# Only 3 volts at fuel pump **URL:** \ **Category:** Power/Fuel\ **Tags:** pump, mercury, gasoline\ **Created:** [September 7, 2010, 3:38pm UTC](https://community.cartalk.com/t/only-3-volts-at-fuel-pump/54768 "2010-09-07T15:38:27Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Slovac](https://avatars.discourse-cdn.com/v4/letter/s/5daacb/32.png) [@Slovac](https://community.cartalk.com/u/Slovac)\ **Post date:** [September 7, 2010, 3:38pm UTC](https://community.cartalk.com/t/only-3-volts-at-fuel-pump/54768/1 "2010-09-07T15:38:27Z")
I have a 98 Grand Marquis that is not pumping fuel. I checked the voltage at the inertia switch and only had 6 VDC. Underneath the trunk I checked the voltage at another connector and only got 3 VDC. Do you think I have a bad ground? ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [September 7, 2010, 4:22pm UTC](https://community.cartalk.com/t/only-3-volts-at-fuel-pump/54768/2 "2010-09-07T16:22:17Z")
Check the fuel pump fuse. This is fuse 1, 20 amp, located in the under hood fuse box on the right front of the engine compartment. Tester ---
**Author:** ![TwinTurbo](https://avatars.discourse-cdn.com/v4/letter/t/8baadc/32.png) [@TwinTurbo](https://community.cartalk.com/u/TwinTurbo)\ **Post date:** [September 7, 2010, 4:26pm UTC](https://community.cartalk.com/t/only-3-volts-at-fuel-pump/54768/3 "2010-09-07T16:26:38Z")
> Do you think I have a bad ground? Why guess? You have a voltmeter, measure the voltage drop from the fuel pump “ground” to the chassis “ground” and you’ll know. ---
**Author:** ![Cougar](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/cougar/32/21348_2.png) [@Cougar](https://community.cartalk.com/u/Cougar)\ **Post date:** [September 7, 2010, 9:28pm UTC](https://community.cartalk.com/t/only-3-volts-at-fuel-pump/54768/4 "2010-09-07T21:28:22Z")
I assume that the voltage readings you stated were made using a good ground reference point. I also assume that the devices you tested are on the power lead side of the load. If that is correct then the trouble isn’t a bad ground but rather a bad connection to power. The fuel pump relay is a likely culprit. It would be nice to know where the 3 volt measurement was taken since the voltage is less than the first reading. If the 3 volt reading is after the load on the ground return side then there is a grounding problem also. A good ground point will be at zero volts when compared to a good ground reference point.