Won't Start 1994 Custom

Hey Everyone,
I'm new to the site but have visited just browsing.
Anywaz to the problem I am having.
I had to replace the Intake Plenum due to cracking on the old one. Found one replaced it but as I was cleaning the Intake Mani. I touched the back of the altenator to the engine block and created a spark and fire(opppss) I had the battery removed but for whatever reason reattached it. So now it wont start. I have a Good Battery, Good Starter, Good ALternator. When i turn the key to the on position without starting it the lights on the cluster stay on, the oil,volt,service engine, and temp. stay on. Narmally they would shut off before starting. I have check spark plugs they are ok, I have also check fuel pressure that is ok, Also the injectors are getting power when you try to start. The motor cranks over but wont start. turns the belts and everything. Does Anyone know what this could be. Is their a code i should put into the radio to clear the pass key?

Any info would be helpful. If you need more info to help you better 411 the problem let me know.

Thanks And Godbless,
REO

Hey Everyone,
The motor cranks over but wont start. turns the belts and everything. Does Anyone know what this could be. Is their a code i should put into the radio to clear the pass key? Thanks And Godbless,REO Welcome to AF! The engine turning over and injector pulse would eliminate the "passkey" as a potential source of the problem. The radio has nothing to do with any of this. One important thing missing in your summary; do you have spark to the plugs :confused:

Yes I pulled the spark plug one out and it is sparking just fine

What did you check injector pulse with? You said that you had a "fire" when the positive cable on the alternator hit the block, was this a real "fire" or just arching? Have you checked all the fuses, under the dash and under the hood?

Yes to both fuse boxes and all fuses are ok Inside and under the hood.
ALso yes to a real fire i had paper towels protecting anything from going into the intake mani. that is what caught on fire. (not a big deal) the fire that is. How do you do the injector pulse width i have the book i will looke that up after i sleep.
I was Looking over the Wiring diagrahm and noticed that the red wire from the altenator goes directly to the PCM without a fuse un smart GM "Experts" could this grounding caused something to go bad thru the PCM or simply the PCM itself?
THanks and GOdbless,
REO

Hey HotZ
I have been reading for a little while about this post and that and I continue to see that you say that a voltage spike in the PCM could damage it. By grounding my altenator to battery cable could that have damaged it enough to ruin the PCM. I am going to try the paper clip thing in the morning when get out of work and see what the codes say if anything.
Thanks and GOD BLess,
REO

Hey HotZ
you say that a voltage spike in the PCM could damage it. By grounding my altenator to battery cable could that have damaged it enough to ruin the PCM. Yes unfortunately, voltage spikes can damage the PCM. Even small spikes, like removing the positive battery cable before the negative, can cause the PCM to fail; the same as a home desk-top computer. I have never understood why some sort of “surge protection” was not built into these systems.

I have the newer style 16 pin adapter does that make it a big difference in the way the computer is made or the way it would read out?
I was going to test the 12 pin with the paper clip but how do you do that with a 16 pin adapter if it is possible at all?
Thanks and Godbless,
REO

OK
HotZ I changed the PCM and it still does the same thing. I took the PCM back and got my money back. I Unforunately will take it to the shop down the street and have to pay $ to get it fixed. O well thats life. If anyone has any suggestions please give me them.
Thanks and Godbless,
REO

The start problem first. Do you have spark when you turn the motor over when it arced you could have blown out a fuzeable link or got the coil pack. The radio issue you have to have the code pulled by a dealer and then just have them earase the code setting so it doesnt happen again. RPM

I have check spark plugs they are ok, I have also check fuel pressure that is ok, Also the injectors are getting power when you try to start. The motor cranks over but wont start. turns the belts and everything. Yes I pulled the spark plug one out and it is sparking just fine Yes to both fuse boxes and all fuses are ok Inside and under the hood. Let's summarize what you have found so far; you have spark, injector pulse, fuel pressure, good battery, good alternator, no blown fuses and the engine is turning over, is that correct? If all this is correct, the engine should fire, if it has compression, unless; you have a major vacuum leak, or sensor malfunction.

Have you checked any of the sensor reference voltage and output voltage to the ECU? Start with the TPS, MAP, or MAF, whichever you have.

