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I have finished assembling my Mega SquirtII and have it in and running. It is in my 1987 Pontiac Fiero Gt.
Here is a pic of how it looks now (click to enlarge).
First thing you should do is pull the center cosole and take your stock ECU out. Look over the connectors and make sure you know how to tell what wire goes where(i.e. look at the wiring diagrams and know where the wire that is in A 1 goes). Next you should look over the list I made for what wire goes where, and figure out what wires you need to cut. I also attached the pic from the MS assembly guide and a url to the stock Fiero wiring diagrams.
The stock ECU turns the fuel pump on by applying power to the Dark Green and white wire that is in pin number A 1. This wire will be cut and not used for the MS install. MS does not apply power to the relay to turn it on it supplies ground. What you need to do to make it so MS can tell the fuel pump on is modify the wiring to the relay so that it truns on with a ground single NOT power. To get this done you need to get under the hood and pull out the air cleaner, there are two relays behind the it.
The fuel pump relay is the one on the right. It is easiest to take both relays off to rewire the relay. What I did is cut one of the Orn/Blk wires (both go to the same place) going to the relay and I also cut the Dk. Grn/Wht wire.
I used a heat shrink but connector and wired the Dk Grn/Wht (which is the wire that the stock ECU used to turn the relay on) to the Orn/Blk wire (the wires you connect together should both come out of the relay) and reconnected both them to the Orn/Blk wire. What this does is applies power to the fuel pump relay where the stock ECU normally would.
Next we cut the Blk wire going to the relay. This is the ground for the relay. If you were to not cut this the fuel pump would run all the time, even when the car is off. You should get some Blk wire ~18 gauge and connect it to the Blk wire coming out of the relay (the one you just cut). Run this wire into the cab of the car (I ran in through where on of the shift cable enters the cab) and connect it to pin # 37 of MS. This is what my relay looked like when I was all done.
The next thing you need to monify is the ignition module bypass output circut. In this circut the stock ECU applies 5v to the Tan/Blk wire located at pin D 5. What this does when 5v is applied is makes it so the ECU can control the timing advance while the engine is running. When the car is cranking/starting there cannot be 5v applied or the car will not start. MS has a 5v out but applies 5v all the time including during cranking. What you need to do is cut the Tan/Blk wire and wire it up to a relay (pin 87 of the relay) like shown in the pic below (it is not a pic of the ignition module we have in our car but is wired the same).
The wire that comes off pin 85 of the relay needs to have power only when the key is in the run position, and not during cranking. I ran mine wire up to the stock fuse pannel under the drivers side dash. I hooked this wire into the extra output for the radio. This extra spot is next to the radio fuse and takes a spade connector. Sorr but I did not take a pic of this. Run the rest of the wires according to the pic above.
MS has an on board MAP sensor and you dont need the stock MAP. I ran some 5/16 (not sure on the size) hosing from where the stock MAP gets its vacuume up through the fire wall into the cab and to the MS unit. Here is a pic of where the stock MAP sensor was and the hose running to the left of the screen is the new hose going up into the cab of the car.
Other than that I made a wiring harness for the MS unit. I went to the local electronic supply store and got some multi-color wire, a pinable DB37 female and male connector, and some un-insulated but connectors with some heat shrink. Her is what mine looked like when I was done wiring it up. I got the Male DB37 connector so that I could wire up all of the wires I cut going to the stock ECU pigtail. This way if I need to I can plug the two DB connectors together, hook up the stock MAP sensor, plug the stock ECU in and it fires right up. With it like this if I have a problem with my MS I can go back to stock and I can also now compare how the car runs (stock vs MS) and see if I have made any improvements on how the car runs.
Here is how I have it mounted in the car now, but I am making a peice of sheet metal bent up like the stock ECU. This sheet metal will bolt into the plastic bracket just like stock ECU does and I will just screw the MS to the sheet meatal.
Here is a pic of how it looks now (click to enlarge).
First thing you should do is pull the center cosole and take your stock ECU out. Look over the connectors and make sure you know how to tell what wire goes where(i.e. look at the wiring diagrams and know where the wire that is in A 1 goes). Next you should look over the list I made for what wire goes where, and figure out what wires you need to cut. I also attached the pic from the MS assembly guide and a url to the stock Fiero wiring diagrams.
The stock ECU turns the fuel pump on by applying power to the Dark Green and white wire that is in pin number A 1. This wire will be cut and not used for the MS install. MS does not apply power to the relay to turn it on it supplies ground. What you need to do to make it so MS can tell the fuel pump on is modify the wiring to the relay so that it truns on with a ground single NOT power. To get this done you need to get under the hood and pull out the air cleaner, there are two relays behind the it.
The fuel pump relay is the one on the right. It is easiest to take both relays off to rewire the relay. What I did is cut one of the Orn/Blk wires (both go to the same place) going to the relay and I also cut the Dk. Grn/Wht wire.
I used a heat shrink but connector and wired the Dk Grn/Wht (which is the wire that the stock ECU used to turn the relay on) to the Orn/Blk wire (the wires you connect together should both come out of the relay) and reconnected both them to the Orn/Blk wire. What this does is applies power to the fuel pump relay where the stock ECU normally would.
Next we cut the Blk wire going to the relay. This is the ground for the relay. If you were to not cut this the fuel pump would run all the time, even when the car is off. You should get some Blk wire ~18 gauge and connect it to the Blk wire coming out of the relay (the one you just cut). Run this wire into the cab of the car (I ran in through where on of the shift cable enters the cab) and connect it to pin # 37 of MS. This is what my relay looked like when I was all done.
The next thing you need to monify is the ignition module bypass output circut. In this circut the stock ECU applies 5v to the Tan/Blk wire located at pin D 5. What this does when 5v is applied is makes it so the ECU can control the timing advance while the engine is running. When the car is cranking/starting there cannot be 5v applied or the car will not start. MS has a 5v out but applies 5v all the time including during cranking. What you need to do is cut the Tan/Blk wire and wire it up to a relay (pin 87 of the relay) like shown in the pic below (it is not a pic of the ignition module we have in our car but is wired the same).
The wire that comes off pin 85 of the relay needs to have power only when the key is in the run position, and not during cranking. I ran mine wire up to the stock fuse pannel under the drivers side dash. I hooked this wire into the extra output for the radio. This extra spot is next to the radio fuse and takes a spade connector. Sorr but I did not take a pic of this. Run the rest of the wires according to the pic above.
MS has an on board MAP sensor and you dont need the stock MAP. I ran some 5/16 (not sure on the size) hosing from where the stock MAP gets its vacuume up through the fire wall into the cab and to the MS unit. Here is a pic of where the stock MAP sensor was and the hose running to the left of the screen is the new hose going up into the cab of the car.
Other than that I made a wiring harness for the MS unit. I went to the local electronic supply store and got some multi-color wire, a pinable DB37 female and male connector, and some un-insulated but connectors with some heat shrink. Her is what mine looked like when I was done wiring it up. I got the Male DB37 connector so that I could wire up all of the wires I cut going to the stock ECU pigtail. This way if I need to I can plug the two DB connectors together, hook up the stock MAP sensor, plug the stock ECU in and it fires right up. With it like this if I have a problem with my MS I can go back to stock and I can also now compare how the car runs (stock vs MS) and see if I have made any improvements on how the car runs.
Here is how I have it mounted in the car now, but I am making a peice of sheet metal bent up like the stock ECU. This sheet metal will bolt into the plastic bracket just like stock ECU does and I will just screw the MS to the sheet meatal.
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