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No Spark?

Tiny
JOHNPUNDERWOOD
  • MEMBER
  • 1999 GMC SUBURBAN
  • V8
  • 2WD
  • AUTOMATIC
  • 145,000 MILES
My 99 Suburban won't start - it died on I-30 in Dallas, TX. It cranks but has no spark. (Spark test done) I changed the plubs, wires, distibutor cap & rotor and have had the Ignition Module checked. Do you have any other ideas?
Monday, December 7th, 2009 AT 11:23 PM

11 Replies

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
No snapping blue spark continue to troubleshoot the ignition system-power input to the coil/coil packs,coil's resistances,distributor pick-up coil, ignition control module, cam and crank sensors and computer

This guide will help

https://www.2carpros.com/articles/how-to-test-an-ignition-system
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Tuesday, December 8th, 2009 AT 4:33 AM
Tiny
JOHNPUNDERWOOD
  • MEMBER
  • 3 POSTS
I have now checked the Ignition Coil and the only thing left that I can figure is that it is the Ignition crank sensor. Is there any way to test/ check this before purchasing a new one?
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Wednesday, December 9th, 2009 AT 8:16 PM
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
The CPS is tested with an ohmeter. Generally the sensor will read between 300-350 ohms. Also, check to see that the pick-up magnet is centered in the sensor housing. It should be positioned perpendicular to the flywheel teeth, with an air gap of 0.020-0.060 in. An adjustment to the high side, say 0.040-0.060 in. seems to work best.

This video will show how to replace the crankshaft sensor.

https://youtu.be/sKo7xRWVNqY

Please run down this guide and report back.
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Wednesday, December 9th, 2009 AT 8:27 PM
Tiny
HAWK1061
  • MEMBER
  • 2 POSTS
  • 1999 GMC SUBURBAN
  • V8
  • 4WD
  • AUTOMATIC
  • 120,000 MILES
This is the 7.4l V8, K2500.

Tested for spark, no joy. My question is how do I determine if the ignition module is bad, if there is a problem with the coil, if the distributor/rotor is shot, etc? I removed ignition module and coil, took to a local parts store who 'checked' module and said was bad. I asked them to check the new module to verify it was good, he tested and it was bad. Tested another module from their stock, was also bad. I assume the counterperson had no clue how to test. Can I test it and if yes, how?

Same question on the coil, how do I know if it's shot or good?

Thanks guys.
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Friday, July 17th, 2020 AT 11:31 AM (Merged)
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Hello, With a distributor ignition, I take the coil wire loose from the distributor, hold close to engine ground, have helper crank it, while I watch for spark to jump from the coil wire. If there is spark, but, nothing at the plugs, I change out the cap and rotor. If no spark and the coil wire is good, I check for input and output signals from the ignition module, if there is input and no output, I suspect the module. I also check primary circuits to the coil, small wire connector. There is probably an ohms spec for your coil, don't have it in front of me. I probably over-simplified just a little.
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Friday, July 17th, 2020 AT 11:31 AM (Merged)
Tiny
HAWK1061
  • MEMBER
  • 2 POSTS
Thanks jdl. Turns out it was the ignition module. It starts now but.

While working on the truck I had the battery disconnected. Once I got everything put back together (say 2 days without battery power), I was able to start it up VERY easy (like the settings were lost and so it was running on default settings). Over the next few days, it seems that sometimes it takes two or more cranks to start, it seems to run rough at first (sometimes) and I'm smelling unburned gas in the exhaust. There is no check engine light on which I would expect to see if there were some serious problems. The air filter is completely new so it's not a lack of air getting in. What would cause it to run rich in this day of electronic engine controls? And shouldn't a rich/unburned gasoline condition trigger a DTC?

One final observation. When I took off the air intake system while working on the truck, I noticed that the bottom of the inside of the throttle body has what appears to be a brownish/yellowish stain. At first I thought it was oil and tried to wipe it off, but it's not liquid, it appears to be solid. Almost seems like gasoline that has pooled over time and turned to laquer. What is this a sign of?

Thanks for your help.
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Friday, July 17th, 2020 AT 11:31 AM (Merged)
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
I'd want to see what the 02 sensor/s are doing and look at the fuel trims. You can put a fuel pressure gage on it, do some testing.
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Friday, July 17th, 2020 AT 11:31 AM (Merged)
Tiny
CRAZYCUTTER34
  • MEMBER
  • 1 POST
  • 1998 GMC SUBURBAN
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 225,000 MILES
Driving down road 98 vortec 5.7 just died and quit running, now cranks cranks cranks then slow crank like it could be timing, im not getting any spark but am getting fuel, I replaced the crankshaft sensor and the distributor is a few months old
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Friday, July 17th, 2020 AT 11:31 AM (Merged)
Tiny
THIS IS MIKE
  • MECHANIC
  • 686 POSTS
Hello,

This sounds like the PCM has gone out but to be sure lets run the codes these guides will help us fix it.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

and

https://www.2carpros.com/articles/how-to-test-an-ignition-system

Please run down these guides and report back.
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Friday, July 17th, 2020 AT 11:31 AM (Merged)
Tiny
JCDOWLING
  • MEMBER
  • 1 POST
  • 1991 GMC SUBURBAN
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 175,000 MILES
Was running great moved it to back yard unhooked small trailer with small raft and went to move the burb outta the yard, wont start. Cranks just fine, looked at fuel line, is pumping fuel out of the line no fuel coming out the jets, took a sparkplug and touched it to housing no spark. What could it be?
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Friday, July 17th, 2020 AT 11:34 AM (Merged)
Tiny
ISLAND_PRIDE71
  • MEMBER
  • 62 POSTS
No snapping blue spark continue to troubleshoot the ignition system-power input to the coil/coil packs, distributor pick-up coil, ignition control module, cam and crank sensors-
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Friday, July 17th, 2020 AT 11:34 AM (Merged)

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