Tag1128

As stated in the title I have a '97 Camaro with the LT1 engine with a crank no start condition. It died as my fiance is driving down the road and then would not start. I have read shoe boxes website and almost every form or thread out there based on the matter in the last few days so please don't flaming with bunch of links cause guaranteed I've clicked on them.

What I've done so far...
Fuel pump is priming, can smell fuel and have fuel coming out the Schrader valve on the rail when I press it. Tried to rent a pressure gauge but they didn't have it nor one to buy. Sprayed some starting fluid in the throttle body and not even a bump or jump just cranking. Battery is fully charged, and has proper ground.
Pin A on ICM harness has system voltage of 12.xx along with pin D. Pin C has continuity to ground with less than half an ohm when grounded to battery terminal and positive lead on pin C. Pin B has been producing around 2.2v AC while cranking and grounded to the header with the meter up to the window cause I'm solo. Opti harness plug on valve cover next to evap solenoid I believe shows 5v 5v 12.xxv and I have continuity to ground. Ohmed out the pcm pin 3 I believe to wire D on opti harness and got .2 ohms.

Replaced the ICM on a whim and prayer because no one around me could successfully test them. Still no go. Showed 5.85k ohms on all three prongs across coil. Bought a new coil, in the process wire from opti to coil crapped out and tore, used wire from cylinder 1 to substitute for now since no one had anything in stock today. Not 100 percent it's making contact now so whether my new coil is the fix is kind of still up in the air until I recrimp the old wire tomorrow and know for certain. Got no spark on cylinder tonight while my fiance cranked it either, again going to fix that wire to opti from coil and make sure tomorrow. Once I know for certain then I will stop second guessing it being timing related, like I'm off a tooth or more and just not firing. But again I think with spraying starting fluid I would have gotten some sign of life.

My gut and everything I know is telling me it's not the opti, but could it still be sending the AC voltage and not working right? Is that ac voltage from the pcm a for sure that the opti is sending the right high and low res signal to it? I don't have a scope or know anyone, I know that's a definite test. Also once in a while when trying to crank the security light comes on and doesn't let me crank for a bit. Had a buddy saying this wouldn't be the issue since it died while running. Car has 63,000 miles on it. Cammed, exhaust, just bought it a week or so ago, sweet ride, really don't want to replace the opti spark only to find out it was fine. Could be screwed up cap and rotor? Going to see if I can figure out a way to test spark at coil with my inline tester tomorrow but it's fatter than the Camaros posts so we'll see. Thank you anyone and everyone for the wisdom and help, this forum has gotten me this far and I appreciate it!

Tag1128

Repaired the coil wire while I wait for a whole new set tomorrow. No spark coming out of coil or out of the optispark to the cylinders. New ICM new coil, getting the readings I should I believe. Still stumped being that I'm getting the right ac voltage from the pcm to the ICM which I thought meant the first side of the opti and pcm and harness are working as they should. Really hate to tear this down to find it's abother issue.

Injuneer

You need to actually measure the fuel pressure. A gauge should be readily available on the internet at a reasonably low cost. Have you verified the injectors are pulsing, with a noid light? Have you checked (key on) for 12 volts at the pink wire in each harness injector connector?

Have you scanned it for codes?

Have you inspected the socket on the Opti for the coil wire for corrosion?

Have you reconfirmed you have the required AC voltage on the white wire to pin B of the ICM. That is actually a 5 volt square wave pulse signal, hence the meter produces an intermediate voltage reading when set to AC volts.

Watch the tach when the starter is cranking the engine. If the tach needle moves up a couple hundred RPM, the PCM is getting the Opti pulses.

Tag1128

Yeah my neighbor is supposed to be bringing home a gauge tonight from work to verify. I do not have a noid set, only time in my life I've ever used one is in school, I'm a diesel guy. I will check for 12 volts on pink wires tomorrow.

The tach jumps up to 0 when turning the key and cranking but does not bump and show a few hundred rpm like I believe it should.

The plug wire input on the opti doesn't appear corroded.

And yes I've rechecked that voltage on pin B on the ICM about twelve times now along with the other wires going to coil and ICM and they're all reading as they should.

Called my old mentor and after talking to him he was pretty certain if I'm having no spark out of the coil and the optispark itself and I have my voltages where I need them at the coil and ICM and the ICM is grounded properly and I replaced it, it's the "dumb optispark".

So I ripped it today and despite that one bolt behind the PS pulley on the left middle for the water pump and having to pull the crank pulley off by hand since my shed is a mess, it wasn't horrible.

