SuperSportSS

so ive been having troubles with my 1993 z28 having "weak" spark (yellow/orange colored spark) and like anyone else on a tight budget with their car and someone who doesnt like to tear something apart just to find out thats not what the problem was and have to deal with being bummed out the entire time you are putting your lt1 back together trying to rack your brain on why it isnt getting spark or why its not starting.

but anyways, like everyone on a tight budget you want to find a GOOD USED opti, which is hard to do now days because its hard to believe someone who has one laying around because who knows if its any good right?

well ive found away to check and opti while its not even installed on your car, heres a list of what you need

used opti-spark in question
known good ICM
known good COIL
known good Spark plug wire
known good spark plug
and finally a good opti harness,

what you do is leave your icm and coil hooked up into your car as if you normally would, and take your spark plug wire and connect it to the number 1 CYL location on the what we will call the "remote" opti-spark
and connect the plug into that plug wire just like you would if it were on the car, now sit the plug near a good ground (engine block, header, throttle body ect) now take the plug wire off the opti-spark thats installed in your car and connect it to the coil wire connection on the "remote" opti,

then take and connect your opti spark short harness to the connection it normally goes into (grey plug with 4 wires by the passenger side intake)

now depending on what opti you are using/testing (im using a 95-97) find a 9/16 socket and wrap the timing shaft of the opti-spark enough so the socket fits snug over the shaft but will not allow the socket to slip,

now turn your ignition key ON but DO NOT CRANK THE ENGINE once you have done that you take the drill (i used a dewalt corded drill with a 3/8 drive socket attachment) and slowly (about 1/4 of a trigger) bring the opti upto what you think and idle speed is and watch your spark plug for spark it should be BLUE/WHITE if it is YELLOW/ORANGE it could be a bad opti, if there is NO SPARK AT ALL double check all connections and make sure the plug is near a good ground spot. if everything is good and you still are not getting spark obviously the opti-spark is BAD

i do have a video posted below to show my method of this for PROOF this works,

Disclaimer
I (supersportSS) nor is (camaroz28.com) responsible for any damages, injuries or electrical issues that may occur when trying this writeup,

here is the video.


if a mod would like to sticky this you're welcome too!

shoebox

The spin the opti test has been used and recommended before, but not with as much detail as you have provided. You should also hear the injectors click.

SuperSportSS

i have never seen anything on how to chek it for spark like this, ive heard of spinning it to make sure the bearings are good, but i havent seen anything on the spark aspect of it, i wrote this to help with anyone having no spark issues and not knowing if it was their opti or not. and if they can find a cheap opti or have a spare laying around or even just have a friend willing to loan them theirs to do this test, they will be able to tell if the problem is really the opti,.

but im glad you said that about the injectors because i wasnt getting injector pulse with my opti and when i was spinning my opti i heard the clicking and thought it was just the fact that the other 7 spots for plug wires were not taken my plugs.

thank you for the extra input Rob. i will probably revise this post alittle myself, just to add little details and things i pick up about doing it this way.

Kevin Blown 95 TA

It depends which part of the opti you are testing, but if you are testing the high voltage section, the only problem with that is that your spark plug is not under any pressure. It is quite a bit different in a cylinder that is compressing fuel & air and making power. So the spark plug will fire under higher load and higher secondary voltage when the engine is working hard and a lesser load and lower voltage when it is just idling (or firing in free air) that is why the insulation breaks down under load and you get a misfire. Now if you really want to troubleshoot, you can open the gap in the plug to raise the voltage and hold a ground probe to different areas of the secondary and near the traces of the opti and see if it starts to misfire or crossfire, or you see sparks going to ground through the wire insulation or coil body or whatever you want to test in the ignition system. That spark will jump a pretty good gap, maybe up to 3/8" if you tested it without a plug, but the danger there is wrecking a part that might still have some life in it. Also that spark plug in the video looks pretty crummy. When you get all that gunk over the porcelain insulator, it can lose spark energy through that because at 15kv or whatever it is at, it can conduct current. And, any small crack in the porcelain will probably render it useless too. It will work just to lay the plug ona ground, but is a lot better to connect it solidly with a large alligator clip or something, otherwise you have a poor ground and the plug has to make a second spark where its just barely touching.

