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| wslr Member Since: 18 Jul 2010 Location: Wellington, Somerset Posts: 581  
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The crank sensor wire is shielded. Very often it is damaged after an engine or clutch change because people forget it is there until it becomes obvious, which is usually too late. The earth (shielded wire) is connected to the ECU via the engine loom.
If you want to see if the crank signal is good, the only way is to use a Picoscope and check the waveform is nice and consistent. Also be aware that non Genuine Part/OEM starter motors can be a problem giving out interference on the crank wire (they pass close to each other) and sometimes won't start 'till you bump start it or bypass it. TBH, if it has run OK, and then been stopped, and you get this issue at the next start, perhaps it is something else? If you've got the old ECU in with the later injectors, it may be that the ECU can't control the engine properly as the later injectors have a higher flow rate than the earlier ones that the ECU is presently trying to run. I've seen later TD5's run OK with earlier injectors but not the other way around. |
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26th Aug 2012 6:08pm |
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| v8bobber Member Since: 26 Aug 2012 Location: pembrokeshire Posts: 448 
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Thanks for your reply. I was hoping someone might have a better idea than me. I did wonder if the earlier ECU on the later engine would be a problem. I was reliably informed that the engine would run ok with the wrong codes, and then it needed to be changed for a later type and have the injectors programmed etc.
However i found it really strange that it ran so well for that couple of minutes and only played up when I went to restart it. After that I wouldn't restart although it sounded as if it was trying to. Finally, after much cranking and messing about it started but ran extremely rough and I ended up turning it off. The reason I asked in particular about the shield wire is because it, and the other two wires were only twisted together with tape on them(!) when I have taken it apart to connect the wires properly the shield wire came away from the socket end. The shield wire finishes about 3 inches before the plug. Where should that end connect? Dave |
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26th Aug 2012 7:20pm |
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| wslr Member Since: 18 Jul 2010 Location: Wellington, Somerset Posts: 581
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Now you're asking - TBH, I dont think it ends at all the other end IIRC. It can't be repaired (well not as far as I know).
I had a bitser in the workshop once and it had a similar problem - the guy's usual Devon specialist gave up and he sent it up to us. The loom can't be repaired (I'm assuming that it is an issue) and we ended up fitting a new engine loom and getting another later ECU from Alive I think. Testbook came back with a permanent fault code relating to a transistor failure and on tear-down the ECU had been full of oil from the loom. I think that sorted it out... But this was a non starter though. Yours is starting but running badly. TBH, you are going to be guessing without either a Testbook plugin and a fuel pressure test. If that is OK, you'll need to scope the crank signal. Where are you exactly? There is someone in Bath or Hereford I know who can do this for you if you get the vehicle there. |
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26th Aug 2012 8:22pm |
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| wslr Member Since: 18 Jul 2010 Location: Wellington, Somerset Posts: 581
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Just to add, having read the initial post, it may be worth fitting an injector loom in the rocker cover. If you've got 3 or more injectors messing about because of this loom, then it will run rough with a misfire. Also disconnect the MAF while trying to get it to run. This takes this out of the equation as well then.
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26th Aug 2012 8:25pm |
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| v8bobber Member Since: 26 Aug 2012 Location: pembrokeshire Posts: 448
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Thanks for your help,
I haven't touched it today. You are right in what you are saying about being on a wing and a prayer without proper test euipment. It seems strange that it has run really well the first time and then the second time like its on 3 cylinders. I find it hard to believe that the problem has shown itself between running. If it had started playing up when it was running and then when it was started again started misbehaving. I have yet to find out a definitive answer as to how a later engine should run with the early ECU and late "green" injectors. If I am honest I would like to think that the ECU has sussed that something is now different. Any ideas? Dave |
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27th Aug 2012 6:42pm |
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| wslr Member Since: 18 Jul 2010 Location: Wellington, Somerset Posts: 581
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The Td5 isn't really that clever. Unlike GEMS or Thor on the Range Rover/V8 DII of the time, it isn't a self learning adaptive system. In some ways, that's good for it's more agricultural use.
I'd be tempted to try the injector loom first with the MAF disconnected. If that doesn't work, we can make another plan. |
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27th Aug 2012 6:53pm |
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| v8bobber Member Since: 26 Aug 2012 Location: pembrokeshire Posts: 448
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Do you know how it should run on the "wrong" ECU?
