Centerline
Well-Known Member
This is kind of long, so please bare with me.....
I've been doing a lot of reading on this subject and I have a solution that works... at least for me. The 440 in my '64 Polara sits sometimes for a couple weeks or more between starts and cranking the thing for what seems like forever is getting old. So I decided to supplement my mechanical fuel system with an electric pump just for priming the carb. I figured I'd share this mod with the forum just in case anyone else wants to use this method to solve the evaporation problem with today's crappy fuels.
I took a look at a lot of small electric pumps and decided on the Airtex E8090. Its an inexpensive pump (around $35) and puts out 7+ psi which I figured was enough to supply my Holley 750 with enough fuel to fill the bowls in just a few seconds of operation.
One of the things I read was that some electric pumps will not allow fuel to flow through them when they are not operating. This was a primary requirement and was the main reason I chose the Airtex pump. After speaking with their tech people they assured me it would allow the mechanical pump to pull fuel through it when it was off, and they were correct. It does. My mechanical pump actually puts out 7 psi pulling fuel through this pump.
Now I know what some of you are saying. You can't push fuel through a mechanical pump, but you can. Mechanical pumps have a mechanically operated bellows and two one way "reed" type valves. When the cam lobe puts pressure on the fuel pump lever it pushes the bellows and creates a vacuum in the pump which opens the one way valve on the "tank" side of the pump and sucks fuel into the pump chamber. When the cam rotates and releases the lever a spring above the bellows pushes the bellows back down and forces the tank side valve closed while at the same time forcing the carb side valve open and pushing the fuel through that valve up to the carb. A pretty simple mechanical setup really. So it should be easy to see why an electric pump mounted near the tank should be able to provide enough pressure to force open the tank side valve in the pump, fill the pump chamber and also force the carb side valve open allowing fuel to flow to the carb. And, this is exactly what happens.
There is one catch however..... If your mechanical pump bellows fails there is the possibility you could pump raw gas into your oil pan. Not a good thing. However, this is highly unlikely if your pump is in good condition and you're only using the electrical pump to prime the carb before starting the engine.
One more thing about electric pumps. A lot of people bitch about these small inexpensive pumps and say they don't last long. In most cases these people didn't follow the directions and either installed the pump in the wrong location or just installed it incorrectly. My Airtex pump stated that it needs to be installed as close to the tank as possible.... and for good reason. These pumps push fuel much better than pulling it. The directions also stated the outlet needs to be slightly higher than the inlet. Why they want you to do this I don't know but I'm not about to second guess the engineers who designed this product so that's exactly what I did when I installed mine.
First thing I did was to install a fuel pressure gauge so I could tell what kind of pressure the electric pump would put out while pushing fuel through the mechanical pump. The answer was 6-7 psi. More than enough needed.
The pump was installed just above the right side shock mount. You can see the outlet is higher than the inlet. Plus I also installed a filter between the pump and the tank as recommended by Airtex. If that cross-member looks a little different than yours its because I added a 2x2 .120 wall square steel cross-member between the frame rails to strengthen that area because I'm running air shocks.... but that's another story.
To make sure there was no way I could accidentally leave the pump on I mounted a spring loaded toggle switch under the dash so you have to physically hold it in the "ON" position for it to run. This way you don't have to worry about the pump running if the car is in an accident, rolls over or something else catastrophic happens.
So, does this really work? You bet it does. After sitting for almost a month I activated the electric pump for about 15 seconds and had 6 psi of pressure at the carb. I let it run for another 10 seconds to fill the bowls in the carb and then shut it off. Turned the ignition switch and it started right up. The mechanical pump was providing the carb with 6-7 psi while pulling fuel through the Airtex pump so...... Problem solved.
I've been doing a lot of reading on this subject and I have a solution that works... at least for me. The 440 in my '64 Polara sits sometimes for a couple weeks or more between starts and cranking the thing for what seems like forever is getting old. So I decided to supplement my mechanical fuel system with an electric pump just for priming the carb. I figured I'd share this mod with the forum just in case anyone else wants to use this method to solve the evaporation problem with today's crappy fuels.
I took a look at a lot of small electric pumps and decided on the Airtex E8090. Its an inexpensive pump (around $35) and puts out 7+ psi which I figured was enough to supply my Holley 750 with enough fuel to fill the bowls in just a few seconds of operation.
One of the things I read was that some electric pumps will not allow fuel to flow through them when they are not operating. This was a primary requirement and was the main reason I chose the Airtex pump. After speaking with their tech people they assured me it would allow the mechanical pump to pull fuel through it when it was off, and they were correct. It does. My mechanical pump actually puts out 7 psi pulling fuel through this pump.
Now I know what some of you are saying. You can't push fuel through a mechanical pump, but you can. Mechanical pumps have a mechanically operated bellows and two one way "reed" type valves. When the cam lobe puts pressure on the fuel pump lever it pushes the bellows and creates a vacuum in the pump which opens the one way valve on the "tank" side of the pump and sucks fuel into the pump chamber. When the cam rotates and releases the lever a spring above the bellows pushes the bellows back down and forces the tank side valve closed while at the same time forcing the carb side valve open and pushing the fuel through that valve up to the carb. A pretty simple mechanical setup really. So it should be easy to see why an electric pump mounted near the tank should be able to provide enough pressure to force open the tank side valve in the pump, fill the pump chamber and also force the carb side valve open allowing fuel to flow to the carb. And, this is exactly what happens.
There is one catch however..... If your mechanical pump bellows fails there is the possibility you could pump raw gas into your oil pan. Not a good thing. However, this is highly unlikely if your pump is in good condition and you're only using the electrical pump to prime the carb before starting the engine.
One more thing about electric pumps. A lot of people bitch about these small inexpensive pumps and say they don't last long. In most cases these people didn't follow the directions and either installed the pump in the wrong location or just installed it incorrectly. My Airtex pump stated that it needs to be installed as close to the tank as possible.... and for good reason. These pumps push fuel much better than pulling it. The directions also stated the outlet needs to be slightly higher than the inlet. Why they want you to do this I don't know but I'm not about to second guess the engineers who designed this product so that's exactly what I did when I installed mine.
First thing I did was to install a fuel pressure gauge so I could tell what kind of pressure the electric pump would put out while pushing fuel through the mechanical pump. The answer was 6-7 psi. More than enough needed.
The pump was installed just above the right side shock mount. You can see the outlet is higher than the inlet. Plus I also installed a filter between the pump and the tank as recommended by Airtex. If that cross-member looks a little different than yours its because I added a 2x2 .120 wall square steel cross-member between the frame rails to strengthen that area because I'm running air shocks.... but that's another story.
To make sure there was no way I could accidentally leave the pump on I mounted a spring loaded toggle switch under the dash so you have to physically hold it in the "ON" position for it to run. This way you don't have to worry about the pump running if the car is in an accident, rolls over or something else catastrophic happens.
So, does this really work? You bet it does. After sitting for almost a month I activated the electric pump for about 15 seconds and had 6 psi of pressure at the carb. I let it run for another 10 seconds to fill the bowls in the carb and then shut it off. Turned the ignition switch and it started right up. The mechanical pump was providing the carb with 6-7 psi while pulling fuel through the Airtex pump so...... Problem solved.