Thanks for your info & thoughts. That was where I was headed, was possible fuel. But I have tried turning on the key until lights go out then turn it off & do it again thinking priming but that makes no difference. Even if I do that a few times. I just had a brand new Delphi pump installed & fuel filter. The shop that did it did a pressure & leak down test. Because it was doing the same thing before the new pump. It is weird, It is real erratic, it works fine some times & sometimes it acts up. Sometimes after it sits awhile other times no sitting. It always starts & it runs great. I also thought about an injector leaking sometimes???
I'm headed to Kingman AZ in a few weeks & that is where the shop that did the pump is. I think I will call them & ask them to check the fuel system, to make sure it isn't fuel. I'm pretty good friends with the owner & the service manager they have done work for me for several years & always done right by me.
I'm going to keep looking around. I want to look at the cap & rotor. Since the plugs it is better but not correct.
Thanks & I'll keep this post updated so hopefully it might help others.

 

The reason I suggested the test is that it's possible that the connector at the module isn't making good contact all the time, (there have been issues with the connector). Also, it's possible the connections from the module connector to the pump motor, (inside the module) may have a poor connection, (seen that a few times too). The main thing is to figure out if it's fuel delivery or ignition causing the problem. Most of the time it's easier to eliminate one system and then concentrate on the other.

If an injector(s) leaks, it will show up on a leakdown test. A restricted or erratic injector will not. Distributor cap & rotor is a possibity, if you decide to replace them, use AC Delco and put a dab of silicone dielectric grease on each terminal, inside and out, of the cap. Hope this helps.

 

Yea, that is what I figured was to figure out with it was fuel or ignition. I put dielectric grease on the plug & rotor ends of the wires. But you say put dielectric grease on the inside of the distributor on the contacts???. I will use DELCO cap & rotor if it is determined it is ignition. This may have the original cap & rotor 120,000 miles on it.
Thanks for all you help, thoughts & ideas.

 

Most people look inside the distributor cap and see a white deposit on the terminals and think it's corrosion. They either scrape it off, or replace the cap. The white crud you see on the contacts is crystalized silicon dielectric grease, it's supposed to be there. It is applied to the terminals to improve the connection and prevent corrosion. 120K miles on the original AC Delco cap is not surprising. You'd be hard pressed to find any aftermarket cap go half of that, even when using the grease.

 

You taught me something I have used dielectric grease since the 70s the only time I ever used it inside the cap was on the HEI systems on the rubber cap at the center electrode of the cap.
But I have a new discovery on this Blazer. By accident figured out that if I open the TB some when starting it fires right off. Also every time I cleaned the TB the problem went away briefly. So I took some Lucas injector cleaner & poured some down the idle circuit at the back of the TB. That helped a bunch. The idle & starting improved a lot.
So I'm starting to think I have a dirty or particle blockage @ or near my IAC. Is this a possibility??? What I started noticing that brought me to this was I was noticing an RPM variation @ idle. Sometimes the RPMs would drop back to 500-600 quickly at a stop & sometime slower. When it dropped quickly it seemed to idle weird, maybe a little rough. Bottom line I think I'm not getting enough air @ start up part of the time. Even at idle sometimes. Because pushing on the gas on a TB only opens air, not fuel. TB is basically just an air box.
A question what is involved in cleaning & replacing the IAC?? Anything to watch out for or be aware of??
Thanks Craig

 

The best way to clean the throttle body is remove it, and the IAC motor, from the engine and use a good quality carb cleaner, (not a store brand). By disassembling everything, you can get to, and see, when you have all of the passages clean. GM shop manual says do not move the pintle while the IAC is removed, (it can damage the gears). It's best to replace the IAC if there's a problem, but I have had pretty good luck cleaning the pintle. Don't direct the carb spray at the pintle shaft, the chemical may damage the motor, (plastic parts inside). After you reassemble everything you can do an IAC reset, with a capable scan tool. It will eventually relearn on its own if you don't reset it. The reset just speeds up the process.

Pushing the throttle at start up adds air, but at the same time, throttle position sensor voltage increases which causes the PCM to increase injector pulse width accordingly.

 

So another possibility positioning sensor. I think that is below the IAC motor? I was planning on pulling the T/B today & cleaning it completely checking the PCV & the cap & rotor.
I need to check in on the positioning sensor.
Thanks again & I'll keep chasing this until I get it solved.

 

Well today I cleaned the IAC. It idles better but not the starting issue. I replaced the PCV. I ordered from RockAuto a Delco Cap & Rotor. Will replace it when it arrives. The PCV was original & I have a feeling so are the Cap & Rotor.
Then next week I will take it back to the shop that installed the pump & have them check fuel pressure & leak down. See what they think if the new Cap & Rotor don't resolve the issue.

 

Did you ever find the solution? I have the exact same problem. It will start fine usually, but then every other time it will crank for a few seconds before firing off as if it was not getting fuel or ignition right away. No other drivablility issues, just the occasional start delay.