A fuel odor or fuel leak in the front of the vehicle may be noticed on some 2016-2017 CTS, Camaro;
2015-2017 Escalade/ESV, Tahoe/Suburban, Yukon/XL, and Corvette models equipped with a V8 engine (RPOs LT1, LT4, L83, L86) and 2014 Silverado 1500
and Sierra 1500 models equipped with a V6 or V8 engine (RPOs LV1, LV3, L83, L86).

A fuel leak may be found around the bellhousing or valve lifter oil manifold (VLOM).

In addition, the vehicle may be hard to start, have poor fuel economy, or a wet underhood foam insulator.

These conditions may be caused by a fuel leak at one of the high pressure fuel rail pipe connections that was incorrectly installed during service of another engine component that required the fuel system to be opened, such as fuel rails, fuel injectors, high pressure fuel pump, etc.

TIP:
The engine fuel feed intermediate pipes must be replaced during any service repairs that require one or more of the pipes to be loosened or removed.

If any of these conditions are found, find the fuel leak by installing dye, P/N 88861206 (in Canada, P/N 88861259), into the fuel system via the fuel filler neck.
Idle the engine for 15 minutes and then remove the intake manifold and inspect for leaks.

Tightening a nut is not an approved procedure.
If a leak is found at any nut location, follow these procedures:

Leak in pipe 2 – change only pipe 2 (intermediate pipe 2)
Leak in pipe 1 – change pipe 1 and pipe 2 (intermediate pipe 1 and 2)
Leak in pipe 3 – change only pipe 3 (fuel feed pipe).

Ensure that all interfaces are clean and free of debris before installing.
After installing the new pipes, idle the engine for three minutes and recheck for leaks.

Replace the engine insulator if it absorbed fuel or emits a fuel odor.