Coil Test

[CDOG]

Can anyone tell me how to test this coil? I was having an electrical problem that turned out to be a bad positive cable connection but now she will not start. No spark at all. It was running great before this issue. The distributer is Mallory Unilite also. Thanks.

 

[StnePny]

This may help ...

This what I was told. I would follow the link then go to Mallory for your spec, This is from a friend when I asked him about my MSD



To test your coil off the truck, go to this link and get the info. Then go to MSD and get the coil specs for the test.

http://autorepair.about.com/od/troubleshooting/ss/coil-test-ohm.htm

In truth is should be good unless you dropped it hard a few times or soaked it in water.

 

[Viperwolf1]

When in doubt go to the manufacturer's website.

http://www.malloryperformance.com/InstructionSheetsList.aspx

 

[thegreatjustino]

It's a POS Mallory unit. Almost certainly dead %)

 

[StnePny]

X2 what thegreatj said

I never like them

 

[surveyor5]

Substitute a tempory coil for a test.

 

[CDOG]

Thanks for the links. I was on the Mallory site but did not find a test for my coil. I should have dug deeper. I now think that I may have blown out the photo optic in the distributer. I tried to start it with my battery tester in the start mode because I thought the battery was dead. Turns out it was just a bad connection. May have sent some bad voltage through it. I replaced that thing five years ago and decided that it was a very weak link in the system and could leave me stranded at any time. I will test it tomorrow. Thanks for the help.

 

[ransil]

Your negative battery cable needs replaced too... the bolt on battery lugs are for temporary use only.. not a fan of crimp on butt splices either, they will work for awhile then they will corrode and you will start having problems...

 

[CDOG]

The picture is old, it has been replaced.

So I went to the Mallory site and downloaded the instructions to test the distributer and coil. It says to test the voltage at the negative side of the coil and it should read 12 volts. It read below 2 volts and I replaced the coil with the same model that I had laying around from 5 years ago and it read the same voltage. The ballast resister is really hot after doing the test but I assume that is normal for it to get hot. For some reason, the negative side of the coil is not getting 12 volts. I am not 100% sure that the old coil is good but I think it is. I don't know why the coil is not getting 12 volts. It seems to be a pretty simple system until you get to the distributer and the optics module that seems to be pretty sensitive to voltage. Any Ideas?

I am pissed at myself for not removing that positive terminal and checking it better. It looked good and the fuel pump would run for a little while and then go off just like the lights. I was sure the battery was dying and the crazy readings from the tester are now explained by the fact that I had the clips on the terminals and not the posts. I then tried the start function of the charger/tester and I think thats when I fried something. It was running fine until all that. So frustrated!

 

[Viperwolf1]

The picture is old, it has been replaced.

So I went to the Mallory site and downloaded the instructions to test the distributer and coil. It says to test the voltage at the negative side of the coil and it should read 12 volts. It read below 2 volts and I replaced the coil with the same model that I had laying around from 5 years ago and it read the same voltage. The ballast resister is really hot after doing the test but I assume that is normal for it to get hot. For some reason, the negative side of the coil is not getting 12 volts. I am not 100% sure that the old coil is good but I think it is. I don't know why the coil is not getting 12 volts. It seems to be a pretty simple system until you get to the distributer and the optics module that seems to be pretty sensitive to voltage. Any Ideas?

I am pissed at myself for not removing that positive terminal and checking it better. It looked good and the fuel pump would run for a little while and then go off just like the lights. I was sure the battery was dying and the crazy readings from the tester are now explained by the fact that I had the clips on the terminals and not the posts. I then tried the start function of the charger/tester and I think thats when I fried something. It was running fine until all that. So frustrated!

You only have 2V at the neg side of the coil because the coil's primary resistance is 5x the resistance of the optical unit in the distributor (if that's the only thing attached to the neg side--tach?). And since the primary coil resistance is probably 1-2 ohms, you pretty much have a dead short in the distributor.