Hey all,

man what a day yesterday, i picked up the Chevelle from the dealer where she passed the TÜV vehicle inspection. I was enjoying the nice weather and heading home. Three miles from home the engine just died in the middle of the road. Nowhere to to park. Lots of friday afternoon traffic. :mad:

I popped the hood and started looking for the culprit with a volt meter and found out that i had 12v at the HEI with ignition on and 8v when cranking. But no spark. It is a new Mallory 85 Series HEI distributor, with only 100 miles on it. I had to call the towing service to bring her home. Just when i thought it couldn't get any worse, the weather turned into a rainstorm and we all got soaking wet. :sad:

So today i removed the coil from the distributor and checked if the rotor was rotating - it was. Checked voltage again and still voltage at the terminals was ok.

Now my question is, can I check the coil with an ohm meter? I read in a different post, that resistance between + and - should be rather low (up to 10 ohms) and between the tower and either terminal it should read 5k to 10k. Well, resistance is 3 ohms between the terminals and between the terminals and the tower resistance was infinite. Couldn't get any values even with the 20 Megaohm setting.

Does that mean the coil is bad? I'm still wondering if it is the coil or the module. I'm located in Germany and it's not easy to get that stuff, so I want to be very sure before i order new parts in the states (which i have to!).

Thanks!

Olli

Oh and btw, i got my first "Trailer Queen" pics because of the breakdown, the white spots in the pic are the rain drops :D:

http://www.abcnetworks.de/trailerqueen.jpg

http://www.chevelles.com/techref/ftecref5.html

Well, after reading and doing the following from the article...

Remove the spark tester and all wires from distributor cap. Lift the cap out of the engine compartment for testing. Use ohmmeter set on a "high ohms" scale. First test: Connect between "Batt" ("C") terminal and "Tach" terminal. Resistance should be very low. If not, replace coil. Second test: Connect ohmmeter between Batt terminal and the carbon button in the middle of the cap. Read ohmmeter. Connect ohmmeter between ground terminal (the middle one of the three parallel blades) and the carbon button. Read ohmmeter. If BOTH of the readings in the second test are infinite, indicating an open circuit, replace coil.

... I ordered a new coil in the US. A good hundred bucks and two weeks later i received the coil and measured the new coil with an Ohm Meter. The new coil measures exactly the same like the old. DUH! Installed it - Still no go.

It seems like the articles coil test does not work for the Mallory coils?

Well it seems like i will have to invest another hundred bucks and a few weeks to get a new ignition module, which will be my next try.

:mad:

Just a small note to others with the Mallory 85 Series no spark blues.
Olli

I had a factory mallory HEI ignition module crap out on me right after break-in.

I'm wondering why only 8 volts rather than 12 volts when cranking? :confused:

I think I would try running a jumper from the battery to the coil or BAT terminal.

I'm wondering why only 8 volts rather than 12 volts when cranking? :confused:

I think I would try running a jumper from the battery to the coil or BAT terminal.

I agree with that. In addition, I'd dump that Mallory crap and pick up some MSD stuff. You'll be way happier in the long run.

I thought 8V while cranking was normal. That's what i have read on other postings and pages. After all, the starter uses a lot of power. Also, the engine just died while driving, so the cranking voltage is not what i worry about at the moment. I have tried jumpers from the battery: no change. Thanks for your help so far. I will replace the module next.

Olli

I'm wondering why only 8 volts rather than 12 volts when cranking? :confused:


I thought 8V while cranking was normal.
8 volts is a little low (9-10 is normal) but shouldn't cause any problems with the ignition. Sounds like the module went bad.

8 volts is a little low (9-10 is normal) but shouldn't cause any problems with the ignition. Sounds like the module went bad.

Why is there such a voltage drop Greg?

Why is there such a voltage drop Greg?

Because of the large amperage draw from the starter when it is cranking, especially with original style starters. Mini starters draw a bit less, but will still pulls system (by system i mean the entire car) voltage down some. With a larger and or a newer battery will have less voltage drop than a smaller and or older battery.

Hey all,

after replacing the module, she's finally running again. So guys be careful if you have the no spark blues: The resistance coil test in the tech article does not neccessarily work for the Mallory coils.

