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Main relay, fuel pump and ECU problems.

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    Main relay, fuel pump and ECU problems.

    Hello everyone. I took my 92 Accord on a 4 hour trip the other day. On the way back, I was coming down a pretty big hill and my car just shut off. I pulled over to the side and got crank but no start. My immediate thought was the main relay. I wrestled it out of it's place and smacked it a few times. No dice. I popped it out of its enclosure and inspected the solder joints and everything looked solid. It wasn't clicking when I turned the key though. I then checked fuses. The under hood ECU fuse was fine, but the 15amp one under the dash was blown. I replaced the fuse and gave it another try. I heard the relay click upon the initial key turn but I didn't hear it click again. At this time, I noted that the CEL was on for a few seconds after turning the key, and then it would turn off.

    I gave up and had a friend come tow me home (waited 3 hours in the heat on the side of the highway in northern Nevada lol). When I got it home, I went and picked up a new main relay and swapped it out. Same issues. I could hear it click, but no start. So I decided to get out the multi-meter and do some testing. The grounds I was able to test seemed good. I then tried jumping the pins to power the pump manually and I the relay would click as well as something under the hood but I cant really tell if I could hear the pump. I noticed that the relay was sending 7 volts to the fuel pump constantly instead of priming it for a few seconds. I checked the CEL and saw that it was staying on when the key is on. I am really lost on what to do at this point. Did my fuel pump just suddenly die? My car has 150k miles. But would that explain the blown ECU fuse and a perhaps now dead ECU? Any help would be great. Thanks.

    EDIT: I don't have a lot of time as this is my only car so I went ahead and ordered a new fuel pump (Spectra Premium), fuel filter and also a used 37820-PT3-A04 ECU from eBay. Feel free to chime in suggestions though while I wait for those parts to arrive.
    Last edited by ProjectH22; 07-17-2020, 11:58 PM.

    #2
    Make sure you have spark.If you do, make sure you have fuel.If you don't have a gauge you can take off the fuel line going to the rail. Get a bucket. If the fuel pours out. You have fuel. For my various shutting off issues. One was the ignition switch shutting off the fuel. The other was the distributor cutting off the spark.

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      #3
      The CEL is supposed to turn on for two seconds after turning the key to the "On" position as the ECU goes through its self check. Jump the service connector (blue two socket connector under ride side of dash) and get any code stored (count CEL flashes, long = 10, short = 1).

      Expose the fuel pump connector behind the rear seat, get a long wire and power the pump directly to see if it work or not before going through the trouble of dropping the tank. I've never had a fuel pump on any of my 12 CBs (some I didn't have long).

      I have had an ECM failure that resulted in a no start condition. I don't remember if the specific problem was that it wasn't sending a signal to the main relay to turn the pump on.

      A bad ignition control module is a fairly common cause for a crank-no start situation that happens suddenly like that. When it starts to go, you'll get a shut off, fail to start situation when the engine is good and hot, then it might start and run fine when it cools off (similar to a bad main relay).
      90 LX 4dr 5 spd 396,014 (sold 1/1/2022) - MRT: http://www.cb7tuner.com/vbb/showthread.php?t=201450
      08 Element LX FWD AT 229,000 - MRT: fleetw00d : 2008 Honda Element LX - CB7Tuner Forums

      Comment


        #4
        Originally posted by adecanmin View Post
        Make sure you have spark.If you do, make sure you have fuel.If you don't have a gauge you can take off the fuel line going to the rail. Get a bucket. If the fuel pours out. You have fuel. For my various shutting off issues. One was the ignition switch shutting off the fuel. The other was the distributor cutting off the spark.
        I will check this after work today. I just know that I don't hear the fuel pump priming and I am usually able to somewhat hear it.

        Originally posted by fleetw00d View Post
        The CEL is supposed to turn on for two seconds after turning the key to the "On" position as the ECU goes through its self check. Jump the service connector (blue two socket connector under ride side of dash) and get any code stored (count CEL flashes, long = 10, short = 1).

        Expose the fuel pump connector behind the rear seat, get a long wire and power the pump directly to see if it work or not before going through the trouble of dropping the tank. I've never had a fuel pump on any of my 12 CBs (some I didn't have long).

        A bad ignition control module is a fairly common cause for a crank-no start situation that happens suddenly like that. When it starts to go, you'll get a shut off, fail to start situation when the engine is good and hot, then it might start and run fine when it cools off (similar to a bad main relay).
        The car won't start even after it is completely cold. I let it sit for 12 hours and tried again and got nothing. Where is this fuel pump connector? I thought I had to drop the tank to get to it? And as far as checking codes, I already tried this and no matter what, the CEL stays on when the ignition is on. No flashes, just solid. I tried disconnecting the battery for a while as well as unplugging the ECU itself, all to no avail.

        Comment


          #5
          The CEL is staying completely solid? That usually is CEL 0 which is the ECU.
          Do you have another ECU to test?
          Keep Pushing..

