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Welcome to the CC Forum. Look for poor contract on the IGN SW connectors. Been known to overheat and melt.

One Fusible Link (ORN color) feeds both the O2S Heater and the Fuel Pump Motor. I think you found it.

Disconnect battery negative cable. At the Starter Relay, remove and clean all the eyelets on the Fusible Links. Got to go. later.

Purple wire is fuel pump sending unit (IP gauge). Orange/black is fuel pump motor. Yes

I'm lost here. Don't understand your hookup.

That should work.

Is that with engine cranking?

I only meant to swap your current relays around. If fuel pump relay was a problem then swap in a different one. Electric dc motors that don't spin are a direct short to ground. That why I asked to disconnect the fuel pump connector. No current flow in circuit. Now we're looking for battery voltage along the fuel pump circuit.

Welcome to CC Forum.

Yea, take your time there. Don't want to break any tabs. Fuel pump relay will have that ORN wire in Pin_4 of the 4 relay blocks.

That it. Relay Block Pin_4 has ORN (orange) wire.

Your dropping voltage somewhere. Bypass (jumper) fuel pump ballast resistor. Take voltage reading at fuel pump harness connector again. Swap relays around. Take voltage reading at fuel pump harness connector again.

Yes that. What is battery voltage?

Do this voltage reading again but this time disconnect fuel pump motor.

They had special build in features. 10 minute timeout, 5 minute timeout after that. I wonder if there could be some kind of secondary use (ex: Fans, Lighting etc).

Does valve cover front vent line go to air box?

Isn't there a fixed orifice (2.6mm) on that line?

Thanks on that. Just curious.

Are XJs defogger relay (timed)/switch (3 pole) still available?

Purpose of the "B+ Latch Relay" (aka "Power Latch Relay") is to reset engine idle speed for next ENGINE START. Relay stays LATCHED (activated) for 2-4 seconds after KEY OFF supplying voltage to ECU allowing ECU to reset idle speed.

"B+" is just my quick way of typing 'voltage from the battery positive terminal'. But I see what you mean since the vehicle is equipped with a "B+ Latch Relay". I can be confusing at times.

Got my T-shirt and magnet today. I like the Tee, same as @JMO413, looks good. The magnet is a little dull in the color (red/blue), could/should have been a little more vibrant. But none the less I'm pleased with both. For being bootlegged items, this stuff is pretty cool. Got my eye on the coffee cup next. I wonder who originally requested this stuff.

True. My reference is to a prototype vehicle. It was a one of a kind only.

Once you determine which Relay is the Fuel Pump Relay, remove it and jumper Pin_1 to Pin_4 on the relay block. This will supply B+ to the Fuel Pump at all times. No need for KEY ON.

My first sight/drive of the 4.0L was in a SJ. Engine was non-regulated and ran very strong. Time wise I'll say 1986.