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W reg Corsa 1.2 16v difficult to start when cold but starts and runs fine when warm

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  • [Corsa B 1993-2000] W reg Corsa 1.2 16v difficult to start when cold but starts and runs fine when warm

    Hi All, i have see a few posts on this but none that have come to a conclusion to help my corsa.
    We have had the car (1.2 16v multipoint) for 14 years and it has covered 64,000 gentle miles and the engine has no knocks and rattles. However, now it is getting difficult to start. Yesterday it took 15 attempts. each time it starts, revs, runs for a few seconds then dies. Each time it stsrts it will run for longer until it idles, however, until warm if you touch the accelerator the engine response is erratic and the engine dies.

    Once warm the engine starts, runs and idles fine.

    So far items changed:
    Fuel pump (3bar) and fuel filter
    Lambda sensor
    Spark plugs
    Crank Sensor and cam sensor
    Idle control valve and throttle position sensor
    Water temp sensor
    ECU swapped
    Oil and filter change
    Throttle body cleaned, and injectors tested out of the engine
    Exhaust is fine with no leaks.

    A fault code reader has recorded no faults or anything out of normal with live data.

    Other things tested are MAF and EGR valve, the same problem is there with them disconnected (but the engine management light comes on)

    It is proving difficult to resolve, has anyone else had a similar problem. Was it ever resolved?

    I would be grateful if you could let me know.
    Many thanks, A

  • #2
    Which coolant temperature sensor did you change? On some of them there are two - the CTS on the water pump which tells the ECU how cold/warm the coolant is, and the sender for the gauge which is on the EGR valve. Later versions don't have the sensor on the EGR valve and only use the CTS to do both functions, but from memory the W reg engine probably still has both.

    Have you checked the tips of the coilpack where it connects with the spark plugs. They can crack there and that allows moisture into the material which cause shorting and weak sparks. Try removing the coilpack in the evening, keep it inside somewhere warm and dry, then see if that makes any difference to starting when you refit it the next morning.

    After that I'd look at mechanical integrity - compression and more likely the valve timing. The chains can stretch and/or they can jump a tooth. Poor starting first thing can be down to the timing being out.
    1972 Viva restoration thread -


    • #3
      Hi Taurus.
      Thanks for your reply.
      The CTS changed is the one for the ECU but it made no differance. The temp sender for the in car gauge works fine.

      I have checked the cams and timing 3 times and all is perfectly in time.

      I have also had the coil pack and spark plugs out and get a good spark straight away. They was no sign of shorting out when I tested them. I will lookm again for cracks.

      The interesting thing is that when it is the engine is trying to idle and it is cold, if you press the accelerator the engine will die. As the engine gets slightly warmer the throttle response is there but is delayed. If you press the accelerator the engine response but is erattic and will not hold a consistent rpm ie fast idle, it does not become smooth until the engine reaches temperature. Then the engine runs fine.

      I appreciate your time and hope the extra information helps.
      Thanks A


      • #4
        Sound exactly like most 1970's cars ran on cold mornings - keeping them going at traffic lights on part choke could be interesting. Which tends to give me the feeling there's something affecting the cold running fuel mix. Snag is it's hard to figure it out without being able to see and hear what the engine is doing.

        An ignition problem would so the same of course, though you say you're getting good sparks. (Just worth checking that the battery & alternator are good. The Vauxhall ignition is very power hungry and I've known them crank fine but just refuse to fire properly when the battery is even slightly below par. They need a good fat spark to ignite the rich fuel mix. )

        Double check the battery & alternator. Look for above 12.5v before first cranking in the morning, and towards 14v with the engine running. If the battery seems OK I'd still give it an overnight charge just to rule that side of things out. When you've checked the obvious it's a process of eliminating everything else.

        Check also the ECU and main earth. Use a jump lead to make a temporary secondary earth. Again, just ruling things out.

        Have you checked the fuel pressure at the rail? You say it takes 15 cranks to fire it up. When that happens give it a good cranking then either whip a plug out or sniff the exhaust tailpipe - the plugs should be wet and the tailpipe stink of petrol. You've tested the injectors off the car but are they working on it? Follow the fuel flow. Check for pressure at the rail. Then make sure it's actually getting through the injectors. A failing injector relay might cause poor injection. (It's the same relay as the fuel pump relay so you can always try swapping them round.)

        If the plugs are wet try flooring the throttle as you crank. (You may have done all these but we can't know for sure so worth mentioning.)

        An air leak on the intake could cause similar issues. As can a partially stuck EGR valve. A partially stuck EGR probably won't throw a code but it will admit air into the cylinders which isn't metered which weakens the fuel mix. Disconnecting the EGR won't cause the valve to close if it is stuck. It's worth taking it off (you'll need a new gasket as they are the crush type) and give it a clean with carb cleaner.
        1972 Viva restoration thread -


        • #5
          Hi Taurus.
          Thanks for your reply. I agree if it had a carb you could adjust it and all would be good.��

          Most of what you suggest I have tried.