          Comment


            #6
            **Side note** to ECU problems, older Honda's are NOTORIOUS for ICM issues... (literally a $40 part in the distributor, super easy to change)

            Check your spark when it does the "Crank no spark" check it against the block and look at the color.

            Orange/yellow = No Nueno spark

            White/Blue = Bueno Spark

            Comment


              #7
              Originally posted by ProjectH22 View Post
              The car won't start even after it is completely cold. I let it sit for 12 hours and tried again and got nothing. Where is this fuel pump connector? I thought I had to drop the tank to get to it? And as far as checking codes, I already tried this and no matter what, the CEL stays on when the ignition is on. No flashes, just solid. I tried disconnecting the battery for a while as well as unplugging the ECU itself, all to no avail.
              The CEL stays on indicating that there is a code stored. To get the code, you have to jump the service connector (did you do this?); then the CEL will flash.

              The fuel pump and tank level sensor connector is behind the right side of the rear seat. You do not have to drop the tank to get to the connector. You do have to drop the tank to replace the pump.
              90 LX 4dr 5 spd 396,014 (sold 1/1/2022) - MRT: http://www.cb7tuner.com/vbb/showthread.php?t=201450
              08 Element LX FWD AT 229,000 - MRT: fleetw00d : 2008 Honda Element LX - CB7Tuner Forums

              Comment


                #8
                Originally posted by fleetw00d View Post
                The CEL stays on indicating that there is a code stored. To get the code, you have to jump the service connector (did you do this?); then the CEL will flash.

                The fuel pump and tank level sensor connector is behind the right side of the rear seat. You do not have to drop the tank to get to the connector. You do have to drop the tank to replace the pump.
                I did jump the service connector and the light still just stays solid. IF this is a bad ECU, wouldn't I not have spark anyways? Or will I always have spark regardless of the ECU? I know someone else up there suggested the ICM.

                Originally posted by G. Wiffington View Post
                The CEL is staying completely solid? That usually is CEL 0 which is the ECU.
                Do you have another ECU to test?
                I had to buy one off of eBay. I just made sure it was the same model number as mine, which was PT3. I won't be able to test it until it gets in. I am nowhere near a junk yard or parts car.

                Comment


                  #9
                  I was just trying to make sure you jumped the connector; if it stayed solid, then it is an issue with the ECM. Yes, a bad ECM can cause a no start/no spark issue.
                  90 LX 4dr 5 spd 396,014 (sold 1/1/2022) - MRT: http://www.cb7tuner.com/vbb/showthread.php?t=201450
                  08 Element LX FWD AT 229,000 - MRT: fleetw00d : 2008 Honda Element LX - CB7Tuner Forums

                  Comment


                    #10
                    Originally posted by fleetw00d View Post
                    I was just trying to make sure you jumped the connector; if it stayed solid, then it is an issue with the ECM. Yes, a bad ECM can cause a no start/no spark issue.
                    Okay, well then testing the spark is pointless right now, I assume. I will wait until my replacement ECU arrives to test for spark. I think I may have been the one to fry the ECU, I was trying to test fuel pump by jumping the pins at the main relay and I believe I jumped the wrong ones.

                    Comment


                      #11
                      Best tool you can own is a Honda Service Manual.
                      90 LX 4dr 5 spd 396,014 (sold 1/1/2022) - MRT: http://www.cb7tuner.com/vbb/showthread.php?t=201450
                      08 Element LX FWD AT 229,000 - MRT: fleetw00d : 2008 Honda Element LX - CB7Tuner Forums

                      Comment


                        #12
                        Originally posted by fleetw00d View Post
                        The fuel pump and tank level sensor connector is behind the right side of the rear seat. You do not have to drop the tank to get to the connector.
                        So, the car suddenly runs. I got home from work yesterday and had the idea pop into my head that I should probably check the underhood ECU fuse and it turned out to be blown. I replaced it and the CEL started acting normal again, coming on for a few seconds with the key and then shutting off. Still no fuel pump though. I unplugged the connector you told me about and tried to test voltage but my multimeter took a crap. So, I took my power wire for my sub and jumped it to the fuel pump power wire and got... nothing. I tried again... nothing. I tried a third time and the fuel pump came to life. Excited, I tried to start the car and it started and then died. So, I turned my attention back to the main relay. I tried jumping pins 5-7 and noted that if I did that, the car would start. This didn't work before and I had even tried a new relay at the time but it decided to work this time. If I pulled the jumper, the car wouldn't start. But if I left the car running and pulled the jumper, it would stay running. So, I went to the auto part store and picked up a $60 (!) main relay and replaced it, and now the car starts right up every time with no issues. Even drove it around for an hour last night.

                        I think the fuel pump is going out, because it shouldn't have taken so many tries with direct power for the fuel pump to start working. I have a new one coming anyways so I will probably go ahead and change it along with the fuel filter. I am assuming the long, hot drive was just too much for the aging fuel pump in this car and that's why it shut off in the first place. Not sure what would have originally blown the 15amp under dash ECU fuse. I am the one who blew the under hood one from jumping the wrong pins on the relay, I am sure.

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