Cdti 75 cam or crank sensor

[Armymick]

My 05 Cdti with 186k has developed a starting problem and forums say it is crank or cam sensor is there a way of testing each one. Mine starts sometimes no problem then the next it won’t . It’s an auto so could it be the parking adjustment? it will always start in the end but would rather it would fire up. The battery is new and no water ingress anywhere.Any ideas p,ease.

[COLVERT]

When you get it started does it then run OK.---If it does then your crank sensor is fine.---

Could be one of the other two things you mentioned that's the problem.

[coab]

Crank sensors tend to fail when the car gets warm. If when the car is warm it will not start but an hour or so later it does it the cam or crank sensor. Diagnostic wise they talk to each other and it has been known to show as correlation between the two to show up.

[squall89]

Originally Posted by Armymick

My 05 Cdti with 186k has developed a starting problem and forums say it is crank or cam sensor is there a way of testing each one. Mine starts sometimes no problem then the next it won’t . It’s an auto so could it be the parking adjustment? it will always start in the end but would rather it would fire up. The battery is new and no water ingress anywhere.Any ideas p,ease.

I had the same problem.

in my case it happens with higher probability when the car was warm (switched half an hour or 1 hour before)

[Mike Noc]

Originally Posted by Armymick

My 05 Cdti with 186k has developed a starting problem and forums say it is crank or cam sensor is there a way of testing each one. Mine starts sometimes no problem then the next it won’t . It’s an auto so could it be the parking adjustment? it will always start in the end but would rather it would fire up. The battery is new and no water ingress anywhere.Any ideas p,ease.

As mentioned, if the car runs OK once started the crank sensor is fine. The ECM constantly uses the crank sensor to time the fuel injector firing. The cam sensor is only used at start up to let the ECM know the cam position as the cams only go round once for every two revolutions of the crankshaft. Once it references the camshafts position it ignores the cam sensor until the next start sequence.

If a new cam sensor doesn't cure it then do an injector leakback test - you may have one or more leaking injectors which causes the same starting problems.

[Yorkshire GOC]

Originally Posted by Armymick

My 05 Cdti with 186k has developed a starting problem and forums say it is crank or cam sensor is there a way of testing each one. Mine starts sometimes no problem then the next it won’t . It’s an auto so could it be the parking adjustment? it will always start in the end but would rather it would fire up. The battery is new and no water ingress anywhere.Any ideas p,ease.

If she fails to start again - look at the Rev Counter - if that stays completely still it points to a failing crank sensor - if it flickers then i would be inclined to go with the Cam sensor / injector leak back.