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brownjeff, ASE Certified Technician
Category: Dodge
Satisfied Customers: 13886
Experience:  17 years experience, ASE certified, dealership certified, Service Manager for 15 years,
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2002 Dodge Neon: The fuel tank..fuel gauge..few miles..looked under

Resolved Question:

I have a 2002 Dodge Neon SE. The fuel tank doesn't seem to be venting correctly. The fuel gauge started showing that the car was empty after driving only a few miles, so I looked under the car after driving and was amazed to see that the fuel tank was imploded. I removed the gas cap and with a mad rush of air - the tank went back to its original shape. I replaced the cap and it did the same thing, so I unscrewed the cap and left it loose in the filler neck. That worked to keep the tank vented and the gas gauge worked properly as well. What would cause that kind of vacuum in the tank and why isn't it venting?

Ron Kipple [email protected]
Submitted: 8 years ago.
Category: Dodge
Expert:  brownjeff replied 8 years ago.

There is a control valve in the fuel tank the should regulate the pressure and most likely has failed.


Here is some information on it:


The emission control principle used in the ORVR system is that the fuel flowing into the filler tube (appx. 1" J.D.) creates an aspiration effect which draws air into the fill tube. During refueling, the fuel tank is vented to the vapor canister to capture escaping vapors. With air flowing into the filler tube, there are no fuel vapors escaping to the atmosphere. Once the refueling vapors are captured by the canister, the vehicle's computer controlled purge system draws vapor out of the canister for the engine to burn. The vapors flow is metered by the purge solenoid so that there is no or minimal impact on driveability or tailpipe emissions.

As fuel starts to flow through the fill tube, it opens the normally closed check valve and enters the fuel tank. Vapor or air is expelled from the tank through the control valve to the vapor canister. Vapor is absorbed in the canister until vapor flow in the lines stops, either following shut-off or by having the fuel level in the tank rise high enough to close the control valve.

The control valve contains a float that rises to seal the large diameter vent path to the canister. At this point in the fueling of the vehicle, the tank pressure increases, the check valve closes (preventing tank fuel from spitting back at the operator), and fuel then rises up the filler tube to shut-off the dispensing nozzle.

If the engine is shut-off while the On-Board diagnostics test is running, low level tank pressure can be trapped in the fuel tank and fuel can not be added to the tank until the pressure is relieved. This is due to the leak detection pump closing the vapor outlet from the top of the tank and the one-way check valve not allowing the tank to vent through the fill tube to atmosphere. Therefore, when fuel is added, it will back-up in the fill tube and shut off the dispensing nozzle. The pressure can be eliminated in two ways:

  1. Vehicle purge must be activated and for a long enough period to eliminate the pressure. 2. Removing the fuel cap and allowing enough time for the system to vent thru the recirculation tube.
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