1994 Cadillac Deville - Alternator Problems FIXED

[protraxrptr17]

I got this car as a no-start. Found a bad ignition module and got the car running but it runs terrible most of the time. Decided to check the alternator diode ripple and it was wayyy over 300 mv. Unhook the alternator positive cable and the car runs perfect, so I thought this will be easy. The owner said the alternator was still under warranty, so he brings me another. This time the car won't stay running for more than about 40 seconds. This alternator was worse than the old one. So I get another one this morning. Same deal. What is happening? Can three alternators be bad? The car runs great with the alternator unhooked. WHen you touch the cable to its post, the car starts missing, backfiring, sneezing, coughing, you name it. Gotta be screwing with the pickup coil. The parts store already frowned about giving me the first alternator. What else could it be?

[steven kiser]

just for laughs leave the battery wire off the alternator and run a lead from the battery to the post on alternator. this will allow the alternator to charge. if car runs fine then there is wire leakage in the harness. with scanner hooked up see if all readings are scattering. if they are check ground locations on engine. if it were in my shop i would remove all ground points and check for oxidation. the pcm could have been trashed by the surging from the first alternator.

[protraxrptr17]

OK, I will try that. I have done a little more to it since I posted. I went to the salvage yard and got a used alternator with only 28k miles and had the same problem. I would say that eliminates alternator problems. I also got the distributor out of the same car. After that, it doesn't seem to make a whole lot of difference whether the alternator is hooked up or not. It runs like crap all the time. I got tired of messing with it after that and backed it out. I will go after it again sometime today. I'm gonna start scoping sensors, messing with the grounds, and all that. I think this thing has so many problems that you can really tell when you get one problem fixed.

WHat is the correct cylinder orientataion and firing order an plug wire orientation on the distributor? Shopkey shows number one cylinder to be on the front bank, cylinder furthest from the distributor, but the mark on the balancer passes the timing tab when the rear bank furthest from the distributor comes up.

[steven kiser]

on all automotive engines that have two heads (for the most part, i'm not sure about v.w's and such) one of the heads is forward of the other. may not be much, but it's forward. the forward heads first cylinder is #1. on this particular one it's the right (looking from rear of engine) side.

[scgms1]

Hi,

This is a Deville, not a Deville Concours, right. 4.9L Vin B, right. Hook up the alternator and with the car running badly, run a jumper wire from the battery negative post to a bare spot on the block, intake, etc. How does it run now? Check the engine grounds by the starter. Or you could do a voltage drop test from the block to the battery. I'm guessing it's high.

[protraxrptr17]

Did that. No difference.

[protraxrptr17]

I'm going to work on it again today if everything else goes as planned.

[steven kiser]

on some weird wiring issues i've installed a resistor at the alternator and it's resolved the issues.

[protraxrptr17]

I fixed it. Not real sure what I did, but it's running good so.... I replaced the distributor with one from the low miles junkyard car. Still ran like crap but it was different. Seemed like the timing was way off. After much head scratching, I decided that the balancer had slipped. I could tell that the owner probably wasn't gonna have enough money to get this car if I kept going, so I made my own mark on the balancer to dial in the timing and called it done. Car is still here waiting on money.

[steven kiser]

glad it's fixed but not sure i follow on the balancer slipping. making sense sometimes takes the back seat when it works.

[protraxrptr17]

I think the outside of the balancer had slipped on the rubber, causing the notch marking tdc number one to be incorrect. I used a stopper screwed into the spark plug hole for what I thought was number one cylinder. Roll the engine one way until it made contact. Make a mark on the balancer. Roll it the other way, make contact, make another mark. Between these marks is tdc for whatever cylinder you are working with. Used my new mark to install distributor and set timing.

[steven kiser]

again, i'm glad that the initial issue is resolved but if in fact the outer sleeve on the balancer did slip the balancer is now a time bomb. the balancing sleeve is going to come off. please, don't take this like i'm questioning. i'm just trying to follow............i'm the king of "i didn't think that was possible or i've never seen that before"