help with some connector ID

[dave w]

The fuel pump relay wiring described above seems odd to me.

Typically, the fuel pump wiring high side gets battery+ from a wire with an inline fusible link or a fuse that eventually is connected to the Battery + terminal.

The computer supplies a battery + signal to the fuel pump relay low side, with the other low side terminal connected to ground. When the fuel pump relay high side contacts close Battery + is sent to the fuel pump.

Typically, the oil pressure switch wiring gets battery+ from a wire with an inline fusible link or a fuse that eventually is connected to the Battery + terminal.

Typically 5 PSI of oil pressure closes the oil pressure switch to send Battery + to the fuel pump.

Typically the oil pressure switch fuel pump wire and fuel pump relay fuel pump wire are spliced together so either the fuel pump relay and / or oil pressure switch will supply Battery + to the fuel pump.

Typically ECM Terminal B2 is spliced into the wire that sends Battery + to the fuel pump.

Possibly the wiring diagram shown below is helpful.

Fuel Pump Relay.JPG

[stackz]

I have that wiring diagram sitting next to me at my desk actually and have the notes from binder planet snipped in under it.

it seems weird to me as well but if it works I'm cool with it. I tried taking some overall pics of it. I put a 20a fuse in the connector we think is the ATC. you can see how it just sorta splices into the main harness in the first pic. In the second pic you can see how the oil pressure switch loops back to the pink/black splice and to the orange power wire to the relay. with the way it loops from the tan/white from the ecu and there is nothing left aside from it on the other side of that splice, it kind of has to stay in place as a fused signal I guess? the piece of the tan/white that you see that is cut went to something else not part of the main engine harness (when I grabbed this harness I just grabbed literally everything under the hood as one big mass). but thats why I think this is the fuel pump test connector maybe?
20240314_143328.jpg20240314_143334.jpg

[dave w]

The fuel pump relay actually has 3 high side connectors, that allow for Normally Closed contacts and Normally Open contacts.

The fuel pump power is connected by the Normally Opened contacts.

The fuel pump prime is connected by the Normally Closed contacts.

[stackz]

cool, I will look into more tomorrow. I just finally figured out how to get the pins out of the ecu connector. I'm going to pull them one at a time and unravel this birds nest once and for all so I can lay out all the circuits without them all being twisted up into each other.

I know that will help me better visualize the fuel pump circuit.

[1project2many]

Are you working with a square body R/V harness or the K truck harness? R/V had some different connectors and used some different wire colors.

There are tools to help remove the ecu pins. They are very, very helpful for this work.

[stackz]

K series. Came from a blue 88 truck

[1project2many]

Ahh... Yes, the blue ones are different. ;)

The first year trucks were set up a little differently. The relays weren't all installed on the RH side of the cab in a neat row. The fuse holder is for the fuel pump fuse. It might only have been 15A.