Ignition System Help 94 Z28

[Kiwi_94_Z28]

Will not start, suspected water damage to distributor.

Coil passes test (using DVM), coil module ok (checked with new one), but no spark anywhere. I'm pretty sure it is the distributor and I am in the process of removing it to see if it can be repaired (dried out), oh yeah, anyone got some tricks on how to get the harmonic balancer off?

And, in my Chilton's manual, the diagnostic tables for the ignition system (page 2-2 thru 2-4) it asks to observe the LOW RESOLUTION Signal on Tech 1 (chart 2 of 2)? Dose anyone know where/what Tech 1 is? The only thing I can come up with is that a scan tool might be needed?

Anyone know the story on why the distributors are so prone to water damage (I was having problems with the coolant system and it flooded the whole front of the block. Are there any alternatives to the OEM distributor?

Thanks for any help that can be provided,
Kiwi.

[Joe 1320]

Your crankshaft "balancer" is not per se, it is a harmonic damper. You must loosen the center bolt about 3/4 of the way out, use a standard threaded puller and let the center bolt bottom out against the damper's retaining bolt. If you remove the damper bolt completely, the puller will nothing to push against to extract the damper. Once the damper has loosened, remove the puller and take of the damper retaining bolt and it will come off the rest of the way leaving the hub still attached to the crank. A common question and here's another thread with the same discussion that may be good to read as well:

http://www.f-body.com/forum/showthre...light=balancer

Next, here is a proceedure to troubleshoot the ignition system........

Step 1. Connect a spark plug tester to a spark plug wire and
check for spark while an assistant is cranking the engine.
Check each plug independantly. this checks for open
spark plug wires. Spark in one or more than one wire
indicates the problem is in spark plug wires or optispark.
If no spark exists, go to step 2.

Step 2. Check for spark at the coil wire with the spark tester
while cranking the engine. A spark indicates the problem
is in the distributer (optispark). If no spark go to step 3.

Step3. Perform check on ignition coil.
a: Unplug coil electrical connector and check pink wire for
12v. If power go to b.
b. using ohmeter low scale, hook up the leads to the
primary terminals on the ignition coil. Should indicate
very low resistance. If not, replace coil.
c. Using the high scale, hook up one lead to the primary
terminal, the other to the secondary terminal. Should
not read infinite resistance. If it does, replace coil.

Step 4. Disconnect the ignition module connector and with the
key on, check voltage at terminals A and D on the harness
side of the connector. (pink/black and white/black wires)
If under 10 volts check for faulty circuit from the ignition
module to the coil or check for grounded external coil
circuit. If 10 volts or more, change the voltmeter to a/c
scale and measure voltage on terminal B while engine is
cranking. (white wire). If 0 volts, Have ECM checked. If 1-
4 volts, with the key off, disconnect the module
connector. Install a LED type test light on the positive
battery terminal and probe terminal C on the harness side
of the connector (black wire). The light should illuminate.
If not, check ground wire in the harness to the module. If
the test light is on, go to step 5.

Step 5. Remove the coil wire from the coil and ground it to the
frame. Connect LED test light into the optispark harness
connector red wire terminal C. The harness connector that
you will use is located on the passenger side of the
engine up near the fuel rail. You will need to insert a back
probe pin into terminal C. If the test light flashes when an
assistant cranks the engine, the optispark is suspect. If
no flashes, replace the ignition module.

If the above tests results are correct and there is still no
start, it is tough to to tell the difference between a
faulty module or optispark. Module = Cheap$$, optispark
=moderate $$$.


The whole deal with the optispark is that due to the location, is prone to water contamination. There are two designs. The first is a non vented. It is a sealed (supposedly) system. As electrical energy travels though the distrubuter, ozone builds up within the unit causing corrosion. The second design is a vented system that keeps the opti in a low pressure environment so that the ozone cannot build up within the unit itself using vacuum lines attached to the opti and the intake vacuum circuit. The problem is that the location of the unit hasn't changed. I've found that in order to get the most life from the stock opti unit, dielectric grease must be used on all spark plug wire connections to seal out water and a 90º fitting screwed into the weep hole on the water pump. This weep hole allows water to start leaking as the water pump's bearings and seals wear, unfortunately this weep hole is right above the opti! A 90º fitting and a length of vacuum tubing routed around the opti and below it will re-direct the water when it leaks, saving the opti from contamination.

There are a couple of options to replacement. A billet high dollar (over $500) replacement that is a plug and play, and the Bailey coil per cylinder conversion like what the LS1s use. Both are expensive and not really worth it for your average street car. The stock opti when a few precautions are taken can last quite a long time. Hope this helps.......

