No spark at the coil


Asked by Feb 04, 2014 at 12:10 AM about the 1999 Chevrolet Blazer

Question type: Maintenance & Repair

1999 blazer s10 4.3 automatic losing spark.  I found no spark at coil. I replaced crank sensor and ignition module and coil, spark plug and wires. I replaced the the distributor which includes cam sensors new cap and rotor. The distributor was set with #1 piston tdc and rotor pointing to #6 on distributor housing and harmonic balancer 2 lines pointing to timing chain plastic cover alignment tabs.
Truck started and ran like a brand new truck for about 20 minutes [no spark from coil]. Next day it  started up again after driving for about 40 minutes , I got stuck on the highway with no spark at coil. Got tow home and it started back up again in the driveway.
The next day I left it in park running idle and  it  turned  off  by itself.  Again it had no spark at coil.  
Visually checked everything for lose connection and found none, but truck started again and ran for other  20 to 30 minutes [ no spark at coil].
This time it does not start at all.  Could this be a computer issue?
PS not getting any codes or key security light issues.
I also used my 1997 s10 4.3 pickup truck  and swapped  out  crank sensor,ignition module and coil, distributor and blazer still does  not  start, but pickup starts fine with all new parts that  I had installed on the blazer.

15 Answers


read and switch some relays around in fuse box. look for bad or loose connections under hood AND frayed wires,,, MAF,,,,connections PCM? maybe! seems when it is closed loop you have trouble

5 of 5 people found this helpful.

i would make sure the wires to the coil arn't messed up. 2 possibilities i'm thinking is the ign switch or PCM


I already checked connections and fuses, swapped relays. I did the wiggle wires test. Didn't think it could be ignition switch. I will further check wiring and ignition switch,PCM. I found on the web a site how to test sensors ( this helped and I did found power going to sensors according to procedures.

3 of 3 people found this helpful.

Did you ever find the cause of this? My blazer is doing the same exact thing. I'm on coil pack number 4 in about a month and a half. 1999 Chevy Blazer 4x4 4.3 Vortec I have replaced the following parts: Fuel filter Distributor Cap Rotor Button Spark Plug Wires Crank Shaft Sensor Cam Shaft Sensor Ignition Control Module x2 Oxygen Sensor Battery Coil Pack x3 Cleaned the throttle body, Idle Air Control Valve and EGR valve Fuel Injector cleaner x2 Had fuel pressure tested and it tested perfectly. Fuel pumps comes on, primes and shuts off This morning it died on me and wouldn't start back up, went and got another coil pack because I wasn't getting any fire and it ran enough to get it home. The O2 sensor had came in the mail so I went ahead and put that on as well. Now when you are driving it spits and sputters and sometimes dies. It idles at .6 which is where it has always idled and from what I have researched is where it should be for this model. The engine is quiet and it does not blow black smoke, smell like rotten eggs, the cat does not glow red, the oil and transmission fluid both look and smell normal. I am at a complete loss on how to go any further. There are no codes showing at this point. Before changing out the coil pack again, it would just die when coming to a stop light or if you left it sitting still and running. But 3 coil packs in about a month and a half, something has to be messing them up. Also when I had the throttle body off I could see down inside the top of the motor where the spider injectors are and it was completely black inside except for a small gold spot to the right, which from what I've read means there is a fuel leak. Can anyone please give me some ideas on where to go from here? Update : It will not start again, no fire at the coil pack, putting coil pack number 4 on .

5 of 5 people found this helpful.

Check the voltage on the pig tails to the ignition module and coil with a digital multi meter it cold be low voltage if so Change it

4 of 4 people found this helpful.

I'm not saying that this will help you out,but3 out of 5 4x4 blazer I have had lately,was ignition switch NOT tumbler, but the wiring harness switch, it takes about a hour for a beginner, and 30 to 45 for e experienced mechanic this part runs about $ 50. At local parts store, the quality of aftermarket parts are a bit cheesy,but I have bad goodluch with Oriellys partz& help. I hope this cures your problem I have went to auto parts junk yard & removed one from a total wreck, and it worked great price was $ 10.. The damage on vehicle showed it was running when it hit a ditch. I went home & tur ex switb on for twenty mins & off for 30 to 50 seconds,and it fired right up!! U can call itluck ifu like but I a.Running again for less. Than$ 45.00. Good luck.


Our 1999 GMC Suburban is doing the same as well. Our mechanic said it could be the engine control unit ( computer ). We replaced engine control module, coil, & crankshaft sensor. We now have to replace the pick up coil. There may have been a power surge, ( think that's what he called it). Well, anyway, those parts were affected . Good luck!!


I changed ignition switch, altanaor, ignition module, crank sensor,altanorand bunch of other stuff my blazer won't start it was working just fine no hiccups and I went to start it no start

2 of 2 people found this helpful.

Is the security light on?

3 of 3 people found this helpful.

I have a 99 Blazer 2 door 4 wheel drive just put a new motor in it now have no spark check every wire on it twice can't figure it outit ran before I change the motor LOL

6 of 6 people found this helpful.

I have a 99 Blazer 2 door 4 wheel drive just put a new motor in it now have no spark check every wire on it twice can't figure it outit ran before I change the motor LOLnow I have no spark coming out of the coil have juice everywhere with test light

5 of 5 people found this helpful.

Jeff , I was going thru this forum and seen this old problem , I was thinking g bout how Cheated I was when my blazer quit running. Again I'm very glad I haD your help. I replacing that switch has been a job saved , thank you again.. still running strong!!best 45 bucks ever spent!!

5 of 5 people found this helpful.

Hi dan did you check for power going into the coil ?

5 of 5 people found this helpful.

I got a 1995 s10 blazer im getting power to coil bit its not getting spark when i start the engine my test light just stays constantpower ive changed everything im stumped

1 of 1 people found this helpful.

Hello Wes, I don't know how mechanically inclined you are , but seems if you have power at coil , and you have replaced everything ,turn ignition switch to run position , And if you have a remote starter switch ,try to see if it will run by starting it that way., I have done it by using old broke screwdriver. NOTE !! If you are not familiar with this method DONT TRY IT! A remote starter switch at parts store is generally around 12 to 15 dollars. A real handy tool to have ! You can go under right front fender to get to starter , connect one lead to purple wire & other to large main power cable from battery . Good luck & be careful. Use parking brake if manual trans.

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