1974z28

I own a 1997 Camaro z28. I have had problems with this car recently. died on the highway, couldn't get it started. it just cranks. I checked for fuel and have 41 psi at the Schrader valve. I checked for spark and didn't have any. I changed the opti knowing that it is not known to be good. still no spark I also changed the ignition coil I had on hand and still nothing.
so to date I've changed the distributor, ignition coil, ignition control module, and even the crank position sensor. I am at a loss and need help. if anyone has any direction I can go with this please help. thank you.

Injuneer

Have you scanned it for codes?

1974z28

I do have a scanner and no codes are showing.

Injuneer

Where did you check for spark? At the coil wire? At several plug wires?

Check the white wire from the PCM to the ICM for the pulse that tells the ICM to fire the coil.

Courtesy of Shoebox:

4th Gen LT1 F-body Tech Articles

1974z28

we shot wires to all the components. my buddy seems to think we might not be getting the pulses sent from the pcm. i am gonna try to change the icm plug, maybe it's a break in the wire at the plug. hopefully.

Injuneer

Shoebox's test will tell you if the ICM is receiving the pulse signal from the PCM. That's why I suggested it.

An open on that wire will set a code.

What do you mean by "shot wires to all the components"?

And to repeat a question, where did you check for spark?

1974z28

we checked for spark at the plugs. we also checked the ignition coil, ignition control module, and even checked the crank sensor to see if they were working right. pierced wires going to the icm and the crank sensor to check for power with the car cranking. the one thing we never seemed to get at the icm was the pulse from the pcm. gonna reshoot all the stuff tomorrow. gonna start at the icm to see if I'm getting the pulse from the pcm.

1974z28

just did a bunch of reading. I'm thinking it could be the sensor inside the distributor. when I changed that I only changed the cap and rotor. still gonna look at some wires tomorrow before I make a decision.

Injuneer

The crank position sensor (CKP) has NOTHING to do with running the engine. It was only added to the LT1 engine in the 1996 model year to meet OBD-2 requirements for misfire detection.

The optical cam position sensor in the Optispark distributor is all that is required to time the sequential fuel injection and spark. There are two signals produced by the cam sensor. The low resolution pulse signal identifies the cylinder approaching TDC on the compression stroke. If that signal is missing, the PCM sets code P1371, and the PCM shuts down fuel and ignition. That code does not turn on the SES light.

The PCM uses the low resolution pulse (with fine tuning derived from the optical sensor's high resolution pulse signal) to fire the coil, by sending the timing pulse signal on the white wire. If there is an open circuit to the ICM, the PCM sets code P1351.

But you indicated you have no codes, and had replaced the distributor. Each of my questions was intended to help you work your way back from not having spark at the plug, through the coil, ICM, PCM and finally to the Opti.

1974z28

alright thank you guys. I changed the opti and the car fired right up. it wasn't sending the signal to the pcm to give the pulse. thank you for all the resources, knowledge and diagrams.

Nightrider1984

I'm new to this site I'm having the same exact problem bought my 97 ls1 camaro off somebody ran really rough had it scanned showing low resolution code as well as crank sensor put new crank sensor and opti when hearing that's common for these cars...problem I had first go around I put opti in wrong not having dowel in correct slot seen a score mark so I return and put in new one made sure was at tdc and in correct slot still no spark changed plugs wires ignition coil and ignition module still no spark I tested with meter and have power to harnesses and checked trigger signal from pcm to coil and getting voltage when cranking could it be the opti faulty not sending signal...all fuses are good just lost tryed scanning again but from disconnecting battery not showing codes

Injuneer

Read the first paragraph in post #9.... the crank position (CKP) sensor has nothing to do with running the engine.

If you have a pulse signal on the white wire from the PCM to the ICM (not the coil), it proves the PCM is getting the required low resolution pulse signal from the Opti.

4th Gen LT1 F-body Tech Articles

How is the ground connection at the stud on the head that the ICM/coil bracket bolts to?

Where did you check for spark - at the plugs, at the coil, both?

What brand is the Opti?

If the cause of no start was lack of low resolution pulse from the Opti, if you extended the cranking to continuous 15-20 seconds, the PCM will set code P1371, and you should be able to pull it. Does the tach jump up two or three hundred RPM when you are cranking the engine?

What does the SECURITY light do when you are cranking the engine?

Nightrider1984

I checked for spark at both coil and several plugs with with two different types of spark testers nothing, as far as ground you ask to icm and coil would think it's ok but I confused cause who ever had this had several things attack to the bolt for ground I'll try and send a pic, when I cranked needle not jumping,please don't laugh when I ask is the ses light the Red Bulb in the car blinking not some anti theft system light lol...

Injuneer

You're going to have to clarify your car description. The 1997 Camaro Z28 has an LT1 engine, not an LS1, unless someone did a major engine swap.

On a 97, on the dash gauge panel, it says “Service Engine Soon", just to the right of the tachometer RPM scale. It should light up for a few seconds when you turn the key to "run", and then turn off. If it turns on at any other time, you have to use a scanner to pull the trouble codes. The SES light will also flash if the PCM (computer) detects engine misfires. A blinking LED on top of the dash is part of a security system, optional or aftermarket.

Download Owner's Manual:

https://my.chevrolet.com/content/dam...aro_owners.pdf

Injuneer

There are normally many wires grounded to the ICM/coil bracket stud. You need to verify that pin "C" on the ICM is grounded correctly following the procedure I linked in post #12.

http://shbox.com/1/coil_loc.jpg