Sign In


Average FSD temperature after 60mi. driving distance, at 60 m/h and 77°F ambient temerature

Conditions Pump mounted FSD cooler mounted*
with high fuel level 163°F 131°F
with low fuel level 192°F 131°F
and hauling an enclosed trailer 208°F 136°F
and with a non operating lift pump 217°F 136.4°
New FSDs of the latest version, #34583, have been used in the test.
Test vehicle: 1997 4WD aut. 4.10 rear end, 245/75-16 tires, 3901 Kg GVWR, fully equipped no A/C

The difference in FSD temperature, between the two mounting positions, will be even greater with “dry diesel and/or higher ambient temperature.

With time, the pump mounted FSD will also gradually increase in temperature due to its decreasing clamping force to the pump.

The pump mounted FSD failure mainly occurs at its peak temperatures , affected by

  • Low fuel level
  • Low clamping force of the FSD to the pump
  • High ambient temperature
  • Non operating lift pump
  • High engine load