I need some guidance with OBS wiring

oh and disreguard my post #5. i thought he was talking about powering the fuse block with the injector wires. but all he was powering was the pcm which im sure draws next to nothing. so injector positive should be just fine for the pcm.

I'm still scratching my head on this one too. Does anyone know where I can hook this brown wire up to, to retain my battery light?

I guess it would depend on what year your swapped engine is. Mine is a '99 and uses one wire on the alternator. Later years used more than one wire to feed the PCM and the idiot ligtht.


After doing some research, I found that the idiot light is actually a feed to the alternator. There is a whole description in the service manual on how the system works. But for now, the info you need is that the brown wire goes to the "B" terminal on the alternator plug. Below is a schematic. This info is out of the '99 GM service manual. I believe this should work for you.



http://i488.photobucket.com/albums/r...s/scan0285.jpg


http://i488.photobucket.com/albums/r...s/scan0286.jpg

Thanks Mickey. I appreciate it, man!

If I don't hook it up, would the battery light stay on, or off?

I don't really need it, but if it stays on, that would be kind of annoying.

If you hook it up, the light should go out. Depends on the year of swap engine though. Like I said, this schematic is from the '99 GM service manual. Different years could be different. It's worth a try.

Yeah, mine is from an 03 express van. It is a bit different. Terminals a and f are unused, b is red, and c is brown. I'm willing to bet either one would work.

Try the brown one. You may just get lucky!!!!!.

One last question. I have a stand alone harness with it's own relays. It just needs a fuel pump control ran to the relay, constant 12v from the battery and a keyed 12v source.

Can I snip off the TBI fuel pump relay and use all of those wires to power the new stand alone set up?

I'm pretty sure the gray wire will control the fuel pump, and the pink wire would be a good keyed 12v source. Please correct me if I'm wrong.

If I understand your question correctly, I don't think you can use the original fuel pump relay control wire from the original PCM. I left my original PCM in the truck thinking it would be able to power my original fuel pump relay. This setup doesn't work because the original PCM doesn't "see" any crank or cam signals from the new engine. So, all it does is prime the system. After 2-3 seconds, it stops power to the fuel pump relay because the old PCM thinks the engine stalled since it "sees" no signals.
So, this is not a viable source of keyed 12V since it's controlled by the old PCM. Hope this helps.

the gray wire is what feed the power from the relay to the fuel pump then across from that one there is an orange wire that supplies power to the relay, there should be a green wire with a white tracer that is the relay control from the pcm and a black with white tracer for ground. There might also be a red wire with a connector on the old relay but dont worry about that one. That is only to jump the relay if you had to. What I did with my fuel pump relay was use the relay from the truck and connect the fuel pump relay control wire from the new pcm and connect it to the control on the old relay.