Its fuel, spark or air. Trick is to catch the problem while its happening.

AC Delco parts: Some parts can cause all kinds of problems if they are not AC Delco such as fuel pumps and ignition components. Other parts don't matter or may even be better. My favorite brake pads are not AC Delco and I've gone 100,000+ miles on after market rotors, suspension parts, radiator, AC compressor, ... In a thread a while back a guy went through I believe 4 after market fuel pumps in weeks until he went to a Delco.

Spark: When its running good pull a plug wire and see what 1" of strong blue spark looks likes so you can pull a wire when it wont start to see if you have a spark problem. Just any spark is not good enough - 1" of strong blue spark

Fuel: Again, an after market pump can become weak or die in weeks. You need to do the fuel pressure test in the sticky. These trucks are finicky about fuel pressure behavior and leak down, not just any fuel pressure. Just squirting fuel out of the schrader is not enough information. Nothing wrong with the suggestion to also have the gauge ready for when it wont start because the problem may be intermittent. The proceedure in the sticky also tells you if you have leakage in the system which can be the pump, injectors, regulator, lines.

Air: What do your vacuum lines look like? Have you ever cleaned your throttle body? Have you checked the air intake assembly and clamps for leaks? PCV valve?

Codes: Not every condition that can cause running problems throws a code. The prime objective of the ODBII system is emissions. Most things after that are dealer codes to help them fix your car faster and few of us have a code reader that reads all the GM codes. I bought an old used one that does on eBay but it was still stupid money and not worth it for most of us. Les can get you hooked up for reasonable coin with capability that's really good for some special and useful live data like misfire counters and CMP retard. If you have scanning capability we might be able to learn the cause of your problem even without codes. Things to check:

Fuel trims
ECT values
Map values
MAF values
Throttle position values
misfire data
O2 sensor behavior
........

I encourage you to determine if its Spark, fuel or air before you start parts swapping because going down that rabbit hole can get very expensive and frustrating. We help a lot of people who come here with an introduction that includes a list of parts that have been replaced and no joy yet. The shame of that is not just the wasted money but in some cases a perfectly good AC Delco part was replaced with an inferior aftermarket part. My AC Delco distributor has 205,000 miles on it and going strong as is the case with many OEM parts on my truck. If you have been parts swapping that's OK, I did some of that while I was learning in my past lives but your here to get help and learn so its all good.

George

 

Ok, I have been driving this blazer for a while (a few months after the problem started) and the Blazer has trouble starting after I fill it up with gas. What a weird problem. What can you think it could be?
Thanks.

 

That may have something to do with your emissions system like the vapor purge valve/solenoid.



George

 

This was the problem. To summarize my Blazer was having occasional starting problems. This was first an intermittent problem ( which made it difficult to diagnose) but began happening more frequently over time, especially after filling up at the gas station. The replacement was the Evap Emissions Canister Purge Solenoid, located at the the intake.

 

Nice work, glad you got it fixed.

George