My 04 trailblazer abruptly died on the road. Took it to a shop and came out with a new fuel pump but still turns over but won't fire even with either. Checked all the standard fuses and relays. Put a new ECM in. Relearned the security system and still no fire. Got another new ecm with security, VAT system disabled. Still turns over but won't start. Not wanting to spend much if anything more but not sure what to do if I did.
Died and won't start.
- Thread starter Demitch
- Start date
Welcome to GMT Nation...
Start by Performing some "Basics Tests":
Air:
If the Engine cannot develop sufficient Compressive Force to SQUEEZE the Ingested Air & Fuel Vapor Mixture... then the Engine WILL Not Ignite the Mixture with enough Power to Run. So, Perform an Engine Compression Test as per THESE Instructions:
troubleshootmyvehicle.com
troubleshootmyvehicle.com
Electrical Shorts:
Engine Harnesses that have been Chewed Through by Rodent Infestations under the hood can present with WEIRD NO START and SUDDEN ENGINE STOP conditions that even Very Experienced Shop Mechanics may overlook.
Check the entire engine area for any signs of Mice Nesting, Feces Droppings and Dried Urine being present. If you find ANYTHING like this... Cover your Face (N-95 Mask) & Hands (11mil Nitrile Gloves) with Protection from getting a HANTA Virus Infection from handling or cleaning up such things. Use a BRIGHT Flashlight to Locate any Damaged or Shorted Wiring and perform Solder & Sealing Wiring Repairs. Be Very Fastidious.
Spark:
Next, ...Visit THIS Link and obtain a Can of Starting Fluid Spray:
Remove the Resonator Box and while someone Cranks Over the Motor using a FULLY CHARGED BATTERY... Spray a VERY SMALL AMOUNT of Starting Fluid into the Throttle Body Inlet. If the Engine briefly "Fires Up"...then you will have Eliminated most of the possible Electrical Problems from the actual Solution.
However, if you get NO SPARK Response... Remember that only One, Single Coil with a "Dead Short" on the GM LL8 4.2L Engine... is enough to PREVENT the Motor from Starting. Follow THESE Simple Procedures for Testing ALL of the COPs:
easyautodiagnostics.com
Fuel
Is the Fuel Tank EMPTY? Remember that the Fuel Gauge on the IPC can be Wrong...and with Gas Prices being what they are, Fuel Thieves are always Out & About and WILL use Tactics like Pouring Water into the Tank to Raise the Fuel Up High Enough to Suction Out Fuel. So... Don't Overlook the Obvious.
Next, Check for Fuel Pump Circuit Activity by having someone Turn the Ignition Key to the "ON" Position while you LISTEN for the Fuel Pump to Prime for only 3-5 Seconds. Do this several times to Confirm that the Ignition Switch is also NOT part of this Problem as long as the Pump tries to Prime after each Key Turning Event.
If the Fuel Pump Responds... move on to performing a Fuel Pressure Test (2002-2004 Chevrolet Trailblazer 4.2L) as per THIS Video:
...and for Later Model GMT360 SUVs with the "Return-less" Fuel Line Delivery to the Fuel Rail... THIS Clever Dude came up with the means to Test the Fuel Pressure in this manner:
Engine Timing:
If the Crankshaft Sensor (CKP) has Failed or if the Camshaft Sensor (CMP) and the (CKP) cannot reconcile their positions with each other due to an Over Stretched Timing Chain... then the Fuel Air Spark Events will NOT be IN TIME with each other well enough to allow the Motor to RUN. Period. Check out THIS Topic for Testing the (CKP) Sensor... HERE:
easyautodiagnostics.com
Start by Performing some "Basics Tests":
Air:
If the Engine cannot develop sufficient Compressive Force to SQUEEZE the Ingested Air & Fuel Vapor Mixture... then the Engine WILL Not Ignite the Mixture with enough Power to Run. So, Perform an Engine Compression Test as per THESE Instructions:
How To Test Engine Compression (2002-2009 4.2L Chevrolet TrailBlazer, GMC Envoy)
How To Test Engine Compression (2002-2009 4.2L Chevrolet TrailBlazer, GMC Envoy)
Electrical Shorts:
Engine Harnesses that have been Chewed Through by Rodent Infestations under the hood can present with WEIRD NO START and SUDDEN ENGINE STOP conditions that even Very Experienced Shop Mechanics may overlook.
Check the entire engine area for any signs of Mice Nesting, Feces Droppings and Dried Urine being present. If you find ANYTHING like this... Cover your Face (N-95 Mask) & Hands (11mil Nitrile Gloves) with Protection from getting a HANTA Virus Infection from handling or cleaning up such things. Use a BRIGHT Flashlight to Locate any Damaged or Shorted Wiring and perform Solder & Sealing Wiring Repairs. Be Very Fastidious.
Spark:
Next, ...Visit THIS Link and obtain a Can of Starting Fluid Spray:
Remove the Resonator Box and while someone Cranks Over the Motor using a FULLY CHARGED BATTERY... Spray a VERY SMALL AMOUNT of Starting Fluid into the Throttle Body Inlet. If the Engine briefly "Fires Up"...then you will have Eliminated most of the possible Electrical Problems from the actual Solution.
However, if you get NO SPARK Response... Remember that only One, Single Coil with a "Dead Short" on the GM LL8 4.2L Engine... is enough to PREVENT the Motor from Starting. Follow THESE Simple Procedures for Testing ALL of the COPs:
How To Test The Ignition Coils (2002-2004 4.2L Oldsmobile Bravada, 2004-2007 4.2L Buick Rainier)
GM 4.2L Index of Articles
Fuel
Is the Fuel Tank EMPTY? Remember that the Fuel Gauge on the IPC can be Wrong...and with Gas Prices being what they are, Fuel Thieves are always Out & About and WILL use Tactics like Pouring Water into the Tank to Raise the Fuel Up High Enough to Suction Out Fuel. So... Don't Overlook the Obvious.
Next, Check for Fuel Pump Circuit Activity by having someone Turn the Ignition Key to the "ON" Position while you LISTEN for the Fuel Pump to Prime for only 3-5 Seconds. Do this several times to Confirm that the Ignition Switch is also NOT part of this Problem as long as the Pump tries to Prime after each Key Turning Event.
If the Fuel Pump Responds... move on to performing a Fuel Pressure Test (2002-2004 Chevrolet Trailblazer 4.2L) as per THIS Video:
...and for Later Model GMT360 SUVs with the "Return-less" Fuel Line Delivery to the Fuel Rail... THIS Clever Dude came up with the means to Test the Fuel Pressure in this manner:
Engine Timing:
If the Crankshaft Sensor (CKP) has Failed or if the Camshaft Sensor (CMP) and the (CKP) cannot reconcile their positions with each other due to an Over Stretched Timing Chain... then the Fuel Air Spark Events will NOT be IN TIME with each other well enough to allow the Motor to RUN. Period. Check out THIS Topic for Testing the (CKP) Sensor... HERE:
How To Test The CKP Sensor (2002-2004 4.2L Oldsmobile Bravada, 2004-2007 Buick Rainier)
GM 4.2L Index of Articles
Last edited:
Mooseman
Moderator
Compression would not cause a sudden engine stoppage. We have an extensive thread in the FAQ on crank no start issues. Post #5 gives initial flowcharting and what to check.
Cranks but won't start
Cranks but won't start
Mooseman
Moderator
Since his is an 04, he has the return system and the test post next to the filter under the truck but you could still use this method instead of crawling under the truck. I wish I had found this way for my 07 before I broke the test port and had to replace the whole fuel rail. I should cut off the inlet pipe from my old rail and use that in the future.
