Testing Hall or Optic Sensors

Work through each point below to find your problem.

  1. First ensure that the setup in Hyperspace is done according to the startup procedure. This means you will only have a P1 and P4connector on the Mercury2. The other connectors must be open, except for the Comms cable. Open the software and connect to the Mercury2.
  2. Ensure that the correct firmware is loaded into the ECU or TCU for the specific trigger pattern of your engine. You can click on information button to verify.
  3. Make sure the Jumper settings are set for Hall sensors. On Mercury2 the 2-pin jumper must be closed. You may now crank the engine without the other connectors.
  4. Ensure that battery volts on the Real-time Volt Bar does not fall too low. A healthy battery will crank at 11 volts and higher. Under 9 volts, the sensor signal becomes weak and falls below the voltage threshold of Mercury2. Note: If it falls below 10 see chapter about ‘Power Connection’.
  5. Look if any error codes are displayed at the bottom. If there are errors remedy the fault. See Error codes.
  6. Look at the RPM signal in the Real-time Display while cranking. It should show 200 to 300 rpm consistently. If it shows erratic readings and runs wild do not proceed to start! It must be constant. It means the edge setting is wrong or incorrect firmware or there is interference on the trigger signal and the Mercury2 sees them as trigger pulses.
  7. If it shows no error and no RPM it means that the Mercury2 does not pick up the signal from the crank sensor. Proceed to testing the crank sensor itself.
  8. Make sure you use the correct sensor size with your crank trigger wheel size. If the magnet of the sensor is larger than the gap in the teeth, then your signal will be very week. Rather use a gear with less teeth for the diameter or a sensor with a smaller sensing diameter. If you can’t see the magnet protruding from the sensor, put a bit of iron filings on the tip. The magnetic field will show the diameter of the internal magnet immediately. In this case you may enlarge the sensing distance it the signal is strong enough. See the illustration below.

Testing the sensor.

  1. The hall or optic sensor requires power to operate. So it cannot be dry tested like a magnetic sensor.
  2. First measure continuity from the ECU ground to the sensor ground. There should be 0 ohms as the earth comes from the thin black wire coming from the harness to the thick black earth of the Mercury2.
  3. Measure continuity from the sensor power to the Mercury2 ignition power that comes from the key. There should be 0 ohms.
  4. Now measure continuity from the sensor signal to the ECU input for that sensor, see the drawing. You can disconnect P1 and measure on the pin.
  5. The fastest way to test it is while it is powered in the circuit. While P1 is connected switch the ignition on.
  6. Measure at the power at the sensor between negative and positive. You should measure around 12V DC.
  7. Now unbolt the sensor from the engine. Measure DC volts between sensor negative and signal. It should be 12 volts and if you bring a metal object to the sensor it should go to 0 volt. The logic may be reversed for some sensors. As long as you see the step change. On optic or some hall sensors you may need to move a plate between the sensor and transmitter part. If the voltage doesn’t go to less than 1 volt, then it means the ECU will not detect the change.
  8. If you don’t measure the 12 volt on any condition on the sensor signal, it may be the pull-up jumper is not in closed position. If it is then disconnecting the sensor signal wire and measure at the ECU side for the 12 volt. If you measure 12 volts, it means the sensor output is damaged and short the signal wire to ground. If you don’t measure 12 volts then the ECU does not provide power through the pull-up resistor.
  9. Now bolt the sensor in place and measure on the signal negative and positive with AC volts. Crank the engine and you should see 12 volts AC.

Errors and misfire during running or starting.

If the startup procedure tested correctly but you get errors during starting the engine, read through the following points.

  1. The ignitions’ coils may generate interference spikes on the crank sensor wires. Ensure that the sensor wire is screened as close to the sensor as possible. If you connect to a distant connector there is usually a screen pin that has to be connected to the Mercury2 harness screen.
  2. The coils may spike the Mercury2 and it may want to restart. This may be to incorrect supply currents or relay wiring. An indication of this error is that the software will lose connection momentarily to the ECU. A restart error will come up.
  3. Errors that comes at higher RPM’s may be due to a trigger wheel that is not balanced or is buckled. Sensing distance may be too large. It could also be due to a small gear teeth pitch, or a sensor with a large sensing magnet. The sensor may require an extra pull-up resistor.
  4. Ensure that the test signal next to the crank sensor is off.
  5. The RPM on the sensor signal could fade, this could be due to the gap between it and the trigger wheel been too close or too far apart.
  6. Incorrect sparkplugs may generate feedback which leave spikes in the trigger signal. Normally resistor plugs are used for COP engines and non-resistor plugs for HT leads. Note: Ensure that you use carbon HT leads and not copper leads. Cracked lead also generates interference. A trick is to look at them in the dark while it idles. It will show flashes in the dark.

Mercury2 pull-up

The Mercury2 use an isolated digital input to allow for magnetic sensor tap-in. For hall sensors an external jumper will connect a 1K pull-up resistor internally to the 12-volt power from the key. If this power is erratic due to other switching elements, then it may cause secondary triggering or interference of the input. To remedy this, you may add a 1K pull-down resistor to minimize the rippling effect on the power. If this does not help you may open the jumper and add a 1K pull-up resistor to 5-volt power from the ECU P1 pin 9. Alternatively use a relay to power the Mercury2 directly from the battery. Then the ignition power is only used to activate the relay. See the drawings below.



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