[Kiwi_94_Z28]

Thanks for the help...

I'm only getting about .25 VAC on pin B (white) and when I use an engine code scanner I do not get code 12. So this is probably a fault in the ECM/PCM right? Anyway to test this or know of a place that can test the ECM/PCM?

[Kiwi_94_Z28]

What's involved replacing an ECM/PCM, any special dealer stuff or can you just throw the new one in?

Thanks again

[Joe 1320]

PCMs usually don't come with chips or programs, you'll have to have a program inserted into it before it will function. Most dealerships require the PCM to be in the car for programming. Some are stepping up to the plate with better computer stuff, allowing a PCM to have a program flashed into it's memory right on the bench. If you don't want to go through the dealer, you'll have to find a tuner who does programming.

[Injuneer]

Originally posted by Kiwi_94_Z28
Thanks for the help...

I'm only getting about .25 VAC on pin B (white) and when I use an engine code scanner I do not get code 12. So this is probably a fault in the ECM/PCM right? Anyway to test this or know of a place that can test the ECM/PCM?

What kind of "scanner" are you using? A "short-the-pins" scanner is the one that will display a 1 - 2 flash on the SES light when it "connects", but that type of code scanner will not work on any F-Body after 1993. 1994 and up do not even use the DTC 12 "handshake".

You need a "real" scanner... the "Tech 1" is the GM factory scanner ($1,000 and up). You can use AutoXray, ScanMaster, the "upscale" OBD-I Actron (not the $30 pin scanner), or software from Diacom, TTS DataMaster of FreeScan. If the problem is in the optical section of the distributor, it will set DTC 16 for loss of the low res pulse, or DTC 36 for problems with the high resolution pulse. If the problem is in the high voltage section of the OptiSpark (cap/rotor), no codes will be set, although you might get DTC 42 for the problems that causes with the rest of the system.

Make a quick check of the two 4-pin harness connectors for the OptiSpark. Corrosion can cause the loss of the high and low res pulses, or contamination of the signal. One connector is on the Opti, at about 11:00 o'clock looking from the front of the engine. The other is the gray "test connector" on the bracket on the passenger side of the intake manifold. The one on the Opti is often the culprit, generally not the gray one.

Shoebox has an online guide to pulling the damper pulley off.

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

I've never found it necessary to start backing out the centerbolt.

You need to get one of the scanners I mentioned on it, and check for trouble codes. That should get you pointed in the right direction.

[Kiwi_94_Z28]

Thanks again for the help...

Got a new scan tool and as mentioned above, the retrieved code was 16 (Ign System problem, loss of low res pulse signal). So that means it’s the Optispark right? Is there anyway to fix it (or even test it, resistance check etc?) or is it best to get a new one?

Thanks,
Kiwi.

[Rob B (shoebox)]

If you have checked your opti harness as Injuneer suggested, looks like time for a new opti.

If you ever want to buy GM parts, use either of the guys below. Wholesale prices and no rip-off shipping.

Dal Slabaugh: 877-448-5451
email: lockitup@bright.net
VanDevere Buick/Pontiac/Olds Akron, OH

or

Jason Cromer: 877-726-8295 or 850-243-8826 (direct parts dept ph #)
email: parts@samtaylor.com
Sam Taylor Buick/Cadillac Ft. Walton Beach, FL

[Injuneer]

Its not unusual to find DTC 16 as a "stored" code. Seems like a hiccup at startup, as the PCM searches for the low resolution pulse pattern can cause it to set sometimes, even with a healthy Opti.

Pull the "PCM BAT" fuse (panel at end of dash in 94) for 30 seconds to clear the stored codes. Then put the fuse back in, and try and start the car. Check for codes now. If DTC 16 is there, you have a confrimed problem with the Opti. When the PCM sets an active DTC 16, it shuts down the fuel system, pump and injectors.

[Kiwi_94_Z28]

Yep, code 16 repeats. Just pulled the optispark off and it was full of water!

Are there any special precautions with the little drive shaft? It looks like it only goes in one way? When I put the new optispark in is there any special instructions, timing etc?

Thanks again...

[Rob B (shoebox)]

Just line up the little "keyway" on the splined drive and you should be good to go. Make sure the opti fits flat on the mounting surface by hand. Don't pull it down by the bolts.

[Trans Am]

Check the coil again with a calibrated spark tester. I had the same problem and the coil checked ok using the DVM but it was too weak to fire the plugs. I had spark tough. It wont cost you much , I hope thats the problem Good luck!

[Kiwi_94_Z28]

Thanks to all who gave help!!

Replaced the opti and my Z is back in action