[Healeys] Escaping air!!

Bob Spidell bspidell at comcast.net
Tue Jul 1 06:34:31 MDT 2008


   Paul,
   re:
   "Is it normal practice to fit pipes to the vents on a BJ8?"
   According to (at least) one SU fuel pump book I have read there should
   be  flexible tubing from the unvalved vent at the diaphragm end of the
   pump  body.   The  flexible  tubing  should  be routed to a clean, dry
   location.   AFAIK,  Healeys  were  never  fitted with such vent tubing
   (surprised  Burlen  didn't know this).  I installed one to vent in the
   boot.
   Sometimes, there's a cylindrical plastic cover on the check valve.  It
   doesn't come with new pumps, however.
   re:
   "I  called Burlen UK who make the pumps and they had not heard of this
   problem  before but assumed that the pump was creating excess pressure
   from within and was expressing it through the valves."
   I  don't  buy this explanation.  The valves are one-way to either draw
   fuel  into  the  pump or expel it to the carburettors--there should be
   little, if any, air passing through them unless there are leaks in the
   system (or the tank is empty).  The pressure created is limited by the
   strength  of  the  spring  behind  the diaphragm (SU fuel pumps should
   produce about 3psi, give or take).  Excess pressure usually results in
   flooding at the carbs.
   bs
   Paul Baker wrote:

   I thought you might be interested in an update on this after I have
   had a chance to do some investigation.

   It would appear that air is escaping or being released from either
   the vent at the plastic housing end or at the metal body end. It is
   difficult to work out from which it is coming as its very intermittant
   and with the noise of the engine.

   I called Burlen UK who make the pumps and they had not heard of this
   problem before but assumed that the pump was creating excess pressure
   from within and was expressing it through the valves.  Their view was
   that if the pump was not leaking and working fine then it should be
   ok.  They were surprised that as the pump is mounted under the rear
   seats that neither of the two vents had pipes leading rearwards from
   the pump as they felt that water could get into the pump through the
   vents and be causing this problem.  As I said before, the pump has
   been on the car since 1991 when the car was rebuilt and has not caused
   any problems.  Is it normal practice to fit pipes to the vents on a
   BJ8?

   As I have a new SU electronic pump which I had kept as a spare, I will
   put that on the car and keep the old one as the spare.  It will be
   interesting to see if this one, plus vent pipes, makes the same
   noises.

   Paul

   67 BJ8

   66 BJ8

   65 Sprite

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Bob Spidell           San Jose, CA            bspidell at comcast.net
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