I have a complete TPI unit, harness, and computer out of a '92 GTA T/A. I am putting it in a 1989 C1500 that currently has a 350 TBI. Can I just modify the TBI harness to work with the TBI computer or do I need to change both out? I want to keep my RWAL(rear wheel antilock) and don't want to use the VATS. I have both books( C1500 and T/A)and the harnesses are identical with the exception of the fuel injection leads and the cooling fan leads. Any info. would be greatly appreciated.

This can (and has been done) on the stock harness with the stock computer. Remember, the calibration (EPROM) will need to be swapped for a custom unit if you plan on keeping the stock computer. If I remember correctly, the injectors get wired in parallel. There is a shop that I read about in a car mag that does this kind of swap and has eproms set up for it. Give me a couple of days and I'll see if I still have the mag.

[This message has been edited by Dan W (edited January 01, 2001).]

89 truck as I recall is a 747, 92 GTA, should be a 730. 747 uses a 2 connector ecm and the 730 is 3. There is a far bit of rewiring but should be enough wires to handle it. I think you've look up and compared wiring from a 89 TPI to a 87 TBI for them to look very similiar. A 165 to 747 is very close.
The 730 will need to be redone a little to use the 747 Optical speed sensor, but all that is in the DIY_EFI archives. You'll need to double check but if you leave the DRAC stuff intact you should be OK, on the brakes.
Zerox, everything and put it side by side, and then note what EXACTLY need changes, not a huge deal, but good planning pays
HTH

Thanks for the replies. It is true my truck came with the 747 ecm and I do have the 730 from the GTA. When I compared the two diagrams from the Haynes manuals, they harnesses are identical with the exception of the injector leads and a 12V source to the ecm for 1 bank of injectors. If I run the 12V wire and tie in the leads for the 8 injectors, will I have to use the 730 ecm? I personally don't think it will work with the 747 due to parameters for injector pulses.

Grumpy,
Can you provide any info. on the 7730 ecm. I understand that I need to use it for my swap but I want to make sure that I wire up only what I need. The 2 harness connectors are the same but I need id for each pin to ensure same functions. Also need to know what I "have to use" on the third plug-in on the 7730 ecm. Any help would be greatly appreciated. P.S. Getting my old man involved in programming chips since he is a electronics tech. retired from Conoco.

Thanks, Nick

This might seem funny but: I have a -88 C-1500 truck and got a -91 GTA engine, harness, and ECM. Its done and working. Actually I´m uppgrading allready. e-mail me at 396tpi@iobox.com.

You might call Street & Performance, or go to tunedport.com. They do TPI/LS1/truck swaps all the time - even sell a kit to do it. They might be able to answer some of your q's.
SC

If you go over to DIY_EFI Incoming, there are pinouts for both. Then just a matter of comparing them. As far as only what you need, well that really is your call. Personally I run no A/C, and I always run the rad fan thru a Radiator fan switch rather then thru the ecm. CCP, and EGR are legal issues.
HTH

Grumpy,
Thanks for the info. on the site, has a lot of great info. I'll let you know how things come out in a few days.

Nick