98 nissan maxima 3.0lt white smoke and smells like gas out the tailpipe and it is leaking gas out of tailpipe too.

It would be unlikely gas is coming out of the tailpipe. The fuel regulator can leak internally and externally. If there is an internal leak with the regulator, the vehicle will be overfueled and will run poorly if at all with black smoke out the tailpipe and most likely the check engine light on/flashing. You may experience a fuel smell. If the regulator is leaking external, there will be a definate fuel smell. You may also have an injector or injector seal leaking as well. Depending on the engine size 4 or 6 cyl, it can be hard to spot an injector leak. However, a fuel p;ressure regulator can easily be located and checked for a fuel leak.

Possible, but it would be a rough engine spin.
Check the fuel level in the carb, or the fuel pressure from the pump as well.

Gas coming out of TailPipe - Nissan Forum ' Nissan Forums

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Jul 5, 2009 - Can the FPR be the cause of fuel coming out of the tailpipe? Lots and Lots of fuel... I don't mean a drop here and ... unburnt fuel spewing from exhaust and flooding cylinders
Apr 7, 2013
white smoke,smell of fuel,dripping unburned fuel, all coming from ...
Mar 10, 2009
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dirty injector.

Hello Anonymous,

Were I you... (my best guess)
I would be looking for a BLOCKED EXHAUST...

(in my opinion)
probably the number one REASON AUTOZONE
sells so many (pointless) OXYGEN SENSORS...

Those new OXYGEN SENSORS Pretty much
complain as well as the old ones did...

The logical equivalent of buying a NEW
THERMOMETER... because you have a fever.

Check out the whole system costs on AMAZON,
eBay & rockauto... BEFORE waltzing into any
exhaust shop...

Catalog:
http://www.rockauto.com/en/catalog/nissan,1999,maxima,3.0l+v6,1356780,exhaust+&+emission

Catalytic converters ($$) C.A.R.B. Compliant available
1999 NISSAN MAXIMA 3 0L V6 Catalytic Converter RockAuto

C.A.R.B. specific details (2 day ship'n, About $280)
More Information for DAVICO 169750

Exhaust shop should be able to test...
(OXYGEN SENSORS... save your $$$$ = nah)
Hope this helps

Carnac the Magnificent

If the oil level goes up, something has to be leaking into the engine oil pan.
That would either be gasoline from the injectors or coolant from the radiator. If you are not adding coolant, it could be a leaking injector.

white smoke means oil or coolant burning. black fuel. performed a cooling pressure test and see if u loosing pressure.

You are most likely leaking leaking coolant. Does white smoke come out your tailpipe? Is the floor on your passenger side wet at times?

blown head gasket. black smoke means that oil is getting into the cylinder.

Rich fuel=black smoke.
Oil burning=blue smoke
Coolant burning=white smoke