89 L98 Automatic,

Just died on the freeway with a few coughs and sputters after a full throttle shift from second to drive, Was pulling nice and strong, Can't say I heard anything really ominous to to indicate a timing chain problem. When pulled over tried to reset the computer to see if it would start again with no luck, towed it home,

No spark now or code other than the 12 reference. wondering if I should have checked for a code before reseting the ECM. Figured I should also be due for a fuel pump, but seeing I'm not getting any spark to the plugs....
Tested with only one plug out and an inductive timing light. Have power to the Coil and tach.
Sometimes turning over it gives a slight hint that it might want to fire.

My Clinton and other manual not handy was hoping to find some diagnostic info easy to store, access on my laptop......if anyone has any good sites for easy to follow instructions diagnostics before I start replacing parts.

I just changed the plugs and cap and rotor recently, 4 months ago, 100k + tune up probably. (last rotor turned out to not be bolted down, Was hoping it just came loose again), Ran pretty much the same for all these years, erratic idle sometimes, changed the injectors a few years ago when it appeared to be running rich and a little more erratic at one time, Quite a few of them were bad.
Equipped with an MSD coil and Accel module and probably have a 100k on them 5 + ? years old. Also have an adjustable fuel regulator but haven't got around to checking the fuel system pressure seeing there's no spark.
Also have an aftermarket chip in the computer. Of which is a rebuilt unit replaced when I got the car 7 or so years ago. (Produced a MAF code, That was expensive, buying a new MAF and Computer but ended up modifying the extra MAF for better performance till it eventually failed)

Seems there lots of info available for diagnosing the later LT1+ models and that system well interconnected into the ignition system and found reference to a couple terminals on the coil to test for the early model to see if it's working, but not sure which ones they are.

Without my manual handy also wondering if the computer comes into play with these. Looking at the system appears the computer shouldn't effect spark if there's power to the coil and tach terminals on the distributor so presuming the module or Coil are not working.

Thanks in Advance.....

 

Just a thought. Check the wiring harness that conects to the module.These do fail.

 

Most any good parts house can test an ignition module. What does the inside of the cap look like?

 

Put a .05 to 0.1 Mfd capacitor across the primary of the spark coil and pulse the primary with 12v and hold a ground wire within 1/2 inch of the secondary. If you have a capacitor from an old points type distributor, you can use it. Each time you disconnect the 12v from the primary you should get at least a 1/2 inch snappy spark. The spark module can be tested by an auto parts store.

 

Cap just like new inside, (recently changed) just had a little carbon dust on the rotor tab coil contact point.
I have had the Red wire fall of off the distributor one time, the holding tab is broken and that the first thing I checked. But it OK there, Have no idea where else to look in the wiring harness but will look in the daylight, (usually sleep days and not usualy up during daylight or need to do other stuff when I am)

I still have my original module and coil somewhere, Either buried at home or in storage across town. (Might be cheaper to buy a new one than look for the others)

I like the idea of bypassing? Testing the module with an old point capacitor. But also don't have one handy. probably have a few of unknown capacity in storage across town. either automotive, M/C, Snowmobile.

And need confirmation of what/where the the Primary and secondary wires are...

On the HEI distributor The primary ?(Red) wire being the Main power into the Coil. ? Which wires to check for ohms on the coil? If I recall I have yellow and red on each side and the center inside is the fixed ground tab.? Probably different colors on the OEM coil.

And ? ohms presume to test across the colored wires or to the ground tab ? or to the center rotor contact inside.

 

The problem you're describing sounds like a classic fuel pump failure. (I've had the problem twice before with two different '89s - one at an auto-x and the other on a cross-country trip outside of St. Louis.)

While testing your ignition components won't hurt, the test for the fuel pump is rather simple. Turn your ignition on, but don't try to start the Vette. (I can hear the fuel pump relay kick in while seated in the driver's seat, but the real test is in the engine bay.) Using the Schrader valve on the passenger side fuel rail, tap into the fuel system with a pressure gauge. You should see between 40-43 PSI as the fuel pump fully charges the fuel system. Low pressure indicates either a faulty fuel pump or clogged fuel filter. No pressure could be a failed pump or a failed fuel pump relay.

Good luck with your troubleshooting!

 

http://members.shaw.ca/agent86/Ignit...Electrical.pdf
http://members.shaw.ca/agent86/Ignit...System-EST.pdf
http://members.shaw.ca/agent86/Ignition.pdf

 

Thanks Agent 86, .....

Just what I was looking for....

The pictures make it a bit easier for us, a little slow or relate better to visual confirmations that diagrams offer.

Note: In the Ignition PDF, steps 13-17 appear to be missing. So anyone else having the same problem be sure to go through all the PDF's.

After testing the coil and if good, The page says goes to step 13, But the next page oddly only has steps 9-12, 18-20, (the section 3 pages and all there) and an unnumbered Diagram for testing the Pickup Coil with no explanation, Ohm readings for it like for the coil, while the diagram shows where to hook the ohm meter up for two different tests.
Presume that's where steps 13-17 are supposed to be, (and a printing error from the original) and maybe not necessary following the other Ignition System-EST PDF Flow chart which appears to test the pick up coil indirectly, Never heard of the Pick up Coil failing anyway......but must happen.

 

I see what you mean, my scanner was a POS and failed to pick up the rest of the image. I have another scan, that should show it. I'll dig it up.

 

http://members.shaw.ca/agent86/6D-31.pdf

 

Thanks again,

Everything one needs to know about a C3 - C4 HEI distributor and how to trouble shoot it.

 

I replaced the original link with another version, one that has all the info.