would a ****ed coolant temp sensor stop my car from starting as my car sometimes wont start.Then when i start pumping the accelerator it starts with i a big puff of black smoke out the exhaust it seems fine once started been told it could be the coolant temp sensor am not getting any error codes on the dash its a turbo 2000 1998 btw

 

Possibly as the ecu isn't getting the correct temp reading so it doesn't know whether it's a cold,warm or hot engine it's trying to start.
I had a starting and dodgy cold idle problem with no CEL ,changed the sensor and it sorted it.
Also the crank sensor is another one that can casue poor stating

 

Does sound like a CTS problem.

 

how much are these sensors?

 

£28ish i think for the temp sensor the crank sensor though i understand to be a lot more possibly over £100 although i may be wrong.
There are plenty of impreza breakers out there if you decide to buy 2nd hand sensors

 

40 quid from stealers or 10 quid from ebay second hand

 

 

is the crank sensor the one near the coolent temp sensor under the alternator

 

Yip.

 

coolant temp sensor is on the back of the coolant pipe running across the engine. you access it from the back.
cps is at the front under the alternator. you access it from the front.

 

Not on a later classic it isn't.

 

Can be coolant, crank or cam : I changed the first 2 on my classic to try to resolve a hot start issue, didn't really make much difference. Changed the Cam sensor and problem solved immediately : that sensor was the one I thought was NOT relevant to starting, only used when engine running but it is obviously not the case.