Fuel Pump Installation
The fuel pump is going to be mounted in the same location as the Pro-Jection pump which is located on the passenger side frame rail above the rear spring perch. The new pump hangs a little low, not that it would be hit by anything but sticks or brush could get tangled in the wiring. A protective shield may be fabricated to keep the pump safe.
The pump was temporarily wired up to test operation and run the Jeep to check for leaks. The Jeep started right up and only needed slight carb adjustments to get the idle correct.
It was a worry that the electric pump would be too loud. When the Jeep is not running is makes a mild hum but is un-noticeable when the engine is running.
OK, Small Change
In further reading the documentation accompanying the pump it was indicated that a filter should be installed before the pump and not after. This makes sense as to keep contaminates out of the pump. In looking at the setup further it was determined to remount the pump forward more to place the pump above the skid plate for better protection.
Oil Pressure Safety Switch
As discussed earlier an oil pressure safety switch will be installed to shut down the electric fuel pump in when the engine is not running. Since the AMC engine only has one oil pressure outlet a tee was installed to plumb the pressure switch as well as the gauge tube. The outlet uses standard brass fittings and can be found at home improvement stores.
The oil pressure switch cannot handle a draw of more than a few amps and it is recommended that the pump be powered through a relay. In addition an in-cab switch will be installed to allow the pump to controlled. A single-pole double-throw (SPDT) switch that operates in the following way will be installed – ON, OFF, MOMENTARY ON. This switch will remain in the ON position during normal operation, the OFF will allow the pump to be turned off, and the MOMENTARY ON will bypass the pressure switch and run the pump to prime the carburetor if the Jeep has sat a while.
The switch was ordered from Grainger and was manufactured by NKK Switches. Part # NKK-S309T
Below is the wiring diagram we will be using. A 10 amp circuit from the Painless Fuse Block will power the pump through the standard “87” automotive relay. The fuel pump relay is on the right.
Tuning and Results
After double checking wiring, hoses, bolts, etc. we started up the Jeep. Not surprising it started immediately and seemed to run normally right away. We let the Jeep warm up and adjusted the choke mechanism and took the Jeep for a short ride. The Jeep’s performance was very nice and only minor idle adjustments were needed.
We believe the Jeep runs much better and seems to be smoother and have more predictable throttle response. Fuel mileage seems to have improved a little too.
Years Later – 2016
Had the opportunity to off road the CJ after a 10 year hiatus and carburetor performance was flawless except in extreme uphill angles. I actually put it to the test on a steep rock pile, the idle got a little rough but the engine never stalled.