 | Home > Puma (Tdci) > Puma not starting after stalling.[SOLVED] Likely fuel filter |
 
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| andy63 Member Since: 30 Jun 2023 Location: north east Posts: 521  
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On the testing of your sensors...if they are like the 2.2 cam and crank they are hall effect with digital outputs..the only conclusive test is with a scope.. You can use a multi meter but it's not conclusive or exact.. The resistance value can take a while to settle if in fact it does..unless you have known values you don't know what to expect etc etc.. If the meter settles you can pass a metal object close to the sensor and the meter reading may alter, but again it's not really a positive and conclusive test.. That's why if you do your own maintenance on these it's worth investing in a cheap two channel scope.. 👍😁 |
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28th Oct 2024 8:42am |
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| andy63 Member Since: 30 Jun 2023 Location: north east Posts: 521
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I was going to edit the above post and show a known good cam and crank trace ...but I'll just add it here..as i can't see anything edit function
Ignore the green trace its no1 injector.. the blue is th crank and red the camshaft sensor outputs👍  Click image to enlarge |
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28th Oct 2024 8:53am |
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| andy63 Member Since: 30 Jun 2023 Location: north east Posts: 521
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Youer welcome..the point i was trying to make is you can check sensors with the right equipment rather than fire the "parts cannon "😲at the truck..
You could be replacing sensors needlessly .. Long time ago I got fed up with that attitude by professional garages, of changing parts till they solved a problem ..or not.. at your expense of course.. when there is equipment about that they should be using to help with diagnostic.. Anyway I'll not start a rant..hope you get sorted👍 |
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28th Oct 2024 3:20pm |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 20413
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Just bear in mind the VCV doesn’t produce any DTC’s so you have to observe failure characteristics the old fashioned way, you can’t plug in and look for any suspect code.
Moisture, water contaminated fuel and vehicle sitting not ran for a long time will be bringing and end to it faster. Using fuel additive like Millers will help a lot with preventing wear and tear (and diesel bug), but you’ll always have some wear. Sadly duff out of the box VCV’s or fuel contamination is things that you can only hope to mitigate. Lack of top end power in 5th and 6th, and rough idle when completely cold in winter are signs.. |
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28th Oct 2024 3:45pm |
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| andy63 Member Since: 30 Jun 2023 Location: north east Posts: 521
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I've not been around defenders long enough and in no rush to have fueling issues caused by a faulty vcv valve, but a faulty valve causes running issues which should be visible in terms of rail pressure fluctuating wildly or not in sync with the demanded fueling..
There is equipment about to allow mechanics to check all this.. It's fair enough to know an engine and it's common faults, and replace a part that is the usual suspect, but personally I'd like some sort of tangible proof that I was on the right lines.. I'm not sure how many times I've read that folk have replaced valves 3 or 4 times .. that is pushing the bounds of probability a bit in my book , but again until I experience the issue and do my own diagnosis ...I'm not denying that if you change a part and the issue goes away...that the part changed was the issue.. I did have a quick look a while back at the vcv % duty cycle against rail pressure..it is possible to study them and if you have known good examples a duff ie..sticking in one position or not moving freely valve should be detectable.. I think i have that trace downloaded already.. Click image to enlarge |
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28th Oct 2024 4:17pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17418 
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Andy, the VCV signal in the trace above looks to me more like a PAM signal rather than a PWM signal. Why do you think it is PWM? Thanks.
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28th Oct 2024 4:24pm |
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| andy63 Member Since: 30 Jun 2023 Location: north east Posts: 521
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Sorry blackwolf, I am not explaining that trace properly..
I'm sure i posted it on another thread recently with a better explanation.. The red trace that is just visible at the bottom of the page is the pwm or duty cycle trace.. the line above it is a maths channel facility I have to show what the duty cycle of that red trace is in terms of a percentage.. And the blue trace is the rail pressure sensor.. The beauty of a scope trace is i can go back and examine it in more detail at my leisure.. Which is what I'll do now with that hardly visible red trace ..and I'll post a picture of the duty cycle that you can't make out in the picture I posted..... But none the less the line above it is it's duty cycle percentage.. Hope I've covered that well enough.. |
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28th Oct 2024 4:49pm |
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| andy63 Member Since: 30 Jun 2023 Location: north east Posts: 521
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Right I'm back lol
So I've pulled that red trace up on to the screen, which is the vcv duty cycle.. the issue is the time base is so long that it's just a massive red trace from about 16v down to 0v.. Click image to enlarge But by zooming in many times you can see the switching from 16v down to 0v..the duration of that switched pulse been the duty cycle..which is shown independently by that maths channel in the original photo.. Sorry I've duplicated the 1st photo.. I'll re post it Last edited by andy63 on 28th Oct 2024 5:07pm. Edited 1 time in total |
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28th Oct 2024 5:01pm |
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| andy63 Member Since: 30 Jun 2023 Location: north east Posts: 521
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Sorry this is the zoomed in trace showing more clearly the duty cycle..
Click image to enlarge |
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28th Oct 2024 5:05pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17418
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Ah, thank you. I agree that that now does look like a PWM signal.albeit with a fair bit of noise.
As you say the time base makes it hard to see. Thank you. |
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28th Oct 2024 5:41pm |
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| andy63 Member Since: 30 Jun 2023 Location: north east Posts: 521
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Youer welcome.. I'm not the best at explaining things and often get confused😫
Just to end , here is a vcv trace at a time base that allows a clearer picture of its duty cycle at tick over without having to use a zoom feature.. you can see the maths channel in use but as the duty cycle is steady at tick over at around 20 odd% it's a flat line. It's worth a mention that the change in vcv duty cycle can be measured in micro seconds as you use the accelerator..😳 Click image to enlarge |
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28th Oct 2024 6:03pm |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 20413
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Good work Andy - presumably you are recording specs with a healthy VCV?
Physically when I took my old one out that was faulty, I did take a look at it internally and there was minor scoring on it, I think that affects its lubrication and actuation, and occurs over time. You are correct that you can check other features downstream so to speak such as fuel rail pressures etc, are you planning on comparing a vehicle with healthy VCV vs one that is faulty?  |
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28th Oct 2024 6:44pm |
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| andy63 Member Since: 30 Jun 2023 Location: north east Posts: 521
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Ahh cheers , but honestly, nothing really structured ..I'm basically just messing around trying to learn how to use a scope..
It is a great bit of kit but it's not all straight fwd..there is often no easy way of getting to the sensor and actuators without a lot of work...a lack of correct wiring diag and manufacturers information to the man in the street makes it more difficult to understand at times.. Ideally I would first like to build up a library of known good traces on most of my trucks components.. And that's without taking in to account the features of the scope it's self which have to be got to grips with.. I'm keen enough and interested but it's all low on the list of priorities at the min as most of my time is taken up looking after me elderly mum... She is 98 and still at home with some help👍😲 |
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28th Oct 2024 7:34pm |
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| Waka56 Member Since: 08 Nov 2023 Location: Hamburg Posts: 162 
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I agree with you, but the 2 sensors were 30€, if it's not that, I'll have to get it sorted by someone else that will definitely charge me a lot more. I do not own a garage here and I only managed to park it in a paid area, so its gonna be costly real soon unfortunately. I have a multimeter, but if the reading are not enough to decide if faulty or not 
It's park right in front of work, I'll bring my OBD reader before work tomo. What kind of scope are you using Andy? Making my Defender great again. (Or trying to at least xD) |
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28th Oct 2024 8:25pm |
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