Go Back   Corvette Forum > C4 Corvettes, 1984 - 1996 > C4 Tech/Performance
Sign in using an external account
Register Forgot Password?
Register Search Today's Posts Mark Forums Read FAQ Vendor Directory
Search
C4 Tech/Performance
L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine Sponsored by
J&D Corvette

Welcome to Corvetteforum.com!
Welcome to Corvetteforum.com.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, at no cost, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, join Corvetteforum.com today!


Corvette Store
 
 
C7 Parts & Accessories
C6 Parts & Accessories
C5 Parts & Accessories
C4 Parts & Accessories
C3 Parts & Accessories
C2 Parts & Accessories
C1 Parts & Accessories
Wheels & Tires
Sponsored Ads
 
 
Vendor Directory
  
Reply
 
 
 
 
Thread Tools Search this Thread
Old 03-13-2009, 07:12 PM   #1
rs/ss 67
CF Member
 
rs/ss 67's Avatar
 
Member Since: Feb 2009
Location: West Chester Pa.
Default Testing optispark out of car

Is there a way of testing the optispark when it is out of the car ?

Steve
rs/ss 67 is offline   Reply With Quote
Old 03-13-2009, 07:27 PM   #2
MikeC4
CF Senior Member
 
MikeC4's Avatar
 
Member Since: Oct 2004
Location: Austin Texas
Default

You would need a power supply and DVM. I suppose an oscilliscope could also be used to check the high and low resolution pulses if you have something to continually spin the Opti driveshaft.

Here is an On Car method of testing. You could extrapolate what is needed to do this off car as well.


The opti has two functions in the spark process. The first thing that happens is as the cam turns, the optical section of the optispark picks up the signals by the rotation of the shutter wheel. The pulses are sent to the PCM via the optispark electrical harness. The PCM processes the signals along with other sensor input and determines the proper time for the coil to fire. The PCM sends a signal to the Ignition Control Module (ICM) and it, in turn, causes the coil to fire. The spark from the coil travels through the coil wire back to the secondary ignition section of the optispark (cap and rotor), to be distributed to the proper cylinder.

If the opti is never sending the signal to the PCM, the PCM will never send a signal to fire the coil.

Here is some testing you can do. Refer to this diagram:



Disconnect the ICM connector. Leave coil connected.
Turn key to ON.
Check for dc voltage with a digital meter at harness terminal "A" to ground and and also "D" to ground. Note: Use a high impedance meter (at least 10 megohm) when dealing with the PCM.
Result should be 10v dc or more on both terminals. If you get no voltage, use the diagram and chase back toward the coil and the ignition fuse. Power for the ICM comes from the ignition fuse and through the coil, so any of that could be bad.
If you have good voltage, switch the meter to ac scale and connect test leads to terminal "B" and to ground. Observe meter while cranking the engine. You should see between 1 and 4 volts ac (those are the pulses that trigger the coil to fire).
If you don't see the proper ac voltage the problem could be the optispark, the harness to the optispark, the PCM or any of the wiring in between. Visually inspect all the connections you can get to for poor contact or corrosion.


If you are successful using an oscilliscope, this is what the pulse train output should look like from the high and low resolution timing wheel:



MikeC4 is offline   Reply With Quote
Old 03-13-2009, 08:35 PM   #3
rs/ss 67
CF Member
 
rs/ss 67's Avatar
 
Member Since: Feb 2009
Location: West Chester Pa.
Default

Mike,
Thanks, I will reinstall it on the engine tomorrow and get to testing.
rs/ss 67 is offline   Reply With Quote
Old 03-13-2009, 10:44 PM   #4
MikeC4
CF Senior Member
 
MikeC4's Avatar
 
Member Since: Oct 2004
Location: Austin Texas
Default

Since you have the Opti off, did you open it up and inspect the cap and rotor for carbon tracing, coolant or water intrusion ?

These units are easy to disassemble using a deep inverse torx socket. You can get a cheap set at Harbour Freight.

What symptoms lead you to believe that your Opti is bad ?

MikeC4 is offline   Reply With Quote
Old 03-14-2009, 05:57 PM   #5
rs/ss 67
CF Member
 
rs/ss 67's Avatar
 
Member Since: Feb 2009
Location: West Chester Pa.
Default

I have a spare Opti that I wanted to check before I did the upgrade to the later style vent system, My son was helping chase down an oil leak and he gunked the engine without my knowledge and now it is popping thru the passenger side exhaust and it is very hard to start and keep running, I checked for water under all the injector harnesses and pu;;ed all the wire conectors on the manifold and blew them out with air--same systems are present so I will be tearing into it I guess.
rs/ss 67 is offline   Reply With Quote
Old 04-19-2011, 12:19 PM   #6
stephenpen
CF Senior Member
 
stephenpen's Avatar
 
Member Since: Nov 2008
Default

I know its old but I have a quick question.

