: 94 eldorado limo no start



andyfanshawe
02-18-06, 08:30 AM
Hi all. I am in the Uk, and have just been out to a 94 eldorado that broke down 3 years ago!! There is no spark and no injection pulse. The engine is the LT1 with the distributorless ignition system. Power is getting to connectors A and D of the ignition module just above the coil. A 3V AC signal is getting to connector B. This proves to me that the PCM is signalling the coil to fire. Am I corect so far? The module has just been replaced I was told (looks new). I scoped the white/black wire at the coil and got a small waveform. The coils primary resistance was 0.6 ohms, and the secondary was 8K ohms. Are these correct?

How do I access the self diagnostic mode on this? Which buttons do I press?

Thanks for any reply.
Andy.

caddycruiser
02-18-06, 11:56 AM
Hi all. I am in the Uk, and have just been out to a 94 eldorado that broke down 3 years ago!! There is no spark and no injection pulse. The engine is the LT1 with the distributorless ignition system. Power is getting to connectors A and D of the ignition module just above the coil. A 3V AC signal is getting to connector B. This proves to me that the PCM is signalling the coil to fire. Am I corect so far? The module has just been replaced I was told (looks new). I scoped the white/black wire at the coil and got a small waveform. The coils primary resistance was 0.6 ohms, and the secondary was 8K ohms. Are these correct?

How do I access the self diagnostic mode on this? Which buttons do I press?

Thanks for any reply.
Andy.

Huh? Are you talking about a Fleetwood? The Eldorado is a FWD coupe...

CadillacSTS42005
02-18-06, 04:01 PM
its def not an eldorado. its gotta be a fleetwood.

andyfanshawe
02-18-06, 04:08 PM
Sorry, yes! Don't get many of these in the UK!

andyfanshawe
02-18-06, 04:37 PM
Yep, sorry. It's a fleetwood!

Andy.

N0DIH
02-18-06, 09:44 PM
Ohmage on the coil sounds good, doesn't sounds like it is a bad coil. Primary side is always pretty low in resistance.

Any chance you have an oscilloscope? This is most important way to troubleshoot a bad Optispark.

According to the FSM for troubleshooting no start:
1. Any DTC's set for 16, 18, 41, 42, 46, or 48? Troubleshoot these codes first.
2. The FSM asks to check for rpm while cranking, this may be hard to tell w/o a Tech 1 tool.
3. Is Coolant temp (pointer 24) close to real engine temp? Press off and warmer till light test starts. Then press fan control till you reach 24. Then press "outside temp" button.
4. Ensure TPS voltage is below 2.5v at closed throttle.
5. Check for spark on 2 wires.
A. If yes, any injector fuses blown?
B. If no, then is fuel pump running when key is turned on?
C. If yes, check fuel pressure
6. If no spark, check for spark at coil wire (should be 8 sparks per revolution.
A. If no, disc igintion coil module connector, Pins A-D for voltage to ground.
1. If >10 voltage on both, Check B to gnd and crank, voltage should be between 1-4 volts.
a. If yes, then check terminal C with test light to B+ (battery +), light on, if not on, then open coil ground, if on, faulty ignition coil moduel connection or faulty coil module.
2. If <10 volts on both, faulty ignition feed to coil, or grounded external coil ckt, or faulty coil.
3. If either terminal is under 10 volts, there is a faulty ckt from terminal to coil, faulty coil connection or bad coil.

I have more if you need it, let me know or anyone else with a FSM...

This is from 1994 Cadillac FSM, Chart C4 (not C4A)

andyfanshawe
02-19-06, 04:56 AM
Thanks for that. A very comprehensive reply indeed. Yes, I have an oscilloscope. I will get back to the car and try some more. Thanks again. Will report back.

Andy.

Katshot
02-19-06, 07:30 AM
Common issues I've had with '94 LT1s:

1. Bad Opti-Spark Dist.
2. Bad coil wire.
3. Bad distributor harness.

These are all due to corrosion problems.

andyfanshawe
02-20-06, 08:33 AM
Right. Here goes.
Voltage at ign module A and D okay, and also tested with test lamp. Ground at C okay (test lamp). Signal at B is a perfect waveform from the PCM, so it is obviously trying to fire the coil. No HT from coil. The ig. amplifier has been replaced already, and still no spark.
I have removed the coil from the head for testing. In the meantime, I pulled the codes from the onboard diagnostics. 1 code: 41-EST circuit, high voltage. What does this mean? With all the testing done on this car before me, it may have been set by inappropriate prodding!!

Thanks for any help.
Andy.

andyfanshawe
02-25-06, 08:39 AM
Fixed! The coil had gone down, even though the primary and secondary resistances were okay.
Thanks to all that replied. Much appreciated.
Andy.

PS Sorry I called it an Eldorado!