need to solve a surge tank problem

Belgian1979vette

Belgian1979vette

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I'm getting ready to piece up for my efi install.

I'm going to run a surge tank under the hood to keep the high pressure pump supplied with fuel under all conditions. This surge tank was normally to be fed with an electric fuel pump. However I would like to have this low pressure pump only to run when the level in the surge tank is getting low. Any ideas on how to accomplish this ?
 
I'm feeding mine off a mech pump on the block but with a small bypass on top of the surge tank that goes back to the tank in case low pressure delivery is more than the high pressure pump demand. It's also a nice way to burp the surge tank from any air trapped inside. I would simply run the low pressure pump all the time. Otherwise you'd have to use some small float activated swith
 
I'm sure something could be fabricated, but it would be unnecessarily complex. All I've seen run a low pressure pump, mechanical or electric, full time. They're either vented to return to tank, or a carb float/needle & seat shuts off flow into the tank.
 
Have you seen Aeromotive's foam-surrounded, in-tank fuel pump? I've not tried - but the theory seems sound.

Alternatively, a friend built a surge tank from some black pipe and fittings - other than looking like a pipe bomb (and being teased unmercifully because of it) it's worked well for him.
 
Twin_Turbo said:
I'm feeding mine off a mech pump on the block but with a small bypass on top of the surge tank that goes back to the tank in case low pressure delivery is more than the high pressure pump demand. It's also a nice way to burp the surge tank from any air trapped inside. I would simply run the low pressure pump all the time. Otherwise you'd have to use some small float activated swith
Click to expand...

I have been thinking about that as well, but the bronze tipped fuel pump pushrod that's in there doesn't look like it will last a long time. I wouldn't want to open the engine because the pushrod is mushroomed.
 
SuperBuickGuy said:
Have you seen Aeromotive's foam-surrounded, in-tank fuel pump? I've not tried - but the theory seems sound.

Alternatively, a friend built a surge tank from some black pipe and fittings - other than looking like a pipe bomb (and being teased unmercifully because of it) it's worked well for him.
Click to expand...

That's more or less what I've built for it. It is by far the best solution, apart from the tank feeding issue.
 
the surge issue was one of the reasons that caused me to build my own tank. In my tank, I surrounded the pump with a box... so far, no starvation issues even with a mostly empty tank
 
SuperBuickGuy said:
the surge issue was one of the reasons that caused me to build my own tank. In my tank, I surrounded the pump with a box... so far, no starvation issues even with a mostly empty tank
Click to expand...

Yes, You can fit a pump in there if you want, but my pump is an external unit. It will be mounted lower so it will be constantly under pressure.

I'm inclined towards using my factory fuel pump, but I doubt the brass tipped push rod though.
 
Just a note : I was checking the Summit fuel pump I had here. What a piece of crap...pump wouldn't work. Took it apart and the thing was al rusted up and had metal shavings all over the place. The axle coming from the electric motor was glued in the rotor....of course it says : Made in China.
 
Belgian1979vette said:
Just a note : I was checking the Summit fuel pump I had here. What a piece of crap...pump wouldn't work. Took it apart and the thing was al rusted up and had metal shavings all over the place. The axle coming from the electric motor was glued in the rotor....of course it says : Made in China.
Click to expand...

I have a basically stock replacement tank from way before I bought my '72, in '95, it looks new inside, but with FI, I had a surge problem, finally got tired of it, and put in a steel air tank of about 5 gallon size....it fills off gravity from main tank, fuel is sucked from bottom of air tank, return goes into top of air tank, it vents to the evap canister, T's off in the line, and main tank return line is plugged....only issue is, the stock tank will stop draining with almost 2" of gas in the bottom, using the stock sending unit/float crap....I really need braze/weld/solder in a drain further forward, so as to get ALL the gas outta there......I actually ran outta gas last summer, and still had ~2" in the bottom of the main tank, the aux tank is lower than the main tank....I miscalculated the affects of my right foot.....;):cussing::amazed:
 
Me too

I'm also working on my EFI set-up. I've also decided to try a surge tank solution with an in-tank 255 LPH high pressure pump. I've fabricated a 5.5 in dia x 12 in tall (14cm dia x 30 cm tall) tank that will mount to the frame behind the right rear tire. That is where my existing electric fuel pump is mounted. The surge tank bottom will be well below the main tank. The tank will be fed by a low pressure electric pump and vented back to the main tank. Bad news is I just tested my existing LP electric pump and it doesn't have a free flow rate bigger than the HP pump at 3 bar so I have to get a bigger pump. My plan is to match the LP free flow output with the HP 3 bar output with a factor of safety so not too much will be returned via the vent. I considered letting the LP pump deadhead and use the internal bypass like in the carb application but that would leave a large air bubble in the surge tank.

If this method doesn't work well, I'll do like SBG and fab a tank with baffles and a sump. I'm not worried about fuel delivery issues. Pump noise could be an issue, but, since I can't hear the current eletric pump over the sidepipes I took this path as a simpler solution.

Grampy
 
You can use this to vent the tank.

http://www.summitracing.com/parts/abt-tf350-8

I don't think you'll run into problems with the low pressure pump. If it can feed the carb with fuel it will provide enough to provide the amount of fuel the FI will use. If hp ratings for the engine in question remain the same that is.

I was advised to use the Howard composite pushrod for the factory pump.
 
That type valve vents to atmosphere and is OK for the main tank but since I'm continuously pumping to the surge tank I'll have to have a return line to the main tank. If you use a surge tank with a float valve you could use that type of vent.

Grampy
 
Grampy said:
That type valve vents to atmosphere and is OK for the main tank but since I'm continuously pumping to the surge tank I'll have to have a return line to the main tank. If you use a surge tank with a float valve you could use that type of vent.

Grampy
Click to expand...

WHY would anyone need to use TWO pumps??? I fail to see the need,

I blocked off the mechanical pump years ago, and never looked back....

two electric pumps is just weird.....

the pump sets on the frame rail lower than the tanks, one drains into the other, and fuel returns to the lower/smaller tank.....vents are run parallel to the evap can.....simple/quick/easy.....

:eek:
 
mrvette said:
Grampy said:
That type valve vents to atmosphere and is OK for the main tank but since I'm continuously pumping to the surge tank I'll have to have a return line to the main tank. If you use a surge tank with a float valve you could use that type of vent.

Grampy
Click to expand...

WHY would anyone need to use TWO pumps??? I fail to see the need,

I blocked off the mechanical pump years ago, and never looked back....

two electric pumps is just weird.....

the pump sets on the frame rail lower than the tanks, one drains into the other, and fuel returns to the lower/smaller tank.....vents are run parallel to the evap can.....simple/quick/easy.....

:eek:
Click to expand...

The tanks in our cars are not baffled like original EFI's are. That's why you could run into a problem with fuel starvation while cornering with an almost empty tank.
 
Original EFI 82 has a non baffled tank, original EFI F bodies don't have a baffled tank either apart from a useless silly little pickup box. Easiest is to not run the tank lower than about a 1/4 full or weld a sump on it.
 
Gene,

Two pumps are to prevent running out fuel as you did with a usable amount of fuel in the main tank. If you gravity feed the small tank and lose the syphon in the main tank pick-up the frame rail pump may not be able to pull through the surge tank. 2 pumps are absolutely more costly and complex but more bullet proof as well. Simplest and cheapest solution is to run an external pump and keep the tank full but you know the downside to that.
Other solutions include multiple in-tank pick-ups, tank sumps etc. each has its advantage and disadvantages. I like two pumps for some anti-theft protection complexity.

Grampy
 
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