V8 fuel tank and pump. One for the experts !!

Hi,

Trying to understand my V8 petrol tank and fuel pump. This may solve a long standing problem with fuel starvation at quarter tank.

Do I understand correctly that the left inlet tube (see photo) fills the cup at the bottom of the pump when fuel level is low ?

And if so, where does it pick up the fuel. I can not see this tube coming from the tank when I am underneath. I want to check if it is sqeezed flat when the new boot floor was installed.

Or am I wrong and is it totally different ?


Thanks !

Is that not the return tube?

Return tube should fill the cup at the bottom as well as the pump feeding its own pot if its like an aftermarket swirl pot design in there

lorri789 said:

Is that not the return tube?

Click to expand...

No doubt you and The Dr. are right.

Can you explain how it works ?

Dr_evil said:

Return tube should fill the cup at the bottom as well as the pump feeding its own pot if its like an aftermarket swirl pot design in there

Click to expand...

Ehhhhh

this is essentially whats going on in your tank





but its all crammed into this so you don't need the low pressure side as its running in the tank rather than out of it







No idea why its not working on 1/4 tank but are you sure its not because its the wrong pump/sender fitted so its not reading correctly and you're actually running near empty when its reading 1/4 ?

Dr_evil said:

No idea why its not working on 1/4 tank but are you sure its not because its the wrong pump/sender fitted so its not reading correctly and you're actually running near empty when its reading 1/4 ?

Click to expand...

Fantastic drawing and pic Doc, will have a study on that !

Pretty sure about qtr tank cause to fill up is 65 litres.

FlyingDutchman said:

Fantastic drawing and pic Doc, will have a study on that !

Pretty sure about qtr tank cause to fill up is 65 litres.

Click to expand...

65 is nothing if thats to full my tanks like 94L

Always thought mine is 80 ltr, or 85. Pretty sure actually.

And the fuel gauge has always shown according mileage etc.

Other thing, why is there a return line from the engine ? Fuel is burned no doubt. ?

Or is this to make sure the engine always gets enough petrol for acceleration, i.e. excess fuel is supplied.


And another question. The tank pump does not reach till the bottom. How does that fuel gets pumped out ?

because you're supplying the engine with far more fuel than it can burn its 36 ish psi at something like 33 gallons per hour

Your V8 cant burn that much so it has to return it to the tank

Ok, thanks,

And another question. The tank pump does not reach till the bottom. How does that fuel gets pumped out ?

the pump should reach the bottom of the tank IIRC

Right.

I have taken the pump out and cleaned the filter etc. Not much dirt in it.

Still no clue why it suddenly started to fuel starve at qtr tank 6 years ago.

Maybe I should empty the tank and have look in it. :confused2:


Thanks for explaining the fuel tank and pump.

Tells me a lot :5bhurray:

no idea why it'd start starving now if its been working so long

The Quest continues !


I can now rule out the pump.

In that light this thread is a success.

Keep us posted

You see dem springs on the pump in the pic doc posted?

The idea is that you put the pump in and then push the top down before you fit the red ring.

The pump is spring loaded into position sat in the bottom of the tank.

If your springs have gone or seized or something it might be having bother.

And the little cup is called a swirl pot, the bag filter sucks fuel up and the pump pumps it to the engine, but when the level of fuel gets below the level of the pot fuel is not guaranteed so the fuel return keep the pot full regardless of how much fuel is sloshing around outside.

Also the fuel cools the pump so it has to flow plenty.

I didn't see any springs on mine when I had it out.

From what I could see is that the swirl pot was closed at the bottom, and filled from the tube on the LH side of the pic.

As Noisy says the swirl pot is kept filled by the return line when fuel is low.

Could that be at about a quarter tank ?

Theres two versions, ones got springs there the others got a tube

swirl pot is kept full at all times!

iirc you should put the seal on and then the orange ring otherwise it is hard to fit