coil readings

circleburner12 · Post by **circleburner12** » Sun Mar 16, 2014 9:32 am

finally got the m38 running after sitting for years. installed new plugs, wires, let it idle for a long time with fresh gas and all of a sudden it dies. like you turn off the ign switch. no fire!. imstalled new cap,points and rotor and coil. still no fire.

? is- i have a innova #3310 multitester and on the ohm's side i have four settings 20m 200k 2k 200. when testing my new coil i get different readings with each ohm setting. so the stupid question is which setting is the correct on for the coil test?.

thxs

Post by **wesk** » Sun Mar 16, 2014 9:49 am

The lowest setting that will accommodate your highest expected reading for each test. With the coil you will use the lowest setting to test the primary for 0.5 to 1.5 ohms and the setting that is high enough to fit the 11,000 to 18,000 ohms of the secondary resistance.

Here's a good How To page: http://billyclyde.hubpages.com/hub/HowT ... ultiTester

circleburner12 · Post by **circleburner12** » Sun Mar 16, 2014 10:05 am

with meter set on 200 and with pos on pos and neg on neg, im getting a reading of 11.7 on primary. with meter set on 200k and neg on neg and pos on the center of coil im getting a reading of 11.3.

with the meter set on 2k primary reading is .012.

so im guessing this new coil is reading to high on the primary. and is bad.

thxs

Post by **wesk** » Sun Mar 16, 2014 10:16 am

Have you disconnected all the wires from the coil before taking the reading?

Looks like you are still not using the correct range for each reading or are misinterpreting the readings. My guess says your coil is good and your 11.7 reading is actually 11,700 and your .012 reading is actually 1.2

circleburner12 · Post by **circleburner12** » Sun Mar 16, 2014 10:51 am

sorry wes, should have mention the coil is out of the dist. testing it on my work bench. and your prob right! my knowledge with a multi tester is very limited. so i tested the coil with each setting. and this is what it read

200- pri-11.7 sec- no reading
2k - pri- .012 sec-no reading
200k- pri-00.0 sec-11.3
20m- pri-0.00 sec- 0.01

these reading are digital diplay readings.
i know this subject has been talk about over and over. but thxs for your help!. thxs

Post by **wesk** » Sun Mar 16, 2014 4:36 pm

Not seeing the dash of your Ohm meter I am not sure what range you are reading in the 200 spot.

200- pri-11.7 sec- no reading [This range I can't be sure but I am guessing it is two hundred in which case you move the decimal point to the left one for a actual reading of 1.17]
2k - pri- .012 sec-no reading [This is 2,000 so you move the decimal over two and get 1.2]
200k- pri-00.0 sec-11.3 [This is 200,000 so you move the decimal point 3 places and you get 11,300]
20m- pri-0.00 sec- 0.01

[This is way to high at 20 megohms to get any useable reading.]

Having a nice auto-ranging multi-meter is a gift when you are in a hurry. I have been using a Fluke 21 since 1989 and also picked up a Fluke 85 in the late 90's. Both still serve me well.

circleburner12 · Post by **circleburner12** » Sun Mar 16, 2014 5:00 pm

with each setting the digital meter sets the decimal point. so the secondary should read 14,000 to 20,000. if mind is reading 11,300 the is the secondary bad?. thxs

Post by **wesk** » Sun Mar 16, 2014 10:29 pm

The estimated good ranges posted in my photo are based on a good working US manufactured coil. These figures are also temperature sensitive.

I have seen coils with 10,000 ohm secondaries operate just fine. Though they may be more prone to miss or quit as the coil heats up.

WESTCOMVIC · Post by **WESTCOMVIC** » Tue Mar 18, 2014 12:41 pm

Had the same thing with my M38A1. Seemed like someone just shut off the ignition, no splutter or anything. Went the route suspecting an ignition problem...nope, seems needle valve at float stuck and flooded out engine. Worth a look.

circleburner12 · Post by **circleburner12** » Tue Mar 18, 2014 6:48 pm

thxs westcom, tried beating on the carb just in case. as wes said the coil was good. a friend and engine builder came over and we swap all ign parts in and out and I starting getting fire and she fired right up. don't know which ign part was bad but it wasn't the coil. thxs for all the help guys. thxs