Sheri Asks: Gladiator “Catch”?

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Here’s the latest reader question, along with my reply!

Sherri asks: Why did they put the little “catch” in the fuel tank so you need a special funnel to fill the tank with diesel? Is there a nozzle we can put on our diesel tank that will allow us to fill the tank without using the funnel and still fill our other diesel vehicles normally? I believe there is a way to disable this, but I hate to hack a new vehicle.

My reply: I’ve dealt with this myself; the problem derives from two things. The first thing is that some diesel pumps have larger diameter nozzles meant for big rigs and trucks and for this reason it makes a mess when you try to pump the diesel into a car or a smaller/newer diesel-powered vehicle like the Gladiator. The other problem is idiot-proofing. Some people will pump gas into a diesel. To try to avoid that, modified fill necks have been installed – which also serve as “vapor recovery” devices for emissions control.

The easies way to get around this problem is to find a station that has diesel pumps with nozzles that fit your filler neck; a funnel also helps, of course – and it’s good to have this in a pinch, when the only nozzle you can find doesn’t fit your fill neck.

I would not modify the Jeep’s fill neck as this might result in a code being thrown and the “check engine” light coming on. It might also cause issues with warranty-related repairs, in the event that becomes an issue.

. . .

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  1. The smaller fill hole in gasoline-powered vehicles is a leftover from the switch to unleaded. Unleaded fuel was dispensed from a nozzle that had to pass through a restrictor in the filler tube. The larger nozzle used for leaded fuel (perhaps the same size that’s still used for diesel?) wouldn’t fit through the restrictor.

    1968 and later gas-powered vehicles are subject to an annual smog check around here. One of the things checked for in vehicles built from 1975 (introduction of cars marked “unleaded fuel only”) to 1995 or ’96 (introduction of OBD-II) is the presence of the fuel filler restrictor. If it’s not there, your car fails. (By comparison, with OBD-II they just trust whatever the ECM tells the tester.)


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