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Thread: OPTISPARK DIAGNOSTICS, or is it something else ?

  1. #1

    Default OPTISPARK DIAGNOSTICS, or is it something else ?

    This is a thread based on Optispark diagnostics and tips that you can use to accurately diagnose these systems. This is a guideline for ALL OPTISPARK SYSTEMS. Camaro, Firebird, Corvette, Impala can all use these tips.

    NOTE: These test tips are under the assumption that there is NO SECURITY LIGHT ON or ANY VATS ISSUE!!!!!

    NOTE: Make sure that when you turn the key to ON, BUT NOT START, that the check engine light comes on. If it doesnt, there is a problem with the ECM

    #1, FUEL PRESSURE should be 41-47 PSI with the key on and the engine NOT RUNNING. It should not drop more than 5 psi in 3 mins.

    #2, MAKE SURE your coil wire running from the coil to the OPTISPARK distributor cap has the conduit on the wire and that they are fully seated. When you are inspecting the coil wire, look INSIDE the terminal boots, checking for any rust or green colored oxidation. . Aftermarket ignition wires are prone to allowing moisture under the boots and corroding the connections between the coil and optispark.

    #3, test your fuel injectors for correct resistance. L99, LT1 and LT4 all have injectors at 12.5 ohms resistance. Tolerance is 1.0 ohm

    #4, test for fuel injector pulse using a 12 volts test light. The key with Optispark to see if its working without a scan tool, is to see if the ECM is pulsing the injectors. If the low resolution signal coming out of the optispark is not there, the PCM will NOT pulse the injectors. Use a paper clip on the clamp end of the test light, and gently TOUCH the test light to both terminals of the injector connector. The test light should flash when a helper trys to start the engine. If it does not flash, the low resolution signal is not being seen by the engine control module.

    With these simple test, you can determine if you have a problem with the sensors within the Optispark or something else.

    If there is any other questions, you may post them below.

    This information is property of c4c5specialist and thecorvettemechanic.com and is not for reposting on other internet sites.
    GM World Class Certified Service Technician.
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  2. #2
    Join Date
    Dec 2011
    Location
    Northwest Indiana
    Posts
    10

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    Hey Paul, those are some EXCELLENT tips! I probably could have used those earlier this year. I was helping our club president try to troubleshoot a situation where his '94 would randomly die out on him. My first thought was the ICM was on the way out and he tried replacing that but had the same issue. I hooked my fuel pressure gauge up and he had good fuel pressure. I have two scan tools, one OBDI (12-pin) and one OBDII (15-pin), but a '94 uses an OBDI system with the OBDII connector so I couldn't hook anything up there. Did the paperclip trick and found no codes. We actually did try replacing the coil wire and thought we had it for a while but the problem came back again. He finally took it to his mechanic who traced it back to the Opti. Put in a new MSD unit and he's had no problems since. I'm just hoping the Opti in my '92 behaves itself for at least a few more years!

    Another point of interest this post brings up is in having a few basic troubleshooting tools available. When I bought my car, I figured with it being a nearly 20 year old car, I would eventually need to learn how to work on it at least a little myself or go broke. I already had a good set of basic hand tools, but I went out and invested in a set of service manuals for my year Corvette, an OBDI scan tool, a fuel pressure gauge, a vacuum gauge, a hand vacuum pump, and a 12-volt test light. I already had a decent volt/ohm meter, so now I was pretty well armed. If a problem comes up, if nothing else, I can at least take it to a mechanic and tell him that I've already done "this this and this", and here's what I've found.

    Ron
    Last edited by screamin_conure; 12-20-2011 at 03:54 PM.

  3. #3

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    HI there,

    Excellent points on the tools, very valuable items to have.

    Allthebest, c4c5
    GM World Class Certified Service Technician.
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  4. #4

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    Hi Paul.
    congrats on the new web site.
    its been awhile since i was talking to you about my 93 lt1 convertible and the problems i was having. turned out to be a bad opti. water pump and opti was only 3 yrs old when the pump leaked and took out the opti. my new delco pump and opti are about 3 months old and the motor just burped and spit out a 36 code. so I assume the opti is going bad again. is there anything i should be looking for that would cause it to fail again.
    thanks Mike the plumber.

  5. #5

    Default

    Hey Mike,

    Let me look into this and we might be able to help you further!

