Mazda guru needed

Hi Guys,

I have an interesting problem with a Mazda MX5 details below. As it is a job in my business, I will donate a proportion of the profit to the forum so we can all share the love. Any thoughts and input would be most welcome.


1999 Mazda MX5 1.8 L Automatic.


Vehicle will fail to start,


Vehicle will fail to start after being driven for a period long enough to reach operating temp. This fault will not stall or stop the car while driving or idling. The frequency is varied, from 1 week between occurrences up to 1 month, the car is used most days. Ambient temp is varied, and not a factor. When car will not start, if left for 1-2 Hrs it will fire up and on some occasions will go into (as the customer reports ) a limp home mode. Normal operation will resume after a short drive.

Customer reports a strong smell of fuel during and after starting attempts, So fuel delivery and injection pulse is evident. On the only inspection when in failed mode, there was no ignition (spark) but I was unable to inspect for coil voltage. The ECU has no stored fault codes, I use a Snap-On scanner. Local Mazda dealer cannot extract any codes either. I have not yet been able to have the car at the work shop while in fail mode to re scan in live data mode.

I under stand that due to the large amount of information being gathered by the ECU, A logic chip is used which blocks fault coding unless it is detected after X number of occurrences in a given number of start cycles.?

I am still digesting technical information on electronics, but it is my belief. That if the failure was due to a faulty cam angle or crank angle sensor there would be no injection pulse? Coil primary & secondary resistance as per spec (according to Mazda) Next is to have the ECU bench tested under duress, Hot, cold & vibration cycle. This will be undertaken shortly.

The customer is concerned as to the reliability of this car as it his wife s vehicle, Mazda have basically said Don t know, can t fix it He has contacted Mazda Australia and only been referred back to the dealer. Catch 22 at it s best. As it is out of guarantee they just don t want to know. He has been referred to me by a mutual friend of ours (he is a retired nuclear engineer) so he has a brain in his head. So I feel I should at least. Have a go. Any ideas?
Do you
have the same problem?
Tuesday, November 27th, 2007 AT 9:49 PM

1 Reply

Ive seen a lot of Sensor difficulties, do yourself a favor, try trh simplest of all the crank sensor. Pulse or no! My som's Taurus had the same problem, and all it took was un-plugging and replugging it. Since he was dumping the car, we didn't trace it, but I think that's were the problem lies! Donate a portion to ME. Aren't you one of our MODS?
Was this
Tuesday, November 27th, 2007 AT 10:45 PM

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