how to convert your dpfi harness to a mpfi harness

[twinkie]

here is the instructions on how to convert your stock 88-91 civic dx dual point harness to a multipoint harness

How To Install...
Multi Point Fuel Injection
 


Tools
Pick Tools (for depining plugs)
Soldering Gun/Iron
Heat Gun (helps a lot for Heatshrinking)
Sewing Needles (for depinning the ECU)
Electrical Tape (for wrapping wires together)
Heat Shrink (for covering and sealing exposed soldered connections)
18AWG Wire

Parts for ZC (supposing you have a complete engine)
Injector Resistor Box (most all Honda ones will work but I recommend getting an Si one)
PM6 Si ECU (good), PG7 Integra ECU (better), or PM7 ZC ECU (BEST!)

Parts for MPFI on DPFI engine
MPFI Manifold (D16A6, Si engine)
MPFI Distributor (D16A6)
Injector Resistor Box (most all Honda ones will work but I recommend getting an Si one)
Injector Plugs (if your Manifold doesn't have them)
PM6 Si ECU

Instructions

What is Multi Point Fuel Injection?
For the 88-91 Honda Civic (and some previous Civics) there were two types of fuel injection. One was Dual Point Fuel Injection (DPFI) which had a system of 2 fuel injectors shooting fuel into a common plenum where the fuel randomly was sucked into whatever cylinder was on the intake stroke at that time. Almost like a glorified carb system. It was good for gas mileage but terrible for performance. The other type of fuel injection was Multi Point Fuel Injection (MPFI). It had 1 dedicated fuel injector for each cylinder (so 4 for a 4 cylinder). This wasn't as good for gas mileage (though far from what I would consider bad) but was much better for performance.

How can I make a DPFI car MPFI?
All it takes to make a DPFI car into MPFI is basically swap around about 6 wires, thats it, not hard at all. MPFI wiring can be done in about 3 hours or less, probably less (especially if your new engine is already MPFI, and you aren't taking any parts off a DPFI engine to make it into MPFI). The main things you do is swap around some wires at the ECU, run some wires into the engine bay, and run a couple wires to a resistor box. Heres how to do it step by step...

Do it right the first time!
Whenever you do any wiring on your car always solder the wires together and put heatshrink on them for a perfect connection and seal. You will thank yourself in the long run. Also where possible use OEM clips and harnesses from a MPFI car, it will give you a better connection and a cleaner look.

ECU Wiring
The basic idea of wiring for the ECU is you are cutting some wires, adding wires to the ones you cut and running it to the engine bay, or swapping around some wires you cut and attaching them to each other. Here specifically are how they are supposed to be wired. But first here is a diagram of how the ECU pinouts are numbered, the side you are looking at would be the female side (the holes) with the wires coming out of the back of it. If you are still confused by how the pins are number than click here for a picture of the side you are looking at.



*This diagram of the ECU Plugs is taken straight out of the Helm's Manual for the 1989 Honda Civic. Some other MPFI instructions have the plugs a reversed way, or the HASport way. I use the Helms way.

