Code: 3666-5 engine fuel supply lift pump relay: current below normal Cat 320e TFX00748. 5 amp fuse, position 19, keeps blowing. I traced and tested ohms for all the wiring coming out of that fuse and I found no problems. What else could it be?
Try this and see where it gets you........
Would the EFLP Relay be relay #16 on the lower right?
Note L doesn't apply to that machine (multi machine schematic). Mark and then swap the two I've circled.
Here's the parts breakdown of the fuse/relay panel. The relays are all the same P/N so you could switch them around for testing.
I’ve swapped the two relays, no difference. I checked resistance on wires 106 on the backside of the fuse panel, wire X976 from the back side of the fuse panel all the way to the lift pump and wire G797 from the fuse panel to the engine ECM. Nothing over 5 ohms. I'm confused on how to create the short for the circuit. Do I keep the connector for relay #16 plugged in, pull out the relay and create the short where the relay plugs in?
Are you checking each wire for continuity to ground?
Does fuse #19 fail with relay removed? Does fuse #19 fail with pump unplugged? Regardless, have you actually inspected the wiring bundle behind the fuse panel? Enough rub points to hide your issue. How 'bout, have you changed or gotten any new fault codes?
I don't have any other codes popping up. Fuse will not pop with relay removed and it will not pop with the pump unplugged. I have not cut zip ties and traced wires behind the panel, nor have I checked each wire for continuity to ground. I will check those both here shortly.
Well, make a test harness to power the pump independently, using a ground to frame and a 5amp fuse from 24 volt at the battery. Does the pump run? Or, does the test harness fuse blow?
Is lift pump working ? @Nige PS52712
To the OP. Check your messages..........
I used my power probe and sent 24V to the pump and I cannot hear or feel it running. I assume that means pump is the issue? But if I take the connector that plugs into the pump and use a jumper between the 2 wires, it still pops the fuse.
Based on that statement I'd say your lift pump is toast.
New Pump is ordered. I will know tomorrow if that was it.
Unless you put a resistance in that jumper to simulate the load of the pump armature/coil/whatever the jumper will permit the circuit to draw (almost) infinite current. Ergo, fuse blows. It's not rocket science. Did you order the rest of the parts it needs as well.? Edit: Just saw your message.
Did the replacement transfer pump & the fuel line mods fix the problem.? Enquiring minds want to know.
The new pump fixed it. I’m waiting for the rest of the parts to come in on Tuesday. Thank you all for the help.
I am having the same issue now, but when I send 24V to the fuel pump with my power probe, it runs fine. What else could keep popping that 5 amp fuse?