91RS_Charlotte

iTrader: (1)

In the process of preparing for my engine swap from a 1991 3.1L MPFI and replacing it with a 1985 5.0L TPI while maintaining the speed density setup, I did a bunch of looking around to find out what I needed to do to the wiring harness. While all of the information is out there, it required a lot of piecing things together, so I came up with the attached files (the zipped file is an Excel version).

There may be something like this out there already, but I couldn't find it, so now that I am up and running, I thought I would share this in case someone else finds it useful.

Let me know if you find something that is off and I will update the files.

Disclaimer: I make no claim that this is 100% accurate and that you won't blow your car or yourself up if you use it.

Credits: Most of the information came from crossreferencing info from the Autozone wiring diagrams and other docs found at http://www.eecis.udel.edu/~davis/z28/ , http://www.austinthirdgen.org/index.php?pid=19, or http://chevythunder.com/

P.S. There are other variances beyond the ECM in the wiring such as no A/C relay on the TPI, so be sure to look into the body wiring diagrams closely when making the swap.

diehard92

hey i tried to download your file but it want let me. i have a 90 3.1 camaro and i im about to put a built 305 TPI system in it but i dont know if i have to change any thing or a lot of stuff like my speed senser gauges and the rest. or can i just unplug the harness from the dash plugs and plug in the TPI right in to it can you give me some feed back on this so i dont miss my car up thanks

91RS_Charlotte

iTrader: (1)

Sorry, for some reason I can't get any of the zip files from here to open either and I can't post a direct excel file. I saved it as a pdf, see if that works. If not, you can pm me with an email address and I will just send the file to you.

As far as what you have to change, it depends on what you are doing. Every swap is unique. I put an 85 TPI into my 91 3.1 and kept my same computer and wiring harness and just modified the harness. Because of that, I did not have to make any changes to the guages, but did have to change the connectors on the harness in several places to match the older connectors. If you are putting an older ECM in with the new motor you will need to make some changes to the gauges since the newer ones are electric and the older mechanical.

I don't claim to be an expert in this area. This was my first swap, so I'm sure there are others here that can be of more assistance. I just read the forums here A LOT and made good use of the websites mentioned in the OP. My best advice would be to go to the autozone site, select your vehicle, then click on "Repair Info", then "Vehicle Repair Guides", then "Chassis Electrical", then "Wiring Diagrams". Then print out the diagrams for your current setup as well as the ECM/Engine you are going to use and study them very carefully.

Best of luck!!!

91RS_Charlotte

iTrader: (1)

Oh, just a few more things I thought of.... If your putting an older TPI in, but keeping the current ECM, some of the sensors from the 3.1 will actually transfer over. Off the top of my head, it seems like I used the knock sensor, MAP sensor, and the oil pressure sensor. The vacuum can and that whole assembly can also remain from the V6.

Pocket

iTrader: (24)

Good info in here

sum_drummer_16

to use the v6 harness out of a 91-92 camaro on a 90 tpi, what do i need to change on the harness beside adding two plugs for the additional fuel injectors because both will be speed density and use the same computer.

91RS_Charlotte

iTrader: (1)

Several factors will determine what you have to change. The simplest is if you are using a manual trans, no egr, no A.I.R, & no A/C.


Some things you will have to change are as follows:

• EST/Coil: Not positive on this as mine was older, but the 3.1 has a seperate coil instead of coil-in-cap, so I would bet the connectors will be different, but the wiring colors/functions are the same.
• Aux. Coolant Fan: If you use an aux coolant fan and want it wired like the factory, you will need an additional relay (see A/C note) and will need to connect into the grey fan pressure switch line. Will also need an Aux coolant fan switch and all connectors.
• Converter Control Solenoid & 4th Clutch Switch (ignore if manual trans): the 3.1 has a temp switch that bridges these two circuits that will need to be removed. The Converter Control Solenoid circuit goes to F6 and the 4th Clutch Switch circuit goes to D14.
• EGR Solenoid & Air Select: The 3.1 unit has 3 wires (Red, Brown, & Lt Blue) going to it which control the device. The 5.0/5.7 has seperate circuits for the EGR and A.I.R. valve. The EGR gets the Light Blue, the AIR gets the Brown. The factory wiring for the 5.0/5.7 for these two is Grey and Pink/Blk respectively.
• A/C Compressor Circuit: The 3.1 uses a A/C compressor relay. The 5.0/5.7 does not. The relay has 2 Dark green & White wires, 1 Dark Green, and 1 Pink/Blk. The Pink/Blk can just be disconnected as it is not used. Remove the relay and connect the 2 Green & white and the 1 green wire together. One of the green/white wires runs to the ECM and needs to be repinned from F1 to C9. (Note: If you need a relay for the aux coolant fan, you can use the no longer needed A/C Comp Relay)
• If you have a manual trans, you will need to move the Shift Indicator from F6 to F1 after you move the A/C circuit.

