I have a 94 LT1, PCM & wire harness from a 1994 Cadillac Fleetwood. I have searched and searched here, lt1swap, etc, etc to no avail...For now I just want to run the engine on the stand to verify it is worth swapping. Can anyone tell me what wires I need to hook to what just to make the engine run..not concerned with anything else at this time. ANY help would be greatly appreciated. Thanks

 

No real reason to run it on a stand.

If you want to verify oil pressure all you need to do is mount it up on a cheap harbor freight engine stand and assuming the pan/heads are installed, and its filled will oil, install the starter and turn it over with with an oil pressure gauge installed. Turn it and watch the oil pressure. A starter will only spin the engine around 150-250rpm, so its nothing crazy that you can't deal with by simply putting some sand-bags on the feet of the stand. At that point you might as well check cylinder cranking compression too.

Other than that if you want to go further and actually hook the engine harness up, you are gonna need something much sturdier than a HF stand as a running engine will apply MUCH more torque to the stand. You will also need to hook up the entire harness outside the car. Not sure what harness you have, but if you have a stock harness you'll need to convert it to Standard alone first (which you kind of have to do to swap it into a 3rd gen.)

 

Okay so say I want to drop it in my 87 Z. Only concern is engine running (for now) no radio, blinkers, brake lights, wipers, etc etc. Could I follow this and have it run in car?

C210 (black) pin C ORNG wire- batt feed to PCM 10A fused



3 eyelet connectors in harness near coil / module connector, eng block grnd + 2 grnds near starter (black / white stripe)



C230 (blue) pin G PINK wire- Key 12V+ feed to PCM (run a wire from PIN G pink wire to the pink wire at IGN switch)



C100 (black) pins A, K PINK wire - key 12V+ feed to inj’s 7.5A fused (run a wire from PINS A,K pink wire to the pink wire at IGN switch)



C100 (black) pin G PINK wire- key 12V+ feed to coil & ign module 10A fused (run a wire from PIN G pink wire to the pink wire at IGN switch)



C220 (neutral) pin J DK GRN / WHITE wire- FP relay control 12V+ connect to one side of relay coil, other side to ground. Now wire FP with 15A fuse



C230 (blue) pin E DK BLUE wire- fuel enable signal, (here I would use the bypass module)

I understand for the time being it would look messy and all. I just want to get the LT1 in, have fun and then thin the harness this winter when I can’t do anything. Thank you.

 

Personally I would do a mini rebuild with rings, bearings and gaskets, put aluminum heads on it and a cam. But that is just me. I like to know that the engine will be solid before swapping it.

 

Ok here’s my delima. Also have a 97 LT1 that I know is good. It’s from a T/A. Has PCM and engine harness only, rest of harness was cut at I’m assuming firewall as there is no fuse box or relays anywhere. What would be the best option, try to make it run as is OR keep the PCM and find a new uncut harness?

 

Without knowing exactly where/how the harness was cut, its hard to say if the harness is usable.

But you say the engine is running? Running in what? Currently installed in your car? Another car?

The C100 connector contains both Engine, and body harness connectors. Most of the body connector stuff like lights/signals/etc are on one side of the connector, and the rest on the other.

The Thirdgen engine harness however, does have some tie-ins for stupid things like blower high speed relay.

Alternatively, you can buy a Painless stand alone harness and go from there, but that's about $750. However, that harness is long enough to hide the PCM inside the car in the stock location. Which really cleans up the engine bay.

 

I have 2 LT1s. One is a 94 from a fleetwood. Never heard it run, that’s why I mentioned the stand. The other is a 97 from a TA I heard run previously. Harness has been cut on both (not by me) no fuse block, no relays, but, all engine sensors, accessories, radiator, fan, etc appear to be there…as well as the Red, Black, blue and clear PCM connectors. I’d prefer not to go the painless route unless absolutely needed. I appreciate your input. Hopefully someone can shed some light. Thanks again.

 

Upon inspection the 97 LT1 (from a T/A) appears to be intact 100% minus fuse box. Has all C(xxx) connectors. Didnt see a fuse block from what I could see in storage. Can the car still run without fuel pump and fan relays? Can I use a fuse block from another GM car or truck and how would I go about doing that? Also what wires go from lt1 harness to pink, red andpurple at IGN switch? I have already searched goldsswagon, shbox, lt1swap, etc. IDK if i missed it or what, please can anyone help? I am excited to do this swap! Also dont want to go the "painless" route id prefer to rework the OE harness myself. For now I just want the car to run. Not worried about any accessories. Thanks

 

There is a giant thread that has all of the info you should need already about marrying a 4th gen harness to a 3rd gen. Its what I used to build mine.