I have a 2000 Blazer LT, 4.3 V6, Auto, 120k miles that has been great for me until recently. Currently it will not start, it will crank and crank but not start. I'll begin my story from the beginning and hopefully won't bore you to death. Here's the deal:

Two weeks ago I was going about 50mph and felt a slight loss of acceleration. It was like I let off the gas and was instant but I noticed it. I felt it again the next day twice but it wasn't doing anything else. The next day, it stalled when I was in a parking lot but started right up. I checked all the fluids and it was little low on coolant and transmission fluid. I went to Autozone, had my battery tested and brought the fluids back to spec. The battery tested fine. Now, the next day, the Blazer stalled while I was going about 50mph and I had to pull over, of course I lost all power steering and ABS so that was fun. The car did not start right up like before, it only cranked, but after about ten minutes of waiting, it started up. It died once more on the road before I finally got to another autozone. This time I took the battery out and they tested it fine again. They tested the Ignition module and that also checked out. I bought some ignition cables and changed those when I got home. I also tested the ignition coil with an ohmeter and it was fine (gave me the same readings as a new one I bought so I did not replace it). At this point, the car started up but would die after a few minutes. I replaced the ignition switch and the blazer ran fine until I stopped at Walmart and then it wouldn't start again. It cranked and cranked for four hours but di not start. I got to another autozone in my trusty kia and bought a new coil to test it out, distributor cap and rotor. I tried the new coil and nothing. Then I replaced the rotor and the blazer started up on the first try.

I got home and drove it around for an hour or so, satisfied I went back home. The next day it started up fine and I drove to another store only to have it not start again when I came out. I replaced the distributor cap, bought another rotor from Checker in case the other one was defective, replaced the fuel filter, and nothing.

So Sunday, i went back since I left it there overnight, and was testing the wires for spark, when the battery died. I got it charged at autozone, put it in, and the car started right up. I finished checking the ires for spark and they all gave an orange-ish spark but it was spark so I figured they are at least okay enough to start up. The car then died after about ten minutes but started right up. I replaced the fuel pump relay to see if that would do it. It didn't shut off for the rest of the day/night until yesterday evening when it died at a Checker when I was returning all those parts I didn't need. I got the battery charged again but it would not start. Only cranks.

So that's where I'm at. I have tried everything I can think of except for the ECM, alternator, and changing the plugs. I'm stumped. The fuel pump starts up and everything when I turn the key, I have all lights on my dash. Sorry about the enormous post. I appreciate any ideas. Thanks.

Also, i have not experienced that slight loss of power anymore, and it runs beautifully when it is running. Smoother than ever. it just doesn't start now. I have triple checked the cables, rotor, cap and everything is installed correctly.
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So I got home today after work and the blazer started up on the first try without problems. I have no clue why. I didn't change anything from last night when it was dead to today. I shut it off and started looking at all the fuses, they all look good. I pulled out each "IGN" related fuse (IGN A, B, C, E, there's no D) one by one, attempting to start the car after each fuse was removed. As expected, the Blazer would not turn on in each occasion except for one. When removing the 50A IGN C fuse, the car will start up normally, as if it was never removed. Is this normal, or could it mean that fuse is bad? Thanks again

If you never replaced your fuel pump yet, that could be your issue. Mine never gave me a warning like that, it just died as I was going home from a cruise night.

I would have to agree. Your story sounds very much like mine, except was always happening to my wife. Messed with it for several weeks. Final indication was erratic fuel gauge. I finally changed the pump assy. and have not had a problem in over a year.

Yesterday, when it started up after sitting all day, I turned it off and then it wouldn't start again. I began checking for spark again and once again the battery died. I took it to Autozone and the battery was pretty much dead so I bought a new one. Went home, installed it, and the blazer started right up. I ran it a little last night and started it and shut it off many times and it was behaving well. Today I left it home since I didn't trust it to get me to work, but when I got home I ran it probably ten miles to a few stores to test the stopping and starting and it has not shown any problems. Hopefully it was just a bad battery after all (replacing the burnt rotor, cap, wires, and fuel filter probably helped too) but I don't have my hopes up too high since it may shut off at any moment still. I'll give it a week of running it before giving it a thumbs up. I'm going to change the plugs tomorrow too since they probably never have been changed. I'll post back with results.

I had a simular intermitent problem that turned out to be the distributer itself. Just something else to consider if the problem persists.

Hello,
I had the same thing happen to me with my Chevy truck and it turned out to be the fuel modulator. It took the mechanic a few days to figure it out because it didn't happen all the time. I don't know if this will help,but that was the problem I had.

it isnt ur battery. i drove with a bad fuel pump for over a year and a half. sputtering stalling all the above. the cold was the hardest. i had the original pump still in mine. their cheap to replace if you look in the rite spot. i mean the pump only not the sending unit

Yea, I figured it wasn't the battery but it was just weird that on two different occasions, it started right up with a fresh battery. It died again a couple days ago and the fuel pump stopped buzzing so I'm hoping that's what it is now. I gave the fuel tank a couple hits and tried to start it and it started up and died after a couple seconds so I'm pretty sure it's the pump. I ordered one off ebay for around 80 bucks compared to the one at Autozone for $270+. I figured I only need another year or two from the blazer but it will probably last a bit longer. I'm waiting for it to ship so once I get it and throw it in, I'll let you guys know how it turned out. Thanks

Turned out to be the fuel pump. That rearmost harness is a lot of fun to bolt back on. Thanks for the help.

dont go cheap on your fuel pump. You say you only need a year or two? Well plan on replacing it again!! Cheap is no good when it comes to a fuel pump.