Feeling pretty good right now, since finally found time to really get stuck in sorting the persistent cam sensor failiure issue on my beloved 156 2.4 jtd 10 valve. After removing aux belt and pulleys, timing covers etc, and thoroughly researching the correct method to adjust the timing belt tensioners, I bit the bullet and released the tension from the belt and removed the cam pulley. Before I go any further, perhaps I should say I made a bad decision and put my Alfa into a main dealer to solve this issue. I know, I know. They went down the obvious route and changed the cam sensor - result; fault still present (P 1320 - open circuit at cam sensor); they also tried a replacement ECU, shimmed the tappets, checked wire connectivity, with a similar lack of success.
Determined to get to the bottom of this, (amongst other things), I ordered a new cam pulley, as my Alfa specialist ( no relation to the main stealer), told me that they had come across other Alfas ( although petrol engined models), where the disc on the rear of cam pulley, thro which the sensor reads the signal, had broken the welds and was ruining the timing in relation to the crank sensor ( acts together with the cam sensor to provide the timing signal to ECU).
Well ( and this is the crucial bit!), on removing the cam pulley, it was immediately apparent that there is a lug, cast into the cam pulley which locks into a corresponding cutout, like a poor mans woodruff key, which was broken, and still in the end of the camshaft. No wonder my poor Alfa was running so badly. I also noticed that the countersunk Allen bolt ( one of two bolts locating the cam sensor) had recently been undone by using a chisel on it!!!) The hamfisted bodging peasants!!
Wierd, since my allen key removed it quite easily
I am fairly certain this will be the cause of the P1320 fault, and would like to insert the damaged pulley right up the main dealers main oriface!!!!
So, my fellow Alfa owners the moral of the story is twofold; one, don't assume your cam sensor is the fault when you get this code ( and I would be wary of using the technique of cable tying your timing belt up if you change the sensor, because this lug on the rear of the cam pulley is obviously not the strongest in the world,and if you misalign it when you tighten the bolt back up....SNAP! New pulley required!) and second....FOR THE LOVE OF GOD, DON'T USE A MAIN DEALER!!!!!
Happy Days to you all!