    Paul
    GM World Class Certified Service Technician.
    Like us on Facebook: www.facebook.com/corvettemechanic
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  6. #6
    Join Date
    Oct 2013
    Posts
    1

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    Hi Paul,
    New to the site. We have a friend's 92 with an intermittent cranks-yes, no-start problem. We finally got it to fail. No trouble codes, has spark, will start on starting fluid, no injector pulse. The friend had replaced the water pump some time in recent history, but this problem did not immediately surface. Read about the system's weaknesses. Info on the low res pulse sketchy. Read to measure the pulse either at the connector or to pin C5 on the green connector. Did that, makes voltage on cranking using vom. Where do I go from here?
    Thanks Tom L

  7. #7
    Join Date
    Jul 2008
    Location
    Ontario, Calif.
    Posts
    2,978

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    If you have spark and pulse from the injectors I would look at fuel pressure. The pump or regulator may have gone bad.
    2015 Stingray Z51 w/ Magnetic Ride Control & 8-speed Automatic


  8. #8

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    Quote Originally Posted by Tom L View Post
    Hi Paul,
    New to the site. We have a friend's 92 with an intermittent cranks-yes, no-start problem. We finally got it to fail. No trouble codes, has spark, will start on starting fluid, no injector pulse. The friend had replaced the water pump some time in recent history, but this problem did not immediately surface. Read about the system's weaknesses. Info on the low res pulse sketchy. Read to measure the pulse either at the connector or to pin C5 on the green connector. Did that, makes voltage on cranking using vom. Where do I go from here?
    Thanks Tom L
    hi Tom,
    If you have spark, the next test is to check your injectors. Do they all have the correct resistance? If your resistance is wrong, this will shut off the ECM driver and it will not pulse the injectors at all.

    Allthebest, Paul
    GM World Class Certified Service Technician.
    Like us on Facebook: www.facebook.com/corvettemechanic
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  9. #9
    Join Date
    Oct 2015
    Posts
    1

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    Hello Paul using an otc 4000 scan tool I can see HIRS AT 200an LORS at 3 that seem right

  10. #10
    Join Date
    Oct 2015
    Posts
    1

    Default no spark after engine gets hot

    hi, I did diagnostic, got h 16, ran tests. All good.When engine gets warm the engine dies and wont start until engine cools.Looses spark. I put new opti distributer on 11 months ogo .I dont drive the1994 very often.Is there a replacement for the 94 style unvented distributer?
    Last edited by bobby g; 11-02-2015 at 05:16 AM. Reason: change question

  11. #11
    Join Date
    Jan 2016
    Posts
    4

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    Need Help debugging No start of 1994 Camaro Z28 5.7 l 70,000 miles.
    Died on road after filling tank. Jerked hard and would not restart. Towed to loacl Gas station repair shop. They wanted to replace PCM. I said no and towed car Home. I got an OBD 1 Scaner. I has Code 36. No High Res from optispark. Have the 5 volts from both PCM to High and Low Res to OPTI. 12 volts on Distributor Ignition Feed and Ground on Low signal. No AC Volt when cranking starter from Ingnition Control. Are there any other tests I can do to test the OptiSpark before replacing?

    Would be thankful any Help.

    Harald Kolter

  12. #12

    Default

    HI there,

    Your vehicle will start without the hi res signal to the ECM, the LOW RES signal is the one that if missing will not allow it to start.

    Your signal is a square wave signal to the ECM.

    Allthebest, Paul
    GM World Class Certified Service Technician.
    Like us on Facebook: www.facebook.com/corvettemechanic
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  13. #13
    Join Date
    Jan 2016
    Posts
    4

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    Paul

    What is my next step. I have a Scanner OBD 1. Can that help trouble if the opti spark is working? I your Step 1 above what tool is used to check the Fuel pressure. The Scan tool or Preasure gage which i do not have.

    Harald

  14. #14

    Default

    HI there,

    Something basic like this is your fuel pressure testing gauge.

    http://www.amazon.com/Actron-CP7838-...tester+kit+otc

    Another thing you will need is a spark tester like this.

    http://www.amazon.com/OTC-6589-Elect...n+spark+tester

    This will tell you if you have spark going to the spark plug

    http://www.amazon.com/Astro-7898-Del...oid+test+light

    This tool allows you to load the fuel injector harness to see if the ECM is pulsing your fuel injector correctly.

    These 3 tools will give you a baseline diagnosis of where to proceed.

    Allthebest, Paul
    GM World Class Certified Service Technician.
    Like us on Facebook: www.facebook.com/corvettemechanic
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  15. #15
    Join Date
    Jan 2016
    Posts
    4

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    Paul
    I tested for spark with spark tester at main coil contact. No Spark. Tested inspector for resistance 12 on 2 units. Used test light test of injection singile. No light flashing 12 volt + to injector hardness. I have not done Fule pressure test yet. Is it nessicalry at this point? Do these test results piont to the PCM or OptiSpark?
    Harald

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