Wiring Colors and Functions 
 DPFI  MPFI 
Pin #  Wire Color  Function  Wire Color  Function 
A1  Yellow 2  Aux Injector  Brown  #1 Injector 
A2  Black 1  Main Relay/Ground  Black 1  Main Relay/Ground 
A3  Yellow 1  Aux Injector  Red  #2 Injector 
A4  Black 2  Main Relay/Ground  Black 2  Main Relay/Ground 
A5  Red 2  Main Injector  Light Blue  #3 Injector 
A6  Green  Purge Cut Off Solenoid Valve (Coil)  Green  Purge Cut Off Solenoid Valve (Coil) 
A7  Red 1  Main Injector  Yellow 1  #4 Injector 
A8  Yellow 3  Sedan LX A/T   
A10  Red  EGR Solenoid Control Valve (Coil) (A/T only)   
A11  Blue/Yellow  EACV (Coil)  Blue/Yellow  EACV (Coil) 
A12  Green/Black 2  Main Relay  Green/Black 2  Main Relay 
A13  Yellow/Black 2  Main Relay  Yellow/Black 2  Main Relay/Injector Resistor Box 
A14  Green/Black 1  Main Relay  Green/Black 1  Main Relay 
A15  Yellow/Black 1  Main Relay  Yellow/Black 1  Main Relay/Injector Resistor Box 
A16  Brown/Black  Ground  Brown/Black  Ground 
A17     
A18  Black/Red  Ground  Black/Red  Ground 
 DPFI  MPFI 
Pin #  Wire Color  Function  Wire Color  Function 
B1  White/Green  Hazard Fuse  White/Green  Hazard Fuse 
B2  Orange  Tandem Control Solenoid Valve  Blue 1  Fast Idle Control Solenoid Valve 
B3  Yellow  A/C Clutch Relay  Yellow  A/C Clutch Relay 
B4  Yellow/Green  Radiator Fan Relay  Yellow/Green  Radiator Fan Relay 
B5  White/Yellow  Alternator  White/Yellow  Alternator 
B6  Green/Orange  Check Engine Warning Light  Green/Orange  Check Engine Warning Light 
B7  Green/Orange  A/T Shift Position Console Switch (Park, Neutral)   
B8  Blue/Red  A/C Switch  Blue/Red  A/C Switch 
B9     
B10    Orange  Crank Angle Sensor 
B11  Green/Black  A/T Shift Position Console Switch (Drive)   
B12    White  Crank Angle Sensor 
B13  Blue White  Main Relay  Blue White  Main Relay 
B14  Blue 2  To Yellow, To Alternator  Blue 2  Alternator 
B15  White 1  Ignitor Unit  White 1  Ignitor Unit 
B16  Yellow/Red  Speed Sensor  Yellow/Red  Speed Sensor 
B17  White 2  Ignitor Unit  White 2  Ignitor Unit 
B18     
B19  Green/Red  Electric Load Detector  Green/Red  Electric Load Detector 
B20  Brown  Ignition Timing Adjusting Connector  Brown  Ignition Timing Adjusting Connector 
 DPFI  MPFI 
Pin #  Wire Color  Function  Wire Color  Function 
C1  Orange  Crank Angle Sensor  Blue/Green  Cylinder Position Sensor 
C2  White 4  Crank Angle Sensor  Blue/Yellow  Cylinder Position Sensor 
C3  Orange/Blue  TDC Sensor  Orange/Blue  TDC Sensor 
C4  White/Blue  TDC Sensor  White/Blue  TDC Sensor 
C5  Red/Yellow  TA Sensor  Red/Yellow  TA Sensor 
C6  Red/White 1  TW Sensor  Red/White 1  TW Sensor 
C7  Red/Blue  Throttle (Position) Angle Sensor (TPS)  Red/Blue  Throttle (Position) Angle Sensor (TPS) 
C8  Yellow  EGR Lift Valve Sensor   
C9  Red/White 2  PA Sensor  Red/White 2  PA Sensor 
C10  Green/White 3  Brake Switch  Green/White 3  Brake Switch 
C11  White 1  MAP Sensor  White 1  MAP Sensor 
C12  Green/White 2  EGR Lift Valve Sensor/Pa Sensor/Ignition Timing Adjusting Connector/TA Sensor/TPS Sensor/TW Sensor  Green White 2  Pa Sensor/Ignition Timing Adjusting Connector/TA Sensor/TPS Sensor/TW Sensor 
C13  Yellow/White  EGR Lift Valve Sensor/Pa Sensor/TPS Sensor  Yellow/White  Pa Sensor/TPS Sensor 
C14  Green/White 1  MAP Sensor  Green/White 1  MAP Sensor 
C15  Yellow/Red  MAP Sensor  Yellow/Red  MAP Sensor 
C16  White 3  O2 Sensor  White 3  O2 Sensor 
*All info adapted from the Helms Manual for the 1989 Honda Civic 



The ECU is located under the carpet of the passenger footwell...




