[Racinfan83]

I have a Mallory electric fuel pump on the Nova. The problem is that if the car sits for any length of time (two weeks or so) without being run - I have to get out the air hose and the rag and pressurize the tank with the pump running to get it to prime. Any suggestions on how to fix this??

 

[Vin63]

Is the pump drawing the fuel from the top of the tank, such as the OE fuel sending unit and pick up? Most electric fuel pumps are designed to be efficient pushers, not pullers. This means most electric fuel pumps operate best when mounted at or below the level of a sump, so that there is constant fuel at the pump via gravity. Otherwise, you'll cavitate the pump and it will not last very long.

 

[Racinfan83]

It is attached to a oem fuel tank. The pump itself is mounted pretty high up, and the rubber line to it goes up from the tank line to the filter which is mounted up on the frame rail at the highest point to keep it up and out of the way. I dont know if I can lower the pump any - but may be able to redo the line. You think this "loop" in the line could be causing it??

 

[Vin63]

If there is a loop in the line, then it would make things worse. It's kind of tough on electric fuel pumps to "draw" or "pull" fuel - they are much more efficient at pushing a column of fluid. On stock applications where fuel is drawn from the top of the tank, electric fuel pumps are often used as lift pumps to augment the mechanical primary pump that is more effecient at pulling the fluid - e.g., some of the diesel applications.

 

[Racinfan83]

Thanks. I have to live with the tank as it is - but I can try to get the line so that it doesn't go above the level of the pump. This issue didn't happen until I got my exhaust ran out behind the tires and we had to mess with the fuel line placement. I had no idea that the pump won't "suck" the fuel out. Thanks for the info and I'll see what I can do! :yes:

 

[Vin63]

No problem...it's more that the electric pumps are not as efficient at drawing fuel, so eliminating any loops in the lines between the tank and the pump will help.

 

[tpinovaII]

One of the reasons you see so many fuel cells in the trunks of cars at the dragstrip is because it makes it easier to mount the fuel pump below the tank. As stated earlier, electric pumps are designed to push fuel. Mounting the pump below the tank lets gravity work in your favor. A cheaper alternative is to add a fuel tank sump kit and mount the pump as close to the tank and as low on the frame as is reasonably possible. If you are really on a tight budget and have fabrication skills, you could build your own sump.

http://www.hotrod.com/howto/70438_gas_tank_weld/index.html

 

[TomM]

The problem is that if the car sits for any length of time (two weeks or so) without being run - I have to get out the air hose and the rag and pressurize the tank with the pump running to get it to prime. Any suggestions on how to fix this??

Stop letting your car sit for that long, why would you neglect your Nova this way.......oke:.............

Seriously......do they make a check valve you could install inline?

T,

 

[veno]

there is another soloution.. a auxiliary sump... not one on the OEM tank but a 1/2 gal box mountd slightly below or at least half the CL of the tank.... where the pump has a steady supply or a resivior to draw from......

 

[Racinfan83]

UPDATE: I went out and changed the line so that it is flat with the inlet of the pump instead of going up about 8" from the tank line to the frame and back down. Turned the key and presto primo! :yes:
I do not like how the line is - but it will work for now. I looked all over to see if there was an alternate spot to mount the pump - not many options at all. With the 2 1/2" exhaust running up and then dumping behind the tires it kinda took all my space. The only conceivable place I could put it is on the back of the wheel hump just above the tank and that's no better than what I have - and it would put the pump at an angle which I don't know if you can do that or not. It works for now. Seems like I only have time to fix stuff on this car so it WORKS - not to fix it right....

 

[Vin63]

Good to hear, Eric. Hopefully, that will keep you up and running.

Yeah, ideally it is best to have the electric fuel pump supplied with fuel by gravity from the bottom of a tank as in a sump. It's just hard on an electric fuel pump to run without fuel going through it even for a little bit.

 

[6NOVA4]

UPDATE: I went out and changed the line so that it is flat with the inlet of the pump instead of going up about 8" from the tank line to the frame and back down. Turned the key and presto primo! :yes:
I do not like how the line is - but it will work for now. I looked all over to see if there was an alternate spot to mount the pump - not many options at all. With the 2 1/2" exhaust running up and then dumping behind the tires it kinda took all my space. The only conceivable place I could put it is on the back of the wheel hump just above the tank and that's no better than what I have - and it would put the pump at an angle which I don't know if you can do that or not. It works for now. Seems like I only have time to fix stuff on this car so it WORKS - not to fix it right....

on my old 70 I used a holley red pump mounted near the tank in the rear hump area. I ran it as low as I could so it wouldn't have issues like what you had. Basically was put between the rubber line coming out of the tank and the steel line that was bolted to the body. I also ran a fram steel fuel filter after the pump. I feel its better to push the fuel thru the filter then pull it.

 

[Vin63]

I also ran a fram steel fuel filter after the pump. I feel its better to push the fuel thru the filter then pull it.

Be careful about not having a filter before the electric fuel pump because debris or particulants in the fuel is often just as damaging to the fuel pump as starving the pump.

 

[tnblkc230wz]

I have a Mallory pump on my stock tank as well. Below are pics of how it is mounted. The bracked is made out of 16 guage steal and works very well. It is attached to the trunk floor with two 3/8 inch bolts with nylon lock nuts. The best of all is setup actually siphones the gas out of the tank. I have to pinch off the fuel line to unhook it. I never have a problem with priming the pump.

 

[tony]

Be careful about not having a filter before the electric fuel pump because debris or particulants in the fuel is often just as damaging to the fuel pump as starving the pump.

^^^^ X2 !!! :yes::yes::yes:

 

[Racinfan83]

I do have a cheap filter between the tank and the pump. I figure cheap is better than nothing...
230wz - I like that setup a lot! I probably have the technology here at home to fab up a bracket like that and move mine to the center. That would get it away from the exhaust as well which would be good!
I got it so it works for now. Thanks for the pics of yours!!!! :yes::yes::yes::yes:

 

[6NOVA4]

Be careful about not having a filter before the electric fuel pump because debris or particulants in the fuel is often just as damaging to the fuel pump as starving the pump.

true dat. It's worked for me so far.

 

[BillsNogo]

Where did you mount elec. fuel pump 3rd gen?

I currently have my fuel pump and fuel cell mounted in the trunk, but have an opportunity to pick up a like new gas tank with a sump for $50. It would be nice to have my trunk back, and have searched on this site that it is necessary to mount the pump low as they are pushers, not pullers.

So, where have you 3rd gen guys mounted yours that was out of the way?

 

[The Big Al]

There is a trick. Even with pump mounted above tank.

You have the fuel lines on both intake and exit sides run in the up position.

This causes a fuel trap in the pump.

If one of the lines is running in the down position the pump will became dry.

 

[slickman]

Why don't you just switch over to a mechanical pump, Holley makes some nice ones?

UPDATE: I went out and changed the line so that it is flat with the inlet of the pump instead of going up about 8" from the tank line to the frame and back down. Turned the key and presto primo! :yes:
I do not like how the line is - but it will work for now. I looked all over to see if there was an alternate spot to mount the pump - not many options at all. With the 2 1/2" exhaust running up and then dumping behind the tires it kinda took all my space. The only conceivable place I could put it is on the back of the wheel hump just above the tank and that's no better than what I have - and it would put the pump at an angle which I don't know if you can do that or not. It works for now. Seems like I only have time to fix stuff on this car so it WORKS - not to fix it right....