors. I hope it makes a difference.

Still need to finish the wiring. I want the truck for a fishing trip this weekend. But my garage has another Trooper in it and it's miserable outside. It's been snowing a little bit, despite the fact that it's bloody April. WHY WON'T WINTER END!?

[Canyonero]

I have sacrificed the glove box to the cause. But the ECU is finally off the floor. Behold!



Yes, I know my radio housing doesn't match. Some cocks in Portland stole my stereo. I think I'll just paint it flat black someday.

[greener]

Hey, I'm finally about to pull the trigger on a crate 3.4 (GM part number 12363230) to do my swap.
Any west coast folks have a supplier they can recommend? The place I found is just a GM reseller and wants $2100 for the engine and shipping.

Thanks, and thanks Canyonero for all your swap information tidbits.

[Canyonero]

Where on the West Coast are you? Crate swap should be pretty easy for you, compared to what I got myself into. She's running and driving great now though.