Water pump makes some scary noises when you turn it by hand. Definitely needed to be done I would think. Ordered an ac Delco optispark for the extra dough, or it's a napa acdelco echelin or whatever it is, it'll be here in the morning.

​​​​​​So if this fixes this that means that it still was the opti even though it was sending and the pcm was putting out to the ICM? Guess that's the part I'm trying to wrap my head around. Still not clear but taking a chance because I can't let this car keep sitting. Thanks again!

Tag1128

Yes and no codes. Changed the opti today and no luck but thank God I did because the water pump was horrible no idea how it didn't explode missing ***** and the seal. Changing the opti, ICM and coil have all done nothing. The tach jumps up to 0 and sometimes on occasion does a weird jump to 500-1500 for a split second but only noticed that when battery voltage was getting lower.

I ohmed out the black connector on the pcm all four wires going to opti pigtail that is new with opti. All ohmed out fine. .02 ohms all on. Even wiggled the hell out of the computer, harness while ohming out wires all separately and no change all consistent .02 ohms. So there's no reason why the pcm shouldn't be getting a signal input on that side of the spark circuit to my knowledge from the diagrams and words of wisdom I've seen. As far as the output side of the spark circuit like I said I'm seeing 2.2volts Ac which tells me I'm getting a signal to the ICM from the pcm which should all the ICM needs to connect the ground for the coil circuit. The coil circuit has system voltage at all three, one from fuse going to coil one teeing to coil and going to ICM and the third wire has system voltage minus the resistance of the coil so like 8.88v or so on the other end of the coil. You would think some sort of signal would make the brand new ICM say ok let's ground the circuit. Again ICM has power on A and D while key on and while cranking, also ohmed those wires so harness from coil to ICM has been ohmed and voltage dropped. C has good ground. B on ICM is getting PCM ac voltage or rather a square wave. Again I have no spark whatsoever coming out of coil at all and it died while running. Like I said I've voltage dropped or ohmed out every wire in this circuit and have replaced every component in this circuit except the pcm that's been jarred around for how long. My neighbor is going to bring home his power probe so we can power the coil ourselves, although that just proves it has ground and power the ICM just isn't doing it. Which leads back to the computer being screwy. I should mention the computer was flopping in that hole not tied down or anything. I've read it's never the computer or this or that but this all points to it. Me not getting a couple hundred rpms on the tach when I just put in a brand new opti is fishy. And yes I know could be bad opti out the box but I'm not sold on that.
just figured I'd re clarify the crank sensor is only obd II related and there to meet epa guidelines for cylinder misfires correct? Going to unplug it just for the hell of it, but I wanted to make sure again. Like I said bought this car for a good price, good for the seller, and it really sucks boggling my mind over this. Going to talk to a friend who's a regional at AutoZone see if any of his stores can still test pcms, or maybe he can loan me one. Any advice is always appreciated, thank you!

Tag1128

Are there certain pcm wires I should be testing for main power or ground, how do I start going down the pcm road without swapping with in a new one. Main power or ground wires, need to search a pin out of the pcm plugs. Any tips for that is again appreciated. Thanks again.

Injuneer

Download (free) the 1996 factory service manual, courtesy of GaryDoug. 99% valid for 97.

https://www.mediafire.com/?40mfgeoe4ctti

You can also use Shoebox’s 1995 PCM wiring diagrams and connector pinout charts, which are marked up to show the 96/97 changes.

4th Gen LT1 F-body Tech Articles

4th Gen LT1 F-body Tech Articles

The crankshaft position sensor is not required to run your engine. This can be verified in the factory service manual.

You indicate the tach needle moves upwards when cranking the engine, but only to “0”. The fact it moves is what is important, someone may have screwed around with the tach needle.

chevykid

FYI: if your old opti is original factory, i would save the electronics and optical disc inside because 80-90% of the new opti's have trash electronics.

chevykid

the tach reading +/- 200 RPM while cranking is very important! it tells you the computer is reading the opti, but jumping around 500 - 1500 is showing erratic signal from opti which could be from bad electronics in the opti (like an autozone opti)

Tag1128

No unfortunately my old opti was a MSD piece of junk. Put in the Acdelco 300 and change one. Wondering if the tach jumping is part of a pcm issues or just the fact I had 11.40V on the car when noticing it and trying to crank it. My only next step I can logically think of it to test the PCM and if I can't get a clear answer out of that cross my fingers and replace it and hope for the best. Thanks guys for the input.

chevykid

if you want to rule out the opti get one from this guy ( https://www.ebay.com/itm/23386716529...sAAOSwyfpfT7O3 ) he test them under simulated real conditions, heat test and everything and uses the Mitsubishi optics in them.