          Battery and alternator good. Charging at 14v. Jumping it as well as a battery made no difference.

          Fuel pressure. Have tried the relay trick and also got a new pump. With injecors out the engine all fire with a strong spray. With injectors in the car and no plugs in all cylinders are wet with fuel. Fuel is returned to the tank so the prv is also working.

          Have had throttle body off cleaned and checked for air leaks. Non present.

          The all sensors that are disconnected when engine is running throw a fault code that go out when reconnected. The live data does not show anything when the engine is running and is the same as similar corsa that runs fine.

          I have tried disconnecting the maf, but that made no difference. I thought it was a sensor / electric issue, something the readings or resistance change with temperature. However the new ecu or additional earth's to ecu, coil pack and engine made difference. Now I think it is something that controls the cold start fuel air mix that is not ecu controlled or monitored.

          I tried disconnecting the egr valve, it did not effect starting but did throw a code. However if the egr was just stuck, not showing a code would this affect the fuel air mix? The vacume pipe to throttle body is clear however will need to check if the valve works. Sounds like a off engine job as redex has not made any difference.

          Modern engine control is more complex them the old manual choke. Pity!

          Thanks for your help. A


          • #6
            You've certainly tried all the usual suspects. So it is worth removing the EGR valve. If the valve is stuck slightly open then it will be admitting air to the cylinders that is throwing the metering out. Disconnecting the EGR won't make any difference if the valve is physically stuck. It might be worth considering fitting a blanking plate as it eliminates the EGR once and for all. The engine will actually run slightly better with it blanked off. Leave the EGR connected though. You may find you get the EML on at motorway speeds and a code for the EGR, but just ignore that.

            You have fuel present in the cylinders. You have sparks. The timing is good. The engine runs well once warmed up. It's got to be something throwing the cold start out.

            Bunging in Redex won't get to the EGR as it recycles exhaust gases - by which time the Redex has been combusted.

            Really hoping looking at the EGR sorts it.
            1972 Viva restoration thread -


            • #7
              Hi Taurus.

              Just an update.

              Coil pack. Took it off, heated it up in the oven. Back on car. Engine still the same.

              Egr valve. Took it off. Checked it. Valve closed. Cleaned it. Back on car.

              Engine still the same. First 3 times to start, Revs to 1500 then dies. On tries 4,5&6 revs to 3000, tries to keep going but stalls. Try 7, revs to 3000, drops back to less than 500, sounds like it is firing on 2 cylinders, then dies. Try 8, revs to 3000, drops back to 500 but engine keeps running, improving as it get warmer. Until it is up to temp any throttle applied nearly induces a stall. Engine is happy to idle but will not run fast idle or be held a consistent rpm.

              Once warm, 90 deg.c runs fine until rad fan cuts in. No eml on.

              Hot start, fine.

              Warn start, starts fine but will throttle respons is for the engine to die until hot.

              With engine running I disconnected sensors in turn. All made eml illuminatre apart from Lambda and cam sensor.

              I am convinced the problem is related to cold start (like a carburetor out of tune) but this is proving very difficult to find.

              Any ideas welcome.


              • #8
                In that situation I'd refit the EGR having checked it was fully closed but do not connect it. The EML shows but ignore it. The engine will run as though the EGR is blanked. I've had some weird things with EGRs sticking and responding to ECU inputs with no fault codes present.

                The rpm it's pulling suggests air is getting in other that via the throttle control and therefore air metering (unless you can see the throttle opening more than it should.)
                1972 Viva restoration thread -


                • #9
                  Hi. Been a while since I have posted but now it is the spring I thought I would have another go at the non starting corsa b 1.2 16v.

                  Over the winter I found a donor car and have replaced other engine management parts. And guess what. It still will not start on the key. It turns and tries to start but will not catch. However if I spray petrol in the throttle body it starts and will then run fine. Over 2 hours it was started over 20 times. However this is from warm not hot just warm. Left overnight it will not start in the morning without the manual petrol injection.

                  Reminder. I have replaced.
                  Fuel pump, filter and pressure regulator
                  Sensors: crank, cam, water temp, throttle position, idle control, Maf, lambda, coil pack and ecu.
                  New spark plugs and air filter

                  No fault show on scanner with engine running or not. Egr valve checked and OK.

                  I have tried the coil pack and get good sparks, and also had the injectors out and they initially fire as a pair and then sequentially as they should. When running the engine sounds great and I have leak tested the induction side as well.

                  However on the key it will not start from cold.

                  As mentioned before, I think it is (like old car choke) cold start fuel air ratio related. As the engine is fine once started and car drives great.

