Electric fuel pump questions

zoegrant

zoegrant

Well-known member
I have installed a new aftermarket fuel tank on my 36 coupe.
this tank was purchased from TANKS INC...it is not the same configuration as the original but was listed to fit a 36 coupe.
The original tank had the fuel outlet at the bottom of the tank so gas flowed naturally out of the tank.
This tank has the fuel line going in to the top of the tank attached to a tube that goes inside to the bottom of the tank...
So here is my problem.....I have installed an electric fuel pump that does not pull the fuel thru to the carb.
the electric fuel pump I am using is 6 volt with a 2-4 lbs pull.
The tank has 5 gallons of fuel but does not seem to be able to pull the gas thru the lines to the carb.
The pump is trying to pull the fuel from the tank but to no avail. I am thinking that the electric pump does not have enought pulling power to suck the fuel up to the top of the tank so that it can then proceed forward to the carb.
I am thinking of changing the pump from a 2-4 lb to 4-6 lb pull.
What do you think ? Could there be any other reason that you can think of that would cause a no fuel flow with an electric pump ?
When the fuel pump is turned on and the fuel line is disconected I do feel the pump blowing air forward so I presume it is working correctly.
My first thought was that the connections were not tight and that I might be sucking air so I tightened all connections but all is the same.
What do you think is happening ????????????
 
Is the pump mounted near the level of the bottom of the tank? If the pump is at or below the lowest point that the fuel is in the tank, the feed line to the pump would be a siphon and should present very little resistance to the pump. Pumps are must better at pushing than at pulling. I would also double check your fitting to be sure there is not an air leak.
 
You want the pump mounted as close to the tank as possible. Electric fuel pumps push the gas easier then pulling it. In the past with TANKS type with the fuel pickup at the top i mounted the fuel pump to the rear crossmember.

With a pickup tube off the top of the tank it keeps any junk or dirt from getting into the fuel line within reason. Or water that might collect in the tank from moister
 
Also , dont increase the fuel pressure as the float anx needle wont take it. Volume and flow is what most motors want and not pressure.

Stock flathead is ok on 1/4 fuel line, start adding more carbs 5/16. A big OHV motor 3/8
 
Should the gas cap be vented ?????
There did not appear to be any air leaks in the fuel line & pump I installed.
I disconnected the fuel line in front of the electric pump and when I put my finger up to the pump inlet it does suck against my finger. Although I am not sure how strong the suck should be on my finger.
When I unhook the front of the electric fuel pump hose from the fuel line and listen to it when the pump is turned on it sounds like the pump is sucking air from the tank.
I hate to pull the new tank down again but will have to if I do not find the problem
The pump is located close to the tank and it is set down lower than the tank.
Any suggestions before pulling the tank ?
 
I have an extra electric fuel pump but it is "NOT" 6 volt...it is 12 Volts, can I use the 12v pump to test to see wether it is a bad pump causing my no gas issue on my 6v car ???
 
Disconnect the inlet (suction) side of the pump (place a pan under the line) and blow into the tank with your mouth or very low pressure. Gas flowing out through the line would indicate an open path and defective pump OR vacuum leak. Once you get the siphon started the pump might be able to carry on but I would be suspicious of it.
 
To answer the vent question, every tank has to have a vent somewhere. If your pumping fuel out of the tank, something has to replace it, air.
 
40cpe.....I used an after market tank from "TANKS" so blowing into the tank will not cause the fuel to come out as the fuel comes out from the top of the tank not from the bottom like the original tank.
There is an 8 1/2" long tube that the gas has got to come up thru to get to the fuel line and then the electric pump and gravity will take over.
I am going to try a new electric pump and will post how I make out..
p.s.....I forgot that the tank itself is vented with a rubber tube with a rollover valve.
 
zoegrant said:
40cpe.....I used an after market tank from "TANKS" so blowing into the tank will not cause the fuel to come out as the fuel comes out from the top of the tank not from the bottom like the original tank.
There is an 8 1/2" long tube that the gas has got to come up thru to get to the fuel line and then the electric pump and gravity will take over.
I am going to try a new electric pump and will post how I make out..
p.s.....I forgot that the tank itself is vented with a rubber tube with a rollover valve.
Click to expand...

Why would that have anything to do with blowing into the tank to see if fuel comes out of the fuel line? It has nothing to do with the fuel line exiting the bottom or top of the tank. In either case the fuel comes from the bottom of the tank! It will tell you if the tube is not really at the bottom of the tank or clogged. I think you can blow hard enough to move fuel 8 1/2 inches up a tube!!! :)
 
My truck ran out of gas last year, put in some gas, but it wouldn't start. I could hear the pump running but no pressure on the gauge. Blew a little air into the tank and all is well now. "stupid is, what stupid doez"
 
Had the same problem on my 35 with a tanks tank. I didn't have enough gas in the tank to get it primed. Added gas and it started working.
 
ok...just tried a new electric fuel pump and still no gas...UGH
I was thinking that the tube came detached and was lying in the bottom of the tank so I tried to siphon and gas came right out.
It acts like the fuel pump is sucking air but all connections are tight.
I am stumped :(
 
IF the pump is working and IF the tube to the tank is open, then you have to have a connection issue.
 
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zoegrant said:
ok...just tried a new electric fuel pump and still no gas...UGH
I was thinking that the tube came detached and was lying in the bottom of the tank so I tried to siphon and gas came right out.
It acts like the fuel pump is sucking air but all connections are tight.
I am stumped :(
Click to expand...

Blow into the ga tank ! It'll push the gas till it gets primed .
A siphon will be created no matter if the tanks outlet is on the bottom or top , just start the flow . If you blow air into the line with the cap on , it should expand the tank like a ballon and also push the gas out of the line when you stop .
 
Jseery....I did blow into the tank and gas is bubbling and I can mouth siphon gas out..
Planojc....I have about 6 gallons of gas in the tank
Ol`Ron...I will use my compressor to blow more air into the line going to the tank to see if that helps...Will report back...
THANKS TO EVERYONE FOR COMMENTS ON THIS PROBLEM
 
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