Fiat Punto cold start problem

We have a Punto that is very difficult to start when cold - it otherwise
runs ok - at the moment it is simply refusing to start at all. It is
almost certainly a fuel problem - there is a good spark present. We
checked the ECU coolant sensor and it measures about 7kOhms when cold,
which we think to be correct, and it has +5V supply to it. On switch-on
the fuel pump can be heard to prime - so that would appear to be ok.

Can anyone suggest anything else to try?

I had a similar problem with my 2000 (51 plate) Punto where the car would
not start on random ocassions. I traced the route problem down to the
flywheel motion detector had failed.
This means the car turns over but the motion detector does not detect the
engine turning over so it does not send a pulse to the coil and engine
management systems so they do not pump fuel or provide a spark at the
plugs. areplacement cost around £30 and is only 2 screws to replace. There
are 2 of these motion detectors, on on the flywheel at the bottom of the
engine and the other at the top of the engine.

The other problem could be the coils, there are 2 on the Punto however it
is unlikely that both would fail at the same time. You would normally get
2 cylinders firing, so my gues the the motion detectors. They could be
disconnected electrically or either one could have failed.

The lower one is easy to locate as it is near the bottom of the toothed
fly wheel and has a cable (4 mm diameter) coming out from it and leading
up to the wiring at the top of the fan belt / engine.

Try starting the engine while an adult assitant with some mechanical
knowledge taps the the engine close to the sensor with a hammer. Make sure
the hammer / fingers etc are well away from moving parts. If the engine
starts then the problem is a failed detector module. Likewise the top
motion detector is almost identical to look at, try tapping it while
trying to start the car. If it starts then the top one needs replaced. It
is most unlikely that both will fail together.

Good Luck, wotnotagain

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