Residual fuel pressure

[softtouch]

I am pretty sure fuel cannot be compressed. So how is the residual pressure maintained? Is the spring loaded diaphram in the regulator supplying the pressure?

 

[desertrat]

I am pretty sure fuel cannot be compressed. So how is the residual pressure maintained? Is the spring loaded diaphram in the regulator supplying the pressure?

Aren't fuel lines flexible or are they all metal now?

 

[aps45819]

On fuel injected cars, the gas tank is pressurized. If it doesn't bleed off the system stays under pressure

 

[desertrat]

On fuel injected cars, the gas tank is pressurized. If it doesn't bleed off the system stays under pressure

What device do they use to pressurize the fuel tank? Why do I not feel a rush of air and gas fumes when I take the cap off? There might be a bit of pressure, but not much.

 

[glhs837]

On fuel injected cars, the gas tank is pressurized. If it doesn't bleed off the system stays under pressure

What device do they use to pressurize the fuel tank? Why do I not feel a rush of air and gas fumes when I take the cap off? There might be a bit of pressure, but not much.

Actually, they are kept in vac, that way it's a negative pressure deal, any break in the seal lets air into the tank, not fuel vapors out in the open. Vac is supplied by the engine, of course. Dodge calls its system the NVLD. But the lines after the pump are kept in pressure, some bleed down over time, others stay pressurized for some time.

But in any case, ST, I am pretty sure the pump itself has a one way valve that maintains the pressue, but I could be wrong.

 

[Merlin99]

I am pretty sure fuel cannot be compressed. So how is the residual pressure maintained? Is the spring loaded diaphram in the regulator supplying the pressure?

If the fuel pump isn't running, there isn't any pressure. When the ignition is turned on, the fuel pump relay comes on first to build the pressure before the engine starts turning.

 

[Chris0nllyn]

If the fuel pump isn't running, there isn't any pressure. When the ignition is turned on, the fuel pump relay comes on first to build the pressure before the engine starts turning.

True, but there is still some pressure in the lines when you turn the car off.

This is why you shoul bleed the lines before working on the fuel system.

It's not much, but enough to give you a spray.

 

[Merlin99]

True, but there is still some pressure in the lines when you turn the car off.

This is why you shoul bleed the lines before working on the fuel system.

It's not much, but enough to give you a spray.

True

 

[MMDad]

I am pretty sure fuel cannot be compressed.

Why do so many people think that liquids cannot be compressed?

 

[glhs837]

I think the disconnect is the difference between being compressed, and being pressurized, at least under pressures encountered in the average vehicle.

 

[Merlin99]

Why do so many people think that liquids cannot be compressed?

Most people go by waters seeming uncompressability. All matter can be compressed, but some things take so much pressure to see a density change that they are "uncompressable". Water at 15 K PSI has only changed density slightly over 1%.