Re: Help with hooking up an electric pump.
Posted by Thomas Wilcox On 2009/2/7 13:22:17
Here is another set up, combining several approaches mentioned, with both an electric and mechanical pump. This is the set up that is on my 34. The electric pump is installed with a bypass line and check valve and wired to a momentary on/off switch. The mechanical pump is installed in a standard fashion. Immediately before the carb a T is installed. On the descending portion of the T, a restriction fitting is placed, and then a fuel line that returns to the tank. The restriction fitting is sized so that +80% (approx) of the fuel pressure is delivered to the carb, the remaining pressure drives fuel back to the tank.
With the set up, the mechanical pump runs faster, but shallower. Fuel is constantly being re-circulated. The electric pump is only needed for priming if the car has been sitting a while, or to briefly add a little pressure if a vapor lock is being experienced.
The benefits:
1) The recirculation of fuel keeps the fuel system cooler and greatly diminishes the potential for vapor lock.
2) If the mechanical pump begins to fail, the driver will notice before the pump completely fails.
3) If the engine stops, the pump stops.
4) If the engine begins to starve for fuel do to a vapor lock, a very brief pulse from the electric pump will clear the lock.
The drawbacks:
1) The mechanical pump diaphragm may wear more quickly. I'm not sure of this yet. I've driven the car approx. 2000 miles with the set up, and it is still good.
This system worked great on my trek from Minnesota to Warren, OH (approx. 925 miles) last summer. We were regularly driving all day in +85 degree weather. We would experience vapor lock (engine stumbling) when the fuel tank was nearing empty. A brief pulse with the electric pump would clear it up, and a re-fuel would solve the problem for another couple of hundred miles.
Tom
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With the set up, the mechanical pump runs faster, but shallower. Fuel is constantly being re-circulated. The electric pump is only needed for priming if the car has been sitting a while, or to briefly add a little pressure if a vapor lock is being experienced.
The benefits:
1) The recirculation of fuel keeps the fuel system cooler and greatly diminishes the potential for vapor lock.
2) If the mechanical pump begins to fail, the driver will notice before the pump completely fails.
3) If the engine stops, the pump stops.
4) If the engine begins to starve for fuel do to a vapor lock, a very brief pulse from the electric pump will clear the lock.
The drawbacks:
1) The mechanical pump diaphragm may wear more quickly. I'm not sure of this yet. I've driven the car approx. 2000 miles with the set up, and it is still good.
This system worked great on my trek from Minnesota to Warren, OH (approx. 925 miles) last summer. We were regularly driving all day in +85 degree weather. We would experience vapor lock (engine stumbling) when the fuel tank was nearing empty. A brief pulse with the electric pump would clear it up, and a re-fuel would solve the problem for another couple of hundred miles.
Tom
Attach file:
(41.21 KB)
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