Recently I have been having problems with my 2008 ford focus tdci diesel staring in cold or damp weather, tried priming the engine by turning the ignition on and off allowing the glow plugs to warm up and light to go out, three to four times before cranking the engine over.  It struggles to start with white smoke come out of the exhaust, another few attempts of turning off and on allowing the glow plugs to warm up on each crank before it starts, lots of white smoke.  However once the engine is warmed up it, restarting the engine ,it starts quickly as it does when the weather is not cold or damp. The car sit outside all year round, just had a service and it passed mot in June this year, any suggestion of what is, as i would like to solve this problem on the next service. For now I have sprayed the coil plugs connection and glow plugs with GT85 lubricant, penetrant and water displacer spray, hopefully it will keep the damp and wet away from these part and help to start the engine easier in cold and damp weather, I will post the results of the GT85 spray.

Colin 

Tbh it sounds like you need a new set of glow plugs.  Which size engine is it, 1.8?

Thanks Russ, yes the engine is 1.8tdci, I see how it goes with the spray for now and get the glow plugs tested when I'm off work next week, I thought glow plugs lasted a cars lifetime, Colin

Depends how long you keep a car I guess but 10 years is good going for original glow plugs, the constant heat cycles damage them over time just as the element on your toaster or kettle get weaker before eventually burning out altogether.  It's not unusual to replace glowplugs after about 8 years/80k miles but some don't even last that long!

Yes the car has 89k miles on it, still hard to start pre heating a few times then cranking over a few times allowing glow plugs to heat up. Runs better once started with the spray for the first quarter mile, spray seems to keep dampest out, but as you say new glow plugs are most likely needed, thank colin