How can I test them using a digital volt/ohm meter? This is on my chevy truck, so it has the coil in the cap style.

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91 Z28
Come see The Vicious...

 

Most then like you'll have to pull the distributor out anyway. Then just take the cap off and disconnected the pick up coil from the module and measure its resistence. I believe it needs to be under 300 Ohms.

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1991 Z28 6.0 TPI

360 4 bolt main block, TrickFlow 23 degree heads, CompCams CS270HR cam, Harland Sharp roller rockers, Accel base, SLP siamesed runners, 52MM SLP Throttle Body, Hooker Headers, Flowmaster catback, MSD6A ignition, Home made ramair system, 2500 stall, bullet proof 700R4, aluminum driveshaft...

 

What exactly is the problem here? No start? Driveability issue? Usually a P/U coil is not the problem on a no start but can be the cause of some funky driveability issues if it gets cracked. The secondary ignition coil is much more likely to fail since it operates at much higher voltages and is more exposed to the elements. Anywaysss..... You can test the secondary ignition coil by ohming it out from the positive to negative lead on the coil and making sure that it is not open but that does not give you any idea of it's condition - just if it has completely failed. It can still be giving you weak spark. Put a spark tester on the end of a plug wire and watch the color of the spark. If it is a nice bright blue spark, than the coil is pumpin some good juice out. If the spark is a faded yellow or white color, than the coil is on it's last leg........

Some ideas
Good Luck!

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1987 GTA L98 MD8
355, TFS Heads, LT4 Hot Cam
My GTA

The Minnesota F-body Club

 

The problem is no-start, or very hard start, due to the fact that the spark is really weak. I'm thinking that the problem is the coil because it seems the most likely culprit. But I hate to go buy another one until I'm sure. The module is good, has already been tested. I figured I might as well test the p/u coil while I'm in there just to be sure. My other primary suspect is the starter. Bear with me here... the problem began right after putting on the new starter. It just cranks and cranks. I thought maybe the starter is pulling too much power or something. The ground on the distributor is good, and there's 12 volts to the coil when the key is on, but only 8 when it's cranking. And the spark is noticibly brighter (but usually not enough to start her) when the battery is jumpered to another vehicle. The battery is good also so that's not the problem. So that's the story. I haven't had much time to investigate, so that's all I know for now.

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91 Z28
Come see The Vicious...

 

Vicious,

It's time to get "vicious" with your DMM. Set on the resistance scale, you should read about 0.05-1.0 ohms on the primary coil winding, and 6,000-30,000 ohms on the secondary side. The pickup coil should read between 500-1,500 ohms between the leads, and infinite resistance to ground from either lead.

Testing the HEI amplifier/switch module is very difficult without mocking up a power supply, trigger device, and dummy load. It is generally easier (and usually free) to remove the module and have it tested at an auto parts store.

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Later,
Vader
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Justice and Freedom will Prevail
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