timnfxr

If you're going to spin the opti multiple revolutions, it's a good idea to disable the injectors by pulling their fuses (F9 & F10 on a 93), to prevent loading up and washing the cylinders with fuel.

shoebox

IIRC, there was a person that had his engine run by surprise when he had someone crank the engine while he had a substitute opti connected to the engine harness spinning it by hand (the original opti with a bad optical unit was still on). So, the PCM thought it was getting a good signal and sent signals to the ICM and the coil provided the spark through the old opti cap and rotor. Of course, it ran erratically only for a moment or two.

SuperSportSS

In my case of not getting good hot blue/white spark this was a total success if you ask me, my opti would missfire the plug and wasnt sending pulses to fire my injectors. This optispark was and i used a plug that was 800 miles old and i just wire wheeled it to clean the connection.

The point of the video is not to show plug quality but to just show that if you think it may be your optispark causing your issues (whatever they may be) you can bench test if you will an optispark you know is good without having to spend a few hours taking your engine apart, but you do make good points in your post, about how the spark does react differently IN the cyl compaired to out of it in free air..

I didnt pull my injector fuses just out of not knowing but yes you should. Unless you are trying to test and see if the opti os whats stopping you from getting your injector pulses.

SuperSportSS

Thats pretty cool to know kinda makes you wonder if there isnt away to remote mount an opti and have it work in a better spot then under the water pump

Injuneer

If you have spark, even if it's weak, you have the signal from the optical cam position sensor. If you have that signal, that's all the ECM needs to fire the injectors. The Opti doesn't provide a separate signal directly to the injectors. Your problem sounds like it's elsewhere. No need to test for the cam position signals - the ECM does that and sets codes if they are not present. You could test for the pulse signals by plugging the Opti into the short harness, attaching a volt meter to the correct wires in the harness, and turning the Opti slowly by hand, watching to see if the voltage switches between 0 - 5V as the Opti turns.

A potential failure of the Opti cap is the dielectric material in the cap that separates the bare conductors that route the cap buttons to the correct plug terminal. As the dielectric strength breaks down, the conductors can crossfire, but if there is only one plug connected, that problem will not show up. Nor will it show up at the very low voltage required to fire the plug to ground in open air, as Kevin has already explained.

GaryDoug

A forum member asked me to help test his Opti out of the vehicle. This is what I did to test it up to 155 *F. The drill was set to rotate it about 50 rpm, just fast enough to see good waveforms. The test revealed that the power input to one of the circuit boards was intermittent and opening at higher temps. That was successfully repaired.

shoebox

The reason the opti is in the location it is, is to provide the most direct and accurate sensing of rotation (more accurate than the previous rear mount distributor). It is about as good as you can get without going to the coil on plug setup.

Injuneer

And using a system like the LTCC takes the high voltage section out of the equation, if you feel that is a problem.

SuperSportSS

I was up all night lastnight working on my z28 and when i lose injector pulse i loose spark also. And it will be all out of the blue, ill have spark (very very weak spark) and ill hear the injectors clicking. Then ill loose spark and then i dont get spark anymore. And when that happens i plug in the test opti and im getting good strong spark and i can hear the injectors clicking,

And on a side note. I RAN my lt1 with the optispark that im using as a test opti given it didnt run very good because the timing wasnt correct due to being not correctly installed but it was enough to let me know ok i have to change my entire unit most likely. So i took the test opti apart and its BONE DRY inside. Looks like here a drop of water has been insode this thing. All of the contacts looked good. So im probably going to be switching over to a vented opti. That will be the next write up unless someone else has done it?

Injuneer

When you lost both spark and injectors, did you check for codes?

Shoebox has the vented Opti conversion info.

SuperSportSS

Yup checked for codes and nothing. So i think it has a bad optical sensor and its not throwing a code, every bad optispark ive had always never throws a code. I dont get it. You guys that get codes are lucky.