Brodeh
Member Since: 08 Jul 2015
Location: Sydney
Posts: 4
  
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| Fixed- Intermittent start - 4.0L Petrol V6 |
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I’ve an Australian Disco 3 with the 4.0L petrol V6. For the last few months its been experiencing intermittent starting problems. I found a few references to similar symptoms on various forms but no confirmed solutions. As it didn’t throw any fault code when it occurred I opted to ‘let it develop’. Just recently it developed sufficiently to become a permanent problem.
The vehicle would turn over, fire on all 6 cylinders only once and then stop. The fuel pump maintained pressure at the rail. The immobiliser was working correctly. I was able to test this as I have a key blade with no transponder or remote for watersports, which when used in the key barrel prevents the engine from turning over at all (and will log also log a fault code).
No fault codes were ever logged or warning lights illuminated when the fault occurred. I was able to monitor and log the voltage drop when starting the vehicle using my IID tool and compare it against when the car works correctly. There was no discernable difference.
The vehicle has had recently had new a starter motor, alternator and runs dual batteries that are maintained on a ctek charger whenever the vehicle is in the garage.
Based on the symptoms I assumed the engine did not know it was rotating. Using the diagram in the workshop manual, 303-14A describes the electronic engine controls for the 4.0L. Only two sensors detect rotation: The Crankshaft position sensor (CKP Sensor) and the Camshaft position sensor (CMP Sensor).
I bought both sensors from Rovacraft, who deserve a mention as they were the only Parts supplier that keep stock of these sensors in Australia (I have no affiliation, only appreciation).
Given the ease of access I opted to change the Camshaft sensor first following the removal and installation instructions (18.30.24) in 303-14A. She fired up right away!
I cleared any fault codes using my IID tool. Unplugged the sensor and was able to reproduce the exact same symptoms. Again no fault codes were logged. I plugged the new sensor back in and she fired up. I did a few other checks to assure myself id fixed the problem and it’s now been fine since.
I thought id share this for anyone who is left with a dead vehicle and despite the best preparation is still left flummoxed for a while.
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 28th Dec 2015 1:49 am |
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garrycol
Member Since: 06 Dec 2010
Location: Canberra
Posts: 1130
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It is amazing what a bit of common sense deduction will do - well done.
It is a shame that the stealers do not do the same - they would have already replaced your fuel pump, injectors, battery before they even got to the cam and crank sensors - and they would have charged you for the unnecessary work.
Cheers
Garry
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| 28th Dec 2015 2:26 am |
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ostland
Member Since: 16 Jan 2009
Location: Capital!
Posts: 90
 
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Thanks very much for this useful info on V6 Petrol. As there aren't many of these about, it is really very useful. I recall a while ago that someone in the US had uploaded his engine problem to YouTube. He showed that the engine failed to start unless he disconnected cylinder 1 before turning the key. Not sure whether this was the same issue but I think he was also pointing to a problem with the sensors.
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| 28th Dec 2015 11:40 pm |
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