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Philippe, I would go with Diagram #2, but eliminate that 10' of line between the 2 pumps. I have my Jeep and my pickup both set up that way. All I use the electric pump for is when it's been sitting for awhile and I know the gas has evaporated out of the carburetor. I use it to refill so that I don't have to crank and crank and crank to re-load the bowl from the tank with the mechanical pump. As for this helping you out in case of a breakdown, consider this: When a fuel pump "fails", what exactly happens? 99.9 times out of 100, it's because the rubber diaphragm inside develops a hole. When it has a hole, the pump can no longer suck. The way the mechanical pump works is that the plunger pushes the diaphragm against a return spring. Once it's pushed, the spring forces it back down, and it's actually that RETURN SPRING that is supplying the pumping pressure, not the pushrod. All the pushrod does is that after the spring pushes down the diaphragm, pushing the gasoline to the carburetor, the pushrod from the engine cam hits it again and knocks it back up to "re-cock" the spring. Then the spring again pushes the diaphram down, which does the actual pumping. Now. If you're driving down the road, and that diaphram springs a leak, one of 2 things is going to happen: The fuel pump will begin pumping out onto the road, or else it will begin pumping into the engine crankcase. Either way, the engine's going to die, or at the VERY least, performance will suffer terribly due to lack of enough fuel being pumped to the carb. Now: Do you actually want to switch on that electric pump and begin pumping fuel at x-gpm into the crankcase (or onto the ground) with the engine running? I wouldn't think so...... So in that case, your Diagram #1 would be the better choice, but I've never seen anyone do it that way. Keep us advised, if you do.... you will need the solenoid valve, as you've indicated, just because that would prevent the above scenario that I've described. But that could be a manual control, so you could switch to the other pump. Chances are, if you need to switch, you've already stopped the car to figure out what's going on under the hood. But if you are going to install that "solenoid" or whatever, you may as well install a second one downstream of the electric pump, so that in the event that something fails in the electric pump, you can prevent the mechanical one from "back-feeding" through it. So there's my 2 francs. :-) Keep us posted! --Brooks in Dallas Philippe Courant wrote:
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