SoCalManche

With CPS plugged back in, same reading shows for pins 11 & 28 that showed for the disconnected CPS = .32-.35VAC.

As far as the way it is suppose to operate when you turn the key to ON, no it does not prime. However, when you throw a jumper wire in the relay socket, it will continuously pump until you pull said wire.

Define confirmation that it's good? I did a bench test on it via direct battery hook up, plus jumpering the relay circuit engages the pump too. I initially bought a new pump when the issue first started, and hooking it up showed the same symptoms as the other pump.

So should I buy a new CPS? Or would the low voltage be a byproduct of the resistance in my grounds?

Dumb question; am I supposed to check the CPS side? I have been checking the engine harness connector, not the unplugged CPS sensor. I checked the CPS and it showed .32V on crank.

Initially, you caught my mistake. I was on DCV because I didn't see Ohm say "vac." I switched it to ACV and same thing; 0V.

I unplugged the CPS from the harness and tried both back-probing and directly sticking the leads into the plug of the harness. I got 0V when cranking. This is with the fuel pump relay in the socket.

Are you meaning disconnect it from the flywheel?

Well I truly appreciate it, so thank you.

Sounds good. If you keep showing me which things to test, I'm sure we could find the gremlin. And I'd be more than happy to buy you a few Venmo beers to say my ultimate thanks.

Checked continuity, and the multimeter beep was quite loud and constant, lol. (Sorry neighbors)

I will go check to see if it has that setting, which I'm sure it does. But are you sure it is pin 85? I checked pin 85 to T6, and it was 0V. I checked 86 to T6 and it was a bit wonky for sure, but mV showed up.

Yes, I see that now. So how do I accurately test that? With a jumper wire between 85 and 86, using that as a point to connect with T6?

Which pin do I check for continuity with T6? I'll go do it right now.

I probed all the fusible links when the issue first arose, and they all had battery voltage. I could check again though.

So I know (A) on the harness for the pump is the ground since I soldered an additional ground to it, but do you have on hand which terminal (B) and (C) are? Are there that many connectors to make a distinction such as that?

Are you referring to the fusible links that attach to the starter solenoid? Couldn't we check for voltage if jumper wire took the spot of the relay? So what is the best way to go about this? Basically slicing open all the split loom and chasing wires?

So can you explain that to me like I'm five so I do the test properly? I can do that tomorrow after I pick up my 64" lead extensions from Napa. Well...hopefully they're long enough...

No, with relay installed, fuel pump does not engage.

I don't really know how to explain this since, as I've mentioned before, I'm bad with circuits and wiring and stuff. But if the jumper is only connecting two of the five pins in the relay circuit, thus pushing a direct current to the pump, would that mean there's an issue with one of the other pins, since all five are connected with the relay itself? That probably makes no sense, but it's a thought that came to mind.

I mentioned the RPMs fluttering to paint a better picture of how the engine is responding to the jumper wire versus the relay.

Correct.

So I concur with my initial assessment; With the relay in the socket, the RPMs flutter when I flip the key to START, to where the engine will FIRE, but it is an extremely rough FIRE (to be expected considering the minimal fuel added to TBI). With the jumper wire in the socket, the RPMs do NOT flutter at all, and it makes no attempt to FIRE. It will crank like a madwoman, but no FIRING occurs.

I am aware it seems confusing, but that is correct. Jumper wire will keep the truck from starting somehow, but will engage fuel pump. Relay will not engage fuel pump, but will let truck START. I will go out again to verify for sure that truck will not START with jumper wire. Edit: I just re-read you, Ohm. Truck will not START with jumper wire. It will just continue to crank. But again, let me go see if I can make it START with jumper.

So same thing is occurring; With relay in relay socket, the truck will START with fuel added in TBI. With jumper wire in relay socket, the truck will not START with fuel added in TBI.