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vapor lock

Subject: vapor lock
From: Jarl/Carol <>
Date: Mon, 23 Dec 1996 22:01:48 -0800
I wonder whether your problem is vapor lock or fuel starvation. Does it
ONLY happen when hot? The fittings on the fuel pump are installed with
fiber washers and they crush and gradually become loose. If on the
intake side they can draw air. There is a filter in the bottom fitting
(remove cap take out nylon filter and clean) and there is a brass screen
filter soldered to the fitting at the bottom of the tank where the pipe
attaches. This screen often is mostly clogged by corrosion (it is very
fine) You must drain the tank, disconnect the line, clean the screen,
and reinstall. Before you start working on anything, check the output.
THIS APPLIES TO ALL MGs: a minimum pump output would be 10 gal per hour,
more is better - a good SU can deliver 20. If you do the math 10 gph
equals about a pint and a third per minute (.6 liter/min). Disconnect
the hose from the rear carb and pump into a jar and see how long it
takes to pump a pint or half liter. If it takes too long, your filters
are clogged, or the line under the car is crushed, probably by a jack
that slipped. Keep the end of the hose under the surface of the gas
accumulating in the jar, if you get bubbles, you've got a leak on the
intake side of the pump. (the latter applies to TC/TD only) Now you've
got some idea of what you are looking for, good luck! Vapor lock ONLY
happens when the gas on the intake side of the pump becomes so warm that
it boils under the vacuum condition of suction. Since the gas in Rocky's
short hose is under pressure, it would not boil easily and would
normally only cause a problem when you park for a little while after a
drive.   Jarl

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