156 - cutting out, not restarting

[tuscan_thunder]

Mrs t_t's 156 has, in the past week, cut out twice and thereafter refused to restart.

The first time I put down to lack of fuel and the car sitting on a slope but that's not the case in the second incidence.

When it's cut, the starter turns fine, turns the engine, but it won't fire. Then, apparently randomly, it will start. Temps are normal, in the second case it wasn't fully hot.

The MAF's just a few months old, lambda the same, everything else seems normal: plenty of fuel in the tank, plugs ok, it runs and pulls fine when it is running. The fuel pump primes and cuts out properly when the ignition is switched on.

I imagine it's some kind of sensor issue but not sure where to start looking.

thanks in advance

[wadgebeast]

Probably the MAF, even if it is new, and especially if it's a bosch one.

[RicksAlfas]

I will bet you a large tub of Waxoyl it's the crank sensor. They go open circuit when they are hot so the car won't restart until it's cooled down - usually about the time the RAC arrive and then look at you as if you are an idiot.

[tuscan_thunder]

are they a bu**er to fix?

any idea of cost if I take the lazy route and get a garage to use it?

[tuscan_thunder]

http://partfinder.smpeurope.com/index.html?p=156&a...

would this be the correct part?

There seems to be two part numbers for crank sensors for the 2litre engine. It's a CF3 engine I have a believe.

[RicksAlfas]

tuscan_thunder said:

are they a bu**er to fix?

any idea of cost if I take the lazy route and get a garage to use it?

Think it cost us about £90. Usual thing - £20 part, but two hours labour!

[Jimbo.]

I will bet you a large tub of Waxoyl it's the crank sensor. They go open circuit when they are hot so the car won't restart until it's cooled down - usually about the time the RAC arrive and then look at you as if you are an idiot.

Been there, done that!

[falkster]

As said before it will be crank sensor. IIRC it fools the engine into thinking it is overheating so cuts the engine to stop any damage.

Cost me about 25 quid!

[RicksAlfas]

falkster said:

As said before it will be crank sensor. IIRC it fools the engine into thinking it is overheating so cuts the engine to stop any damage.

No. It tells the engine the position of the crank so it knows when to start the ignition. When the sensor is old it can go open circuit when it is hot - i.e. it doesn't work so the engine doesn't know which position the crank is in. This is why the starter motor will whirr but the engine won't start. As soon as the sensor cools down it begins working again which is why if you have this problem the engne always starts first thing in the morning but might not do after a short stop e.g. petrol station.