EFI Fuel Relay Problem

Discussion in 'The Projects Forum' started by akajee, Jan 16, 2007.

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  1. akajee

    Thread Starter New Member

    Jan 16, 2007
    Hi All,
    I am having a problem with my EFI fuel relays. I have Toyota Corolla. The first day I experienced the problem, my car would not start. I then traced the wire leading to the fuel pump and applied power from the battery and the fuel pump kicked in so this confirmed that the fuel pump stil works. After much troubleshooting, I found following:

    1 small 4 pin relay in side the car by the kick panel (circuit opening relay)and another larger 4 pin relay (EFI Main relay) in the engine compartment fuse box.

    When inspecting the relay inside the car, I found that it was working. This relay does not have any numbers so I had to open it and check on the inside. When + and - is applied to the coil, you hear a click. So I added an additional + to the (number 30 pin) in the relay and connected a test light to the other pin and it worked. This relay has a resistor across the coil.

    I also tested the larger relay in the engine compartment fuse box with the same results.

    So I think the relays are not faulty...(could be wrong)

    So I went further to the socket where the circuit opening relay plugs into and found the following:
    Normally Pin 30 is the pin where direct + is applied but on the socket, this wire runs to the fuel pump.
    One side of the relay has + that is bridged to the other pin socket and the other side of the coil has a - which I think is controlled by the ECU. See attached pic.
    So I test the theory and connect the same relay as in the car using a test light and the power can get re-routed out on the "number 30" pin.

    The car was sent to a couple of auto electricians and the last auto electrician said that the ECU has a burnt track which he showed me. When a wire is run from the ecu to the - terminal on the circuit opening relay, it works, So I need to repair the track on the ECu and test the existing wire that runs to the relay - but I do not think that it was the cause of the problem.

    Currently I am running a relay (same spec) connected up. I removed the original circuit opening relay. Took ignition power from the socket for two of the terminals and earth from the body of the vehicle and the last wire runs to the fuel pump. But what happends occasionally is that the EFI main relay fuse in the engine compartment MELTS:confused:. This tends to happen when I try to start the car but the key may slip in my fingers and I have to restart. The problem with this setup is that the fuel pump runs when the ignition is set to on.

    How it normally suppose to operate is that when the ingition is moved to START, it is suppose to run the fuel pump for a few seconds and then get another source of of power.

    I am not sure if all this makes sense to anyone but any help would be appreciated.

    we can gmail chat if anyone can assist: akajee@gmail.com
  2. beenthere

    Retired Moderator

    Apr 20, 2004

    I'd be worried about a partial short in the fuel pump. Keep the gas tank full, just in case. I found a problem in a car's wiring by the smoke test once. I just wrapped the fuse with foil and shoved it in the clip. The insulation melted off the wire leading to the short. In your case, this could blow up the gas tank.

    Can you find a Chiltons manual (or the equivalent) for the car? Mine has all the electrical diagrams in it. It's always good to have some idea of the wiring before jumping in.
  3. mrmeval

    Distinguished Member

    Jun 30, 2006
    Is the fuse in the +12v line going to the pump? If so I'd suspect the pump if it's popping at start.

    I'm not sure why the track was burned in the ECU, that would indicate that at some point that trace received a high current. It could have been that the voltage inside the unit was shorted to ground and that trace was in the way OR a voltage came from outside IN to the ECU. You can replace the trace with an insulated wire, the wire itself should be about the same as the width of the trace.
  4. Søren

    Senior Member

    Sep 2, 2006

    You could probably find the wiring diagrams for your car on the web - Try here
  5. Søren

    Senior Member

    Sep 2, 2006
    Sorry, just realized I brought up a dead tread (don't know why it was linked to on another recent page though).
    Last edited by a moderator: Dec 27, 2012
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