94chevyrocket

Hello all.I have a 94z28,LT1.My engine cranks but will not start.A friend of mine tells me there's no spark.He concludes this by disconnecting a wire ,putting in a loose spark plug-placing it against metal-while I crank the engine.He says if there's not a "spark",coming from the plug/wire(which is connected to the distributor)-then the dist isn't shooting spark.I'm wondering if this is the correct way to determine if there's no spark,and if so-would this mean I need a new opti or could there be another issue causing this?Thanks

parkers Z28

" Shoebox " has something about this in his signature
Did you scan for trouble codes ? is the engine light on ? have you checked the ICM ??
check this out. www.shbox.com

94chevyrocket

Thanks-well I scanned for trouble codes-got nothing.It's an OBD1 scanner.I called the company/explained that there are no codes and the car won't start.They tell me,OBD1 scanners only tell you if any sensors are bad.Great;so all my sensors are good but the car won't freakin start.I 'm familiar with shbox ,I'll go w/ the schematic for the opti,and test the electrical connections

parkers Z28

Don't forget to check the coil , coil wire , ICM
There is a sticky for free scan tool on here ...located in computer diagnostic & tuning

Injuneer

Somebody gave you a BS answer. There are numerous codes in OBD-1 that cover things other than sensors. Go to shoebox's page linked above and look at the code list. Nowhere near as many as OBD-2, but still useful.

What "scanner" are you using? Hopefully not the $30 box that shorts the ALDL pins. That will not work on a 94.

94chevyrocket

I'm using the AUTO XRAY AX2500 Codescout.I bought it on amazon-it got good reviews so I figured it would be useful.Their customer service guy is the one who gave me the BS about it only reading sensors.I checked the coil/module-no juice,I replaced both,getting juice-still no spark.Looks like it's the OPTI but I want to be sure before I spend the $ and disassemble half my engine LOL.Thanks, any other feedback would be helpful,and If I find anything out,I'll post it for others,in case anyone else has a similiar problem

Injuneer

Does the scanner confirm that is has in fact connected to the PCM?

The Opti has two "parts"..... the optical cam position sensor, and the high voltage section (conventional cap & rotor). The cam position sensor will set codes, although the fatal code, DTC 16 does not turn on the SES light. But it does shut down the fuel system (pump and injectors). There are no codes for the high voltage section, and OBD-1 has no misfire codes.

If you had a problem with the high voltage section (cap/rotor), you would have spark at the end of the coil wire, but no spark at the plugs. What do you mean by "getting juice"? Do you mean you checked the points on the ICM and the coil that are supposed to have 12V, and they do have 12 volts, and the points that are supposed to have ground are in fact grounded?

Did you check for a voltage signal on the white wire from the PCM to the ICM? That signal is the ultimate result of the information the optical cam position signal supplies to the PCM.

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