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  • [Corsa B 1993-2000] Intermittent fault possible crank sensor

    Hi all,

    I am new to this forum and working on corsa's. I have a 2000 corsa B with the 1.0 12v x10xe engine. Sometimes the car will start perfectly and run all day long but other times it won't start at all. The eml light is on all the time. I have tried a snap on scanner but it won't read.

    Please help.

    Any more info required I will try my best to answer them.

    Thanks

    Ben

  • #2
    On those you need to use op com to check the codes. If the EML is on there's something wrong.

    Easy to check if it's the crank sensor, when it won't start check for fuel pressure at the rail, use the valve on the rail to check for pressure.
    1972 Viva restoration thread - http://www.thecorsa.co.uk/projects-b....html#post1534

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    • #3
      Hi Taurus,

      I have checked and it has fuel pressure on the rail at all times. I have found that there is a buzzing when the ignition is switched on it will start. If it doesn't buzz, it won't start. It sounds as if it might be a sensor on the throttle body?

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      • #4
        If it always has fuel pressure at the rail then it isn't the crank sensor. If you've got a laptop Opcom is very cheap and it's just about the only thing other than main dealer facilities which is guaranteed to work on the 12v electronics. Otherwise you've got to do a bit more detective work......

        There is often a buzz when you first switch the ignition from the fuel pump relay, but if that was the fault you'd again notice lack of pressure at the fuel rail when it won't fire. Next time it won't fire check if the plugs are wet after cranking. You can get injection relay failure which means you get fuel to the rail but the injectors won't fire. It's an identical relay to the fuel pump relay (originals are purple).

        See if you can track down where the buzzing is coming from. They don't usually make that noise so something isn't right.
        1972 Viva restoration thread - http://www.thecorsa.co.uk/projects-b....html#post1534

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        • #5
          Hi Taurus,

          If this has worked out fine I should have uploaded a picture of the part which buzzes when the ignition is switched on. It slightly opens the butterfly in the throttle body. I have disconnected the connection and although the eml stays on, the engine runs smoother, would that part be changeable and would that fix it and just get it eml switched off?
          Click image for larger version

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          • #6
            Idle control valve - take a look at the "how to" section, there ought to be details how to clean it. It would be worth cleaning the throttle body generally whilst you're at it. If it's buzzing and you've got intermittent starting it may simply be gummed up.

            If you can't clean it, or it doesn't do the trick, then a replacement can be installed.
            1972 Viva restoration thread - http://www.thecorsa.co.uk/projects-b....html#post1534

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            • #7
              Hi Taurus,

              I took it off yesterday and cleaned it as best as I could. I put it back on and no buzzing from it and it started perfectly and ran sweet. I went to it this morning and although it didn't start on choke (ran for around a minute without revving it), [restarted it and revved it slightly for around a minute, ran as sweet as a nut]. I now have a very strong suspicion that the icv have gone West. Am I correct? If so I will put one on.

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              • #8
                If it's starting OK and running OK then it sounds like cleaning it did the trick - if I've read what you wrote right.

                It shouldn't really rev on startup - if it was then maybe it was sticking.
                1972 Viva restoration thread - http://www.thecorsa.co.uk/projects-b....html#post1534

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                • #9
                  Hi Taurus,

                  Yeah you read right, just doesn't seem to start on choke. I may put another one on next week to ensure reliability of it starting as my mom (who owns it) really isn't that good at car mechanics and I am not always available when she needs to go to work.

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                  • #10
                    Hi Taurus,

                    Sorry for the lateness of the reply but I need help again. I brought a china clone op-com reader off eBay and plugged it in. Upon reading the information it won't let me connect to the engine ecu although it will let me into the eps part and the immoboliser. I have now done some more digging on it and found that when it won't start (I crack the fuel lines 17 & 19 mm and no fuel is coming through) is this crankshaft sensor or blocked fuel filter or is it the ecu. The fuel pump relay clicks in when you switch the ignition on and clicks out after a few seconds of the ignition switched off.

                    I am now getting pee'd off with it now and contemplating scrapping it unless there is a simple fix.

                    Also can you bypass the crankshaft sensor or not.
                    Last edited by crazyimpnut; 30-08-2015, 01:01 PM.

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                    • #11
                      I crack the fuel lines 17 & 19 mm and no fuel is coming through) is this crankshaft sensor or blocked fuel filter or is it the ecu. The fuel pump relay clicks in when you switch the ignition on and clicks out after a few seconds of the ignition switched off.

                      I am now getting pee'd off with it now and contemplating scrapping it unless there is a simple fix.

                      Also can you bypass the crankshaft sensor or not

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                      • #12
                        The fuel system is designed to run a short prime when you turn the ignition key, so the fuel pump relay should click and the pump runs for a second or two. Then it shuts down.

                        It then waits for a signal from the crankshaft sensor to tell the ECU that the engine is turning before triggering the fuel pump relay again. So if there is no fuel coming though then the usual cause is crankshaft sensor failure. You don't want to try bypassing because it's a safety system, it is designed to tell the ECU to provide fuel only when the engine is running, so in a crash when the engine is stopped the fuel supply is cut off. It's also pointless because although crankshaft sensors fail quite frequently they are cheap and reasonably easy to fix. Access has to be from underneath but it's a single 8mm torx bolt that holds it in place. I use a normal 8mm ring spanner on them because it's easier most of the time.

                        You won't usually get a fault code for a failed crankshaft sensor because the ECU reads it as the engine not turning - sometimes you do get the code for incorrect engine rpm but only about 10% of the time.

                        You don't need a genuine article sensor on these so any local factors or ebay will do. If you're anywhere near me I've got a couple of spares lying around if you want to check.

                        The crankshaft sensor is basically just an electro-magnet and the coils crack with time. They often fail when hot as the coil expands and breaks circuit, then start working again as they cool down. So starting from cold, running a couple of miles then cutting out, refusing to fire when hot but re-starting 10 minutes later - common symptom.

                        To check fuel pressure just use the valve on the rail - easier than undoing fuel lines.
                        1972 Viva restoration thread - http://www.thecorsa.co.uk/projects-b....html#post1534

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                        • #13
                          Hi Taurus,

                          Thanks for the reply again. I think that I may put a crankshaft sensor on it and try it. Do you recon that it will put the eml out when I put a new crankshaft sensor on? I only cracked loose the fuel lines to absolutely guarantee that if the fuel was coming through or not.

                          Many Thanks again

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                          • #14
                            As said, it's rare for a dud crankshaft sensor to throw a code and therefore trigger the EML - but about 10% of the time they do throw an incorrect engine rpm code when the crankshaft sensor fails - so you'd really need to read the codes present to know for sure. (Remember to clear all fault codes before checking to make sure you get only current faults being recorded.)

                            If the EML is constantly on then chances are there's something else amiss.

                            The way to check for crankshaft sensor issues is to leave depressurise the fuel system (ie leave overnight or bleed the pressure off at the fuel rail);
                            then turn the ignition on but do not crank the engine - check for fuel pressure at the rail to prove the priming run has happened - this will confirm that the fuel supply, fuel pump relay and ECU are functioning;
                            then crank the engine and check for pressure at the fuel rail - fuel present means the crankshaft sensor has told the ECU that the engine is turning - no fuel present means it's failed.

                            Check the ECU earth as well, sometimes a secondary earth helps - the system works by earthing the fuel pump relay via the ECU.
                            1972 Viva restoration thread - http://www.thecorsa.co.uk/projects-b....html#post1534

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