Hello all here is my issue and I am looking for some help of where to go next. Car is a 1995 LT1 Z28. I drive it everyday. Last week I was driving it home from work and it shut off completely. I got it into a parking lot and tried to start it, it just turned over 6-8 times and no start. This car until now would always start on first try even when hot. I left it for an hour thinking heat soak of some type and came back to the same issue, 8-10 revolutions before it fired up. When it did start I now have a check engine light and fans are running. This car has had very few check engine lights ever so I was very surprised. Here is history of parts and what I've checked so far.
Optispark (Pantera EFI/Redline Engine Management/Lance Nist) 13 months old
Coil and ICM 15 months old (ICM has spacer mod)
Plugs and wires 15-18 months old
Fuel psi at rail with key on 39-40 psi
Fuel pump 12-13 years old
Fuel pressure regulator 13+ years old
I was able to use a Snap on scanner to clear the code and it started hard again and set the code immediately. I looked the optispark harness over for anything obvious and I'll try to check it for voltage soon. I am trying to figure out if I am having more than one problem at once, if the problems are related and why they would show up all at one time. Is it possible I have a slightly weak fuel pump (not enough fuel) or bad engine coolant temperature sensor (water pump sensor) that is causing more fuel than needed? The dash temperature gauge has seemed normal so I assume that reading comes from the sensor in the driver's side cylinder head. I am just stumped that it won't start like it used to, has the ses light on and has a constant DTC 36. Thanks for any advice.

 

DTC 36 is high resolution failure on the opti. I would start buy inspecting the wiring coming to and from the opti.

For the CTS, when you has the scanner plugged in, were you able to see temperature? The ECU uses the temp from the pump sensor where your gauge cluster uses the driver side head sensor.

 

I will try the scanner again to check the temperature. When I first plugged the scanner up and the car was cold (45-50 degrees air temp) I believe the reading was 50.

 

Have you checked for spark at the coil wire?

Go ahead with checking for the pulse signal on the white wire from the PCM to the ICM, using SHOEBOX’S method:

4th Gen LT1 F-body Tech Articles

What brand is the Opti? Does is have a permanently attached “short Opti harness”, or is it an older design that still requires the factory short harness?

 

The opti is from Redline Engine Management-Pantera EFI and was sold to me by Lance Nist. I got his name from this forum or LS1tech as a reasonablely priced good Optispark option. My harness is normal GM with plugs on both ends, not built into the opti.

 

Okay voltage is 11.61 at the ICM connector at the Pink wire and also white wire. I believe that is A and D on shboxs diagram.

 

Let me rephrase, my connector in the car is ABCD, pink, white, black, white. That doesn't exactly match the shbox diagram but testing in A and D gave 11.61 volts.

 

Have you checked for spark at the coil wire, or at the plugs?

Rob/Shoebox cautions in his procedure that the diagram (from the GM factory manual) has the pins labeled in a different order than they are on the connector.

You have to measure the AC volts on the white wire, pin "B". That is the 5 volt pulse sent by the PCM to tell the ICM to fire the coil. Because it's a pulse, you have to set the meter to AC volts, + probe to the white wire, - probe to a good ground, while cranking the engine It's all in his procedure. If you get 1 to 4 AC volts on the white wire while the engine is cranking, the Opti is good, at least the low resolution signal, which is all the engine need to run. It does not need the high resolution signal to run, but is will lose a bit of timing accuracy without it, and can cause a rough idle sometimes.

The Redline/Pantera Opti is new to me... don't recall anyone mentioning it on this site. The only one that seems to be reliable is the Petris, and he is out of stock:

https://petrisenterprises.com/

 

I looked into Petris before I got the Pantera one. It has been flawless until now. I tried to check AC voltage at B connection and got around 3.0 but as it was cranking it showed 0 and kept flashing thru numbers as high as 3. I checked a second time and go no reading when cranking.

 

Sounds like the meter may have been on DC volts.

Third try - Do you have spark at the coil wire, and at the plugs?

 

Meter was on AC but maybe it's a cheap meter? DC worked great. What is best way/recommended way to check spark at coil wire and at the plugs?

 

If the reading was staying in the 1-4 AC volts range, it's OK. It's the zero that seems strange. Was the engine cranking slower than usual?

To test for spark at the Opti end of the wire from the coil to the Opti - pull the Opti end of the wire off the Opti. Pull the boot back so the metal terminal is exposed. Using insulated pliers (not your bare hand) hold the metal terminal near (within 1/16”) the engine block. While someone cranks the engine you should see a strong blue spark jumping between the end of the wire and the block.

If you see the spark, the PCM is receiving the low resolution pulse signal from the Opti, and sending the ICM the signal to fire the coil, and the coil is firing. Reconnect the coil wire to the Opti. Next, pull an easily accessible spark plug wire, and hold the metal end of the plug wire near the block, looking for the spark while the engine is cranking. If you have spark, the Opti is successfully passing the voltage from the coil to the plugs. The ICM might break down when the engine heats up, but if you have spark when cranking it cold, it is something beside the ignition preventing it from starting.

Is the SECURITY light on? Is it flashing? When the starter is cranking the engine, does the engine attempt to fire, perhaps causing a backfire. That could be a timing problem, or the rotor in the Opti may have come loose - not unusual if the screws that hold the rotor were not tightened with Loc-Tite to prevent them from coming loose.

 

No security light. There is also no backfire when cranking however the last time I was cracking today the battery lost enough voltage to continue cranking so I'll need the charge the battery tomorrow. I was able to connect the Snap on scanner before the battery lost its juice and the coolant temperature sensor looked like it was reading correctly, 45 degrees and that was about the temperature in my garage. I will try to check for spark tomorrow or Tuesday. I do have another coil I could swap out just for a try.

 

The spark test is not looking specifically at the coil. It is a check of the complete system from Opti, to PCM, to ICM, to coil.

 

I will check tonight or tomorrow (Tuesday). I'm really leaning towards the Torqhead 24x system. I'm tired of having to maintain this specific area of my car on a yearly basis. Yes it's costly but I plan to keep my car since I've already had it for 20 years anyway. Yes the Optispark, one coil and ICM work well when they work but you can't argue with getting away from an optical sensor that can get oil and coolant soaked and moving to magnetic pickups and individual coils with a more modern computer. More modern technology doesn't lie in my opinion.