Got a non-start situation on a 91(H) UK TT manual and a third party diagnosis suggests the "Crankshaft Position Sensor".

 

Couple of questions...

 

Where will I find this located on the engine?

 

If a replacement is needed, is this a straightforward unbolt/bolt with a trolley jack DIY task?

 

Where's best place to get one and what do they cost ?

 

Thanks for your help,

apprentice

also known as the CAS mate , crank angle sensor , Its the round unit with the big plug that goes into it on the front of the engine on the right hand side by the cam cover. Also check the PTU if its a non start situation. No jack needed to get to it.

How was it diagnosed ?. Before replacing the CAS unit make sure the connector is free from any contamination, that is both ends, i.e. including the PTU end.

How was it diagnosed ?. Before replacing the CAS unit make sure the connector is free from any contamination, that is both ends, i.e. including the PTU end.

 

Recovery guy made the diagnosis on the basis of battery fine, fuel supply in and out fine, plus my confirmation that it repeatedly wanted to stall... and finally did!

 

No fault code diagnosis was or has subsequently been made.

 

PTU??... where and what's that.

 

Thanks for inputs guys.... will check CAS unit later and will take heed of contamination concern.

I'm pretty sure than CAS failure will cause the engine to cut out immediatly. Your symptoms sound like PTU problems.

What happened, misfiring which got worse till it stopped and wouldnt start again?

I'm pretty sure than CAS failure will cause the engine to cut out immediatly. Your symptoms sound like PTU problems.

What happened, misfiring which got worse till it stopped and wouldnt start again?

 

Managed to start car but very reluctantly, thought it was a fuel starvation as it was very low on fuel and believed I dragged some water/crap into the fuel system. It wouldn't idle, misfired and it kept wanting to cut out. Took it for a run in the vain hope that if it was crap, I could clear it - not to be, it stalled and wudn't restart.

 

Does that point moreover to PTU?

 

If so what does that the PTU do and where is it?

The PTU (Power Transistor Unit) is basically a hi-tech distributor and is about the most common fault on these cars.

It was replaced with a series 2 unit they were that bad.

It's fixed to the front left of the cam cover (opposite side to the CAS), just behind the radiator hard pipes.

It's a small black box about 4" square with metal heat sink fins on it.

Check the connections on it are clean but more than likely it's failed in the hot weather.

 

If you have to buy a new one then make sure it's the series 2 type and don't get it from Nissan as they want about £400 :o

 

Maybe someone local can pop over and try theirs...

Anyone local to Guildford who would be prepared to allow me to try their PTU???

 

I would be extremely grateful!

 

Thanks,

apprentice

PTU failure is usually affected by temperature, i.e. when it gets hot, it will stop working, allow to cool and all fine again (MK1 PTU that is).To test the CAS unit, firstly mark its position (scribe a line or tipex) and remove unit. With connector attached, turn on the ignition (dont engage starter or your f*****d) and manually turn the shaft the the CAS unit clockwise (looking from the front). You should hear the injectors clicking and the fuel pump pulsing fuel. To test your plug coil packs and the PTU output, one at a time remove and use a spare spark plug start the engine to see if it sparks.( You could try that when it refuses to start to check the PTU)

Continuing from this, if the PTU was replaced, and the car starts and runs but is lumpy, like its running on 5...what could be causing this? Would it be an O2 sensor?

Continuing from this, if the PTU was replaced, and the car starts and runs but is lumpy, like its running on 5...what could be causing this? Would it be an O2 sensor?

 

No, running on 5 would be caused by bad coil, bad injector, or the wiring to one of them somewhere.

Apparently the car was running fine before the PTU went. In order to diagnose the problem the guys removed the plugs and leads. My problem most likely lies around the connections?

It sounds like a scooby at the moment, but I love it!

Just to confirm the plugs and leads were not removed.

 

Been to a garage today who have diagnosed the problem relating to the injector plugs or coil on the right hand bank as you look at the car (middle plug)

 

Car is booked in on Monday to have the plugs changed for new ones and they seem sure that this will resolve the problem.

make sure they clean the injector contact pins as well as they also get badly corroded. You could tighten the sockets in the injector plugs so as to be a tighter fit and fit them to the injector several times to remove any deposits, that may just clear the misfire.

Further update

 

Went outside and had a little play, removing plugs, and everyone removed caused the engine tone to change apart from one (which I would class as the 5th plug)

 

Car is parked in a garage and quickly became fumey (is that a word?)....would this again tie in?

 

So from what I can see, its either a dodgy connection, broken wiring or a buggered coil pack...can anyone confirm for me?

 

BTW Apparently the car was plugged into a diagnostic machine last week after the PTU was changed and showed nothing wrong (een tho running on 5)

 

I may be covering old ground, but I am just looking for a little back up to calm my nerves....

 

Apart from this problem the car is in fantastic condition and is UK spec.