Inside the car at the ECU...
To depin the wires from the ECU plugs you need to pop out 2 white clips at the top and bottom of the plug, then from the front side you need to use a needle (or something thin but strong to pry the pin out of the plug, its a pain in the a s s to do, all I can say is keep trying)...

Old vs. New methods
One thing I found out was the following instructions are sort of the old way of doing it. Originally whoever figured all of this out made more work for themselves by having to solder all this stuff he cut up. But if you think about it you can do this a lot easier by following the steps after this one...

Tried and true method
-Pins B10 and B12 are empty meaning there are no wires going into them as a general rule, however some models have a wire at B12 (if you have one that is one there that is one less wire you will need to move).
-Pins B2 and B11 have wires going into them but they are not used for anything (weird, but trust me on this one).
-Take the pin/wire from B2, depin it (this means pop it out of the plug) and pin it (pop it into plug) into B10's empty spot, how you have a wire at B10.
-Take the pin/wire from B11, depin it and clip it into the B12 spot, now you have a wire at B12.
-Cut the orange C1 wire and white C2 wire "in half" (by cut in half I mean cut the wire making sure to leave enough wire so you can strip and solder them to another wire later). Now when dealing with cutting I will refer to the side of the wire coming from the interior harness as the harness side, and I will refer to the side of the wire coming directly from the ECU's plug (direct ECU connection) as the ECU side (the only plug in question for this step is the ones that go into the ECU).
-At the ECU plug, for C1 and C2 solder and heatshrink wires to them and run them into the engine bay (I did this via the A/C grommets). Mark these wires with a piece of tape saying C1 and C2 on it. Because if you are like me you were using black wire which all looks the same so you need to make sure you know which is which.
-Now connect and solder the ECU side of B10 onto the harness side of the orange C1 wire, then do the same for the ECU side of B12 and the harness side of the white C2 wire.
-Cut wires at A3 and A7, solder and heatshrink wires to the plug side of A3 and A7 and run them into the engine bay, make sure you mark them. Now you should have 4 wires running into your engine bay.

Swap and switch method (less cutting and soldering)
-Pins B10 and B12 are empty meaning there are no wires going into them as a general rule, however some models have a wire at B12. If you have wires there depin them and pull them out.
-Depin C1 and C2 from their plug and plug C1 into B10s spot and C2 into B12s spot. By doing this you just saved yourself the need to solder any cut and solder at least 2 wires.
-Pins B2 and B11 have wires going into them but they are not used for anything (weird, but trust me on this one).
-Take the pin/wire from B2, depin it (this means pop it out of the plug). Now solder and heatshrink on a length of wire long enough to reach into the engine bay all the way to about 1ft after the fire wall. I say this because I like to add a plug right after the firewall later on so you can unplug your whole engine harness if you ever need to. You can do this in comfort outside of the car. Once you are done pin this wire into C1's now empty spot.
-Take the pin/wire from B11, depin it and solder and heatshrink a length of wire onto it just like you did for B2. Once you are done pin this into C2's now empty spot.
-Cut wires at A3 and A7, solder and heatshrink wires to the plug side of A3 and A7 and run them into the engine bay, make sure you mark them. Now you should have 4 wires running into your engine bay.

[twinkie]

Inside the car at the ECU...
To depin the wires from the ECU plugs you need to pop out 2 white clips at the top and bottom of the plug, then from the front side you need to use a needle (or something thin but strong to pry the pin out of the plug, its a pain in the a s s to do, all I can say is keep trying)...

Your wiring will look something like this...





*I redid my wiring so that I had a plug placed right after the firewall that would allow me to quickly disconnect the Cylinder Position Sensor and 2 of the Fuel Injector wires, good for if you ever have to remove the engine again. The engine harness can now stay right on the car, all you have to do is remove the 2 main plugs and the custom one I added now to remove the engine. There is a tab right under the interior/engine harness plug where another plug can fit. So I added one right there...



I got the plug from the junkyard and just soldered onto the length of wire I cut off.

Engine Wire Harness...
For anyone wondering the answer is no, you cannot simply plug an Si engine harness into a DX car, it just doesn't match up. The easiest way is to modify the DX harness. Also when you swap harnesses you will have 1 white plug left over from a sensor that the DX had that MPFI do not, so don't be concerned.


