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RIP
RIP, Lead Technician
Category: Car
Satisfied Customers: 5591
Experience:  A.S.E. Master Technician, Advanced Level, Smog - European, Domestic, & Asian -- Car Category Mentor
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1992 toyota pickup truck-4 cyl--fuel pump--getting no power ...

Customer Question

1992 toyota pickup truck-4 cyl--fuel pump--getting no power to fuel pump in tank. All relays and fuses under hood are working. Is there a second relay in the cab? What could be preventing power from getting to fuel pump?
Submitted: 6 years ago.
Category: Car
Expert:  RIP replied 6 years ago.

Hi, welcome to JA.

  • The fuel pump gets it's power from the circuit opening relay and the circuit opening relay gets it's power from the EFI relay...commonly the EFI relay or the engine computer are faulty...does the check engine lamp come on when you turn the ignition to ON? If not, you need to check the EFI relay first, usually the EFI fuse next to it has failed.

graphic

 

RIP, Lead Technician
Category: Car
Satisfied Customers: 5591
Experience: A.S.E. Master Technician, Advanced Level, Smog - European, Domestic, & Asian -- Car Category Mentor
RIP and 11 other Car Specialists are ready to help you
Customer: replied 6 years ago.
the check engine light does come on and the EFI relay is functioning correctly. I can hear it clicking and feel it pulling in when the ignition is turned on. It does heat up though when the ignition is left on. Is that normal? Also, a previous owner has installed a jumper wire and tied it into the hot wire of the fuel pump. If this is connected to a constant power supply, the pump will run continuously. Will that work or will it damage the pump?
Expert:  RIP replied 6 years ago.

Running the pump continuously can damage it when the ignition is just in the ON position...the EFI relay should not be getting hot, and feeling relays click does not confirm that they are operational. Do you have access to a voltmeter for testing? You'll need to test the EFI and Circuit Opening Relays at the wires themselves under the relay box using the wiring schematic above.

Rip

Customer: replied 6 years ago.
Where is the circuit opening relay located? We looked under the passenger side kickplate and only found the engine control computer. The EFI relay is easy to find in the fuse box under the hood. What should the normal voltage be? 12v?
Expert:  RIP replied 6 years ago.

The EFI relay has (4) wires: with the key in the ON position and the relay installed, the Black/Yellow, Black/Green, and White/Red wires should have power (around 12 volts)...the White/Black wire is ground for the relay. If the relay "clicks" more than likely the Black/Yellow has power and the White/Black has ground - these are the electromagnet part of the relay...but if the Black/Green has no power the EFI fuse or wiring is bad, if the White/Red has no power, the EFI relay is bad...the cicuit opening relay's location is posted below..

graphic

 

Customer: replied 6 years ago.
I checked the EFI relay with a test light and with the key in the "on" position, three leads have power and the Black/white lead has no power.
It also clicks when the key is turned on.

I suspect that the circuit opening relay may be the problem. How can I check that to be sure it is working?
Expert:  RIP replied 6 years ago.

Go to the circuit opening relay, clean the wires off well so you can see the colors, can you list all the wire colors for me? Also, testing with a 12 volts test lamp can be inaccurate, especially when dealing with relays, but since that EFI relay is grounded and not triggerd by ground the test lamp is alright to use there.

Rip

Customer: replied 6 years ago.
I removed the ECU and could not locate the circuit opening relay in the location on your diagram. Behind the ECU there are two cube shaped items with many wires going into and out of them. A gray one and a smaller white one. The gray one looks like a connector. The white one looks like a block with wires. Is this the circuit opening relay?
Expert:  RIP replied 6 years ago.

The circuit opening relay should be under the hood, against the firewall on the passenger side...is this where your looking? Not in the passenger compartment inside the cab...

Rip

Expert:  RIP replied 6 years ago.

Sorry I just double checked, the illustration may be incorrect...see the info below and look under the passenger kick panel where the right foot rests...

PURPOSE
The circuit opening relay is responsible for providing power to the fuel pump.

LOCATION
Located behind the right kick panel.

OPERATION
Power is applied to the STA terminal of the relay from the starter when the ignition switch signals cranking mode. This allows the fuel pump to operate until the engine starts and runs under its own power. A signal from the Air Flow Meter (FC), keeps the relay closed until the ignition switch is turned OFF and de-energizes the EFI Main Relay. The fuel pump operation is then interrupted.

 

graphic

 

Customer: replied 6 years ago.
There is nothing under the hood that remotely resembles anything like the relay shown in your diagram. The only thing on the passenger side firewall is the windshield wiper motor and the pollution control canister.
Expert:  RIP replied 6 years ago.

Sorry, I left a post above after I said it was under the hood...have you seen the second location?

Rip

Customer: replied 6 years ago.
Since we are getting power to the EFI relay, doesn't that mean that the circuit opening relay IS working?

Which is the wire supplying power from the circuit opening relay to the EFI? and then to the fuel pump? Is the white/red the power to the pump or the black/green?
Customer: replied 6 years ago.
The only thing visible are the two boxes I mentioned earlier. Is the circuit opening relay way up under the dash? If so, I cannot see it and pulling the dash is probably more than I can handle tonight. Does the fact that we have power to the EFI relay mean that the circuit opening relay is working?
Expert:  RIP replied 6 years ago.

No, just becuase the EFI is supplying power to the Circuit Opening Relay, does NOT mean the COR is powering the fuel pump...the COR sends power to the fuel pump via a Blue wire, have you found this relay under the passenger kick panel as I corrected earnlier?

Rip

Customer: replied 6 years ago.
Is the circuit opening relay way up under the dash? If so, I cannot see it and pulling the dash is probably more than I can handle tonight.

There is a blue wire leading down from way up under the dash. I assume this is going to the fuel pump from the COR. Should I check to see if I have voltage in this wire?
Expert:  RIP replied 6 years ago.

No not yet, did you look under the KICK PANEL? This is the side panel where the passenger's right foot would rest, hence "kick panel." The relay should be under there according to the location I found afterward. We need to find this relay before testing and should not probe any blue wires until we know it is from this relay, especially if your using a test light.

Rip

Customer: replied 6 years ago.
We removed this kick panel and found the engine ECU. Then we removed the ECU and found the two connectors I described earlier. (the gray and white ones) There is nothing else visible without removing the dash. The blue wire (the same as the one at the pump) is visible leading down from somewhere high up under the dash into and out of the white connector and back into a harness leading back out toward the rear of the vehicle (to the fuel pump).

It seems apparent to me that the COR is not functioning correctly. Can this be purchased at a local auto parts store? Could running the truck out of gas cause this?
Expert:  RIP replied 6 years ago.

No running the truck out of fuel will cause a weak fuel pump to go out, but not the COR...the COR is common to fail on it's own. Below is the cost and part number at the dealer...i think you can order one from AutoZone as well, if you have one in your area...you may be better off going down to a local junk yard and use the part number below to get a used one for about $5-10, since they're not too cheap. I'll see if I can find any other location illustrations, but from all my information, it should be near the enigne computer which you've already found.

 

Parts Information
PartOEM PartPrice
Fuel Pump Relay
Circuit Opening Relay8591035010$75.76Notes
LaborSkill
Level
Mfg.
Warranty
Standard
Fuel Pump Relay
ReplaceB0.40.7Notes

 

Customer: replied 6 years ago.
Thanks for the help. At least we narrowed it down to the COR.
Expert:  RIP replied 6 years ago.

No problem, let me know if you still have difficulty finding that relay or replacing it. Happy Holidays if I don't here from you...

Rip

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