Turns over but will not start

Hi and thanks for using 2CarPros.com.

If it will not start, either you lost spark or fuel. Here are two links that explain how to check both:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

https://www.2carpros.com/articles/how-to-test-an-ignition-system

As far as being towed as you described, it makes no sense to me.

Here are directions specific to your vehicle for checking fuel pump pressure:

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2004 Chevy Truck Suburban 1/2 Ton 2WD V8-5.3L VIN T
Vehicle  Engine, Cooling and Exhaust  Engine  Fuel Pressure  Testing and Inspection  Fuel Pressure Gage Installation and Removal

Fuel pressure gage installation and removal
Fuel pressure gage installation and removal
Installation procedure

J 34730-1A Fuel Pressure Gage
Caution:
Refer to Gasoline/Gasoline Vapors Caution in Service Precautions.
Refer to Fuel Gage Leak Caution in Service Precautions .
Remove the engine sight shield.
Remove the fuel rail pressure fitting cap.
Connect the J 34730-1A to the fuel pressure valve. Wrap a shop towel around the fitting while connecting the gage in order to avoid spillage.
Install the bleed hose on J 34730-1A into an approved container.

Removal procedure:
Remove the bleed hose on the J 34730-1A from the approved container.
Remove the shop towel from around the fitting and discard into an approved container.
Disconnect the J 34730-1A from the fuel pressure valve.
Install the fuel rail pressure fitting cap.
Install the engine sight shield.

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The pressure specifications for your vehicle are as follow:

Fuel Pressure (Key on, Engine off) 385-425 kPa (55-62 psi)
Fuel Pressure (vin Z) 335-375 kPa (48-54 psi)

Check these two things and let me know what you find.

Take care,
Joe