Does anyone know what our stock fuel pump puts out (LPH)?
*1991 Ford F-250 Dual tanks

 

On a 96 it's 105 LPH for the 8 cyl and 95 LPH for the 6 cyl. The 91 may be different but should be similar

 

What engine ya got?

Adrianspeeder

 

On the 96 it doesn't matter. They all use the same pump. The higher pressure fuel regulator on the six causes more case leakage on the pump reducing throughput. Again, the 91 may be different.

 

I have a 5.0L w/ in tank fuel pumps.

 

The reason I'm asking is because I'm installing a 6 psi supercharger and I don't want to run lean.

 

There's a problem with the Fuel Delivery Module on the twin tank trucks. Aside from the fump, suction filter and the level sender, the FDM also includes a pilot-operated check valve to prevent the fuel from returning to the wrong tank. It is a necessary part of the system but AFAIK is not included on any of the aftermarket pumps. I don't know if it's possible to fit a higher-flow pump to the stock module.

The stock pump will support something on the order of 285-315 HP.

 

What about a inline fuel pump? Is that something that could work w/ our setup?

 

An inline pump will deliver fuel to the fuel rail, but you need to work out two things:

Which fuel tank is it drawing from?
Which fuel tank does it return the excess to?

If you cut an inline pump into the existing line, it would reduce the discharge head on the stock pumps to zero, so their throughput would increase somewhat and the stock return line select check valves would still operate. However, I doubt that the output of the stock pumps would go up THAT much. Look around on the net. Try to find a pressure/flow curve for a Walbro 105 or 110 LPH pump and see what it goes to at the lowesr PSI shown on the chart. You could then cut in an inline pump that was 10% smaller than that lowest number. Since the next pump size up is AFAIK 155 LPH, you would need to see a rated flow of about 170 LPH @ 0 PSI from the 110 LPH to go up to a 155 in-line. I doubt very, very much that you're going to see that kind of number.

Even a 155 is only going to accomodate something like 420 HP max. What is your target HP? Start with that number and work backwards to size your injectors and pump(s)

EDIT
The blower will require that you have either a larger pump and injectors than shown by the normal calculations (flow varies as the square root of pressure drop so you need to overcome the increased manifold pressure) or some means of increasing pressure such as a boost referenced fuel pressure regulator, which again requires a larger pump.

There's lots of stuff to work out and the blower manufacturers haven't really paid that much attention to dual tank trucks. If you were willing to lose one tank, things might be a bit simpler.

 

I found a fuel pump kit from Vortech. It comes w/ all the hardware needed and a Hobbs switch. It's a 155lph pump.Vortech part# 4FB101-002
I think this is the only way I can use an in-line fuel pump w/ a dual setup.