It also involves a good deal of adding/removing wire length as things are simply laid out differently. I had the non-SD harness to pull connectors from which made things much easier, but I was able to use 60-70% of the 3.1 connectors. As the motor was older, things like the alternator voltage regulator connector were different. Hopefully you won't run into that since yours are form the same era.

I'm sure I missed a thing or two so someone else feel free to join in.

Hope this helps & good luck!

Note: All info provided is best effort. Not responsible for fried ecms or explosions

grassyflats

far out
i was just thinking about this swap and
now here it is...
curious though
with all this work...why not go with the 5.7?

91RS_Charlotte

iTrader: (1)

I wanted a 5.7, but a 5.0 that had been recently rebuilt, ran great, came with a donor car, and was cheap came along. This car isn't really a race car or anything anyway. It will never see a dragstrip and is more likely to be used for mountain drives, etc... It is a sentimental car as I have had it since it was new, so this is more of a restoration than a performance upgrade anyway. For this purpose the difference in power between the 5.0 and the 5.7 isn't really that big of a deal.

That said, I am considering putting something really nasty into the donor car for fun once I am completely finished

sum_drummer_16

well this works out really nicely for me then. i did a five speed swap a few months ago, no emissions will be going on the car, and i happen to have walked into a v6 harness and computer for free

i've been looking for a harness for about 3 months, but using the v6 harness had never occurred to me. this is truly brilliant, yet so simple. and it will definitely be a nice upgrade over the crossfire injection

91RS_Charlotte

iTrader: (1)

You will also need a V8 memcal for the computer and either a correct prom or burned prom to match your setup or you can use the v6 memcal with a burned prom, but will not have limp home mode.

This info is really for going from a v6 to v8 within the 730 ecm range. Because of this, I do not have any of the gauge or other interior ECM wires marked in my tables. If you are putting this into a 1983, some of these may be different. I know you will need to hook up the VSS in your trans (the WC T5 should have one). I don't know too much about the crossfires, but you may need to change out your fuel system to support the 45-50 psi required for TPI instead of the 12 with crossfire. Probably some other changes as well.

However you decide to do it, best of luck on the swap!

sum_drummer_16

i do need to change the fuel system, and i found that i can get a prom off of summit for pretty cheep. the v6 and v8 do use the same computer though, right? if not a remanufactured computer from advance auto is only 60 bucks

91RS_Charlotte

iTrader: (1)

Yes, both use a 730 ECM. If you are not going with emissions stuff, I would advise getting someone to burn a chip for you or else your ECM will throw codes and while you can just pull the light, it is helpful to having it working on a new engine to make sure nothing is wrong.

sum_drummer_16

okay, probably another stupid question, but i dont know much and havent heard much about the memcal. i realize i need a v8 memcal, but does it have to be from the 730 ecm? or will a v8 memcal out of the computer from an 85 or 83 work? and then engine size, 305 vs 350 doesnt change the memcal, right?

91RS_Charlotte

iTrader: (1)

Not a stupid question at all. Yes, you need a 730 v8 TPI memcal. 305 vs 350 is important if you plan to use the memcal as it is. If you are going to get a prom burnt (which if no emissions equipment is used, I would highly recommend), then any 730 v8 TPI memcal will work. To allow a custom prom to be used, you will want to get a Moates G1 adaptor (http://www.moates.net/product_info.p...products_id=32).

sum_drummer_16

so if i were to come up with the memcal for a 350 tpi, would i still need one of these? and i am planning on having the emissions all bypassed in the program along with the vats

91RS_Charlotte

iTrader: (1)

Yes. The memcal has the prom and the EST controls. The prom is soldered to the memcal. You plug the G1 in place of the memcal within the ecm and then plug a custom prom and the memcal into the adaptor. With this configuration, the ecm gets the prom info from the custom chip and the est info from the memcal.

I think I have read something about being able to flash the prom on the memcal, but I'm not really familiar with that method. Perhaps someone else could offer more info.

mr.chevy

I am in the the middle of swapping a 2.8 to 5.7. All the harnesses I have found are cut up or plugs are broke but my 2.8 harness is perfect can it be converted? Thanks