Cheers :beers:
Olli

I am aware of some errors--generally minor, but irritating--in the Tech Reference article; I don't have access to edit it.

What were your actual ohmmeter readings?

Remember that you need TWO "infinite" or "open circuit" ohmmeter readings in that second test to verify the coil is defective.

[edit note: changed "out of spec" to "infinite or open circuit"]

Hi Schurkey,

resistance was 3 ohms between the terminals and infinite between either of the terminals and the carbon button. Couldn't get any values even with the 20 Megaohm setting. I also checked my Multimeter, but it was working properly.

Anyways, the coil was not bad, as i found out later when i received the new coil and it had the same readings and the car wouldn't start. After replacing the module today, car starts without any problems.

Thanks
Olli

Ok. I need to think on this a bit, and do some more research; you may have lead me to discovering another error.

I'm gonna have to push for some editing on the Tech Reference article.

Now my question is, can I check the coil with an ohm meter? I read in a different post, that resistance between + and - should be rather low (up to 10 ohms) and between the tower and either terminal it should read 5k to 10k. Well, resistance is 3 ohms between the terminals and between the terminals and the tower resistance was infinite. Couldn't get any values even with the 20 Megaohm setting.

Second test: Connect ohmmeter between Batt terminal and the carbon button in the middle of the cap. Read ohmmeter. Connect ohmmeter between ground terminal (the middle one of the three parallel blades) and the carbon button. Read ohmmeter. If BOTH of the readings in the second test are infinite, indicating an open circuit, replace coil.

I need to confirm how you connected the ohmmeter. The coil will have two colored wires--probably yellow and red; but possibly white and red. Are these the + and - you are referring to in your first post? These wires would be the outside ones of the three side-by-side wires in the cap. They'd also be the ones that you used to get the 3-ohm reading in the first test.

(they'd kinda look like this when you flip the cap upside down: I I I )

If you connected from the yellow (or white) wire and carbon button; then the red wire and carbon button, the test is invalid. You need to connect to EITHER of those colored wires (Yellow/White OR Red--either one) and the carbon button; then from the ground terminal (Black) to the carbon button.

Or, in other words, you need to connect to the carbon button and either outside terminal, and then carbon button to the middle terminal.

So, if you did indeed use the ground connection; I have to think about what's going on; and then correct another error in the article. If you connected using only the yellow/white and red wires and the carbon button, you got a wrong connection and an invalid result.

Please confirm so I know what to fix. Thanks!!!

Schurkey

Sori to jump into this post but I too trying to correctly test a coil to correct a weak spark ignition problem ......Schurkey you seem to have a good understanding of this and I not sure I checked it correctly either ........can you look at my post and comment

http://www.chevelles.com/forums/showthread.php?t=185742

Schurkey,

you are right. I'll have to admit, I messed up the test. Shame on me. Well at least i paid the price for my own stupidity - a new coil plus the shipping and taxes to Germany. I should have read better, but sometimes reading english tech articles isn't the same like reading tech articles in my native tongue.;)

I never figured that i could have measured the wrong wires, because there were only the two! I thought they were like plus and minus (ground)... Oh well!
The black wire (the real ground) is screwed to the metal around the coil, just under the Mallory cap. That's why i didn't see it, or maybe i saw it, but i didn't think i should use it for the test.

You put a lot of effort in this and i am really sorry that i messed this up.:(

Thank you for clearing things up!

Olli

Schurkey, you are right. I'll have to admit, I messed up the test. You put a lot of effort in this and i am really sorry that i messed this up.:(

Thank you for clearing things up!

Olli
I'm in contact with the folks at Team Chevelle about updating the Tech Reference. I'm thinking I'll revise the text and add some photos. I'm sorry that the mistake was so expensive for you; that's my motivation to improve the Reference and (hopefully) remove some ambiguous instruction.

Unlike the eBay Guides which can be revised by the author, I don't have access to the Tech References for editing--so I'll need to pass on the revised text to the Moderators (or to Al) before it gets updated.

I spend a day in Germany--Berlin--and I have to say you do SO much better in English than I do in German. (I basically know three words of German.)

Thanks for the response; I don't know what I'd have done if you hadn't verified the connection problem.

Schurkey