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Uncle Bubba

2nd Gen Dual Lift Pump Design

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Dual Lift Pump Plumbing

This is intended to be a guide to the minimum requirments to installing parallell dual lift pumps on your truck. These pumps should never be plumbed so that they run through each other as this can place a severe restriction in the flow in the even that one goes bad or even just gets weak. This can be done using any pumps you wish and you can add filters and anything else you want to it but you have to have the parts described.

I’ll start by explaining the system pictured here and some of the reasons as to why it is built the way it is just in case it gives somebody else any bright ideas. I’ll follow that with just a basic diagram of the requirements to any system you want to build.

post-32-145494292487_thumb.jpg

In my case I built this one to cover all the bases. Both pumps are mounted on an aluminum base. In the event that I needed to work on them I would remove two bolts holding this base to the frame rail and a fitting on each end of it and I could pull the whole assembly out and work on a bench instead of on my back with fuel dripping down my arms.

I installed a pressure gauge on one of the pumps so that if I had both pumps running and lost some pressure I would be able to look at the gauge and know which pump was dead at a glance. I later added a switch so that I could control the on and off for each pump independently and that did away with the need for the gauge but it was there so I left it.

I also use a small piece of rubber mat behind the pumps. It’s probably not needed and never called for in any instructions I have ever seen but in my mind I think it helps absorb some of the road shock and vibration that can’t be good for electrical motors. You can buy isolators for this but they are expensive and not very durable.

Most important of all here. Every LP I have ever seen has an in internal bypass built into it to control fuel pressure. The two round red barrels you see in the lines are one way check valves. They prevent the stronger pump from feeding fuel backwards through the weaker pump. You have to have one of these on the outgoing fuel side of each pump.

Now if you’re designing your own system the diagram shown here shows all the requirements. Past this you can do anything you want to personalize it. (Excuse the artwork, it's not a strongpoint)

post-32-145494292505_thumb.jpg

You have to have the following:

1. A T-fitting splitting the lines someplace before the first Lift Pump.

2. A T-fitting bringing the lines back together someplace between the second lift pump and the filter.

3. A one way check valve on the outgoing fuel line of each pump.

Recommendations:

1. Either a switch to turn each pump on and off independently or use a Hobbs Pressure switch on the second pump so that it will turn on automatically if your fuel pressure drops below a pre-set psi.

2. Get rid of all the Banjo bolts and replace them with High Pressure Fuel Fittings. They only cost a few dollars each and the Banjo’s are probably the single most restrictive points in your fuel system.

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