The TPS is simply a potentiometer used to vary voltage. The best way to check the voltage is with a scanner, but if you do not have access to one, you can use a DMM. You can probe the terminal with a paper clip to check voltage. The TPS WHITE wire, is the PCM reference signal and should measure 5.0v with ignition on. (Engine does not need to be running) The BLUE wire will show variable voltage from a closed TB position, usually .45v, up to WOT, where it should measure between 4.0v to 4.2v max. The BLACK wire is ground.

I am going to try the paper clip thing in the morning when get out of work and see what the codes say if anything.
I have the newer style 16 pin adapter does that make it a big difference in the way the computer is made or the way it would read out?
I was going to test the 12 pin with the paper clip but how do you do that with a 16 pin adapter if it is possible at all? Your 1994 is an OBD2 hybrid. It is part ODB1 and part OBD2; hence, the term “OBD1.5”. Your 16-pin connector is OBDII and you cannot get flash codes like on the OBDI 12-pin. Most scanners will not work here, however the GM "Tech-II, Snap-On MT2400, (with correct key) Actron CP9140 & CP9150 will work. Try your local Advanced Auto Parts, they sell Actron scanners and some of them use the CP9140 to test customer cars. I use a Matco Tools 9640B professional enhanced scan tool on the 94-95. It has the 16 pin OBD11 connector and reads the OBD1 model specific codes, as well as Global OBDII codes.

One more thing; be sure all vacuum lines are connected properly, especially the one for the power brake booster?
BTW, when you changed the ECM/PCM, did you remove the prom from the existing unit and install it in the new one?

OK well haven't checked the voltage on either the TPS or MAF. Will do that now even though its late. See what happens. As Far as the scanner I can't get it to a store even tough its less than a 1/4 away. LOL I plan on taking it to my local mech. That we use and is very reliable. I let him work on my baby which is my Fancy Car so he is good.
Thanks For All the help and Godbless,
REO

OK HOTZ
Just a quick update the white wire is 5.3 or so and the dk blue is .5or so
So they are reading good im assuming a few up isnt going to kill it. I want voltage specs for all sensors and wires is thier somewhere to get that?
Thanks

Even though you have fuel pressure and injector pulses, you might try spraying in some starting fluid while cranking and see what happens.

OK HOTZ
I want voltage specs for all sensors and wires is thier somewhere to get that? Thanks
The PCM sends a 5.0v reference to all sensors used to interrupt engine parameters. Each sensor in turn, varies voltage feedback to the PCM based on current operating conditions.

Hey Hotz,
Ok well had the car towed to the shop and come to find out there is absolutely nothing wrong with the car. Well there was but wasn't a major issue.
THE PROBLEM,
WHen the intake plenum starts to leak wether it be inside towards the engine or outside. It gets coolant in the cylinders and just needs to be flushed out. It took him about 10-15 mins just pushing the accelerator and letting it go here and there as he heard the way the engine was going. He stoped once to allow the starter to cool down and then went at it agian. Got it started and off I was able to go.

So in sort didn't even have to do anything but turn over the engine till it was clear and started. I wouldn't recommend you do this unless you know about cars. Now that I know I wont have any trouble if there is ever a next time.

I recommend some sort of sticky for this as the plastic intake plenum is a common problem.

Thanks and Godbless to all,
REO

Thanks for the Feedback! Glad to here you have the PA running again. Standard shop procedure would dictate; anytime you have a coolant leak into the combustion chamber, you must remove all the spark plugs and turn the engine over repeatedly to flush out any residual antifreeze/coolant. If the plugs were contaminated with coolant, the fire will be weak at best, and will not provide enough spark for combustion. Cleaning the plugs with carb cleaner may, or may not work. After cycling, the engine over with the plugs out, you should install a new set of plugs before starting!

We have many thread discussions relative to the Series II plastic (96-up non- Supercharged) intake “EGR burnout” problem; however, this does not apply to the 1994 PA. The 1994 has some problems with LIM gaskets, but not the typical EGR passage burnout problem as mentioned.

WHen the intake plenum starts to leak wether it be inside towards the engine or outside. It gets coolant in the cylinders and just needs to be flushed out
BTW, external coolant leaks cannot be ingested into the combustion chamber! :grinno: