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1992 Toyota Pickup Fuel Pump operation

Tiny
ACECOPIER
  • MEMBER
  • 1992 TOYOTA PICKUP
  • 6 CYL
  • 4WD
  • MANUAL
  • 179,000 MILES
Very frustrated. Problem started with starting truck up, would run for a few seconds and stall out. Replaced fuel filter, with no change. Replaced fuel pump next. With the ignition key on, there is 12 - 14 volts going to the fuel pump harness. Disconnected harness, connected volt meter, as soon as starter turns engine over, the voltage goes to zero. I took my battery jump box, and connected to the pump harness direct to verify operation. Pump operates. After doing this, I reconnected the harness and turned engine over, it will run long enough to burn the gas injected by me operating the pump, then stalls out. I've checked the EFI main relay to verify it"s operation, checks ok. I have no idea why I'm losing the voltage once the starter engages. I would greatly appreciate any help on this. I've spent a ton of time trying to troubleshoot this. Thanks to anyone who may have seen something similar, and can help me. If you would prefer to call, my # is 508-735-0932.
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Thursday, July 23rd, 2009 AT 6:37 AM

10 Replies

Tiny
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  • MECHANIC
  • 75,992 POSTS
Try blocking the airflow meter flap wide open and attempt to start and tell me what happened
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Thursday, July 23rd, 2009 AT 6:45 AM
Tiny
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My Haynes repair manual gives a good location diagram on the 4 cyl. However, I have a V6 3.0 EFI, and I'm not sure where this meter is located. The written description says passes through the air cleaner assy. I looked around the air cleaner assy. Area, but not exactly sure what I'm looking for, tried to find something around the assy. With a wire harness going to it. If you can give me a rough idea where to look, I'm sure I won't have trouble finding it.
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Thursday, July 23rd, 2009 AT 8:30 AM
Tiny
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  • MECHANIC
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Do you see something like this

Test the meter and also the circuit opening relay and the EFI relay


https://www.2carpros.com/forum/automotive_pictures/12900_mass_airflow_meter_1.jpg

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Thursday, July 23rd, 2009 AT 8:39 AM
Tiny
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  • MEMBER
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Yes, I'ts mounted on top of the filter assy. I'll check it right now. I did check the EFI relay. The relay checks ok. Is the circuit opening relay the one mounted in the cab, behing the ECU? I have not checked the circuit opening relay due to the fact that the EFI relay checked ok, and I ssumed that the circuit opening relay suppled voltage to the EFI relay, but will check anyway.
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Thursday, July 23rd, 2009 AT 8:48 AM
Tiny
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  • MEMBER
  • 7 POSTS
Just wanted you to know that the voltage I had before from the harness is gone now. The truck harness that supplies voltage to the pump. Working on stripping the casing off, and reparing any wires that need to be fixed. The white/black wire is in tough shape. Once I get voltage back to the harness, I'll try the air flow meter flap, and let you know what happens. Thanks so much for your time. Be back to you shortly.
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Thursday, July 23rd, 2009 AT 11:20 AM
Tiny
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I did what you suggested once I got the voltage back in the supply harness. I opened the air flow meter flap, and held it open with a screwdriver. The truck fired up. I let it run for a minute. As soon as I touched the accelerator, it died out. I tried repeating the process, and have not been able to get it started again. Based on this, what does it mean? Is there something else I have to do? (Other tests), or does the air flow meter need to be replaced?
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Thursday, July 23rd, 2009 AT 12:21 PM
Tiny
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Test the airflow meter using the repair manual procedures before you condemn it.
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Thursday, July 23rd, 2009 AT 3:37 PM
Tiny
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I checked the resistance in the repair manual, and it all checked out ok. Now I really have no idea which way to go with this. I was actually surprised that opening the flap actually made the truck start up, prior to this, I didn't even know what an air flow meter was. The meter tested ok, so now what?
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Thursday, July 23rd, 2009 AT 4:04 PM
Tiny
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The Fc terminal of the meter grounds the circuit opening relay-Check and test the COR

The EFI fuse powers EFI relay than powers the COR

Do this find the diagnostic check connector and jumper the Fp to Batt-the fuel pump sholud come on it bypasses the relays turn igniton On.


https://www.2carpros.com/forum/automotive_pictures/12900_EFI_and_COR_fuel_pump_circuit_1.jpg




https://www.2carpros.com/forum/automotive_pictures/12900_EFI_1.jpg

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Thursday, July 23rd, 2009 AT 4:22 PM
Tiny
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I just wanted to say THANKS! It turned out to be the circuit opening relay. I just got back from Toyota, put the new one in, and it fired right up. I really appreciate your time and effort on this. I will recommend this site to everyone I know, and you will be getting back extremely positive feedback. Thanks again, Have a great weekend.

Mike
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Friday, July 24th, 2009 AT 10:06 AM

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