Spring drive-limped home

old51fordman

old51fordman

Member
After a wonderful drive in my 1933 sedan, it began sputtering home. I made it to my driveway but it said "no thank you" to the steep incline to my garage.

It is a fuel issue in or near the gas tank.

I have a low pressure electric assist pump in line but run off the normal gas pump except after it sets a long time or if i have a vapor lock problem.

I have no desire to run just off of an electric pump.

I changed the fuel filters (yes i have a couple in line). The electric pump which previously would not run (presumably due to reaching pressure limit) would run after the new filters. I finally got the car running just a bit ago after opening and priming the gas line and the mechanical fuel pump.

My gut says that I have not yet solved the real problem.

I don't remember any screen on the gas inlet in the tank. Please correct me if i have forgotten.

If it is not a plugged/blocked inlet before the electric pump, I am left with the theory that the electric pump is beginning to fail and may have a break in the diaphragm. It sounds a bit "intermittent" like every so often there is a hesitation in its operation.

If the electric pump is failing could that cause the mechanical pump to not be able to suck through it?

Finally if my memory serves me correctly, and I replace the electric pump, I want to keep it below 5psi. I have a vague memory of trying a pump on our '47 ford coupe that topped out at 7 psi and I think I remember that being enough to push down the needle valve in the carburetor and causing it to flood.

So--if i get a new diaphragm pump should it be under 5psi ( i don't want to put a pressure regulator inline.)

Do you have any other ideas or advice?

Thanks for the advice
 
Vented or non-vented gas cap? Drive it for a while and unscrew the gas cap.If you hear a "woosh",replace it with a non-vented cap.Just a guess.
 
It's the opposite way around. If you hear s woooosh when undoing it, you need a vented cap.

Willit Stop said:
Vented or non-vented gas cap? Drive it for a while and unscrew the gas cap.If you hear a "woosh",replace it with a non-vented cap.Just a guess.
Click to expand...
 
If your tank is original, it is vented at the fuel/air tank unit so it does not matter whether your gas cap is vented or not unless the tank unit vent tube is plugged up. Do you use the original hydrostatic fuel gauge and if so, is it working properly? If not, that could be symptomatic of problems with your tank unit.
 
Have a '47 which has no vent tube on tank. Recently bought a NOS vented gas cap after recent apparent interruption of fuel supply. The vented cap made no difference. Carb, distributor and coil are recent. So problem likely (1) vapor lock or (2) faulty mechanical pump. A non-vented cap can be drilled to allow venting - search posts.

I have similar set-up as you .... an Airtex elec pump at tank used for start-up. Its a flow-through design so it does not restrict the mechanical pump. Both pumps test individually at 3 psi each which I understand is the maximum whereas 2.0 to 2.5 psi is most desirable. Sounds like 5 or 7 psi is too high for a stock carb set-up.
 
Thanks for all the help and comments.

To answer some of the questions:
Yes I do have the original hydrostatic gauge unit. It functions well but I am getting ready to add some more fluid as much has evaporated since we finished it about 15 years ago.

I don't know the pressure of the electric pump I am using but believe it is under 4 lbs. It has worked perfectly for a long time.

The problem is prior to the engine compartment as I was not getting gas out at the connection prior to the flexible line at the pump.

It seems to me the only real options a plugged inlet in the tank (old tanks no matter how well you clean them have rust and/or tar like gas residue) or a dying electric pump.

Can electric pumps have intermittent problems when dying or do they tend to be good or bad?

My plan is to first blow some low pressure air back into the tank from the electric pump to see if there sounds like a restriction.

Am I missing anything?
 
I have an old teleflex inner cable (same as speedometer cable) that I use to run through fuel lines to remove obstructions. Varnish build up can restrict or completely plug a line. Compressed air should flow through a line freely. Any rubber fuel line can be suspect after time due to deterioration, inner collapse, or air/fuel leak A new electric pump might also be in order. Nothing lasts forever.
 
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