NEED HELP Trailblazer cranking but won't start

keile

Original poster
Member
Jan 19, 2017
6
Ohio
Hello everyone. Last Thursday on my way home my trailblazer stalled while stopped pulling out of a store parking lot. Tried starting it back up and it would just crank. Tow driver got it to my house and hooked a power pack up and it started up again. Once he unhooked it, it stalled. I purchased a new battery the other day. Replaced the battery, it started up but stalled after about 5 seconds. And again, won't start back up. Not sure if it was coincidence, but that same day on my way to work, my left blinker was flashing fast. But eventually went back to normal later on. Sensors? Regulator? Pump? Starter? Ignition? Not sure where to start without dumping hundreds of dollars on parts that it may not need. Thanks for any ideas everyone!
 

Mounce

Member
Mar 29, 2014
13,667
Tuscaloosa, AL
Fuel pump suspect. Hyperflash likely unrelated.

When you turn the key to the run position do you hear the fuel pump kick on? Should hear a little motor whine for about 5 seconds after key is turned on.
 

keile

Original poster
Member
Jan 19, 2017
6
Ohio
That's one of the possibilities that I was thinking. I'm currently at work but will check again if I can hear the pump once I get home. I was certain I heard it yesterday when I tried starting it again. Will it still start here and there even with a bad pump like it did? Thanks for the reply. BTW, it's a 2007 4.2 with just a little over 80k miles.
 

Mounce

Member
Mar 29, 2014
13,667
Tuscaloosa, AL
Yes. Completely possible, a lot of times you can get out and kick the tank and make it act right lol. Either way, check for pump sound, then check fuel pressure if it is indeed running because even then it might not be outputting the needed pressure. If that checks out, we'll have to look somewhere else.
 

mrrsm

Lifetime VIP Donor
Supporting Donor
Member
Oct 22, 2015
7,639
Tampa Bay Area
And... Way up at the Front End... Try giving a Look-C at the Combination MAF (Mass Air Flow) and IAT (Inlet Air Temperature)---Sensors for a Goofy Connection if it was recently touched during the replacement of the Air Filter and perhaps got loosely connected.

The MAF Sensor; positioned at the beginning of the incoming air-flow could be dirty enough to require a careful cleaning with CRC MAF Sensor Spray as it measures incoming air using "Weight-Per-Time" in concert with the IAT Sensor advising on how hot or cold the air is because its density and weight changes as a function of temperature. This data is fed to the PCM and while using other sensor data... it manages the Fuel Trims as it tries to achieve a perfect "Stoichiometry" of the Air-Fuel Ratios and keep them adjusted all the time. If it cannot provide the right information... the stalling can happen because of the A-F imbalance when the throttle elevates.

If one or more connector wires to the MAF/IAT are either, Loose, Cut or Damaged... then the sudden break in connectivity could make the engine stall out. Checking these sensors will be an essentially painless and inexpensive process. But… If you can get a scanner on your vehicle and jot down all of the Codes and post them up here… it would help to eliminate any mysteries and get to the bottom of what is really happening right away. Right now... Its just Wild Guess Work.
 
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keile

Original poster
Member
Jan 19, 2017
6
Ohio
And... Way up at the Front End... Try giving a Look-C at the Combination MAF (Mass Air Flow) and IAT (Inlet Air Temperature)---Sensors for a Goofy Connection if it was recently touched during the replacement of the Air Filter and perhaps got loosely connected.

The MAF Sensor; positioned at the beginning of the incoming air-flow could be dirty enough to require a careful cleaning with CRC MAF Sensor Spray as it measures incoming air using "Weight-Per-Time" in concert with the IAT Sensor advising on how hot or cold the air is because its density and weight changes as a function of temperature. This data is fed to the PCM and while using other sensor data... it manages the Fuel Trims as it tries to achieve a perfect "Stoichiometry" of the Air-Fuel Ratios and keep them adjusted all the time. If it cannot provide the right information... the stalling can happen because of the A-F imbalance when the throttle elevates.

If one or more connector wires to the MAF/IAT are either, Loose, Cut or Damaged... then the sudden break in connectivity could make the engine stall out. Checking these sensors will be an essentially painless and inexpensive process. But… If you can get a scanner on your vehicle and jot down all of the Codes and post them up here… it would help to eliminate any mysteries and get to the bottom of what is really happening right away. Right now... Its just Wild Guess Work.

Thanks. I'll check them out asap. Unfortunately my work hours are crazy this week so it's been a pain getting time to mess with it. Also, the scanner that I recently purchased will not read any codes because the battery was switched out to a new one a few days ago. I kinda screwed myself on that one.
 

keile

Original poster
Member
Jan 19, 2017
6
Ohio
So do to a lack of equipment and time to do any good testing on the vehicle, I had it towed to the shop. And it's the fuel pump. Charging over $900. I'm having it brought back to the house so me and a buddy can put it on. So next question would be, any recommendations on a reliable pump? Advance Auto has pump assembly's for $300-$400 and AutoZone has pumps for $100-$200. Thanks again everyone.
 

mrrsm

Lifetime VIP Donor
Supporting Donor
Member
Oct 22, 2015
7,639
Tampa Bay Area
You can get all of the best information about changing the fuel pump by going to YouTube and searching for a particular video on this topic using this expression:

MAY03LT Fuel Pump
 

keile

Original poster
Member
Jan 19, 2017
6
Ohio
You can get all of the best information about changing the fuel pump by going to YouTube and searching for a particular video on this topic using this expression:

MAY03LT Fuel Pump

Step ahead of you. I've been watching his vids for the last week trying to diagnose the problem. Again, thanks a bunch everyone! I hope it's not to much of a bitch to change.
 

keile

Original poster
Member
Jan 19, 2017
6
Ohio
Just a update for everyone. Got the TB up and running yesterday. Installed the new fuel pump. Took less than 2 hours, and 30 minutes of that was getting the two bolts that were rusted to all hell off the support bar. After that it was smooth sailing. Saved myself almost $700 dollars doing it at home. Thanks for everyone's help and suggestions! It will take some adjusting getting used to having a working gas gauge as well!
 

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