Well...there are "fuels" and there are "fuels".
Typically a pump handling flammable fuels (gasoline etc.) will be at very least Zone 2 (division 2), meaning it is in a service where a flammable vapour is not normally present but might be in an upset condition such as a leak. However, if leakage is viewed as more likely, or the component is located in an area where a denser-than-air vapour may accumulate when released, it could be Zone 1 or even Zone 0 (i.e. assuming a flammable vapour will be normally present). Zones 0 and 1 require explosion proof motors per API 500, NFPA 497 etc. and per NFPA 70. Those are codes associated with the selection of electrical equipment such as motors for potentially hazardous services due to fire risk.
In Zone/division 2, explosion proof motors are not required. 3 phase TEFC motors are permitted as long as they contain no arcing/sparking components. Some will argue that the motor needs to be identified on the nameplate as suitable for use in a hazardous area, and that's easy enough to obtain most of the time and it shuts people up so you don't have to argue with them, but I'm still not convinced it's an actual requirement of NFPA 70 (the US National Electrical Code) or the CEC.
In Europe and some other jurisdictions, there may ALSO be rules related to the mechanical components and their ability to generate sparks or heat- not just with the motor.
If your internal gear pump is using single phase AC or is using a DC motor, explosion-proof will be your only option.
If your fuel is combustible rather than flammable, i.e. heavier than diesel (even some diesels have a high enough flash point to be combustible rather than flammable), unless the equipment is operating with the fluid at elevated temperatures, it isn't a Zone 0, 1 or 2 situation unless it is co-located with other equipment. Other rules may apply and may require hazardous area treatment though- you need to know the complete suite of safety and regulatory requirements for your company, region and country to make the right selection.