Ok I am tired of mechanical fuel pumps

[bubba_got_you]

Ok I am tired of mechanical fuel pumps and want to go to a 24v electric pump. How does this change over work? How do I do the wiring and what do I do with the old pump?

[N1VSM]

It's easy. Let me walk you through it from fuel tank to engine. First - the fuel pump: your best bet is to look for a marine (think boat) diesel fuel pump - yes, it works beautifully with gas, too. Make sure it is the correct output (4-5 gph?) You'll have to search the forum for the correct spec's - don't rely on my lousy memory. I bolted my pump to the frame just in front of the gas tank. These pumps push better than they pull - trust me, you'd notice the difference climbing up hill if you mistakenly mount the pump in the engine compartment. When plumbing in the pump, I put in a manual shut-off valve between the gas tank and the pump. As for the manual pump, you can either leave it in line, or bypass it completely. Mine was leaking terribly, so I removed it and covered the hole with a plate sealed & bolted to the hole. Hasn't leaked a drop since. To power the pump, buy an oil pressure switch that triggers at 5 PSI or so. (You can use a "tee" to attach that to the same place your oil pressure sensor screws in.) Run a 24V line to one side of the switch, the other side goes through a 5A fuse to the power lead of the pump. I put in a second line from the switched terminal on the starter (only hot while you are pressing the starter pedal) through an enormous diode to the power lead to the pump. The purpose of the diode is to keep the current from traveling only FROM starter TO pump, not the other way around. Sorry - I forgot the diode spec's I used.

Thinking through the startup process, the line from the starter to the pump is hot while you are pressing the starter pedal, the line from the pressure switch goes hot when your oil pressure hits 5 PSI (rather soon, unless you have terminally bad compression). Shut off or stall your engine and the pump shuts off when the oil pressure drops below 5 PSI.

When done correctly, this setup is completely transparent to the driver, with the exception of providing more consistent fuel delivery that doesn't depend on the engine speed. As for still being waterproof - that's up to your electrical skills.

Hmm ... did I forget anything?

[MSeriesRebuild]

It's easy. Let me walk you through it from fuel tank to engine. First - the fuel pump: your best bet is to look for a marine (think boat) diesel fuel pump - yes, it works beautifully with gas, too. Make sure it is the correct output (4-5 gph?) You'll have to search the forum for the correct spec's - don't rely on my lousy memory. I bolted my pump to the frame just in front of the gas tank. These pumps push better than they pull - trust me, you'd notice the difference climbing up hill if you mistakenly mount the pump in the engine compartment. When plumbing in the pump, I put in a manual shut-off valve between the gas tank and the pump. As for the manual pump, you can either leave it in line, or bypass it completely. Mine was leaking terribly, so I removed it and covered the hole with a plate sealed & bolted to the hole. Hasn't leaked a drop since. To power the pump, buy an oil pressure switch that triggers at 5 PSI or so. (You can use a "tee" to attach that to the same place your oil pressure sensor screws in.) Run a 24V line to one side of the switch, the other side goes through a 5A fuse to the power lead of the pump. I put in a second line from the switched terminal on the starter (only hot while you are pressing the starter pedal) through an enormous diode to the power lead to the pump. The purpose of the diode is to keep the current from traveling only FROM starter TO pump, not the other way around. Sorry - I forgot the diode spec's I used.

Thinking through the startup process, the line from the starter to the pump is hot while you are pressing the starter pedal, the line from the pressure switch goes hot when your oil pressure hits 5 PSI (rather soon, unless you have terminally bad compression). Shut off or stall your engine and the pump shuts off when the oil pressure drops below 5 PSI.

When done correctly, this setup is completely transparent to the driver, with the exception of providing more consistent fuel delivery that doesn't depend on the engine speed. As for still being waterproof - that's up to your electrical skills.

Hmm ... did I forget anything?

The correct pump output is 4-5PSI rather than gallons per hour. The volume isn't as important as pressure since too much pressure capability will overwhelm the carb inlet needle & seat causing the engine to flood. One thing we always do in addition to your set up is install a push button switch on the dash that will activate the electric pump. The purpose for this is in the event you run out of gas, a simple press of the button will run the pump to get fuel from the tank to the carb without having to spin the engine over. This takes the place of the hand lever primer on the mechanical pump. Just makes things a little more efficient.

[N1VSM]

Thanks, Charles. I must have been thinking of sump pumps.

Let's see - a quick calculation: traveling at 40 MPH burning 5 GPH (wrong units on my part) as I incorrectly stated, would mean that my engine would need to get at least 10 MPG to keep running. That's about 8 MPG short of my truck's capability.