Is there anything to stop me taking the injector loom off the old engine even though it's the old type with the black injectors not the green? Am I correct in thinking that the MAF is the one on the air box and the MAP is the one on the inlet manifold ? Thanks again for the help by the way. It's keeping me relatively sane! |
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27th Aug 2012 7:06pm |
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| wslr Member Since: 18 Jul 2010 Location: Wellington, Somerset Posts: 581
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The old injector loom will work with the later injectors.
The MAP sensor is on the inlet on the LH side as you stand looking at the engine from the front (same side as coolant bottle). MAF sensor is next thing just after the air box where the air filter is (not the sensor on the actual black air box, that's the inlet air temp). I've not seen an early ECU run later injectors before - just the other way around. However, as yours ran OK first start, I doubt it is this that is the problem. |
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27th Aug 2012 8:48pm |
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| v8bobber Member Since: 26 Aug 2012 Location: pembrokeshire Posts: 448
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I will certainly try that tomorrow if I get chance.
What is the thinking behind disconnecting the MAF sensor? Dave |
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28th Aug 2012 1:05am |
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| wslr Member Since: 18 Jul 2010 Location: Wellington, Somerset Posts: 581
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From what I've seen with Testbook a faulty MAF sensor works in serveral way.
1 - The readings are exactly half of what they should be, which usually results in running issues of some sort, usually feeling flat below 1800RPM and smoking when cold etc... 2 - The readings are detected as zero under all conditions, at which point the ECU usually realises this and runs a default air flow directly from the ECU software. 3 - With some re-maps, the standard MAF runs out of numbers (i.e. it goes off the scale). On road test with live data running the MAF reading will hit around 630/640kg/hr and then shows a zero to the ECU which makes the engine drop power off. Then as that happens the MAF reading shows again and then hits zero again, making the car feel like it is running out of fuel. This isn't your issue though.... 
If you disconnect the MAF, the ECU will run a strategy where it is pretty much guaranteed to start without too much of a problem. This way we can concentrate on your real issue. |
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28th Aug 2012 9:04am |
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| v8bobber Member Since: 26 Aug 2012 Location: pembrokeshire Posts: 448
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Hi again,
I have spent an hour or so on it again today. I have checked that the screen wire on the plug wire for the crank position sensor is earthed, that is ok, while I was at it I checked the continuity of the wires between the plug and the ECU, that is also fine. I changed the injector loom from the old engine and tried to run it with both the MAF connected and disconnected. No difference. It does run after a fashion now but makes a hell of a racket. I am starting to worry that there is something mechanically wrong rather than just problems with the electrics somewhere. This is video of it "running", sounds alot worse in real life. The only other thing that I found that could be possibly wrong is that the end of the CPS seemed quite scuffed. I don't know if this is acceptable or will bother the running or not. Dave [/img] |
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28th Aug 2012 12:44pm |
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| wslr Member Since: 18 Jul 2010 Location: Wellington, Somerset Posts: 581
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Maybe you've just found the issue.
If the end of the sensor is scuffed, the ECU probably isn't seeing a clean signal. It makes sense as the engine has been changed, and perhaps contact has been made with the flywheel when the engine went in? Can you source a new one (I think they are around £80 genuine), or a known good one? |
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28th Aug 2012 12:48pm |
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| v8bobber Member Since: 26 Aug 2012 Location: pembrokeshire Posts: 448
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I have attached a picture of the end of the Crank Position Sensor. I don't know whether this would be enough damage to make it play up, especially as it ran so well the first time around.
https://s3-eu-west-2.amazonaws.com/i.hubnu...e77d5b.jpg Dave Admin note: this post has had its images recovered from a money grabbing photo hosting site and reinstated  |
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28th Aug 2012 1:43pm |
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| wslr Member Since: 18 Jul 2010 Location: Wellington, Somerset Posts: 581
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The beauty of the Picoscope is you can rule all this out.
I have seen worse but I would change it anyway. From the clip and the problem you have described I would suspect something electrical and this sensor is the source of ignotion timing. I think you should source one even if you borrow a known good one from a mate. |
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28th Aug 2012 1:57pm |
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