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95 Blazer 4.3W Vortec: NO SPARK


Chaindrive
12-03-2005, 10:38 PM
Hi folks! I'm brand-new here and I sure wish I'd done a Yahoo search and found this site months ago (this is "Analog-a-holics Anomymous", isn't it?).

My name is Scott and I have been an Analog-aholic since my first 64 Chevelle super sport back in 1977. I am addicted to simple, sensible vehicles that work or are easily fixed when they don't. That is why I hate this vehicle; a 95 S-10 Blazer (which my wife loves and is the only 'brand-new' vehicle we've ever purchased... and ever will). I would personally rather hand-crank a model T on a cold January morning than work on one more Digital Age computer-chip-on-wheels-piece-of-plastic-made-in-anywhere-except-the-USA-piece-of-junk like this.

Several months ago my wife's Blazer died a few miles from our home. My nephew dragged it back here and I quickly discovered one of two 20 amp ignition fuses in the fuse box had blown. Easy fix. For about 15 minutes of driving. At which point it blew again. This time, I could feed it an endless supply of fuses (even 30 amp) and it would blow them instantly. I thought: "Something is obviously getting hot and then drawing too much current." This was confirmed (in my mind) when the Blazer would once again start and run fine after letting it cool down for an hour or two... for about 15 more minutes.

My first suspects were the coil and coil module. They tend to get hot in use and are mounted with heat sinks. So I replaced them to no avail. I also checked all connections I could as well as grounds in general. Nothing. I bought a used ecm at the junkyard and it 'cured' the problem 99%. That other 1% was an occassional micro-hiccup when a bump or RR tracks were run over. (Uh Oh). No trouble code ever. This progressed to being more and more frequent over the next couple months.

I began really looking hard for a loose connector, bad or burnt wire, etc. I began to systematically replace the crank sensor, the cam position sensor, then the fuel pump, spider CPI unit, plug wires, cap, rotor, and plugs.

I did the fuel pump (and sending unit) because a very bad local garage had recently replaced it while I was on the road (truck driver) and it went out while my wife was at the grocery store. They botched the job badly, breaking a vent valve, not hooking up vent hoses, and failing to seal or replace the sending unit o-ring so it leaked gasoline all over my garage floor after filling it up (and my wall-mounted heater was going!). They also did something to totally fry a 6-month-old battery..? My wife and nephew said it was still cranking strong even as it was being towed away. It was beyond dead when I picked the vehicle up (they wanted to sell me a new battery for $80 of course. Yeah, right.) The guy at Walmart said I must've done something bad to it to have dead-shorted it internally like that (his diagnosis), but gave me a new one under warranty for free...

Now, with mystery electrical gremlins all of a sudden since then, I wasn't trusting a thing those guys did. Besides, I don't want my wife and kids in a vehicle constantly leaking gasoline when full.

Nothing helped, though, and it kept worsening. Soon my wife got in it for work, drove a hundred yards to the end of our drive, came back and drove my Chevy tonner instead, claiming the Blazer was now running so badly she was afraid to drive it. I got in it to drive into my shop, but it was now DEAD ignition-wise. Cranked real well, but zero spark.

Since a used ecm almost 'cured' it, I went to NAPA and told Darrin to order me a brand-new one. Turns out the company they deal with needed my old one first to rebuild... "OK, here it is." A month later, my new computer arrived.

Today, I went to install it and discovered a sticker on the bottom saying I was required to transfer my old "knock module" from my original computer to the inside of this new one.... That would be a pretty neat trick since the morons who applied that sticker already HAD my entire old ecm and had never said a word to either Darrin or me to open the computer and remove the knock sensor before sending it to them to (supposedly) be 'rebuilt' and "flashed"...

I did still have the junkyard computer, so Darrin said to go ahead and use the "knock module" from it and he would call 'the morons' on Monday about getting my original "knock module" back. It would be warranted for me no matter what happened.

Trouble is, NOTHING happened. Still NO SPARK. So I put the old coil and module and crank sensor back on. Still no spark. The fuses are not blowing. No fault codes are being registered. Everthing is new. No spark. No apparent problem.

While waiting for the computer, I began seeking advice from everyone I respected. The most common line (next to "Good luck you poor so-and-so. Glad its your headache and not mine") was: "You've got a bad ground somewhere." So I re-do every stinkin' ground and connection I can locate. I even run NEW grounds using 8-gauge wire from the battery to the firewall, block, frame, and radiator support just to double-darn make sure it wasn't a lack of ground...

I give up. I'm absolutely out of ideas and no one,even the [gasp of total desperation] Chevy dealer, wants anything to do with it or will guarantee they can diagnose or fix it.

This vehicle is a garaged-nightly, babied, cream-puff with only 80K miles by my wife. It is a paid-for P.O.S. that owes me either several thousand more miles or a heckuva weenie roast when I burn the stinkin' thing.

I have to go open the hood on my 69 Camaro every few minutes when working on this Blazer just to reassure myself what a real engine compartment and engine should look like...

Anybody here care to take a stab at what is wrong? You could not possibly do any worse than me, so don't be afraid of being wrong. I could actually use a few wrong guesses, too, I think; just to make me feel a little less stupid.

Thanks and pleased to meet you! Scott

Chaindrive
12-04-2005, 09:25 AM
I have been searching through the forum for similar problems and have come to the conclusion that there are alot of Blazers sitting idle because of similar unsolved problems. If any of them ever were resolved, no follow-up posts were made.

I have gleaned a little info: The ecm will not cause a lack of spark? That could be good news and allow me to check test-able components only since there is no way to test an ecm except replacement I'm told. It seems everyone suggests the crank sensor, coil module, and/or coil as the places to look.

I have already replaced all of these (twice now; even going back to the old ones after the new ecm failed to do anything).

I am now trying to find a schematic showing all wiring for the ignition circuit and information on how to test for proper resistance/voltage values at each component with the key in both 'start' and 'run' and 'off' positions.

I am also considering tearing the dash and steering column apart to check for bad wires coming out of the fuse block and ignition switch. What a nightmare that might be... But recalling how it blew fuses to begin with (ecm #1 ; the original); did NOT blow fuses with ecm #2 (but progressed from occassional jolted "hiccup" to dead ignition over several weeks) makes me wonder if a melted wire behind the fuse block finally gave way. I have juice both in and out of both ignition fuses, but that doesn't mean it goes any further than that. I need to know where that juice is supposed to go from there (which ignition component and wire).

I'm desperate for a little advice here, guys.

It simply makes no sense. There are only a few components in the ignition circuit. SOMETHING is not working, yet everything except the entire wiring harness and ignition switch have been replaced.

Can I truly rule out the ecm (this one is new and is ecm #3)? It may be a faulty design and overly-complex method of delivering a simple spark, but it is STILL just a circuit and has to follow rules of logic.

Your thoughts would be greatly appreciated!

fun2b1
04-11-2008, 06:48 AM
looks like we can add you to the growing list of people who didn't post a follow up:-(

ZL1power69
04-11-2008, 01:09 PM
Thread is over 2 years old. Please refrain from posting in old threads.

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