Ford Focus Mk1 2001 1.6 Petrol UK model
My car usually starts on the first turn of the key but just before
Christmas I found that when left in the cold (freezing weather) for more
than 4 hours on the first turn of the key the car would not start. It
would take 3 to 6 on/off sequences and even then the engine would
sometimes behave if was short of fuel and attempt to stall if the foot
wasn't pressed firmly on the accelerator pedal.
The car would always start first time afterwards even if it had been
running for less than a minute before. When the weather became a milder
again it would start reliably on the first turn of the key, albeit very
The solution was related to the engine head temperature sensor. The
head temperature sensor is located between the two centre spark plugs
and sits down a 'hole' in the engine head. When removing the rubber
cover and the spark plug leads there was water in the hole.
The connector for the temperature sensor can be seen here:
The brown outer coating is wet rust (from the engine head). The clip
holding the connector to its mating half wasn't particularly positive
and there was wetness between the two connectors.
Once dry and cleaned up the car now starts first time every time even
when sat overnight in temperatures below 0C. I assume that previously
the ECU wasn't detecting that the engine was cold and not adjusting
throttle and/or fuel to compensate. At no time did the temperature gauge
which uses the same sensor show any abnormal behaviour.
I'm unsure how the water got in the hole but it could have been related
to driving in heavy rain with deep surface water some time during the
latter part of last year. The cover for the temperature sensor isn't
100% water tight. I don't believe that the coolant from the engine is
the cause as a dozen or so checks since the fix shows no wetness.
I would have thought that the engine gets hot enough to boil the water
away but apparently not with the spark plug and sensor covers in place.
I resorted to making up a smaller nozzle for my vacuum cleaner to suck
the water and any crud out, running the engine up to temperature, then
removing the spark plug and sensor covers to let the residual steam out.
BTW, the metal part of the hose for a Henry vacuum cleaner fits nicely
in the spark plug holes to clean out any crud before removing spark plugs.
- posted 3 years ago