I have a 2003 trailblazer 4.2 l. I stopped at the store and when I came out it wouldn't start again. I've already changed the fuel pump and fuel filter on it, only to find out it's not firing now. What are some things that would make it suddenly stop firing?
Not firing
- Thread starter TBJENN
- Start date
christo829
Member
Most likely suspect is the ignition switch. Fairly easy fix, and relatively inexpensive, but if you do this, make sure it's an AC Delco switch, and definitely don't get Dorman.
Is it cranking and just not firing?
If it's not cranking, ignition switch or starter/starter relay circuit need to be checked.
If it's cranking and not firing, you need to check for fuel and spark.
When you first turn the key to "run" (not start), do you hear the fuel pump prime for about two seconds?
If not, check the fuel pump circuit to make sure the fuse isn't blown and that it's getting power. If it's not getting power, that could point to the switch or fuse. If it *is* getting power, it's always possible you've gotten a bad pump.
If you've got fuel delivery, then you need to check for spark.
Got any codes?
Good Luck!
Chris
Is it cranking and just not firing?
If it's not cranking, ignition switch or starter/starter relay circuit need to be checked.
If it's cranking and not firing, you need to check for fuel and spark.
When you first turn the key to "run" (not start), do you hear the fuel pump prime for about two seconds?
If not, check the fuel pump circuit to make sure the fuse isn't blown and that it's getting power. If it's not getting power, that could point to the switch or fuse. If it *is* getting power, it's always possible you've gotten a bad pump.
If you've got fuel delivery, then you need to check for spark.
Got any codes?
Good Luck!
Chris
It is cranking but not firing. I just changed the fuel pump. The old one would kick on when you turned the key on but since I've changed them, the new one won't. I have to change the harness to fit the new pump also. If I put volt meter on it, only one wire reads 4.99 volts.
It is cranking but not firing. I just changed the fuel pump. The old one would kick on when you turned the key on but since I've changed them, the new one won't. I have to change the harness to fit the new pump also. If I put volt meter on it, only one wire reads 4.99 volts.
That is quite likely the fuel tank level sensor circuit, not the pump power.
The pump power will only be there for two seconds or so when the key is first turned on, or the truck is running or cranking.
That makes sense. Do you have any idea where I should start checking for the firing problem? What would make it suddenly stop firing after I turned it off at the store?
The Ground at G107 services the Left Turn Signal, the Left Headlight AND the Fuel Pump Relay. Cleaning the surfaces and applying Dielectric Grease and re-attaching Ground #107 won't hurt. See the Diagram in Post #5 of THIS Thread:
gmtnation.com
Also... The Quickest way to Eliminate most "Electrical Problems" from your Diagnostic Tree is to get a Can of Starter Fluid Spray and after pulling off the Air Resonator from the Throttle Body, have a Friend ensure the vehicle is in PARK and then turn the Ignition Key to Start/Run. While the Motor Cranks Over... You should spray SMALL amounts of Starter Fluid into the Intake via the Throttle Body "Mouth".
Make certain to "Pull the Fuel Pump Relay" first though, as the idea here is to strictly test the Electrical and Electronic side of these issues. After that, the Engine SHOULD come alive if all of those other 'EE Things' are nominal. If the Motor Fires up during this brief "Sprayed Fuel Injection", then you can isolate the problem as involving the Ignition Switch on down and and throughout the entire Fuel Pump Power Circuit (which also includes Anti-Theft issues as well) and dial in on it this way. Keep an ABC Fire Extinguisher close at hand whenever using this Volatile Stuff.
THIS next Lengthy Thread is just about an "On Topic" as you can get for "It Cranks... But it Won't Start..." issues. Notice the conspicuous and valued presence of @christo829 early in that discussion, too. :>)
gmtnation.com
Electrical Ground locations
While troubleshooting a bad ground I came across some scans of the service manual regarding electrical ground locations for our platform posted on another site. This includes both short and long wheel base, as well as both 4.2L and 5.3L. Credit goes to Wex...
gmtnation.com
Also... The Quickest way to Eliminate most "Electrical Problems" from your Diagnostic Tree is to get a Can of Starter Fluid Spray and after pulling off the Air Resonator from the Throttle Body, have a Friend ensure the vehicle is in PARK and then turn the Ignition Key to Start/Run. While the Motor Cranks Over... You should spray SMALL amounts of Starter Fluid into the Intake via the Throttle Body "Mouth".
Make certain to "Pull the Fuel Pump Relay" first though, as the idea here is to strictly test the Electrical and Electronic side of these issues. After that, the Engine SHOULD come alive if all of those other 'EE Things' are nominal. If the Motor Fires up during this brief "Sprayed Fuel Injection", then you can isolate the problem as involving the Ignition Switch on down and and throughout the entire Fuel Pump Power Circuit (which also includes Anti-Theft issues as well) and dial in on it this way. Keep an ABC Fire Extinguisher close at hand whenever using this Volatile Stuff.
THIS next Lengthy Thread is just about an "On Topic" as you can get for "It Cranks... But it Won't Start..." issues. Notice the conspicuous and valued presence of @christo829 early in that discussion, too. :>)
Cranks but won't start
When I turn the key on my 2004 trailblazer it will not start.Just keeps cranking.I have replaced the ignition switch and it still won't start.Could anyone please direct me on common issues that may be causing my trailblazer to not start?
gmtnation.com
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