Fuel pump not priming as it should. Bad CAS?

[suspectu1]

Originally Posted by JN1AS4

Walbro 255. I installed it. The pump isn't the problem, now the pump wiring may be though. Seeing that the oem fuel pump harness/connectors are +20yrs old now. I would really like to just fix the issue. But hard wiring the pump is the nxt option. I had a buddies car that had +12v wire coming straight from the ecu(idk which pin), but everything else(ground, signal, etc.) came from the factory fuel pump harness/connector. Do you have any info/write-up of how to perform the re-wiring of the pump?

yes sir! just to make sure you understand how the fuel system works on these (and most other) fuel injected vehicles;
1. the fuel pump needs 12V positive and a GND to operate.
2. you can either switch the (+) or the (-) on any device and have it turn on or off.
3. in our case the +12V is provided by a relay that gets current going to the pump as soon as you have your keys to the ON position (ignition). This is where i think you misunderstood the system. The ECU does not provide positive voltage to anything! it only switches the ground of the different electrical loads.
4. it's up to you to decide if you want the ECU to control the pump, or have a manual switch to turn it on and off (i have mine wired through a Painless switch with a momentary on position for priming).
5. if you still want the ECU to switch your pump on and off, then you will need to locate pin 104. This is where you need to ground your fuel pump, well technically your fuel pump relay.

If i haven't lost you, here's what i recommend:
Go buy a new 30amp SPDT relay from radioshack or whatever.

Install it near the ECU.
Locate the wire coming from pin104 of the ECU (black and pink).
Locate a wire providing 12V with the key on the ON position.

Wire the relay as follows:
crimp a 12Ga wire to the one you found earlier (that provides 12V with key ON);
have the end of this wire go to pin 30 of the relay;
make a small 16Ga wire going from pin 30 to pin 85 on the same relay (this is to provide both power and switch the relay);
crimp a 16Ga wire to the black and pink wire coming from pin 104 of your ECU;
have the other end of this wire going to pin 86 of the relay (this is what i was referring to when i said the ECU switches the GND of your fuel pump relay);
pull a 12Ga from pin 87 all the way to the (+) on your fuel pump;
pull another 12Ga from the (-) off your pump to anywhere on the chassis.
You're done!

This way you will have a completely new harness to control your fuel pump, not using ANY of the old stuff to avoid having to track down electrical issues.