Finally received the warranty opti from Chandler Motorsports last week, installed and good to go Friday night. Fired her up in the garage. Let it run for about 15 minutes...no leaks...no problems at all. Shut her down and pulled out the jackstands and went for a ride. She was running great...I got 5 miles down the road and it died. It restarted twice and got me a hundred yards closer to home. Called the auto club and flatbedded the bitch home.

Tried to start it today...no start...it's dead. I scanned it with an Actron 9145 and it detected no codes. I did the opti test from shbox dot com but I want to verify that when it says

Disconnect the ICM connector. Leave coil connected.
Turn key to ON.
Check for dc voltage with a digital meter at harness terminal "A" to ground and and also "D" to ground. Note: Use a high impedance meter (at least 10 megohm) when dealing with the PCM.

does he mean the opti harness or the icm harness? How can I tell if I have a high impedance meter? I tested the opti harness and got 5 volts on A and .02 on D. Does this mean another opti is bad? TIA.

 

There's an easier way to test it. Try to crank it and see if your getting a spark.

 

how do you do that while in the cabin at the steering wheel turning the key? I'm allergic to electric shock anyway...

 

I'm sure everyone is. Have someone help you.

 

everyone I know is allergic to electric shock too...

 

Use a timing light to detect spark, no shocks that way. Post the make and model of your voltmeter if you can't read the instruction manual that came with it to determine the input impedance.

 

A definitions right off:
Input impedance is the resistance to both A/C and DC current in a circuit. In a purely resistive circuit (with resistors only) it would be input resistance. When you add capacitors (storage cells) and inductors (coils) to resistors you usually are putting alternating current into the circuit. This is because both caps and inductors react differently based on frequencies above DC (0 Hz.). With DC for all intents and purposes cap and inductors act resistively.

Meter Impedance:
Meter loading of the circuit providing an erroneous reading is what you are attempting to avoid. IF CRITICAL, and you know the input impedance of your meter you can factor out the load that your meter inserts into the circuit when measuring voltage. Look at it this way, some current has to go into your meter in order to measure the voltage drop across some precision resistors inside the meter to derive the voltage value you see on the display.

If you have an analog volt/ohm meter (with a needle and dial) the usual impedance is 20,000 ohms per volt (2K Ohms/V). So with 12 volts you can expect your meter to load the circuit to some degree offering some level of meter induced error. In automotive troubleshooting usage that degree of loading is usually unimportant.

With most digital volt/ohm meters (DVM) the input impedance is markedly higher. 20,000,000 ohms per volt (20M Ohm/Volt). So the long and the short of it is a digital volt/ohm meters offer higher relative accuracy by not loading the circuit under measurement artificially.

Hope this isn't too technical but based on questions I get from car guy friends many don't know the difference and a little education put out there can be ignored by many but if one guy gets something useful then I am satisfied.

 

Thanks for the education Brian. Since my meter is digital, I guess it's a 20 megaohm, which is better than that suggested by the quote above. I've had it quite a few years and have no manuals for it.

Back to the lt1. If the timing light says there's no sparking, how do you know if it's the coil, icm or opti?

Brett

 

Some parts stores can test the coil and ICM, or you can try replacing them as they aren't expensive. The optispark is suspect if you can determine if you have spark going into the opti but none coming out.

 

I'll hook up the timing light after work today.

 

So I replaced the opti with a warrantied unit. SHe ran for 15 seconds and shut down. Tests showed no spark from anywhere, coil or opti. I then looked at the coil and icm...but they're new! From Advance Auto...prolly have 5 short local trips on em. The Advance opti and water pump I had on this car were bad so I got a refund on both the coil and icm, took that money to napa and got delphi units from them. WOW! The Bird fired right up Friday night!! Ran her about 5 miles Saturday and put about 30 miles on her Sunday. She seems to be back in all her glory! Thanks for the help!

Brett