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240 no start[240-260/86] posted by Karl on
Sunday, 28 June 1998, at 7:37 p.m.
A couple of months ago I posted a message about a no start problem I was having with a B230F 1986 240. I initially traced the problem to a bad hall sensor, replaced it and the car ran for a week and the problem started again. Both harness were looking terrible so I decided to replace both engine harnesses. Replaced the distributor a second time after the harnesses were replaced and it again ran for a few days then died. It usually displays a hard start condition, starting on a somewhat random basis before the hall sensor fails for good.
Replaced the distributor again and it started on the first try. Again this hall sensor only lasted a few days. I have now decided something must be causing the hall effect sensors to die.
I am looking for some information. Measuring the voltages on the wires going into the distributor, the 12 volts is present, the ground is fine, but the center connector has approximately 5 volts. This is measuring the voltages on the connector from the ignition ECU going into the distributor and disconnected form the distributor. With my limited knowledge of hall sensors, I thought there was an input voltage of 12 volts, and 5 volts is generated by the hall effect sensor which is output to the ignition ECU.
Is the ignition ECU operating correctly with the 5 volts on the center conductor to the distributor (when not connected to distributor)?
I am starting to think I need an ignition ECU but would like to confirm it before buying one.
Thanks
Karl
Re: 240 no start[240-260/86] posted by abe crombie on
Sunday, 28 June 1998, at 10:18 p.m.
The five volts on that wire is a reference voltage out of ign ecu. The hall switch makes grounds that effectively modify that into digital signal that drops to ) volts at one reference point before TDC and returns to 5 volts at another point. These are used by the ecu to determine when to trigger coil for spark. The vacuum hose is there to give load signal for the calcualtion of when to fire. Look for any wiring problem that would feed a straight 12 V to hall switch. This would kill it.