View Full Version : Fuel Pump Replacement

03-06-2017, 08:46 PM
New Willys owner and first time poster. Previous owner had installed an electric pump. Looking to replace it with a mechanical. Have an F134 block. My question is single versus dual action...is there a preference or benefit of one versus the other?

03-07-2017, 08:31 AM
The double action fuel pump should really be called the dual-function fuel and vacuum pump. Most old Jeeps have vacuum operated windshield wipers. Manifold vacuum provides the energy to run the wiper motor. Things work well until you find yourself in a rain storm and accelerate to pass someone (not very likely in most Jeeps these days). When you open the throttle, manifold vacuum drops and the wipers stop. Uh -oh ....

The double action fuel pump is really a combination fuel pump and vacuum boost pump. With the throttle wide open, it produces vacuum for the wipers. It helps at cruise speeds, but even with a dual action pump, wipers slow down on acceleration. Some guys have been known to add vacuum reservoirs to provide even more reserve.

If you have vacuum wipers, a "dual action" pump is almost mandatory. (If the previous owner installed an electric pump,did he just run wipers straight off the manifold?)

03-07-2017, 07:41 PM
Thanks for the response!