hall effect sensor gap

[kabaman]

I've been trying to track down a misfire on my car for the last few weeks. I'm running out of things to check. I can't find any spec for the gap between the hall effect sensor and the "octagonal cam lobes" on the dizzy shaft. In desperation I tried moving the sensor as close as I could without touching and the mosfire is worse - so I feel like I'm on the right track.

Anyone know what the correct gap should be? Anyone had problems with this before?

I should note that I took the unit off to replace the vac advance unit. I've had problems ever since but I'd changed loads of stuff so I couldn't be sure that this was the cause of the problem.

Cheers,

Neil

[dwgriffith]

All the info you require can be found here http://landrover-online.dk/L-R%20WSM/defender/Def_...
If you have too much play in the baseplate "bearing" the gap will alter when the vac advance pulls on the plate, if so you may have to go to one end of the specified gap range. You need to use non metalic feelers to set, if you don't have any most business cards are about right. If you get the gap wrong the engine will not run smoothly through the rev range and/or idle very well. If I remember correctly? it's not a hall sensor.

[blitzracing]

You are right, its not a hall sensor, just a fixed magnet and coil. The rotor tip simply closes the magnetic gap. From memory its .2 -.35 mm

[350Matt]

If changing this gap changes the misfire then it may be a problem with the amplifier itself

[blitzracing]

The trigger system is very speed dependent, as it needs a certain rotor speed to produce a trigger voltage. At tick over the voltage is only a matter of millivolts, but rises quickly as the rotor speed increases, so a wrong gap (as in wider) at idle will have a much larger effect. Id be suprised if an over narrow gap is the cause, as this simply increase's the trigger voltage, which is no different to increasing the engine RPM anyway. It may alter the timing slightly, as the the trigger point for the amp would be reached a bit sooner as the voltage rises, but I doubt this would have any significant effect compared to the crude timing system of bob wieghts the dizzy uses. Its certainly worth checking all the wiring very carefully (as in high resistance, corroded or cooked joints) if you have the amp away from the distributor, as the voltages are very small. Start the car and give all the wires a prod' and see if it misfires.