My mind just wouldn't let go of some of the test procedures I got from different people. Shops I talked to just didn't uinderstand why I was asking them if htey had GM experience and understood the GM bypass ECM system. I tried to understand WHY I was testing something, not just how. Growing up with an allen wrench in my pocket to adjust the dwell on my 1965 GTO has found me falling short over the years in the electronic engine department. I went forward with tests I came to the conclusion that some of items I replaced was a total waste of time.
Take the Crank Position Sensor... Since there is no Cam Sensor on the 3.1 or 3.3 V6, both the Fuel and the Spark signals come from the CKP. Since I had spark, There was no reason to suspect it for Fuel signal problems.
I still say there is a problem with the source for the ICM test
in the GM forum Tech section. First of all, the test there test only the CKP. The tests for the 3X loop and the 18X loop are both supposed to show the the 0-6V pulse. So the suggestion that the 18X pulse means that the ICM is bad as not possible. A yes
means that the CKP is working and has nothing to do with the ICM at all. This is a RETURN pulse from the CKP and is taken BEFORE the pulse gets back to the ICM. Please revise the outcome for that procedure. It'* wrong.
Please understand, educational materials are wrong 18% of the time! Federal statistics have shown that over and over. Especially when the engineers that develop this stuff, are not the ones publishing the books! I remember one points and condenser ignition chart
in my tune-up class showed a image of the AC ground in the secondary stinger, grounding to the Negative terminal
of the primary winding in the coil. It took an electrical student to go and tap the teacher on the shoulder and point out that AC grounds to positive
and should be going to the Positive terminal
of the primary winding in the artwork.
I did some hard thinking about the diagram in my service manual for the fuel injectors. I was really confused by what I saw. So I started in on the test procedures for the fuel injectors to try to learn why GM set it up the way they did. I still don't know!
What confused me was the diagram showed that the 6 injectors were split into 2 loops. One with pink & blue wires and the other 3 bank has pink & green wires (looking at the top of my engine I saw the two loops). Then the darnedest thing happens! The 2 loops go into the computer and tie together at the "injector control". I believe I saw this controller on a video as a transistor. This system does not fire the injectors sequentially, but in a batch! All 6 injectors fire at the same time! What the heck? I understand firing the plugs in a batch, but MPI'*??
Well let me move on...
Each injector should test at 12.6 ohms. I tested all 6 and came up with...
(left side of car)
12.7 -- 0.8 <--- can all my friends out there say "Dead Short"?
10.7 -- 12.8
11.2 -- 12.5
(right side of car)
It looks like the injectors go into the intake ports... and they do!
But the open plenum still has enough fuel floating around in the open space that some fuel air mixture can backflow and go into other ports. Up till now the mild thumping I felt on one cylinder I attributed to a bad wire. Guess what? A dead injector is not going to cause a dead cylinder, just a week one. IF I had detected a dead
cylinder 4 months ago, I would have changed the injector back then! Remember I said I changed 5 of the 6 injectors. The one I left looked okay, and was clean in the shoot, BUT it was an off brand aftermarket and thus made a fool out of me!
So I went to the pull it yourself junk yard yesterday and bought a used Rochester Products injector for $6. You bet I took my multi meter and tested injectors until I found one with 12.6 ohms flickering to 12.7. I passed up others with 10 or 11, or even 12.2. In the near future I will change the 10 & 11 ohm injectors so they are all up to par.
Here'* what happened. When the car pulled its first stall, it was up a hill under load. Then after a couple under load stalls, it just started stalling anywhere. The damage had set in.
(Here'* a story for if you are bored. If you're in a hurry, skip to the next paragraph) Well the last day it was on the road was a bear. It stalled 10 times in 5 miles. I had the owner of the Buick following me in my Mitsubishi to push me out of intersections if need be. I even got pulled over by LAPD because while it is legal to tow a car with a rope or chain, it'* apparently illegal to PUSH a car with another car. I handed him my CDL and told him I had pulled cars and read the Veh Code many times and was aware of laws saying things like you can't pull a car with a rope or chain over 10 feet long, and you can't tow a car off a state highway
with a rope, it HAS to be a chain, but I've never heard of this law. He was quite agitated and looked like he was going to write me up. When I told him that the car was running under it'* own power until the last intersection when I motioned my friend to push me out of the intersection, he calmed down a tad. Then I pulled out my AAA card and said I would call a tow truck. He asked why I hadn't called. I said I live 6 long blocks from where the car first stalled (big lie, lol) and had been rescuing cars all my life even with police cars driving by me. He said to park it and get a tow truck and drove away *whew*! So I let the car cool 15 minutes and started it up and drove it *almost* home. She had to push me the last 100 yards.
No disrespect to the kind officer!
So back to what happened...
When one injector shorts, it puts a such a load on the triggering transistor, AKA the injector controller, the controller overloads and just says "I Quit!" and shuts down ALL 6 INJECTORS
Then you start it right back up, and overloads and stalls again.
So, if you ever hear of someone having instant "turning the key off" type stalling, remember that the fuel injectors and those wires are part of what has to be tested under the hood. Not just the sensors and ICM. If you don't it'* like testing 1/2 the car and ignoring the other 1/2. Ask your self this: "Would I check only 3 of the 5 lug nuts on each wheel to find the loose lug nut?"
I drove the car today on all my errands. I think I put about 35 miles on it. I also got a call from the owner to go pick her up from the hospital as her daughter had some GI tests run (maybe it was her injectors? lol)
I pulled in and drove towards them. They were looking past me for my big Park Avenue. It wasn't until I jerked the wheel and aimed right for them and goosed it, that they realized it was their Century lol. Kathy screamed "IT LIVES"! She'* such a movie buff
All the way home she was crying and saying "I can't believe it'* running". I don't blame her, it'* been sitting in my driveway for over 4 months!
So ends the saga of the Century (pun intended)