                  Interestingly, if left overnight the fuel rail looses all fuel pressure, on the key the fuel pump runs and re pressurises the fuel rail when the engine cranks but even after 7 or 8 attempts the engine will fire on a couple of cylinders but still not catch. Subsequent attempt just flatten the battery.

                  I have tried to prime the fuel rail but cycling the key to key position 2 but this does not make the fuel pump run. The pump only runs if the engine cranks. However some articles I have read suggest there is some form of 2 second pre start priming sequence.

                  Has anyone else heard of this. Any ideas most welcome. I am determined to get car to start on the key from cold.

                  Thanks in advance. Adey


                  • #10
                    The fuel lump relay should activate for a priming run when the key is turned to ignition. It then stops until the crank sensor tells the ecu the engine is turning which then reactivates the fuel relay. Check for pressure at the rail with the ignition on but before cranking.

                    The switch is via the ecu grounding the fuel relay. A bad earth on the ecu can cause problems and many times a secondary earth on the ecu solves problems. Check the fuel relay and the crank sensor as well. Dirt on the sensor tip can cause interference with the magnetic operation of the sensor
                    1972 Viva restoration thread -


                    • #11
                      Hi Taurus.

                      Thanks for the reply.
                      As mentioned I have tried but cannot activate the priming cycle of the fuel rail with the ignition turned on. It only pressurises at the moment with the engine starts cranking. I have added an extra earth to the ecu and replaced the crank sensor and both the purple pump and injection relays. I don't think it is the crank sensor as I believe the main function of this is to shut the fuel pump off if the engine stops turning and it is new. But will recheck if weather at the weekend is fine.
                      Also I note there is a fuel tank vent valve. I have not changed this yet but will get one.

                      I will let you know how it goes. A


                      • #12
                        Hi Taurus.As mentioned weather been fine so had another go at trying to start the corsa. Double checked the fuel rail. No fuel pressure if car left overnight. On the key, no pump priming on the ignition cycle. The pump relay only operates when the engine cranks. The injection really works fine. Changed the fuel tank vent and cam sensor. The car cranks fine and after cranking the fuel rail will pressurise, but will not start. A couple of manual squirts of petrol to the throttle body and it fires up and runs a treat. Once started it can be stopped and restarted on the key. I will try another earth wire to the ecu this week. Further ideas welcome.Adey


                        • #13
                          If there is no priming run when you first turn the key but the pump runs when the engine is turning then the relay is OK. The problem is likely with the activation of the priming run. That could be an ignition system problem - but I assume all other ignition switched systems are running since there's no mention of any other problems. Or an ECU issue.

                          If you look at the system it is not too hard to bypass the automatic priming activation and replace it with a manual switch. That ought to at least indicate if that is the problem.

                          It is normal for pressure at the rail to drop overnight.

                          Just worth checking the pump - if the pump running on cranking but the engine is still not firing I wonder if the pump is struggling to build up pressure. When you crank it and it won't fire how healthy does the fuel pressure seem when you press the pin in the middle of the valve on the rail?
                          1972 Viva restoration thread -


                          • #14
                            Hi. Had another go at the corsa and still only limited joy in starting on the key from cold.

                            As mentioned, the fuel rail looses pressure overnight, but when the engine cranks it soon builds up again but the engine struggles to start.

                            I have had the relays out again but cannot activate any form of priming cycle. Does the 1.2 16v have one as it is not mentioned in the Haynes book.

                            Anyway. Introduce fuel in the throttle body car starts and runs. Once this process has occurred once the car will start and run on the key a number of times. I have tried this over 20 times in 2 hours and all is fine.

                            With a fully charged battery the car will start on the key after the 7th or 8th attempt. It will splutter a bit but then be fine as above. If you depressurize the fuel rail it will start on the key straight away. Also disconnect the the crank sensor and the fuel pump stops. The crank sensor only appears to controls the fuel pump as engine turns, it does not appear to control the any priming cycle.

                            The only thing I cannot seam to do is get the car to start on the key if left overnight.
                            Any help or advise on whether this model has a priming cycle and how it works would be most welcome.

                            Thanks, Adey


                            • #15
                              Yes - they all run the priming system on the fuel pressure. If that isn't happening then it's down to the signal activating the relay. You've checked all the usual suspects so my guess is there's an issue within the ECU.

                              As I suggested above, look at a manual switch to bypass the ECU activating the fuel pump relay, that way you can manually activate a priming run. See how it starts then. As said - the relay is activated by being earthed through the ECU so all you need to do is to put a manually switched earth onto the relay. Set this up running in parallel with the standard wiring so you leave the usual wiring in place. That way, once the engine is running you can deactivate your manual bypass. That's a safety issue as in the event of a crash you don't want the fuel relay still activated.
                              1972 Viva restoration thread -