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The nozzle keeps shutting off when I try to fill up my Pathfinder. What can I do?

May 19, 2023

Thank you, Lou, for your insightful tips and articles regarding the EVAP system. I have a 2006 Nissan Pathfinder, and I had a problem with the sending unit in the gas fuel pump. So I changed the entire fuel-pump assembly inside the tank. Once I did that, I went to put gas in and found that the gas-pump nozzle keeps turning off unless I fill very slowly. I also have a gas smell outside of the car. I went to the mechanic, and he basically brushed me off by saying it will take a few times until it gets adjusted. Now what may be the reason for this issue?

Please advise, thank you.

Tim M

Regardless of the vehicle brand, whenever a hard-to-fill situation exists at the gas pump, you have to assume that there is a restriction in the gas fill venting system. In your case Tim, I would start by looking at the vent-control valve solenoid, which is located on the Evaporative Emission Control System (EVAP) canister. This valve is normally open and should flow when you blow air through it. This valve is likely plugged with debris or stuck in a closed condition. The EVAP canister is located beside the fuel tank. The fact that it started immediately after you changed the fuel pump leads me to believe that perhaps you disturbed something in the EVAP canister area. The fuel smell is likely another issue completely, such as a fuel-pump seal that is not sealing correctly.

If my spark plugs are not gapped right, will it knock?

Mike C

Knock and ping are two common words used to describe pre-ignition. Pre-ignition occurs when the air/fuel mixture in the cylinder is ignited by a source other than the firing of the spark plug. Spark plugs that have been installed in an engine with an improper temperature range are the most common source of pre-ignition problems. The spark plug's heat range is defined by the manufacturer and is specified as such, to remove heat from the tip and electrode of the spark plug. If the ceramic insulator or tip exceeds 800°C, this excessively high temperature will cause the air/fuel mixture to pre-ignite. A spark-plug gap that is drastically out of the manufacturer's nominal range may also cause pre-ignition. If the gap is too small, it will have a weak spark and result in a poorly running engine. A spark plug with a large gap will yield a larger ignition source, which in theory might been seen as a benefit, but will cause the ignition coil to fail prematurely. Simply put, any time the combustion is affected in a negative way, there is the potential to see a pre-ignition situation.

Vehicles that pre-date computer-controlled ignition systems would have suffered pre-ignition due to incorrect spark plug gaps. However, modern vehicles have computer-controlled systems that can compensate for most small gapping errors. So, while technically the answer to your question is yes, it will be rare on a modern car and usually only applicable when caused by DIYer trying to outsmart their computer.

Lou Trottier is owner-operator of All About Imports in Mississauga. Have a question about maintenance and repair? E-mail [email protected], placing "Lou's Garage" in the subject line.

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