The Stovebolt Site Forums The Shop Area The Electrical Bay 1946 chevy Pu with 4.3 engine with 92 wire harness

I have a 1946 Chevy 1/2 PU and a 1992 as a donor truck.I have the engine installed and all hooked up with the engine wiring harness and hooked up to the ECM also.My question is do I also have to use the main wire harness to have the engine run right.
Thanks for any info.

If you're using the fuel injection system, you'll need sensors such as the vehicle speed sensor and O2 sensor, etc. Otherwise you'll get a constant "check engine" light, and if you're using a transmission with a lockup torque converter, it won't function without all the sensors in operation. You'll also need the in-tank fuel pump and the wiring to run it.
Jerry

It's been a while since I've done this, but Hotrod is right. You need at least the wiring harness that came with the engine that matches the ECM you are using. As he said you need all the sensors for it.

If you have all this, then you need a wiring diagram for the ECM to tell you which wires are the grounds for the ECM (Seems like there are two for the TBI, but may be wrong). There should also be a wire to furnish constant bat voltage to the ECM as well as a switched batt supply into the ECM.

You can do an internet search for a pinout diagram using the ECMs numbers on the tag. Much better than relying on my memory.

With the wiring harness for the engine and ECM it really isn't hard to make the engine run correctly. When I do a swap like this I like to have the donor vehicle there so I can get everything off of it along with the engine. That way every thing matches.

You will need to adapt the fuel system as hotrod said. Again makes it easier to have the stuff from the donor vehicle.

I did this about a year ago on a 36 F..d. I did use an external pump with the correct rating and plumbed in a return line to the fuel tank.

Hope this helps.

Roy, the TBI gets a fused 12V straight to the injector, and grounds through the quad drivers in the ECM. Injector pulse width is set at a 50% on-time default setting and the amplifiers use the sensor inputs and the O2 sensor signal to add or subtract from that point to fine-tune the mixture. The correction is applied anywhere from 10 to 90 times per second, depending on the clock frequency. Much more accurate than a carburetor!
Jerry

Yes sir. It's a pretty simple set up once you look at it a bit.

I still a schematic floating around here somewhere from my adventures.

I got to do mine twice. The fellow I put this on for decided he wanted to reroute the wires a little to "pretty things up".

He managed somehow to get an ECM ground connection hooked to the hot lug on the alternator. Said he knew he had a problem when the smoke came out.

LOL! Back in electronics school we learned that all electrical devices have a certain amount of smoke installed at the factory. If you let the smoke out, the thing quits working! I've seen it happen numerous times. Some of them have a huge amount of smoke crammed into a TINY box!
Jerry

1. Suggest that you get a relay for under the dash and run your ignition off of it, because your ignition switch probably won't last otherwise. I presume that your old ignition wire is not "ballast" wire, which will not work with FI.
2. An in tank fuel pump is preferable, but may not be possible. I got an external pump from Summit that does well. You will need a return fuel line to the tank, suggest you use the original fuel line as a return and run a new fuel feed line.
3. As stated, you will need a constant source of power to the ECM. I connected mine to the positive battery connection on the starter.
4. I would stay with the 92 wiring harness and shorten and lengthen as necessary. Solder and shrink tape all connections or you will be driven crazy when a crimped lead starts breaking down.

I want to think everyone for all there info.I have the truck running and starting on the inside .Thanks again
Gene