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mdavies

Slow on the uptake? Too sensitive by half?

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“My Engine Won’t Start cum How I Fixed It” stories are not always the most compelling read, especially for those that believe the cause commonplace and should have been checked for immediately.  My apologies where that applies here but my experience may help some.  Even so, summer is here and there is a Grand Prix this afternoon so I will gloss over my novice error - that I myself have warned about here -  also my crash research into OBD scanners, fault code accessibility and the substantial sum for urgent delivery that I paid for my chosen scanner.  All the detail I do give is, I think, relevant.

 

Readers of another thread will know that I am currently exploring yet further enhancement of the Evora NA intake system.  (I may be reporting there again soon.)  That involves replacing the Radium panel that screens the air filter from the engine bay by a new one that I was working on yesterday. It is relevant that it is made from a substantially thinner gauge aluminium sheet than used by Radium for reasons that I won’t go into here except to point out that it is light. Also, only small spanners were used for the same small bolts that retain the Radium design. Cutting and drilling was done on the bench. Many trial fits were needed and so the prototype panel was taken in and out many times and the cables, pipes and connections in that area of the engine bay were brushed against and mildly moved about to do so.

 

I had already road tested the new intake itself without any panel and driven back into the garage - all was satisfactory.  The panel required an awkwardly shaped small bracket that I had spent some time making.  It was that that I let slip. It passed my inadequately positioned “catch-blanket” down to the engine undertray.

 

To remove the undertray - fear of dropping things was a constant pressure on the whole job - I needed to drive up ramps. But the engine then would not start.  It spun over easily on the starter and the dash lights looked normal.  After ............. a while, I concluded that the fuel pump was suspect.  Had its action been more general, I might have considered the  inertia switch sooner, but all the electrical indications seemed normal and I had done nothing that might have affected it.  Surely a pretty substantial smash is needed? But my new panel is located adjacent to the switch, on the other side of a main body frame member.

 

When I pressed the top of the switch it barely moved and there was only the tiniest switch

sound.  (Deliberately, I did not at that point touch the connecting wiring.)  There was no clearly perceptible switching action.  But the engine immediately started.

 

Perhaps my inertia switch is faulty; no problem over three years though.  On reflection it does seem sensible that it only shuts down the fuel pump.  But I can think of nothing that I did that could reasonably have caused it to trip.  Suggestions? 

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If you've been moving metal brackets around the vicinity, maybe you shorted one of the inertia switch wires?

Or something else that tripped it out?

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TADTS. My garage had mine for some harness install and I was to pick it up 1 day ahead of a two week holiday with the Evora. They called 30 minutes before I was leaving the office to pick up they called to tell me that it does not fire up. Turned out to be the inertia switch as they had it put on the lifting ramp and that triggered the switch.

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Michael and Sven, than you for your responses.  I've now done 100 miles since resetting, with many start ups, and no hint of trouble.

 

The reader count is now 80 and no one else has mentioned such an unexplained trip of the switch so, if it is just you and I Sven, it may not be quite a case of TADTS!  Anyway, now I'm aware, it will be the first thing I will check in case of any starting problem.

 

My OBD reader is now no longer urgent but if I can find any fault records with it I will put the details here.  Also I will give my dealer a call and report.  (Unless they are too busy selling Morgans now!)

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It's a very sensitive piece of hardware, perhaps you tapped it with a spanner while fiddling? If you extrapolate that tap with a spanner to how that would have felt to the sensor if it were a frontal impact, it's probably assumed you've hit a wall at 100mph! 

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Yes Bibs, I suppose I must have knocked it somehow. It is heavily clamped to the body frame member though and so actual physical displacement is unlikely. I'm now thinking that apart from the sudden deceleration that it is designed to detect, it must be separately sensitive to a vibration, as you suggest - perhaps as a "side-effect" and perhaps just from some particular angle. (Must look into its design.)

 

In developing the new intake arrangement I had been working around and beside it quite casually to an apparently far greater extent in dealing with the much more substantial actual intake tubing, and even considered repositioning the switch on the engine side of its mounting.  Glad I didn't, now!  After that, I road tested without any problem.  That's why I emphasised how light the panel and the small bolts were in my account above.

 

It also surprises me that the switch being sensitive is not common knowledge - afaik!  Anyway, it is a trivial matter to reset it, and I won't waste half a day if it happens again.

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