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01 chev blazer cranks - dont start


LarryGLack
08-21-2007, 08:08 PM
2001 chevy Blazer 6 cyl ran fine - quit on the road, has not fired any cylinder since. 100,000 miles no recent tune up.

Had spark at coil.
pulled cap (flat) it was dirty - cleaned up ok. the rotor was dirty scraped it with knife. Has spark at end of plug wire.

Poured gas into air intake past throttle plate. no joy.(?) Checked fuel pump pressure (62psi) pump runs 2 sec then shuts off. Continues to run while cranking.

checked voltage on injector low side (manifold connector wire from injectors). (only one) it changes from 12v to 0v when cranking.

checked error codes - did have a lean condition noted. This has been showing up off and on for years. Turned off errors, now get nothing on screen but loop not completed yet. I assume (dangerous) that will go away when it starts. But be all that as it may...
1 it seems to have fuel (used top 1/4 of new tank)
2 it seems to have spark
I think it unlikely its out of time, it went from running fine to not fireing any cyl. any time.
The computer is telling the injector to put fuel in, its unlikely all six failed at the same instant. A bad ground would result in the injector control not pulling down to 0 volts.

Hmmmm, it must be really simple, cause I'm totally missing it! Thanks

old_master
08-21-2007, 09:08 PM
At 100,000 miles, plugs, wires, cap, and rotor, (at the bare minimum) should be replaced, (use AC Delco platinum plugs ONLY). Did you check for blue, (not orange) spark at more than one plug? The stuff you found on the contacts of the cap and rotor, is silicone dielectric, put there when it was installed. The dielectric crystalizes when voltage goes through it, (it's supposed to be there). Make sure you use it on the replacement parts.

LarryGLack
08-21-2007, 11:10 PM
Thanks for the reply Old_Master I did only check one plug wire and the spark is yellow, it jumps 3/8 inch. Would that not be enough to make the cylinder fire? It ran fine just a few hours ago... it has given no problems till now...
I'll pick up the cap. rotor and stuff tomorrow and let you know what happens. Thanks for the tip on the silicon.

LarryGLack
08-22-2007, 05:44 PM
sudden stop and no start condition caused by coil wire. I replaced the cap and rotor, checked for spark at the plug and had none. Still worked at the coil. No spark at the end of coil wire next to distributor. The wire was discolored white and slightly powdered (inside the plastic loom) where it bent around the heater hose, when bent further the insulating outer rubber sheath cracked open!

That wire would work when I checked for spark and then quit when I cranked the engine! Several times! Runs and starts just fine again has 62 psi fuel pressure before starting and 54 when running. The fuel pump might be the next project we need to do... but when it starts acting up probably. I understand GM fixed it so we can't just replace the pump - they can get us for more $$ if we have to replace the entire frame and sending unit also. :-(

Thanks again for the help!

old_master
08-22-2007, 07:13 PM
Funny how stuff happens... worked fine... til it broke!

Spark should be able to jump half an inch with a blue spark.

Fuel pressure at 62psi when the pump is running and the engine off is good. It must remain above 50psi after the pump shuts off. Nowhere in the GM shop manual does it say what fuel pressure should be with the engine running, too many variables. My own experience is mid 50's at 650' above sea level.

A dab of silicone dielectric on each end of each wire, and on each terminal in the cap and rotor, helps the connection, and makes it easier to remove the wires the next time.

If you check around on the net, you can find companies that sell the pump separately. Problem is though, the level sender usually takes a crap around the same time as the pump, so you might as well replace the complete module assembly. They come with a new strainer and the O ring seal.

LarryGLack
08-22-2007, 10:10 PM
Heh, yep - its all good til it breaks... the spark out of the coil will jump an inch and snap blue. Starts out yellow when 1/8 inch away though. I guess the voltage goes up the farther it has to jump... seems odd starting yellow when close. the old ones were blue all the way. I had to purchase the silicone grease separate, I thought it would come with the cap, but not today. I always lube the rubber boots and wire connections. I didn't know about using it on the cap connections internally though.... I ' ll just add that to the list of things I don't know. Its getting pretty long.

Thanks..

applecored1
06-01-2008, 02:25 PM
Changed ignition switch and car started. Went back 1 hour later and car started & shut off after 3 seconds. What could it be?

MT-2500
06-01-2008, 05:13 PM
Is the security light on with key on and go off or stay on.

See if it will start with a squirt of carb cleaner.

If so it is a fuel delivery problem.

What is the cranking fuel pressure?

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