Relay board, Doesn't look right Options

[Coondog]

Still trying to figure out barely running 75 1.8 L jet blues

Looked at relay board and found missing rear window defogger fuse which is no big deal but also saw missing power supply relay fuse ???? Unknown what this is for. Then unknown yellow wire.

[timothy_nd28]

It's good to question, let me show you the path of electrons for fuel pump operations on the Ljet, (this only applies to Ljet).

Lets start at the dual relay in this picture below:
Unfused power straight from the battery enters the relay at pin 88z. After the points close (won't bore you with the details on how this happens), continuity is made and 12vdc exits the dual relay via pin 88d (red highlighted box). Ultimately, pin 88d which is a big black wire with a red stripe goes to the 12pin connector of the relay board on pin 12.

Next: A circuit track inside the relay board connects pin 12 of the 12 pin connector to
pin 13 of the relay board's 14 pin connector. I circled the action in red. Note that there is a junction point at J17 on pin 87. This too is a fuel pump relay, but used for Djets. Even with this relay pulled, pin 13 of the 14 pin connector will still receive power.


Here's a close up of the relay board and what's happening:

I have the current path highlighted in bold red on how it enters and exits the relay board via the 12 pin connector and out the 14 pin connector. The junction (which I highlighted in yellow) can also inject 12vdc to this current path but it doesn't since Ljet doesn't control the operation of this relay.

With that relay pulled from the relay board, the car should remain running. (because the current path highlighted in red has not been interrupted)

Different year Ljet 914's may have some slight variations on how the fuel pump receives power. Some fuel pumps were mounted near the engine while others were mounted near the fuel tank. The 914's with the engine mounted fuel pump, I believe a short wire from the dual relay traveled straight to the fuel pump.