amatuer attempting maf conversion 86 gt frustrated please lend me you brain?

Your post is still very difficult to read. I have attempted to translate it into an understandable format. You will need to make corrections if I mis-translated your original post.

I am using Ford Racing’s MAF conversion harness (the full harness from computer to sensors etc.)
When i try to start the engine, the big green fusible link wire gets extremely hot and melts.
So i think I am missing a ground somewhere-not entirely sure. I got the computer from a junkyard (a9l) and obviously not sure of the functionality to begin with.

If the computer is shot, would that alone cause the main fuse link (connected to + side of starter solenoid) to get hot?
I get fuel pressure and spark
I am not getting any injector pulse.
There are a few wires in the kit i didn't hardwire yet because they aren’t necessary for the engine to run, like the speed sensor and neutral safety switch.
What provides the injector pulse? Is it juice straight from the computer? Where should i start?
I don't have a wire going from engine to firewall as a ground is that absolutely necessary? I heard there is a ground for the injector harness. Where is that located?


FYI: to do a mass air conversion all you needed was a MAF connector and some wires and pins. It is not necessary to buy a complete harness.

MASS air conversion instructions from http://www.stangnet.com/tech/maf/massairconversion.html FREE
A9L (5 Speed) computer from junkyard $100-$150
A9P (Auto or in a pinch, 5 Speed) computer from junkyard $100-$150
70MM MAF from 94-95 Mustang GT - $40-$70
MASS Air wiring harness kit $30-$85

The whole thing is probably less than $300 using junkyard parts.

A9L computers are 5 speed only
A9P computers are automatic, but will work with a 5 speed.

The conversion harness seems to work well for most folks. It avoids the compatibility problems in using a harness from the junkyard. Simple and cheap, actually less work that swapping the wiring harness.
Conversion Harness kits & parts
http://www.mass-air.com/
http://fordfuelinjection.com/index.php?p=54

If the idea of moving & soldering wires scares you, here's a list of compatible Mass Air wiring harnesses.

bbunt302
Just for reference, here's a list of all the compatible years:

89 harness should work for 86-89 as long as you're using mass air.
90 harness will only work in a 90. (B/c of air bags and dual dash connectors)
91 through early 92 harnesses should be compatible (single dash connector, fuel pump relay under driver's seat)
Late 92 through 93 harnesses should be compatible (single dash connector, fuel pump relay under the hood)


Your current problem:
Missing a ground would not cause a fuse link to overheat. You have battery voltage shorted to ground somewhere in the wiring you added. Until you fix the short circuit you won't get an injector pulse.

The Ford racing harness doesn't seem to have a diagram posted on the Internet. If it came with one, I recommend that you scan it and post it. The wiring connectors and wire colors may be very different from the stock wiring diagrams that are available. It is very difficult to troubleshoot wiring problems without a diagram.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

Injector power:
The injector power is provided by the EEC relay that feeds power to the computer. The red wire on the injectors is energized anytime the ignition switch is in the Run position.

The computer does not supply power for any actuator or relay. It provides the ground necessary to complete the circuit. That means one side of the circuit will always be hot, and the other side will go to ground or below 1 volt as the computer switches on that circuit. The computer provides a ground to complete the circuit. When the computer switches the injector lead to ground, the injector fires.

Computer power ground
The computer must have a good ground. The stock wiring harness has two 12 gauge black wires with a green stripe that are the power ground for the computer.
The computer has its own dedicated power ground that comes off the ground pigtail on the battery ground wire. Due to it's proximity to the battery, it may become corroded by acid fumes from the battery. It is a black cylinder about 2 1/2" long by 1" diameter with a black/lt green wire. You'll find it up next to the starter solenoid where the wire goes into the wiring harness
Picture courtesy timewarped1972

The secondary power ground is between the back of the intake manifold and the driver's side firewall. It is often missing or loose. It supplies ground for the alternator, A/C compressor clutch and other electrical accessories such as the gauges. Any car that has a 3G or high output current alternator needs a 4 gauge ground wire running from the block to the chassis ground where the battery pigtail ground connects. The 3G has a 130 amp capacity, so you wire the power side with 4 gauge wire. It stands to reason that the ground side handles just a much current, so it needs to be 4 gauge too.

If you think grounds are not important, it is time to get some more education. An automotive electrical system will not function without good grounds.