NEED HELP Crank no start.

[KCstandard]

I'm brand new to this site. I've heard some great things about it so decided to give it a try. My 06 Chevy trailblazer won't start. Came out of a store one day and wouldn't start. Ran normal up to that point. Won't jump start, Will crank. All lights and everything powers on dash. new battery. Changed spark plugs New alternator. New crank sensor and cam sensor. Getting spark. Fuel pump powering on and checked Schrader valve and fuel is priming in the fuel rail. Cleaned mass air Flow sensor

 

[Mooseman]

From the FAQ: Vortec 4.2L I-6

Cranks but won't start

Go through this thread and report back any additional findings and any codes you are getting, if any. Did you check all the fuses?

 

[KCstandard]

Will do. All fuses are good and there are no codes coming up on my scanner.

 

[budwich]

get some starting fluid and spray it into the intake. IF you have what you indicate in terms of conditions, something should happen (ie. engine should do something). IF nothing, then you need to probably do some mechanical sanity checks around compression.

One other thing, if you turn your key to JUST RUN (ie not trying to start), what indicators are showing on the dash? Do you have an after alarm or remote starter installed?

 

[KCstandard]

Check engine light is only indicator shown. No after market. All stock. Sprayed starting fluid and it almost seemed like it wanted to start. But it didn't. But definitely was different reaction that happened after using it. Now leaning towards some kind of fuel problem?

 

[budwich]

you need to check the voltages for the injectors.

 

[mrrsm]

Welcome to GMT Nation...

The Ever-Necessary Triad for ALL Engines to Start and Run Nominally involves:

(1) Fuel
(2) Spark
(3) Compression *** (Often just listed as AIR... But sadly... THAT IS JUST NEVER ENOUGH)

The GM Atlas 4.2L I-6 Engine Design makes checking Compression a Breeze. One of the ways to perform Compression Analyses is to use the "Through the Spark Plug Hole Method" with a Compression Testing Kit (Hoses and Analog Pressure Gauge) available from Amazon and Harbor Freight:

Eric The Car Guy (In his Early Days) describing "How to Perform a 'Dry-N-Wet' Engine Compression Test:

The second, more comprehensive and FASTER way of doing this is to employ an Automotive Oscilloscope to make a non-invasive examination of the Amperage Draw for ALL SIX CYLINDERS. A BNC Connector "Amp Clamp" is the Tool of Choice and it works by clamping it around the Positive Battery Cable and then Cranking Over The Engine (with the Fuel Pump Relay Removed to avoid flooding the Cylinders with Excess Fuel). There are a number of these Oscilloscopes on the Market now via Amazon and eBay worth exploring for Good Performance for Not TOO Much Money.

In "The Relative Compression Test" ... You will be looking for the comparative variations of Amperage Draw for certain Cylinders that causes Low Amp Draw Spikes on Cylinders that have such Low Compression as to require MUCH LESS AMPERAGE due to the absence of Resistant Compression fighting against the Starter Motor Rotation. The Graphing of this signature measures Voltage over Time and in this manner, will provide pin-point observable problems inside certain Cylinder(s).

Scanner-Danner demonstrates "How to Perform a Relative Compression Balance Test with an Oscilloscope" in this Video. Please note that these Oscilloscope Devices ARE AFFORDABLE now with most being MUCH Less Expensive to obtain versus a VERY Expensive Professional PICO Unit: