help

[RockyMtn Spider]

My mechanic and I are ata head scratch. We put in a clutch and when we installed the sensiors and turnedthe car over it ran like crap. We pulled the sensors out and one had the tiptore off. We saw no obstruction and replaced the sensor. It stayed together but the car will not start. Do we need to reset the computer or? If any one has clue let me know. The coil is new but seems to now be drawing less current. Is there a bench test for the sensors or? The weather has been at 45 F and the moutains are calling so I need to get my jewel running.

[papajam]

Disconnect both sensors (connectors by the washer bottle) and check resistance. Spec is 850-1250 ohms. Ensure that the wire for the top sensor goes to the black harness connector and the bottom sensor wire to the gray connector. Was the flywheel removed for machining?

[RockyMtn Spider]

Yes , the fly wheel was reworked and replace into the car. Put on tdc. The wire was bad at the spacer block on the sensor and was installed. The car ran but very rough. When the sensor was removed it was pulled apart at the tip. We looked and found no reason for the sensor to be damaged. Maybe a loose screw or, but any case..nothing could be found so a secound sensor was installed and hand and hand turned the engine to make sure no anamalies to destroy the secound sensor. All was well, so we cranked the motor and it would not fire. Pretty confident it is elec. related. Smelt unburned gas. Curious it ran well for about two minutes then like crap...then the damaged senor discovery. We put in a third sensor ...same thing. we have I believe is three good sensors as the tack bounces when the key is turned on. Swapped the locations and same outcome.

[RockyMtn Spider]

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[RockyMtn Spider]

Are you with me Papajam?

[papajam]

Are you getting spark?

If so, then the plugs may just be wet fouled (from numerous start attempts). Try a clear-flood start (hold gas pedal to floor while cranking).

If no spark, I'd have to think something may still be up with the sensor(s)/wiring/flywheel because the car ran prior to gearbox & flywheel removal.

[RockyMtn Spider]

Do you know exactly how the sensors work and any thing on the fly wheel that is a magnet or such. The sensors are good but we are not getting any spark. Like the coil is out. Have positive current going off the coil but nothing going out. I heard somewhere that the sensor sends a negative to one side of the coil and that creates the spark. Could the flywheel be missing a part that works with the sensor...maybe gone during the milling of the fly wheel? I am guessing at this point.

[papajam]

With continued cranking, voltage may have dropped below the minimum threshold required in order for the ECUs to work. During cranking, the ECUs MUST see a minimum of about 10.5v or they won't work. Hence, either no spark or no fuel. Check cranking voltage first.

The flywheel has a magnet on it that results in the sensors inducing a signal that goes to the ignition ECU. With this and other inputs, the ignition ECU then calculates when to make/break the ignition coil ground circuit that will produce high voltage from the coil at the correct time. It's possible that the magnet got buggered during the repair. Please have a look here to see where the timing mark and magnet are on the flywheel. I'd think it would be possible to put the engine on TDC #1, remove the top sensor and look at the magnet (although I've done it).

[RockyMtn Spider]

papjam....thnx a lot...this is just right..it appears the magnet maybe gone on my flywheel. No one has given us such good info..the pic says it all..again thanx..we have talked to the Alfa repair shop in town and even bmw repair shops and got all kinds of miss info. we have had the trans out 4 times and this is the first GREAT info. Your info led me to find a flywheel replacement...I found a used one and there it is....that little magnet. I talked to at least 6 shops and no one gave us this info...much indebted to you...thanx. I'll let you know when we get the used flywheel in,,I'll use a different machine shop this time as I think the last one broke off the magnet. Not knowing this and it is my first Alfa...learned a lot through this adventure!!! That's for sure.

[papajam]

My pleasure, Rocky.

Just be sure to align the new flywheel on installation lest the gearbox comes out again.

EDIT: If the replacement flywheel is to get machined, it is MANDATORY that EQUAL amounts be removed from both the disc friction surface and the pressure plate mounting surface. Not doing so can result in all manner of clutch issues. If you need more info on this, please let me know.