Selflr

I just picked up an 83 305 CFI. Guy said fuel pump wasn't getting power. I shot the pump and it's getting it's 2 second prime command but wouldn't run the pump. I pulled the sending unit from the tank and it was destroyed so I got a new one from Summit. I have good power and good ground but the pump won't prime. First Camaro, I'm typically a truck guy. Car will turn over all day. And I can start it with gas in the throttle bodies. What should my next step be here? Thanks in advance.
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Schurkey

If the pump has power and ground--and I mean the pump, not merely the wiring harness near the pump--but the pump won't run...

...replace the pump.

The in-tank wire harness is often corroded.
The pump could be jammed with debris.
The electric motor of the pump could be defective.

Selflr

Yeah boss usually I would agree, but it's a brand new pump and sending unit. I tested it prior to install and it ran fine. I got a bit more diagnosis to do today we'll see what happens.

Schurkey

Failure to run at all, even with a 2-second prime command at the pump, is either the pump or the ground PROVIDED that the 2-second prime command has enough amperage to run the pump. It's possible that there's enough resistance in the circuit that you have power when there's no load (no current flow/amperage draw) but lack power when the pump is connected. This is why I always verify voltage to the pump as close to the pump as practical, with the pump RUNNING if at all possible.

I had a similar problem with my heating control head on my pickup--12+ volts at the molded plastic connector for the back of the control head, with the head disconnected. About 3 volts with the harness plugged in. The wire harness melted a plastic connector downstream from the control head, (behind the glove box) those contacts burnt and corroded so it passed voltage but not amperage.

Similarly, I check for voltage on the ground wire as close to the pump as practical, with the pump RUNNING if possible. Ideally, you'd have system voltage at the pump supply wire, and zero volts on the ground. In real life, GM uses undersized wire so there's always some reduction of voltage (Voltage Drop, VD. Everyone knows that VD is not good.) on the supply side, and often some minor voltage on the ground due to resistance in the wires or connections.

There's more diagnosis that can be done--checking amperage flow with the pump running (typically 6--7 amps) or better-yet, watching the amperage waveform on an oscilloscope using a low-amperage inductive probe--but most folks don't have access to that equipment. With a 'scope, you not only know the average amperage draw, you can see the amperage draw of each bar of the armature, and calculate the pump motor RPM.

Somewhere in that vehicle there's a wire that, if you provide power to it, will run the fuel pump. This bypasses a good share of the control circuitry, leaving only the most-basic part of the harness, and the fuse. Sometimes it's stand-alone, like my Luminas where it's a single wire near the battery. Other times it's integrated into the ALDL connector. Check your wiring diagram from the Genuine GM service manual to see where yours is.

bluiroc

I Have gone through this myself with 2 TPI's. There are kits you can buy to rewire the Pump circuit. I choice to make my own. The Wire in question is a Tan wire. Pink is the Gauge and Blk is the Ground. Verify that, but any how, I use the tan wire to trigger a relay. I up the wire size to pump from relay and the supply to that same relay. The Tan wire runs a gauntlet. A route it should not be asked to do. If you study it on the schematic you may ask "why" too.

Selflr

Update fellas, the pump connector in tank came loose during install. Pulled the pump back out connected it all up and the raley took a **** on me. I can bypass it with a jumper it'll prime then pop the fuse. Running to grab a new relay and then start tracking a short somewhere. We getting there

Selflr

Hey Guys, Thanks for reaching out and the advice. Got her running last night. I purged all my lines new fuel and filter. Tracked a short between the Oil Pressure switch and the Fuel pump Relay. LO used an wire nut and it was popping 10A fuse. Now we are good to go.
Thanks Y'all.