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'94 Buick Park Ave Ultra 3.8 w supercharger ECM?

I submitted this about a year ago but couldn’t find it in the search. The story is rather lengthy, I apologize but here are the sordid details. Previous submission was something like: " Help I killed my friend’s car"

It started when the serpentine,replaced a year ago by myself,somehow sheared the bracket holding the Alt and power steering pump off the block. I was able to drill and tap out the holding bolts from the block. At that time I could not determine what caused this to occur, the tensioner and all the other accessory pulleys as well as the water pump were all in good order. Prior to this event, it was very evident that his harmonic balancer was totally shot and in need of replacement which was then accomplished as well as changing the drive shaft sensor. We also suspected that the Supercharger bearings were poor and after investigation of the internal bearing lubricant, replaced it also with a re-manufactured SC. All the new units were installed without problem and the vehicle immediately started and ran beautifully. However, the oil pressure gauge on the instrument panel registered off the high end.

On re-inspection of the installed units, I noted that I had failed to recognize that the original serp belt problem had also sheared off the oil pressure sending unit on the back side of the block just under the P/S pump. I replaced this with a new one and again on engine start up the oil pressure gauge shot over to the extreme. Responding to recommendations from CAR Talk several different new ones were tried all with the same end result. With the sensor wires disconnected, the engine would still start but the gauge shot to maximum. I then drilled a small hole into the instrumental panel plastic and levered the gauge to zero, this on advice of a Buick dealership service chief (family friend). But on starting the engine again, it over shot. Taking the advice of aanother very experienced and learned electronic auto mechanic(friend), I then shorted the sensor wires and this returned the gauge to zero with a light touch but then immediately back to maximum, thinking that a relay was stuck. After turning off the ignition, I attempted to restart and now I got starter turnover but no ignition. Further testing shows no spark. I have tested and retested every fuse, relay in fuse relay possible and can not find the defect. Could I have burned out the ECM with the momentary touch of shorting the sensor wires? To add to my dilemma. the starter will not turn with ignition after a few weeks of investigation. An OBD will not register any codes to help. It will turn over if jumped at the starter itself.

Other than junking, 350 magnuming the block, should I just break down a try a salvage yard ECM for 35-45 bucks or send it to a re-builder or remanuf. for between 260 to 380 bucks? I have used advice from several car talk biggies, every Mitchel available, All POro and even a GM Service manual troubleshooting step by step to no avail. Car is in beautiful shape, otherwise.

Thank You for your patience with this car killer! Have Mercy.

I suspect there is a problem with the wire going to the oil sensor. It may be bridged to another wire with power on it. For the the ECU problem I posted a reply in your other posting for this problem. It is helpful for others here to not double post for the same problem. Things get mixed up when doing that.

Dear Cougar:
I’m not sure what reply to the ECU problem you are referring to, the posting I did a few days ago (ECM/PCM) or the one I did a year or so ago, that you may have replied to.
I spent a few hours trying to find the old posting, but was unsuccessful. I tried an abbreviated post a few days ago but one of the contributors suggested I presented a more detailed account of what I was trying to seek help for.
Might you describe where the “bridge to another wire” might have taken place since I did not alter any of the oil sensor wiring other than working at the attachment at the sensor itself and I did not alter the connector but merely used a u shaped wire to ground + to -.
Thank You again for your responses and advices.

You’re welcome for the help. Here is a link to the post I was refering to. It was at post #84 when I checked this. To help you find your previous posts you can do a search using your user name.

If there is a problem on the sensor wire I would suspect it to be either under the hood area near the sensor or perhaps under the dash near the gauge. By isolating each end of the wire and checking for voltage on the wire, resistance between the wire ends, or a tie to ground you can prove out the wire lead to the sensor. You could also just run a temporary lead between the two points and see if that helps. The original wire must be totally isolated from both ends to make that a valid test.