 | Home > Puma (Tdci) > Won’t start after new head |
 
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 20430  
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Is the Crank position sensor connected and functioning?
Any DTC’s logged? $W33T $0U7H3RN $UG4R 🇬🇧🏴🏴🏴🇮🇪🇺🇸⛽️🛢️⚙️🧰💪 |
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11th Jun 2024 1:20pm |
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| Simo74 Member Since: 11 Jun 2024 Location: Bathurst Posts: 6  
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Yes it has functioning crank sensor as it will run fine over 1k rpm
Had a EGR flow code, cleared and has not poped up again This has me perplexed |
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12th Jun 2024 4:30am |
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| jst Member Since: 14 Jan 2008 Location: Taunton Posts: 8049  
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Vcv try the old one agian. Cheers
James 110 2012 XS Utility 130 2011 M57 bespoke Camper 90 2010 Hardtop 90 M57 1988 Hardtop |
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12th Jun 2024 5:48am |
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| andy63 Member Since: 30 Jun 2023 Location: north east Posts: 530
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It sounds fuel related that's for sure.. Do you have a low pressure fuel pump in the tank..
Have you any means of checking if the rail pressure rises while cranking? I think that's, where I'd be concentrating my efforts.. |
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12th Jun 2024 7:26am |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 20430
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Perhaps it’s a duff VCV out of the box, you never know.
 $W33T $0U7H3RN $UG4R
🇬🇧🏴🏴🏴🇮🇪🇺🇸⛽️🛢️⚙️🧰💪 |
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12th Jun 2024 3:08pm |
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| bear100 Member Since: 22 Mar 2010 Location: South Wales Posts: 1917  
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I’m sure Ive read somewhere about the injector fuel pipes having issues if reused?
Possibly air getting in? I’ve had issues with a new VCV out of the box too 2016 Range Rover Autobiography 4.4 TDV8 2010 110 XS Utility 2.4TDCI 2010 Range Rover Sport TDV8 (gone) 2007 Discovery HSE TDV6 (gone) 1993 110 csw 200 tdi (gone) 1994 90 HT 300 tdi (gone) 1994 discovery 300tdi (gone) 90 hybrid 3.5 v8 (gone) Range rover bobtail 3.5 v8 (gone) |
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12th Jun 2024 4:51pm |
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| Bulletbrindle Member Since: 18 Apr 2024 Location: Worcestershire Posts: 2
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Have you bled the fuel system?
Any do you have a way to clear all the DTCs? Mine refused to start after I replaced my VCV until I did that. Good luck |
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12th Jun 2024 8:05pm |
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| hornet Member Since: 04 Jan 2010 Location: Western Europe Posts: 361 |
[quote="Simo74"]Yes it has functioning crank sensor as it will run fine over 1k rpm
Had a EGR flow code, cleared and has not poped up again I think you should definitely check the sensor as custom90 suggests, this sensor is essential when starting with starter. you can also start the engine easily by towing, but with the starter a sensor signal is important for starting the engine, which is why the engine turns at least one revolution with the starter until it starts, while it works without diversions when towing. |
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13th Jun 2024 7:52am |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17432 
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The camshaft position sensor is also critical when starting (since without a reading fro it the ECM cannot determine which stroke the engine is on), once the engine is running it is not used. I don't think you have a camshaft sensor fault though because I don't think it would fire at all if this one wasn't working.
It could be a weak signal from the crank position sensor such that the ECM is only picking up something recognisable above a certain engine speed, or it could be a fuel pump problem whereby there is insufficient pressure below a certain speed. It could be a VCV problem although I think this is actually less likely in this case. It could be that the PRV on the rail is leaking so that fuel rail pressure can only build up at higher engine speeds. If I was investigating, the first thing I would be checking the fuel rail pressure when cranking, since this will help narrow down the problem. Note that if the crank sensor is the problem I would expect normal fuel rail pressure when cranking, but the ECM won't be firing the injectors. If the PRV is leaking or the pump is faulty I'd expect low rail pressures and the ECM will be trying to fire the injectors. |
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13th Jun 2024 8:45am |
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| andy63 Member Since: 30 Jun 2023 Location: north east Posts: 530
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I was wondering about the camshaft sensor??
Ie.. If the engine is able to start without a signal from that.. Ie.. You give it some easy start and it randomly eventually fires as all the pots will be fueled.. The crankshaft sensor now sees it's running and away it goes...it no longer looks for a camshaft signal... Is that possible, or must it see a camshaft signal to let it know which cylinder requires firing?? In the normal scheme of things I know that's the case.. But if you fuel all the cylinders with easy start... I don't know?? |
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13th Jun 2024 8:56am |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17432
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I pondered that for a while. The engine will clearly start on ether becuase this requires no fuel to be injected. However I don't think that the ECM will ever try to fire the injectors until it can determine from both the camshaft and crankshaft sensors when to do so, I am pretty sure it won't randomly select one of the two cranks signals per cycle and try it on the off-chance it has the right one, that would be an odd strategy. It would also suggest that with a failed camshaft sensor you'd still have a 50% chance of the engine starting when cranked, and you don't.
So I think it is reasonably safe to assume that with no camshaft position sensor signal the engine will never start, whatever means are applied. It would be easy to test if anyone was willing to unplug the sensor and dump a load of Easy Start in the engine, but I am not going to do this to my engine if I can help it! 
I do think that the fact the engine can be started on ether and then will run on diesel most probably suggests either a very weak low-speed crankshaft sensor signal or a fuel pump problem. Clearly something isn't happening at cranking speeds that then starts to happen at rocket-fuel speeds, and I can't think of many other contenders. |
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13th Jun 2024 12:42pm |
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| hornet Member Since: 04 Jan 2010 Location: Western Europe Posts: 361 |
Interesting, I had previously assumed that the crankshaft sensor was only required for "normal" starting with the starter motor. I often roll slightly down the hill in the morning and let the clutch come in, the engine starts immediately without any turns and without delay. So I bet it would do that without crankshaft sensor at all....
Edit: I checked the WSM, "motor turns but does not start" mentions to check the IFS-Securityswitch. Never ever heard of that! |
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13th Jun 2024 1:10pm |
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| andy63 Member Since: 30 Jun 2023 Location: north east Posts: 530
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Yes makes sense.. I'll not volunteer either👍🤣 But if the op replaces his camshaft sensor and all is well again that would answer the question👍.. |
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13th Jun 2024 1:36pm |
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| andy63 Member Since: 30 Jun 2023 Location: north east Posts: 530
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Hi hornet.. Possibly referring to the inertia cut off switch..
It disables starting while allowing the engine to crank.. I did try it as I was looking for a way to do a relative compression test.. So disconnected it It does throw an error code but that's it.. Once reconnected starts as normal.. |
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13th Jun 2024 1:41pm |
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