No voltage energizing C/OP relay - fuel pump system

Hey-
2004 Tundra full cab v-8 --- Turn no-start condition led me deep into diagnostic hole, fuel pump itself can work when jumped direct to positive battery cable via Fuel Pump relay socket.... relays and fuses themselves check out ok with bench testing.... where I end up is that power does energize the EFI relay with ignition on, but does NOT energize the C/OP relay... schematics I see online seem to indicate power comes from same source to energize both the C/OP and EFI relays, but it is not present at C/OP when I check voltage on the low-side sockets.... if I remove the C/OP relay and jump the switch side sockets is starts right up and runs. Anyone have ideas on where the failure is? I have tested and interchanged relays so it is not a failed relay in the C/OP socket.... ALSO -- If I need to run for 45 minutes at a time and plow my driveway with C/OP jumped is that a problem? THANKS FOR YOUR HELP !!!

 

Have you verified that the ground circuit is good for the relay? I don't see a problem running the truck temporarily with a jumper wire just make sure to put a fuse in it to protect your electrical system.

 

Does your truck have any kind of alarm system??

 

The only thing a relay does is switch a high current load with a low current source. I.E. say a 30A pump can be switched with a 2A signal circuit. So as long as you jump the correct terminals and make solid contact you should be fine.

Also calling @BubbaW for a schematic.

 

@TX-TRD1stGEN -- Thanks for the response - Yes truck has an alarm system from factory - ... It works because this AM I went to lift the popped hood with doors locked and the alarm blew on until I unlocked the door.

@PCJ - Thanks for the idea -- no I have not checked ground circuits, not sure where/how wires might run to do that and it is way too cold up here in CT to spend too much time taking fuse boxes out or testing wires.... HOWEVER you give me an idea, that being there should be one low-side terminal in the C/OP socket with direct continuity to a low-side terminal in the EFI relay socket -- easy enough to identify -- then with ignition on and EFI relay in test voltage from the common C/OP socket to an outside ground and find 12 volts.... which would mean the other C/OP socket would be missing ground. I might then hard-wire a ground to a wire slipped in that C/OP terminal with the relay inserted and it might work... I would still consider that temporary until such time I could adequately search wiring for a problem.

 

@bmf4069 - Thanks, yes I understand the workings -- I just worry that the lack of power where it is supposed to be in the low-amp circuit leaves other unknown problems or glitches to occur -- Hopefully @BubbaW can verify the low amp current interruption as non critical at that part of the circuit chain

 

Wish I could offer anything but We are out of town and grandkids are using Paw for a punching bag. Be late evening before we get home and look up anything . Feel confident others can offer up FSM elec schem until then....Merry Christmas all

 

The c/op (5-3 )only closes when the starter or engine is cranking.

Five is incoming, 3 is it too fuel pump.

Point 2 should show 12v to ground when ignition is on.

Point 1 is controlled by ecm.

 

Hope all are having a Merry. Will await further input from OP and with all the good info provided by everybody(grounds mentioned, relay current source, pin out from schematics) hopefully we will have happy ending.
One question that I keep asking myself is, nothing about a MIL code was mentioned by OP ? Shouldn't an open or short in a fuel pump relay circuit throw a code....P0230 ?

Somewhat basic but thought I'd go ahead and offer a few things. I have provided a pic showing 2 things....proper polarity on meter(red lead pos) and ~12vdc present at C/OPN(circuit opening relay) with key in Start position but not started. Along with the pics shown by @TX-TRD1stGEN and along with the below Fuel Pump Circuit description, the Crankshaft Position Sensor could also be an issue.....Tr1(triac) has to be triggered that sends chassis ground output at FC of ECM to Circuit Opening Relay(C/OPN). That's all I got, family showing up for more Christmas celebration





https://f01.justanswer.com/El_Jared/cd1fed9f-1a7e-4be3-8df7-8b93f5754f9c_tota+fuel+pump+circuit.pdf

 

Did you get this fixed yet? @BEddiet

 

What was the solution here? I am having the same issue with my 2007 Toyota Tundra 2007 Crew Max

 

What happened with this truck?

 

@BEddiet was last seen in October 2022, not sure they're still around.