 

-If you are swapping the engine and the engine is out of the car then swap the DX harness over to your new engine (Si or ZC). If you are adding MPFI to a DPFI I would try and do this next step with the harness off of the engine.
-Throttle Position Sensor (TPS) wires need to be extended, the TPS is a black sensor on the side of the throttle body, there are 3 wires going to it, extend those, always solder and use heatshrink. On the TPS plug on the DX harness you will see 3 wires going to it, yellow, red, and green, in that order (if you are looking at the top of the clip from left to right on the DX clip). Depin and switch the green and yellow wires around so now the order is green, red, yellow. This is because the DX TPS sensor works in the reverse of the MPFI one, so if you didn't do that your car would think it was at redline when it was suppose to be at idle. So if you have that problem you know you skipped this step.
-Electronic Air Control Valve (EACV) wires need to be extended, the EACV is a rectangular box on the back of the intake manifold, it has 2 wires going to it, solder and heatshrink.

Injectors and Resistor Box...
For OBD-0 MPFI cars they require an Injector Resistor Box. The box transfers the high impedance current the DX has and turns it into the low impedance needed for OBD-0 injectors. Without this box your fuel injectors will get fried. You can use most any Honda Injector Resistor Box. I used to have a 1st Gen Integra one in my car, but its big and ugly and looks like a twinkie. At the junkyard I found a box from an Si so I took that and cut the harness off of it and painted it flat black. The one from the Si looks like a mini stereo amp, looks better and takes up less space than the Integra one.

4G Si Injector Resistor Box...

 

1G Integra Twinkie looking Injector Resistor Box...

 

-The DX has 2 injector plugs on it, cut them off as close to the plug as you can. Connect all the yellow/black wires from those injector plug wires and solder them all together. From that combined connection solder on another wire and run it to the yellow/black wire on the Injector Resistor Box.
-Connect the solid yellow wire from the DX injector to the #1 injector (I insert all the signal wires onto the left side of the injector plug, and all the resistor box wires on the right side, though I'm not sure it matters).
-Connect the solid red wire from the DX injector and run it to the #3 injector (onto the left side of the plug, like I mentioned above).
-Connect the A3 wire to the #2 injector (left side).
-Connect the A7 wire to the #4 injector (left side).
-Now run a wire from the right side of each injector plug and connect it to the red/black wires on the injector resistor box (the order doesn't matter from what I've seen).

Cylinder Position Sensor...
The CPS detects when cylinder #1 is at top dead center to help with proper fuel injector timing.

...For DOHC engines such as the ZC

-Connect the C1 wire to the blue/green wire on the Cylinder Position Sensor (a sensor on the exhaust cam of the ZC).
-Connect the C2 wire to the blue/yellow wire on the CPS.

...For SOHC engines such as the Si

-Connect the C1 wire to the blue/green wire on the CPS (the sensor is inside the Distributor on a SOHC engine). For doing this I suggest swapping out to the proper Si distributor plug so it is all plug and play and looks clean.
-Connect the C2 wire to the blue/yellow wire on the CPS.

Also if your engine didn't come with a wire cover try and get one, they make the wiring look a lot cleaner and OEM looking...

 

Notes
When you do this take my word about doing it right the first time. Try and get all the OEM connectors you can get and solder at all connections and heatshrink. When I had my Integra Injector Resistor box with crimped on butt connectors I noticed my car was more sluggish when it was cold than after I installed my Si resistor box with soldered connections and OEM connectors. Also when you do the wiring for the injector plugs make sure you get a pin with a decent length of wiring coming off, then solder on to that, that will ensure you good connection. I originally tried crimping some wire into a pin but you can't solder it because the space in the plug is too small. I ended up having my car running really shitty on 3 cylinders for a long time until I went back and redid it. Another thing is try and use OEM plugs where possible. Get them off of junkyard cars if needed.

Also remember, wire looms are man's best friend. Here is my wiring without looms... MESSY!!!

 

With wire looms... decently clean...