Originally Posted by projectstang92
Thanks. Thats exactly what I needed!
That is not what you need. That is the car wiring.
The fuel pump transistor is out in the middle of the board on the A9 style computer. It is a three wire plastic case NPN transistor. A MJF3055 will work as a sub. (edit from MJE to MJF3055)
The open collector output of that transistor pulls the fuel pump relay "ground" line to ground. The NORMAL way that transistor circuit fails is from someone dumping 12 volts on the test pin, or dumps 12V on the relay coil "ground" line by messing around with the relay or the wiring.
When that transistor gets too much current because someone shorts the fuel pump relay coil, or applies 12V without series resistance to the relay pull down line, it blows a small low resistance "fuse" resistor by that transistor. That resistor goes from the transistor emitter to ground, and acts like a fuse.
It is not a critical value. Anything from 1 ohm to perhaps 10 ohms will work, but it should be low wattage thin film type resistor. This is so the resistor opens if someone crews up the wiring outside the computer.
The normal transistor failure, since it is a semiconductor, is shorted. If the transistor shorts the pump would run all the time.
The normal resistor failure is open. If you overload the transistor the resistor fails open and protects the transistor and the foil traces.
You also could have an open foil trace or via (the plated through connection between traces that swap board sides), but usually it is the resistor if dead pump relay or a bad transistor if the pump relay locks on.
You could have another issue, but this is probably nearly 100% of things that go wrong in the EEC.