Speed of fuel flow in fuel lines? (As in empty fuel line...)

[bill190]

Electric fuel pump. Gas tank in rear of vehicle...

Say you have a bad fuel pump check valve and overnight all the fuel drains back into the gas tank. And the fuel line is filled with air.

How fast does the fuel flow when the pump is turned back on?

Or how long would it take for the fuel to reach the engine?

(This would be assuming that there is a fuel pressure regulator and this regulator is sending excess fuel (air) back into the gas tank via the return line. If this is the way it works?)

 

[patprimmer]

It should not drain back unless an injector or the pressure regulator are leaking. For all but the smallest amount of fuel to get out, air has to get in.

Regards
Pat
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[WGJ]

....or vapour forms during a hot soak and fuel is repelled into the tank via a poor non-return valve.

Bill

 

[NormPeterson]

I assume that you know the pump's flow rating. Estimating the fuel line volume shouldn't be difficult.

How quickly the pump regains its prime is another matter entirely.


Norm

 

[WGJ]

If you've got 2.5mtr of 8mm OD fuel line and a 100 litre per hour pump, you'll need about 3 sec just to fill the supply line.

Bill

 

[patprimmer]

In my experience, electric fuel pumps self destruct fairly promptly if run dry. If I had an efi car that I suspected had lost its prime, I would turn the ignition on and off in fairly short bursts so the pump rollers did not get hot and gaul.

Regards
Pat
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[WGJ]

Depends on how old the vehicle is Pat.
Anything thats less than about 10 years old, or that isn't a top HP machine will probably have a turbine. That doesn't mean to say that it WILL BE turbine, there's still quite a few OEMs using Gerotors and Bosch-type roller cells, just not as numerous as a few years back.

bill190 - what's the pump and/or vehicle in question?

Bill

 

[bill190]

No specific vehicle in question. I just see a lot of cold starting problems on the internet. They take a few minutes to start in the morning, but once they are started they start right up.

So I was wondering if fuel was draining back into the tank by morning (due to a faulty check valve), and the time it takes to start the vehicle in the morning is the time it takes for the fuel to get back in the lines?