What does it mean when 2008 pontiac G5 will not hold fuel pressure and smell gas

FTP - fuel tank pressure sensor , and it's on top of the fuel tank . Have to pull the fuel tank to get at it .

The rubber seal holding the fuel pump is bad and leaking.Here's a link showing you. How to Install Fuel Pump Assembly E3591MN in 2005 2008 Pontiac G6 Chevy...

The mass air flow sensor is in the air intake ---the o2 sensor is in the exhaust pipe and the evap leak is associated with the canister. The sound may be from a bad solenoid valve on the canister

Code 496 is not about the gas cap.
The code means the computer has detected pressure in the EVAP system when it should not be there.
The EVAP system consists of lines and valves that vent the gas tank to the vapor canister and the engine.
The problem could be one of the valves or the pressure sensor. You may need a shop manual to get the diagnostic steps to test the system.

Sounds like a leaky fuel line somewhere and the pressure isn't strong enough to go through the fuel pressure regulator. Try to locate fuel leak by smell.

You will have to pinpoint what the engine is missing...
- Spark
- Fuel
- Compression

All three of these are tested when the engine is being cranked over. There are two way of checking for fuel. Fuel pressure and fuel trigger. Both are very important and must be present for the engine to start. Fuel pressure is self explanatory. You just hook up the gage and see what the reading is. Fuel trigger is check with a noid light. The injector gets unplugged and the noid light gets plugged in to the injector clip. With the engine cranking over, this light must blink. This is the signal to the injectors from the computer. You can have all the fuel pressure in the world, but it wont matter if the injector is not pulsing gas into the cylinder like it should.

Compression tester, spark tester, fuel pressure gage and noid light are all accessible at your local auto store. All three tests play a very important part in diagnosing a no start condition. Be extremely careful when doing these tests.

If it mainly happens when under load, I would change the fuel filter. While a semi clogged filter will allows enough fuel to pass when idelling or at slower speeds, it might not give consistant fuel flow when at higher speeds or under load - like climbing a hill.

LOOK UNDER THE CHECK FOR LEAKING FUEL LINES.LOOK UNDERNEATH CAR AT FUEL LINES RUNNING FROM UNDER THE HOOD TO THE FUEL TANK CHECK THEM FOR LEAKS.

probably spark plug wires,have a full t-up done with plugs,wires,and all filters that should correct your problem.










THANKS,TIM.

2008 Pontiac G5
2008: Base; 4 Cyl 2.2L; "GAS, FI, L61, VIN F" 2008: GT; 4 Cyl 2.4L; "GAS, FI, VIN B"



How to Replace a Fuel Filter
(DIY Complexity: Moderate / Time: 1.4 hours)

Parts:
1. Fuel Filter

Tools:
1. 3/8 in. Drive Ratchet
2. Hose Pincher
3. Flare Nut Wrench
4. Flat Head Screwdriver
5. Socket Set

Steps:
Step 1 Open the hood and locate the fuel filter. If the fuel filter is not in the engine compartment, follow the fuel line from the tank until the fuel filter is located.
o Tip: Safety Tip:Always wear safety glasses when working on your vehicle. Wear other personal protective equipment (PPE) when necessary, for example latex gloves or safety shoes.

Step 2 If the fuel filter has a clear case, inspect the filter element for dirt.

Step 3 If the fuel filter case is not see-through, remove it from the fuel line. Drain the fuel from the filter into a container and inspect the condition of the fuel.
o Tip: Caution: Before removing fuel lines or fuel related parts, make sure that the fuel pressure is relieved from the vehicle fuel system. To relieve the pressure in fuel injected systems, remove the fuel pump fuse and run the engine.

Step 4 Install the new fuel filter making sure that the flow is in the correct direction. The arrow on the fuel filter is the direction of flow from the tank to the engine.

Step 5 Secure the lines back onto the fuel filter. If applicable, reinstall the fuel pump fuse.

Step 6 Start the engine and check for fuel leaks.

Step 7 Test drive the vehicle to check for a rough running engine, hesitation, or lack of power.

Hope help with this.