have you tried swapping your suspect distributor in your corvette into a different car,
or swapping a new and totally different distributor into the corvette,
as it seems like from what you stated that your getting the electrical feed (12 volts to the distributor, )
but no spark out of the distributor, which would make me suspect the distributor may be defective,
or that HEI small base distributor, adapter cable may be defective.
or there's an internal electrical short or ground.
I wish I was local to you and Rick, as theres a whole lot of things that you can do during a hands-on inspection and through simple testing that will be very difficult to adequately explain easily.
an ohm meter/multi meter can be helpful,
but it always comes down to isolate and test,
verify the basics, don,t assume, PROVE!
http://garage.grumpysperformance.co...ouble-shooting-rebuilding-hei-ignitions.2798/
http://garage.grumpysperformance.com/index.php?threads/lots-of-wiring-info-diagrams.317/#post-83877
read these links and
related sub links
pull trouble codes
http://garage.grumpysperformance.co...oven-facts-if-your-in-doubt.13051/#post-84695
http://forum.grumpysperformance.com/viewtopic.php?f=32&t=1401&p=8895&hilit=start+sequence#p8895
http://garage.grumpysperformance.com/index.php?threads/c4-c5-corvette-trouble-codes.2697/
http://garage.grumpysperformance.com/index.php?threads/lots-of-wiring-info-diagrams.317/#post-83877
http://garage.grumpysperformance.com/index.php?threads/adjusting-your-tps-and-iac.168/
http://garage.grumpysperformance.com/index.php?threads/multi-meters.3110/#post-71867
http://garage.grumpysperformance.com/index.php?threads/1990-corvette-no-spark.13857/#post-70888
http://garage.grumpysperformance.com/index.php?threads/diagnoseing-tpi-lt1-problems.1241/
reading links and sub links can help
replacement connectors and pigtails are available
http://garage.grumpysperformance.com/index.php?threads/lots-of-wiring-info-diagrams.317/#post-83877
http://garage.grumpysperformance.co...-auto-elecrtrical-connectors.3105/#post-68805
http://garage.grumpysperformance.co...cting-a-distributor-for-your-application.855/
http://garage.grumpysperformance.co...-idles-and-sometimes-stalls.10688/#post-46397
viewtopic.php?f=36&t=3105&p=8272&hilit=connectors+pigtails#p8272
viewtopic.php?f=32&t=168&p=41767&hilit=connectors+pigtails#p41767
http://garage.grumpysperformance.co...lay-switch-locations-and-info.728/#post-17654
CARCRAFT said:
Easy tests for HEI system:
1. Test for power at the pink BAT terminal. You should have battery voltage w/ the key in the start and RUN positions.
2. Connect the ground side of your test lamp to the battery POSITIVE cable. Probe the TACH terminal on the dist. cap while a helper attempts to start the engine. The test lamp should blink repeatedly as the engine cranks. No blink= bad module or pickup coil. Further testing is required to pinpoint the problem. Blink but no spark = bad ignition coil.
3. Remove the cap & rotor. Remove the green & white leads from the module. Connect your ohmmeter to the green & white leads. You should have approx. 800-1500 ohms depending on the ambient temperature. Open circuit (infinite ohms) = bad pickup coil.
Wiggle the green & white leads as you test. Ohm reading should remain constant if the leads are good. If the reading varies as the leads are wiggled, the pickup coil is bad. You'll often find broken pickup coil leads this way.
4. DVOM (meter) still connected to green & white leads. Set your DVOM to AC VOLTS. Have a helper crank the engine as you watch the AC VOLTS reading. A good pickup coil will produce about 3V AC when cranking. Less than approx. 2V AC indicates a bad pickup coil.
let me take you a little farther...
when you turn the key on.. positive power is sent through the red wire plugged into the BAT side of the HEI cap.. inside the cap you will notice the coil wires have a T shaped terminal.... the red wire goes into the coil.. but it also connects to the right side of the 3 wire harness from the cap to the housing from there to the B+ terminal on the module...
the TACH terminal in the cap.. also has a T terminal.. it also connects to the LEFT side of the 3 wire harness down to the housing and connects to the C connector on the module...
wait.. there is a third wire in the three wire harness... this is where a LOT of problems crop up...
this is the ground strap... it goes into the cap before the coil does.. fits into the middle connection of the 3 wire harness..
the screw that goes through the coil laminations directly over the hooked end needs to have the black wire from the coil..
why.... this is the ground for the coil... without it .. the voltage can build up in the frame of the coil till it flashes over like a lightening bolt.. and can be as loud as a shot gun blast going off under your hood..
the center wire goes down and is connected to the condenser hold down strap and the strain relief hold down..
this is really important.. the spark has to make it back up this wire and to the coil after it passes through the spark plugs..
back to the description...
there are 2 screw that hold this coil cover down.. you will notice the TACH and the BAT markings on it..
test with your test light clip hooked to ground to the BAT side.(red coil wire)... you should get voltage...
test with your test light clip hooked to POSITIVE.. the TACH side.(white or yellow coil wire) .. while somebody cranks the engine...
the test light should flash.. this is because the module is making and breaking ground to the C connection inside the distributer. ....... this should make your test light flash..
i normally just remove the module and take it to the parts store as some of them have module testers... where they plug them in and an automated test is run...
i should probably continue on my HEI description...
the 4 pin GM HEI module..
you can see the pins on the right side of this module..
B is the switched ignition power..
c goes up to the Tach and to the yellow or white wire on the coil.
wait.. where is the ground connection.. see the 2 hold down screws... the rivets going through the plastic when the screws go through them ground the module...
why is the ground important.. .. the module connects the C terminal to ground and then breaks that connection to discharge the ignition coil...
on the left end of this 4 pin module are the terminals that go to the pick up coil...
the pick up coil creates a small AC voltage.. usually just about 1 volt AC.. when the AC voltage comes to 0.3 volts positive. the power transistor in the module turns on and grounds the coil.. allowing the electrons to flow into the coil primary creating a magnetic field..
this AC voltage is created by the reluctor spinning above the pick up coil...
this is the second time i have typed this out tonight.. hmm...
when the tips of the reluctor line up with the pick up coil tips.. the voltage will drop back to zero. at this point the power transistor opens .. breaking the connection to ground.. this causes the magnetic field in the coil primary to collapse through the secondary windings and create a high voltage spark....
as the reluctor tips move away from the pick up coil tips.. the voltage continues its negative swing. then it starts rising again as it approaches the tips again..
one of the most important things you can remember.. there has to be dielectric tune up grease under the module or it will die... if it starts again once it cools off does not matter .. once thermally damaged.. its toast.. it will fail eventually.. leaving you stranded... usually at the worst point..