sensor coil output test??

[Ranger 330V]

I have done all the test except the sensor coil output test on my 1978 140 Johnson...I'm having the backfire problem in another post. I can't figure out my meter for setting up for the sensor coil output test..want to make sure i"m doing it right. talks about setting my meter to "S" and "5" and I don't know what its talking about..maybe I'm reading it wrong..it doesn't say anywhere if I'm measuring voltage or what...I would suspect voltage since its an output test...if someone could help out here that would be greatly appreciated. Thanks! I just have a regular multimeter with the DVA adaptor..did all the other readings and tests and it went well...just can't figure this one out...still have to do the couls too. Thanks!

 

[HighTrim]

Re: sensor coil output test??

To test your sensor coils you do not need the DVA adaptor, only your ohmmeter, or other "specialty volt meters with special readings". In some conditions though sensors may be grounding out to the shield but will not show up with an ohmmeter. This condition may be found by using the condensor tester leakage test, where a voltage of approx. 500 volts is applied to the sensor.

First Ohmmeter test set it to Low Ohms scale to check the resistance reading alternately between the common white lead and the blue, the green, and then the purple lead. The meter should show a reading I believe for your motor of 14 ohms (within 3 either way) at room temp. COnnect the ohmmeter black lead to the white common lead. COnnect the ohmmeter read lead to the blue, green and purple lead leaving the meter black lead connected to the common white lead.

Then turn your meter to High Ohms scale, leving leads disconnected from the PP. Connect ohmmeter between each sensor lead and ground. Infinity reading on each sensor indicates a good sensor. Zero or any reading indicates leads or sensor coil is shorting to ground.

 

[emdsapmgr]

Re: sensor coil output test??

The book assumes you have a Stevens "peak-reading" voltmeter-a common piece of test eqiupment for an OMC outboard. This is a special type of voltmeter. The 5 refers to the volt scale reading on it (0-5v.) The S on the meter stands for SEN, which is probably the output side of the sensor coil. In any event, you run the test while cranking the engine. The sensor will produce a small electrical charge of 0.3 volts or higher. If you get no reading, the sensor is considered defective. I would not think a bad sensor coil would result in a backfire.

 

[mikevi]

Re: sensor coil output test??

is it 0.3 vac? or 0.3vdc? for the sensor output

 

[emdsapmgr]

Re: sensor coil output test??

The factory service manual for your engine does not include information regarding testing the voltage output for the sensor coil in your model year. The only factory service manual tests are the hi ohms and lo ohms tests as High Trim has explained. Later models (by 1986) recommend a voltage test in addition to the aformentioned ohms tests. I have found the voltage tests very reliable. Another expert on the board may know if that voltage test would be a reliable indicator for the sensor coil for your year engine.

 

[mikevi]

Re: sensor coil output test??

1979 35hp 36952A
the manual does call out a sensor output voltage of 0.3 for my engine using a cd-77 meter with the meter settings of S and 5, the question is to translate to moderm day equipment such as a dvm, is the "S" function a reading in DC or AC and or with or without a resistive load, I assume it is not thru the "DVA" since that was meter setting "neg" and a range of 500V for the charge output, that reading would be DC peak volts range 500 volts. I need the definition of the S 5 setting of the cd-77 meter