[lust4speed]

A few thoughts on combinations.

Impossible to pull fuel through a gerotor style pump.

Hard, but somewhat possible to pull through a vane style pump, but the fuel will be spinning the vanes to get through the pump.

Fairly easy to draw fuel through a pulsating pump since it is basically free flowing through check valves. Unfortunately any restriction back at the electric pump is going to create more of a negative pressure and the system is going to be much more prone to vapor lock with the pump off. Besides the negative pressure the physical restrictions of the pump or bypass check valves is going to limit flow and possibly lead to starvation at heavy throttle. Wheelspin (Les) and I did quite a bit of testing on his GTO and the TA and despite our valiant efforts found that the electric pump needed to be running even taking a brisk run up a long freeway onramp. Even though the front pump was a RobbMc 1100HP he was experiencing the dreaded drop out at the top of 2nd gear. Adding the electric pump back near the tank totally solved the problem when the pump was on, but even with the bypass check valves the fuel starvation happen sooner if the pump wasn't on. So he ended up running the pump most of the time. Hindsight says that we should also have added an additional circuit that would turn the pump on with anything over half throttle position.

Also found out contrary to what was said on the internet that adding a 6 PSI electric pump to a 6 PSI mechanical pump didn't keep the output to the carb at 6 pounds. With the electric pump running we were seeing almost 9 PSI so we had to add a regulator before the carb.