CDI Failure modes? Warren?

SC-targa · 05-04-2005, 06:39 AM

I've got an 82 SC that's having a severe engine misfire problem. This started after a partial engine drop to replace a leaking thermostat O-ring. I had to pull the airbox off to get to the O-ring. Since I re-assembled the car, it has not run cleanly at full throttle or above say 2,500 to 3,000 RPM. This has gotten progressively worse till the car is undrivable.

I first assumed it was fuel injection related and I checked the pressures and they are fine. I thought it might be a fuel pump failing, but it meets the min fuel pressure requirements. I've cleaned the injectors in an ultrasonic cleaner, replaced the fuel filter and I've watched the fuel pressure when the engine runs.

The engine now cuts out, even at idle, but the fuel pressure is not varying, leading me to suspect a weak or intermittent spark. I have a new distributor cap and rotor, new plugs and reasonably new plug wires. The coil looks like the original 1982 model, but I haven't checked the date code.

I've pulled the 6 pin connector and it looked clean with no corrosion. I need to listen for the whine from the CDI box, but I can't cay that I ever noticed it.

Warren, or anyone, are these typical failure symptoms of a CDI system or coil? I did a search on several tests for the CDI box, but it seemed like those failures were all hard failures where the car had no spark.

Thanks,

Jerry Kroeger

Early_S_Man · 02:06 PM

Jerry,

It could be the Bosch CDI unit, but there are more likely candidates:

1. Green coax cable, or its' connection to the 600 Ohm pickup coil ... a slip-on connection that pulls straight out from the side of the distributor. If the coax has cracked insulation, or is discolored brown, replace it.

2. The connection at the distributor is impossible to see without pulling the distributor, and even harder to clean.

3. The 6-pin connector from the engine harness can lose connection due to engine vibration ... all of the individual Faston connectors should be cleaned and crimped slightly on the side 'rails' to assure a tight connection in the future.

4. My recommendation for cleaning the entire set of connections goes as follows: a) Use 9% pickling vinegar, either sprayed or rubbed on with a Q-tip ... allow to set/soak for 5 - 10 minutes, then rub vigorously with Q-tips until no more deposits coe off. b) Rinse with spray of distilled water. c) Final rinse with spray of 91% isopropyl alcohol, and blow dry with compressed air.

5. Finally, after verifying that proper operation has been restored ... apply Dow Corning 4, 111, or 112 Silicone Grease to all connections to seal out moisture and oxygen.

Good luck!

SC-targa · 05-05-2005, 05:57 AM

As always Warren, I appreciate your amazing knowledge and suggestions and I''ll try them this weekend. I did check last night and my CDI does whine when the iginition is on, but I expected that since the car fires up, it just runs erratically.

Thanks,

Jerry Kroeger

JBO · 05-05-2005, 06:08 AM

Warren - would delectric grease work OK for your step 5?

Early_S_Man · 05-05-2005, 07:32 AM

JBO,

Dow Corning 4 was the original dielectric grease ... developed in the 1940s to protect US military aircraft electrical & ignition systems from moisture, salt air, and corrosion.

randywebb · 05-05-2005, 10:09 AM

-- Does anyone else wonder how he knows all this stuff? --

And it isn't like the llano Estacado is a center of technical knowledge -- unless USAF has some hidden bases out there....

BTW - where can you buy 9% vinegar? I can't find it anywhere in town. And my town is super heavy into the food thing...

SC-targa · 05-05-2005, 11:09 AM

Goodfellow AFB is out there. That's some kind of intel facility.

Jerry Kroeger

Early_S_Man · 11:24 AM

Randy,

Well, there is a base here [Goodfellow AFB] that has plenty of secret work going on ... NSA, linguistics, satellite imagery, targetting and bomb damage assessment, etc., as well as the not so secret fire/rescue training.

For some strange reason, the grocery stores don't stock the 9% vinegar with the other varies for cooking or salad dressing, etc. You will find it in the 'pickles & canning' section, which means fruit jars & lids by Kerr and Ball.

randywebb · 05-05-2005, 11:39 AM

I know - just a little joke...

But I have not been able to find it at all -- checked a few conventional supermarkets (Safeway, Albertsons..), some of our nautral type places, a hybrid conventional/natural supermarket (PC Market of Choice - no kidding), and a large, you can live there for months place (Fred Meyers). Then I tried to get stop bath or fixer or whatever the 20+ % acetic acid was from a photo shop - no dice. Good selection of batteries for digital cameras tho. Next up: a chem stores place.