To begin with I'll give you a little background on the swap to let everybody know why exactly I have decided for the swap. I have a '99 Si and my brother has a '97 DX. We both have planned on modifying our vehicles but quickly decided to focus all of our efforts on a single vehicle to save money. Given my brothers hatch is already gutted and cage-ready, minor suspension work, etc etc, we decided that we are better off by putting the b-series motor into the hatch and his Y7 into my car.

I thought from day 1 that this would be a straight up swap and I'd be back to driving my car in no time. I've swapped axles, main engine harness, ecu, radiator, pretty much everything for an engine swap to work. I am now to the point where I can drive it. Everything is buttoned up and ready to go, however the car will not start.

I'm getting spark, the starter is turning to motor and everything is working....except I'm not getting any fuel. The fuel pump/main relay is not clicking like it should be when you turn the key and my pump is not turning on to prime the lines. We checked the pump, there is no voltage getting to the pump. We checked the relay, everything is in accordance with Honda's service manual. Checked the fuses, checked everything and for the life of me I cannot figure out why the relay is not working.

The ONLY other things that I can think of that would be different between the two cars would be the interior/dash harness maybe on the C131 harness? Or the ECU is not working. Any help is much appreciated. Thanks

 

the harness is different. You're gonna need to swap out the dash harnesses, or the entire dash, or run a jumper harness. If you're using the DX dash harness with the B16 engine harness, then you'll only have two of the plugs needed for the ECU. The D series engine harness has all three pigtails on it, but the B series engine harness only has two, and the third comes from the dash harness. I ran into that problem when I did a B16 into my '96. If you don't switch the harnesses, then your tach and speedo won't work, and you'll be missing several other things too.

 

I actually was able to start and drive the car with only the two plugs in the ECU before I swapped my dash harness, though. It didn't run well, VTEC didn't work, none of my gauges worked, but it would drive. If you're not able to start it, then I would consider that the ECU may be at fault. Swap the harnesses first, and then see. If that doesn't solve the problem, open up the ECU and see if it smells burnt. I have spare ECUs for both a B16a2 and a D16y7 that I want to get rid of. If you wind up needing one, let me know.

 

Okay, let me just say that we have swapped both engine harnesses too, so to get the B16 to work in the DX we'll need to swap the dash harness in other words. Now, is this true for the Si as well? Meaning, will we have to swap out the DX dash harness for the D16 to work? My problem is we are to the point where we can start the Si with the D-series in it, but it won't.
We are going to swap dash harnesses tomorrow, hopefully, that takes care of the problems. But thanks for the input.

 

yeah, since you did the engine harness, do the dash harness too. The Si harness has the wiring for the secondary O2 sensor on it, so you can swap the exhaust too. since you have both cars, and the good motor is going into the hatch just do a full conversion, and turn the hatch into an Si clone. swap the whole dash, seats, anything you can. the climate control for the Si is way better, and everything will just bolt right in.

 

Haha, that's the problem. I'm the one driving the Si. It was supposed to be a simple motor swap, and I use the word simple loosely. The hatch is going to be a purpose built drag car, so creature comforts are not really needed.

I guess now would be a good time to ask about the door harnesses. I'm guessing they are apart of the dash harness as well? Or are the door harnesses considered apart of the floor harness?

 

https://honda-tech.com/forums/showthread.php?t=2407755

 

Ouch, sorry...if you could change it maybe to "harness help" or something similar that'd be great.

 

shoulda just left the beautiful si alone, but anyway, yeah you wont get it to kick til you re wire for the iac and get the correct dash harness

 

your door locks and windows will still work no matter what. I didn't change any of the floor or door wiring in my sedan when I swapped it, and everything works. That all comes from the fusebox, so don't worry about changing any of that. I'm not sure about the power moonroof on the Si, though. I think that might be part of the dash harness, so you might have to rewire that. I think it's kinda sad that you're neutering your Si, though. What does a '99 Si weigh? about 2300 lbs? Remove the AC, airbags, spare tire, and you're down about 100 lbs from that. Instead of swapping two motors, just build the B16 in the Si. 4-wheel disc brakes, better stabilizers, nicer looks, I just don't see the practicality of all this, but I guess if you just want a racecar, then you can do it your way.

 

yeah, the si should not be molested in this way and yeah the sunroof wont work unless the other car also has a sunroof, the harness is integrated into it