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Home > Technical > Repeated start up on freelander 2 petrol i6 |
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alex_pescaru Member Since: 12 Mar 2009 Location: RO Posts: 4642 |
Install a manometer in the fuel rail port and monitor the pressure of the fuel line after shutdown.
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21st Jan 2013 2:54 pm |
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Munier i Member Since: 20 Jan 2013 Location: South Africa Posts: 9 |
Ok thanks a stack. Iwill convey this to the dealer as I have the car booked in for a further look at the cause.Are there any other possible explanations that come to mind?Another thing,the car seems to start first time on a cold start even though the cranking time is unduly long.As the day wears on and especially once warmed up the issue of repeat start ups manifests but generally I would have to say that it is merely the start up that is problematic;all else including idling acceleration,etc. are normal. |
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21st Jan 2013 5:57 pm |
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alex_pescaru Member Since: 12 Mar 2009 Location: RO Posts: 4642 |
For the moment, I don't know what to say...
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21st Jan 2013 7:13 pm |
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Munier i Member Since: 20 Jan 2013 Location: South Africa Posts: 9 |
Noted and thanks again.I think there is enough in your reply to start looking(and testing for) a possible fuel problem.I have an appointment with the workshop foreman in 2 days and will diplomatically suggest your test as a starting point. |
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21st Jan 2013 7:44 pm |
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Munier i Member Since: 20 Jan 2013 Location: South Africa Posts: 9 |
Had the car at dealer for 2 days and they did all kinds of tests including fuel pressure test as well checked all the necessary sensors( fuel pressure/temp,crank,etc).They even tried to reproduce the fault so that it would reflect on the computer as a fault.No luck.They are as baffled as I am(which is cold comfort really since I am not a mechanic) and now have suggested that they will have to contact the "help desk" in UK for direction.All the diagnosis has been attempted via their computer which does not register the hard start problem,but which they agree is a problem quite evident when an attempt is made to start the vehicle.They are reluctant to do anything at all not prescribed by the computer.Is there still a place for common sense in addressing this problem outside of the realm of coputer technology and in terms of good old fashion skill? My wife has been driving a hired car for the past 2 weeks and this does not sit well.What next? |
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28th Jan 2013 5:52 am |
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alex_pescaru Member Since: 12 Mar 2009 Location: RO Posts: 4642 |
We know that on a gasoline car three things must be working properly in order for the car to function.
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28th Jan 2013 8:53 am |
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Munier i Member Since: 20 Jan 2013 Location: South Africa Posts: 9 |
Just spoke to the technician working on the problem and he says whilst redoing some of the tests after the car was standing for the week-end he heard a noise from the fuel tank which should not be there.So even though the pressure readings are fine they suspect a problem with the fuel pump.This it seems is inside the tank as is the fuel filter and the tank has to be removed to get the pump out for testing.Seems like a major exercise but I am desperate and cannot even contemplate an alternative.By the way forwarded your "common sense" to the technician but he says the abnormal sound in the fuel tank is pointing him in a different direction. |
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28th Jan 2013 9:30 am |
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egipp Member Since: 29 May 2009 Location: East Gippsland Posts: 230 |
Hello Munier, I had a very intermittent fault on my i6 - twice in three years - when the engine ran roughly when driving. The first time I put it down to bad fuel since it cleared up when I refuelled. However, when it recurred some 18 months later on a long drive I was able to check, via the Garmin Ecoroute HD which is linked to my Garmin 1490T and gives various vehicle readings via the diagnostic port on the car, that the fuel pressure was fluctuating wildly during the rough running. The dealership replaced the pump under warranty and there has been no repeat of the problem. My recollection is that the normal diagnostic check didn't register a fault and it was because I had seen and recorded the fuel pressure changes (from between 100 and 700 if memory serves me right, the normal being around 380) that the issue was resolved quickly. It is a long procedure involving draining and removing the fuel tank to get access to the pump and having gone to all that trouble, and bearing in mind the very intermittent nature of my fault, it might be worth changing the pump rather than just checking it. I should say however that I wasn't aware of any noise from the tank, but my fault was when the car was moving at speed so I probably wouldn't have heard anything anyway.
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28th Jan 2013 8:40 pm |
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Munier i Member Since: 20 Jan 2013 Location: South Africa Posts: 9 |
Thanks.All seem to point in the direction of the pump.A physical inspection revealed a clogged fuel filter and fuel pump strainer.I have authorised a replacement.Apparently the filter and pump are sold as a unit and because of the hassle in getting access down there I do not want to take the risk of replacing only a single item or even worse,merely doing a clean up.The pump assembly and filter unit together with ancillary parts is being installed and I should have the vehicle back in a day.I will do a final post after a few days driving on overall resolution. |
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29th Jan 2013 6:10 am |
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Munier i Member Since: 20 Jan 2013 Location: South Africa Posts: 9 |
Cannot believe it but its back to the drawing board!!Fuel pump and filter changed(a 2 day job) and the pressure is fantastic but the start up problem persists.This leaves 2 alternatives right:air and spark? In fact the technician comments that the start up problem has worsened with the better pressure. Whereas before the car would exhibit a start up problem only after standing for a while(30 min),now the problem seems to be on every start.He continues to to tinker around and my utter frusration grows.I am honestly at the stage where I am contemplating combining the principles of air, fuel and spark inside the vehicle and putting a match to the entire problem. |
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31st Jan 2013 12:37 pm |
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pab Member Since: 28 Aug 2012 Location: Now in Mid-Wales Posts: 2006 |
Not necessarily. My knowledge of modern ECU-managed petrol engines is limited, but I guess the basics haven't changed! You may have plenty of fuel pressure, but the correct amount of fuel (and air) still needs to find its way into the cylinder - i.e. the mixture must be correct. Mixture is enriched for cold starting, and if this is not happening, or the mixture is being over-enriched, this may explain problems with starting but not normal running. (It would be like trying to start an 'old-fashioned' engine without using the choke, for those old enough to remember chokes. ) In a modern engine all kinds of sensor readings may contribute to setting the mixture, but unfortunately I don't have sufficient knowledge to suggest exactly what to look for. EDIT: I've found the following:
So you should see a fuel rail pressure of 3.8 bar during normal running, but 4.2 bar during cold starting. I'm sure there will also be cold-start changes to the air supply too. Last edited by pab on 31st Jan 2013 1:30 pm. Edited 1 time in total |
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31st Jan 2013 1:01 pm |
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shiggsy Member Since: 13 Jan 2013 Location: Kent Posts: 799 |
Besides Fuel, Air, Spark you do need a fourth ingredient, timing, no point having a nice healthy spark firing just after your perfect air fuel mixture disappears down the exhaust pipe. How ever you'd think something like a dodgy crank sensor would manifest itself after startup as well.
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31st Jan 2013 1:28 pm |
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alex_pescaru Member Since: 12 Mar 2009 Location: RO Posts: 4642 |
Then check the injectors for leakage. If an injector is leaking, with greater pressure will leak more and an over-saturated/rich fuel mixture will be hard to ignite. Cold starts will be OK as the "old" rich mixture will properly help cold start, but once warm, rapid vaporization of leaked fuel will enrich the mixture too much for the given temperature. And with the electric throttle, you can't purge and un-choke the engine by pressing the throttle like on the old cars. |
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31st Jan 2013 2:59 pm |
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Past master Member Since: 30 Jun 2010 Location: Isle of Ely Posts: 2710 |
This is just a shot in the dark, but on a "traditional" engine the symptoms you describe would either be due to an over-rich mixture or a vapour lock in the fuel line.
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31st Jan 2013 9:53 pm |
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