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Old 20th December 2007, 23:34   #1
Johnny2R
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Default Immobiliser mischief?

I bought my Rover 75 CDT in July 2006 and, after some initial problems with injectors, it has been a delight. Three times in that period, though, it has completely failed to start, and the worst and most serious instance was a couple of days ago. When I say failed to start, I mean it turned over OK, but nothing more, not so much as a cough. Normally it starts straight away without a problem.

Now, each time this complete non-starting has occurred, I believe I have, immediately prior to the non-start, done something slightly different from normal as regards unlocking the car - maybe accidentally re-locking it and then immediately unlocking it again, or something like that. Each time, the car has eventually just sprung back into life as if nothing had happened.

The other day, I had been for a short walk, then got back into my car and felt sleepy, so, deciding a short snooze might be in order, I pressed the button to lock all the doors. I then realised I probably wouldn't be able to sleep so decided to head off anyway and attempted to start the car, but no joy. I immediately thought "Ah, it's that old immobiliser mischief again", so did every permutation of locking, unlocking, getting in and out, etc, I could think of, but it still wouldn't start. I thought it must be something different this time, so called out the recovery people. Anyway, the guy couldn't work out what the problem was and could only determine that no power was getting to the under bonnet fuel pump (certainly I wasn't hearing the normal burring noise before starting). I took a look to see if the ECU was wet but the plenum was dry as a bone. Anyway, just after I'd put the ECU back into place, the recovery guy tried the ignition on and off three times in rapid succession, and bingo, it sprang back into life as if nothing had happened.

Now, it strikes me that this is likely some kind of immobiliser quirk, some bug to do with some sequence of actions which causes it to misbehave (unless there is some other explanation which someone can think of). Has anyone else come across such an immobilisation problem? And is there some way of effectively resetting the immobiliser, some sequence of key fob presses perhaps, that tells it to pull itself together and stop being silly?
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Old 21st December 2007, 07:35   #2
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The immobiliser inhibits the starter motor so if the engine is turning over, it's not that. (If you have the message centre, it tells you when the engine is disabled). If there is no power to the fuel pumps it could be the fuel pump relay.

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Old 21st December 2007, 07:54   #3
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Most common Problem of Non Starting is CAM Sensor.
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Old 23rd December 2007, 07:23   #4
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i am having this problem now, twyce its happened. starter motor turns, wuring from the rear lasts about 3/4 seconds(may be sender unit ). then after 20 od attempts starts up...runs ok when started no problems there.
so to be dim.....whats this sensor and where is it?



:xmas-smiley-019:happy christmas too:xmas-smiley-009:
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Old 23rd December 2007, 14:35   #5
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Immobilser and locking aren't actually linked (other than they both live inside the key head).

The alarm / locking transmits when you press they fob. The immobilser has a transponder chip which only transmits when it's in the ignition lock. The ECUs that receive the signals are different too.

So sorry, the theory doesn't stack up, and as pointed out an immo lockout also prevents cranking.

So cam sensor, fuel pumps, or glow plugs. If it's OK when cold, but always fails with a hot engine, I'd plump for cam sensor too.
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Old 30th December 2007, 12:50   #6
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Quote:
Originally Posted by lowedb View Post
Immobilser and locking aren't actually linked (other than they both live inside the key head).

The alarm / locking transmits when you press they fob. The immobilser has a transponder chip which only transmits when it's in the ignition lock. The ECUs that receive the signals are different too.

So sorry, the theory doesn't stack up, and as pointed out an immo lockout also prevents cranking.

So cam sensor, fuel pumps, or glow plugs. If it's OK when cold, but always fails with a hot engine, I'd plump for cam sensor too.
The odd thing is that 99.9% of the time the car starts without a problem. As I said, this problem has occurred just three times in the 18 months I've owned the car. In each case I've done something unusual with the unlocking immediately prior to attempting to start, hence my suspicion that it was something related. Surely if I had a faulty cam sensor or the like, I'd get regular problems starting, wouldn't I? There is normally no problem whatsoever starting.

As I mentioned, there was no power to the fuel pumps, which would appear to rule them out. How would a problem with glowplugs manifest itself?

Also, how do I check out the fuel pump relay?
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Old 4th January 2008, 15:47   #7
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Default Strikes again!

Hmm, the mysterious complete non-starting has occurred again. I just had an MOT test done (which the car passed, to my relief), and the mechanic could not start the car to drive it away from the test bay. Same again, turns over without so much as a cough. He said he had initially locked the car, then immediately unlocked it again before attempting to drive away (once again a slightly unusual sequence of actions).

I was completely unable to start it, despite numerous locks, unlocks, etc. Then I opened the bonnet, unplugged the RoverRon Synergy unit, plugged it back in again but turned it off, and then it started straight away. So, I turned off the engine and turned the Synergy back on and tried again. Once again it started fine. What might this point to? I doubt it's a fault with the Synergy because on the previous occasions when the problem has occurred, I haven't done what I did this time. It seems to me in some way ECU related, but I can't think how.

Incidentally, the smoke reading in the MOT test was negligible, despite the Synergy being on its highest setting (10), which I'm very pleased with. The engine runs wonderfully and certainly doesn't show its 166,000 miles.
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Old 4th January 2008, 16:23   #8
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Do you have a spare key and have you tried it ??
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Old 4th January 2008, 17:39   #9
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I do have a spare key. I haven't had it with me when the non-starting problem has occurred. Perhaps I'll take to carrying it with me. Why would the spare key help? You reckon it could be some key fob related issue?
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Old 4th January 2008, 19:04   #10
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Interesting.

I still can't see how the locking and immobilser are related. It's not any sort of functional relationship, so it must be something odd like earthing or power supply if it is related at all.

Honestly, there is really no working involvement with immobilser and locking. And the fact that the car turns over backs up that the immo is OK, it wouldn't even turn over if it was unhappy. I'll photograph the inside of my spare key to show you the two unrelated parts, if you like.

There is a pattern, but try to avoid falling into the trap of fitting the symptoms to what you think it is. Take a step back, and try to see what other clues there might be.

Glow plugs: if these aren't working typically it would be cold starting that's a problem. Failure to start after the MOT probably rules this out.
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