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Also, when you replace the crankshaft position sensor, you have to do a relearn procedure, often referred to as a "CASE relearn," using a Tech-II or a fairly advanced scan tool.
That's what I thought also. When I installed my new engine, it ran perfect...no codes. I took it to the dealer for the relearn...said it didn't apply to my '96. I had the cam retard checked..."0"
 
Discussion starter · #22 ·
We had a cool morning here so I fired it up and watched my ODB scanner. Attached is the sensor readings that were pretty much stable for twenty minutes. When it started to die, the RPM's did not go to zero until the engine completely stalled. It's almost as if a timer was on this thing. Twenty minutes, then stall. I thought maybe it was the intake temperature, but it never went over 76 degrees. I guess I can rule out the crank sensor.
 

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Does it run on starter fluid after it stalls? Have you tried that?

No offense, but you haven't even take the first diagnostic steps to determine whether you have a fuel issue or a spark issue. You're throwing stuff at it hoping for a result when you have no idea what's really wrong with it. Trusting blind luck isn't a good diagnostic strategy.


Also, a really good idea if you have the capability to log sensor readings is to log your readings to a file until it stalls. Then look for something that changes/flakes out when the thing dies.
 
nevermind, found it.


To perform the relearn, proceed as follows:

Connect a scan tool to make sure there are no trouble codes stored in the computer’s memory. If there is any power train trouble code other than P1336 (Crankshaft Position Variation not learned), the computer will disable the relearn function until the problem that aused the code has been eliminated. Also, make sure that the engine coolant (check it when the engine is cold) and oil levels are at an acceptable level.

1. Set the parking brake and block the drive wheels. Make sure that the hood is closed.
2. Start the engine and make sure that the engine coolant temperature is at least 158 degrees F. (70 degrees C.)
3. Turn the engine off for at least 10 seconds.
4. Select the crankshaft position variation learn procedure (CASE Learn)on your scan tool.
5. Make sure that the transmission is in Park. Start the engine.
6. Apply the brakes and hold the pedal firmly.
7. Follow the scan tool instructions.

Remember: That you are going to increase the engine speed to approximately 3000 RPM, 4000 RPM, or 5150 RPM. That’s the variation learn fuel cutoff RPM (depending upon the engine), and that it’s important to release the throttle when the engine RPM starts to decrease as a result of the fuel cutoff going into effect. Failure to do such will result in over revving of the engine, causing possible engine damage.

8. Once the engine has returned to idle, check the status of Diagnostic trouble code P1336. If the scan tool indicates that the CASE has been learned, the relearn procedure is now complete. If CASE has not been learned, check for the presence of other power train codes. If any exist, correct the problem, then repeat this procedure.
 
Discussion starter · #26 ·
Ok, so over the weekend I got some ether and tried that. No change. Starts the same as it does when not using ether. I am assuming this rules out fuel system. So now what? Where do I go from here? I know it has to be electronics related. Would the temp sensor cause this?



I should also note that I kept my fuel pressure gauge on while I was testing and it never fell below 60PSI.
 
OK. If it doesn't start or runs bad on ether, and it also doesn't start or runs bad without ether, then you've got an ignition issue not a fuel issue.

Do you have a spare spark plug? can you set it on the AC bracket and connect the #1 plug wire to it? Check it when cold to see what a strong (enough to run) spark looks like. Then when it dies and won't start or run properly, check again with the spare plug attached to the #1 plug wire and check for weak spark.

I think you're going to find a bad coil, bad ignition module or bad crank position sensor. You also might find bad wiring in associated with any of those components. That's where I'd be concentrating now.
 
Discussion starter · #28 ·
I went out just a bit ago and let it run until it died, watching my ODB scanner. I noticed the timing advance was dipping as low as -15 and then bouncing to -25. It normally stayed around -19 to -20. Once the truck died, I cranked it and saw that there was no RPM's showing until it started, albeit for only a few coughing seconds. So, I am thinking one of two things. Crank sensor or distributor.
 
