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Re: [Mgs] Fuel Pump?

To: "Mglist" <mgs@autox.team.net>
Subject: Re: [Mgs] Fuel Pump?
From: "PaulHunt73" <paulhunt73@virginmedia.com>
Date: Sun, 17 Jan 2021 09:49:47 -0000 2/ULCr+X0I0vk4k3L44JcuDsgUN01HaUHuR68QajC7ANgBM+tXGn7ZdT
Delivered-to: mharc@autox.team.net
Delivered-to: mgs@autox.team.net
References: <579080298.451759.1610314370698.ref@mail.yahoo.com> <579080298.451759.1610314370698@mail.yahoo.com> <78.A6.32236.E64C3006@mta4.srv.hcvlny.cv.net>
It's not possible to get vapour lock on an MGB with a standard fuel pump and
carb(s) in good working order.

Once the floats have dropped the float valves open and with the top of the
float chamber(s) open to atmosphere (as they should be) any fuel in the
lines that is being pressurised by the pump will flow in.  Fuel would have
to be vaporising at the rate of about 2 Imperial pints per minute which is
impossible (unless the car is on fire ...) to cause the pump to chatter as
described.  Any vapour in the lines will be pushed out of the lines by the 
pump to be replaced by liquid fuel, just as when filling a dry system.  The 
pump by itself is more than enough to 'prime' the system, nothing else is 
needed.

Vapour lock does happen in very hot condition where you have a engine driven
pump, where due to the lowered pressure in the line from the tank the fuel
will boil more easily.  And the cure seems to be to fit an electric pump by
the tank, as pressurised fuel in the long line and the engine compartment is
less likely to boil.  There are videos of this being don on YouTube.

Poor running and problems hot starting on an MGB in hot weather are more
likely to be down to fuel expansion overflowing into the intake and causing
a rich mixture, or ignition problems, but neither wouldn't be accompanied by
a chattering fuel pump.

PaulH.


----- Original Message ----- 


>I don't know where you live or what the weather is like, but the whole
>story sounds like a classic vapor lock situation.

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