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    Fiat Punto 1.2 8v 2002- intermittent non-start when cold? Archived Message

    Posted by Nick Bell on April 3, 2008, 11:03 am

    Hello everybody,
    Spent ages on this yesterday! Firstly, looked at briefly previous day, load of codes related to coils and injectors on all cylinders open or short to ground, plus "mix strength". Hooked up 'scope to FI and attached ignition secondary probe. Got pulse of 12V when turned on ignition, but flatlined at 0V thereafter. Traced yesterday to F22 open circuit. This supplies EM relay, which in turn supplies FIs, coils etc.. Hoped that this fuse had been intermittently breaking down (can they do that?) but still strange problems after. Could see FI pulse width varying, even at idle, going from 3 msec up to 5msec at times, with no other parameters obviously changing. Oh... and coolant temp was sometimes going up to 126 deg C, with coolant res. cap spitting. Is this overheating a mechanical cooling problem (yes the fan was running) or can it get this hot with a lean mixture?? Fuse didn't blow again but codes returned.

    Would have liked to check fuel pressure but strange type of valve on rail. Have since learnt that inertia switch contacts problematical so will be checking this and pump performance generally when return to vehicle next week!

    Also noticed late in the day that O2 sensor was occassionally going negative, though at times it appeared to be switching correctly. Have flagged this up to the garage as needing replacement but get feeling they want definitive answer rather than replacing things piecemeal! Could this be causing all the anomalies?

    And it wouldn't start sometimes when hot!!

    Had a quick wiggle of, and peered at, the looms to the ECU connectors but no obvious problem.

    Any comments or ideas please?
    Regards,
    Nick Bell

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