I went out just a bit ago and let it run until it died, watching my ODB scanner. I noticed the timing advance was dipping as low as -15 and then bouncing to -25. It normally stayed around -19 to -20. Once the truck died, I cranked it and saw that there was no RPM's showing until it started, albeit for only a few coughing seconds. So, I am thinking one of two things. Crank sensor or distributor.
Crank sensor for sure.

Check for broken wiring first. Maybe clean the connector. If the cover is crunch or mushy, consider replacing the timing cover, too.

Check this post https://www.s10forum.com/forum/f107/overheated-and-wont-start-850995/#post12195575 for more information on changing the crankshaft position sensor. There's a clearance issue, and you will need shim(s) to get it installed correctly.
 
I went out just a bit ago and let it run until it died, watching my ODB scanner. I noticed the timing advance was dipping as low as -15 and then bouncing to -25. It normally stayed around -19 to -20. Once the truck died, I cranked it and saw that there was no RPM's showing until it started, albeit for only a few coughing seconds. So, I am thinking one of two things. Crank sensor or distributor.

Don't let the m minus sign on your advance throw you. For some reason they don't show a positive advance on a '96. I can't remember if it shows the same on my '02 Blazer.
 
Discussion starter · #32 ·
Success! Truck no longer stalls on me. I do still have a minor issue. When I take off from a stop, it hesitates, then goes, but seems like it is misfiring for a few seconds. No codes show on my scanner. It could simply be bad gas. I have no idea how long this thing sat before I bought it. I took it down and filled it up, then added some sea foam. We'll see if things even out or not.
 
Seafoam is generally regarded as snake oil. It will do nothing for the poppet valves. 3M makes a stand alone system for cleaning poppets that is/was recommended by GM to clean them. You would be better off upgrading your spider to the one with real injectors. Have you cleaned the egr?
 
Seafoam???...for what reason?
I'm guessing maybe now that he's resolved the ignition issues, he wants to try his hand at fixing some real fuel system issues. What better way to make sure you have fuel system issues.

To clean out the injectors and fuel lines.
SeaFoam isn't really a good cleaner for any modern (1990 or later) fuel injected engine. We can debate the potential benefits for carbureted lawn mower engines and two stroke chainsaws, but for any automobile, truck or SUV made after about 1990, it will probably do more harm than good.
Seafoam is generally regarded as snake oil.
According to their SDS, it's 3/4 snake oil. The remaining 1/4 is rubbing alcohol (isopropanol). Still, there's nothing good for a modern fuel injected engine in the stuff, and GM has never recommended SeaFoam in the fuel tank or crank case of any vehicle they've made. At least not in the past 50 years or so.

It will do nothing for the poppet valves. 3M makes a stand alone system for cleaning poppets that is/was recommended by GM to clean them. You would be better off upgrading your spider to the one with real injectors. Have you cleaned the egr?
Once the poppets are gummed up and stuck (either stuck open or stuck closed), the pressurized cleaning system is the only possible way to restore them. Even then, it's a really good ideaâ„  to just install a new style spider with the newer injectors.

However, there is a "GM fuel system treatment plus" which is available at your local dealership which is recommended for certain fuel system issues, and can be used as "preventive maintenance" (without affecting GM's new car warranty, and with GM's blessing, or at least some tolerance) once every 2 to 3 months or so in a tank of gas. The GM part number is 88865595 (AC Delco 10-3012). If you read the SDS, and compare it to Techron Concentrate Plus Complete Fuel System Cleaner, it's the same juice with a different label on the bottle. That's the only thing other than gasoline that goes in any of my GM vehicles. I run it in a full tank about 5 to 6 times a year. It will keep your fuel sender in good shape and prevent some issues with gummed up fuel level senders. It also does seem to keep injectors (even the old poppet valves on these engines) fairly clean, provided they aren't already clogged.
 
Discussion starter · #39 ·
Cleaning the EGR and throttle body improved it, albeit only when cool. Once it warms up, it's back just not as bad as before. Thinking it may be the EGR valve not working properly. May take it off this weekend and let it soak for a day or two. Hoping it's just carbon buildup that is causing the issue.
 
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