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(SCOPE103's diagnostic on his 1994 6cyl (3VZE) 4wd (A340H) XCab SR5 truck is Here)
The relay prevents unwanted, unsafe fuel flow (i.e., in case of an accident when fuel line ruptures, engine stalls, airflow stops and COR interrupts power to the fuel pump). COR is the thing that you'd hear click behind the glovebox when you're trying to start a first gen 4Runner. However, it does not affect cranking system.
(In 1986 Runner) COR is located behind glove compartment near speaker and blower motor. Someone had posted about moisture in COR. Possible because:
a) It's near some body seams,
b) Its below where windshield joins the frame- there could be a leak there, and
c) It's near right side wheelwell, where there could be leaks. There are 2 grommets there. One for engine harness, one for antenna. Check for leaks.
MAF-COR-Fuel pump circuit is below. Circuit Opening Relay (COR) has two normally-open contacts (open when no power is applied). Coil 1 of COR is energized by IGN switch while in START position. Once airflow is established due to combustion, MAF contacts provide ground to coil 2 of COR, keeps COR energized and its contacts closed, even after IGN switch is released.
ABOVE SCHEMATIC IS OF THE 1986 22R-E. Fuel pump check connector bypasses the AFM contacts and energizes second coil (clicks) of COR to power FP.
SCHEMATIC BELOW IS OF 1988 22R-E. Fuel pump check connector bypasses contact of COR and directly connects B+ to fuel pump.
To bypass AFM contacts and Jump terminals of Fuel Pump Check Connector* (below) while ignition is on.
Coil 2 of COR will be connected to ground, C.O.R. will click, and good fuel pump with good connections will run. Fuel will flow IF fuel lines are not clogged.
If you suspect Air Flow Meter malfunction, where you hear, feel and smell combustion ONLY WHILE holding ignition switch in "START" position but STOPS WHEN YOU RELEASE THE KEY this is a good test.
Also a good test for C.O.R. coil 2 and contact, as well a fuel pump and connections. * On 1986 22R-E, brown and green wires lead to connector. On 1988 Blue and brown. 1985, 1987 unknown to me.
Keywords:
C.O.R. circuit-opening, how it works, circuitopeningrelay
runs few seconds
Last edited by RAD4Runner; 02-02-2021 at 01:29 PM.
The fuel-air mixture is actually a mass ratio, so the Toyota ECU has to take the intake air temperature into account to convert the volume of air to mass. So we have a temperature sensor in the VAF.
8:05pm 22april2022,,,,my 1986 Toyota motorhome,,,,driven to RV storage lot coupla years ago/health problems intervened til this year,,,fresh battery, 8 gallons fresh fuel,,,,no start, bought a 1986 Toyota FSM/ component locations are strangely omitted.... L@@King to confirm fuel pump is NOT toes-up,,,,unable to confirm Fuel Pump Check Connector til this thread,,,,finally located the Open Circuit Relay...
going to storage lot tomorrow,,,,hopefully i will confirm fuel pump is 'operational',,,,
next,,,, a question, is there a 'generic replacement' for Open Circuit Relay? Local Toyota Dealer advises me NLA,,,,last price $140! (for many years i drove Volvo 240's... most/many Volvo relays had circuit diagrams on relay 'cases',,,,plus THE Bentley Bible give details of relays and components....just my never to be humble logic/Toyota Does Not design/manufacture their own relays, they chose to mark their relay 'cases' with part numbers ONLY. at least a circuit diagram would allow me to exercise the 'alternative option').....why keep the genie in the bottle....seems like this relay has been a common failure ....feel free to chastise me if you disagree....
again thanx for the open circuit relay location hint,,,,red
[QUOTE=red-ryder;52475811...,no start, bought a 1986 Toyota FSM/ component locations are strangely omitted....
... L@@King to confirm fuel pump is NOT toes-up,,,.[/QUOTE]
Ignition on. jump fuel pump connector. You should hear, or feel FP run.
Ignition switch in crank position, you should hear/feel COR should click behind glove compartment. VERIFY that it is the COR, not the starter solenoid you hear/feel clicking.
... a question, is there a 'generic replacement' for Open Circuit Relay?
There might be. However, it's hard to tell pin-outs. Better to go got junkyard and look for one. But then, I doubt if it is the COR that's defective (pls see signature).
[QUOTE]....seems like this relay has been a common failure .c
I don't think so. I do not know of anyone who's had a defective COR in this forum since I joined in 2012
I\ do not know of anyone who's had a defective COR in this forum since I joined in 2012
I hate to ruin you record, but my 87 4Runner, well, it was ours before we sold it, had the COR fail aout 12 or 14 years ago. My lovely wife, who had taken an A&P Mechanics course when she was just out of High School, had a great time guiding the parts guy at our local dealership as to what it was, where it was, how to look it up, etc. Then SHE went down to the dealership, and had to help the parts guy in person. They were shocked at he knowledge of mechanical "things". You know, the old "Women don't know ANYthing about cars" attitude. She disabused them of that idea fast
Funny, the truck is older than the parts guy by about double...
So anywho, yeah, now you know at least ONE 4Runner that had it happen.
Pat☺
red-ryder again,,,,Never was able to hear the COR click...too much noise from engine 'trying to start'AND road noise from passing traffic!..VOM 'advised me' in-tank-fuel-pump was not open, power to FP confirmed was 'toes-up'....working-alone....i used a 70's FOMOCO key buzzer plus 6' of #18 awg 2-conductor to create an audible device to confirm 12v to FP. Next Step FOR Me 'drain n drop' fuel tank. vehicle shows 107,000 miles/obviously the years and miles dictate a replacement!....unsure what pacific-rim replacement FP to use. however when the fuel tank is 'down' i will consider an access panel in motorhome floor, to have an optional access to the FP....my luck a future failure will be with a full tank and many miles away from home.
'
Thanx for the advice...yotatech.com 'Participates'!
01-16-2018, 08:18 AM