I have spark at my coil but no spark at any of the wires. Is this a case of the rotor coming off ? Is the optical side working by telling the coil to fire ? But the distributor side is not distributing spark because the rotor is floating around behind the cap.

Last edited by stephenpen; 04-20-2011 at 09:54 AM.
stephenpen is offline   Reply With Quote
Old 04-19-2011, 07:33 PM   #7
TWISTERUP
CF Senior Member
 
TWISTERUP's Avatar
 
Member Since: Feb 2009
Location: Richmond Virginia
Default

Quote:
Originally Posted by stephenpen View Post
I know its old but I have a quick question.

I have spark at my coil but no spark at any of the wires. If this a case of the rotor coming off. Is the optical side working by telling the coil to fire ? But the distributor side is not distributing spark because the rotor is floating around behind the cap.
If you're also talking LT1 (can't tell by your profile)--the rotor is held on by two screws --the rotor sandwiches the opti trigger wheel in place so if the screws /rotor had come loose--the shutter/trigger wheel would most times also be loose and you likely would have no spark period.

The rotor could be broken in another way-cap could be bad or coil wire may be bad. If the coil wire is good remove the dist. cap-shouldn't be hard to see the problem if you have no spark at the plugs.
TWISTERUP is offline   Reply With Quote
Old 04-20-2011, 10:06 AM   #8
stephenpen
CF Senior Member
 
stephenpen's Avatar
 
Member Since: Nov 2008
Default

I think the 2 little screws backed out causing the rotor to come off. This opti only had a couple hundred miles on it. This is what happened with my last opti. I'm hoping I can install a new cap and rotor it will live again.

If the opti was not working at all I would not have any spark at the coil. If I've read everything right the opti has to functions.

First is to pickup timing off the cam to send spark to the coil.

Second is to take the spark from the coil and ditribute it to the 8 spark plugs.
stephenpen is offline   Reply With Quote
Old 04-20-2011, 08:15 PM   #9
TWISTERUP
CF Senior Member
 
TWISTERUP's Avatar
 
Member Since: Feb 2009
Location: Richmond Virginia
Default

Quote:
Originally Posted by stephenpen View Post
I think the 2 little screws backed out causing the rotor to come off. This opti only had a couple hundred miles on it. This is what happened with my last opti. I'm hoping I can install a new cap and rotor it will live again.

If the opti was not working at all I would not have any spark at the coil. If I've read everything right the opti has to functions.

First is to pickup timing off the cam to send spark to the coil.

Second is to take the spark from the coil and ditribute it to the 8 spark plugs.
Just trying to answer your question -- as i said if the rotor came loose and the shutter wheel became loose (not turning) or damaged the opti decoder no spark at the coil--if the shutter wheel continues to turn with the dist. shaft--spark at coil-none at spark plugs. Try some Loctite on the rotor screws when you go back in the opti.

BTW there's nothing unique about what the opti dist.does the majority of distributors be they -points and condenser--HEI--hall effect--directly or indirectly (via ICM) collapse the field in the coil creating spark then the cap and rotor send the spark to the correct cylinder

Last edited by TWISTERUP; 04-20-2011 at 08:22 PM.
TWISTERUP is offline   Reply With Quote
Old 04-21-2011, 09:30 AM   #10
ScaryFast
CF Senior Member
 
ScaryFast's Avatar
 
Member Since: Jul 2001
Location: Detroit's West Side MI
Send a message via AIM to ScaryFast
Default

You can easily test the opti off the car by plugging it into the car wiring harness and spinning the shaft yourself.

You'll hear the coil popping as it tries to fire the igntion. Just spinning the shaft makes the ECM think the motor is turning over and it will fire the coil. If you don't hear the coil popping you can put a spark testor on it or a plug wire.

Obviously ignition has to be in the "on" position...
ScaryFast is offline   Reply With Quote
Old 04-21-2011, 09:30 AM
 
Go Back   Corvette Forum > C4 Corvettes, 1984 - 1996 > C4 Tech/Performance
Reload this Page Testing optispark out of car
 
 
 
Reply

Tags
c4, coil, corvette, diagram, ignition, injector, optispark, pcm, pulse, signal, signals, test, testing, tests, train, wire, wiring


Thread Tools Search this Thread
Search this Thread:

Click for Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
testing optispark fastrad C4 General Discussion 3 05-12-2014 06:02 PM
Optispark calicokid C4 Tech/Performance 6 07-08-2012 04:48 PM
is there any way to 'bench test' an opti-spark optical sensor dizwiz24 C4 Tech/Performance 3 05-31-2012 09:03 AM
optispark, installation-finding TDC? forrestwa C4 Scan & Tune 4 08-25-2010 10:48 PM
HELP-'92, LT1 Firing Order, OptiSpark Plug Wire Order CarlB C4 Tech/Performance 3 08-05-2001 08:00 PM


All times are GMT -4. The time now is 08:14 AM.


Emails & Password Backup