147 JTD refused to start - problem solved - Alfa Romeo Forum
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(Post Link) post #1 of 5 Old 15-12-11 Thread Starter
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147 JTD refused to start - problem solved

Just had a problem with a 147 1.9 JTD which refused to start this morning. Has a new battery and cranking was just fine; engine turned rapidly but refused to run - not even a hint of wanting to start. Fuel level was fine. Temperature was about +5C. A few days ago started and ran with no problems after being out all night at -5C.

Pre-startup light sequence on dash was completely normal; glow plugs all working; glow plug light went on and off as normal. No warnings.

Hookup to a diagnostics box and laptop (Alfadiag) showed "RPM Sensor" voltage not detected. After diagnostic run the engine control system warning light came on. Faults were erased and a restart attempted, with same result - no start.

Note that internet checks, including this forum, suggested that RPM sensor failure does NOT prevent the engine from starting, but can cause engine to stop running after a while.

Bought a replacement RPM sensor [also known as crankshaft position sensor] (Bosch Part 0 281 002 603). Price was £ 23.00 incl VAT. Part can be obtained from good motor factors; I didn't even bother checking price from an Alfa Dealer.

In my opinion this replacement would be impossible without a pit or a vehicle lift. Luckily a friend nearby has a pit, and we were able to push the car from my place to his.

Sensor removal and replacement not too difficult but access was a pig - even from a pit; the sensor is on the lower rear skirt of the crank-case, under the starter motor.

Sensor is held in place by a single socket screw with a 5mm hex. Removing the sensor after the screw was out was also tricky, as the access was restricted by the exhaust pipe, the drive shaft, etc. and the sensor is a bit out of the way. Sensor has an o ring oil seal on the body which makes it a fairly tight fit. Sensor needed to be "persuaded" out of place with a set of needle-nosed mole grips clamped on the body of the sensor. and a long screwdriver as a lever.

New sensor was fitted in 15 minutes (still a bit fiddly), and connected; engine started and ran immediately.

Another diagnostics run was done to remove the fault code and re-set the engine control system warning light.

I hope this helps someone.


Last edited by sjclark; 15-12-11 at 16:38.
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It is unusual for a crank sensor to fail completely without warning - normally they start to fail, causing the engine to cut out when at low revs when warm......but obviously from your experience they can fail outright. I've not tried to do a JTD - TS models are easily done from above, but the intake on the JTD may preclude it. Well done on sorting your issue!
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This failure was almost without prior warning - there was actully a funny moment the night before when engine took about 3 goes to start, and the successful start took about 6 seconds of cranking, which is much longer than usual for this car.

As regards access from above, it is just plain impossible, as the starter motor is completely in the way.

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Glad you got it sorted mate...

A handy tip for all JTD owners is:
Leave the ignition on for thirty seconds.
Even when the glow plug light goes out, they still aren't up to full heat yet (same with all diesels including HGV's)...
On really cold mornings repeat for another thirty seconds (2nd preheat) and it starts up at the first turn of the crank... That's assuming it doesn't have any other faults like your's had though.

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