[Healeys] Tapitty tapping of Fuel Pump

[Michael Salter]

I think Alan is on the right track but suspect that the vaporization could
be happening on the inlet side of the pump.
The lower pressure on the suction side of the pump combined with the
elevated temperatures due to the proximity of the exhaust can result in
boiling of the fuel in the line before it reaches the pump.
As gaseous fuel is compressible the pump cannot "hydraulic lock" to keep
the points open so it just keeps tick ticking away passing gaseous fuel
toward the carburetors which can be sufficient to keep the engine running.
The situation tends to deteriorate when you try to drive uphill because the
pressure at the pump inlet becomes even lower, as the pump is elevated
above the fuel level, and the engine demands more fuel to climb the hill ☹.
The best solutions are to try to keep the fuel lines before the pump
protected from exhaust heat, ensure that there are absolutely no leaks in
the line ahead of the pump and that there are no restrictions, such as an
inline filter ahead of the pump.
Many modern cars utilize an insulating sleeve over fuel lines to minimize
heat transfer ... may be worth considering.
M


On Sun., Jun. 21, 2020, 10:09 p.m. Alan Seigrist, <healey.nut at gmail.com>
wrote:

> Hi Gary -
>
> If you start hearing the pump run really quickly, it can be indicative of
> vapor lock getting back into the fuel line... can happen at the end of long
> trips.  It's because the fuel starts vaporizing around where the line goes
> into the floats, and the float jet then is no longer cutting off fuel flow
> because it is pushing vapor into the float bowls, which leaks out the
> overflow tube.  As long as your car is running it should be okay, you might
> use more fuel than normal.  Try wiring a piece of wood to the incoming fuel
> line - this is an old trick with Atlantics to act as a heat sink on hot
> days and stop vapor lock on the Atlantics which use mechanical fuel pumps.
>
> Best,
>
> Alan
>
> On Mon, Jun 22, 2020 at 9:12 AM editorgary--- via Healeys <
> healeys at autox.team.net> wrote:
>
>> Yesterday I took my Healey BN& out for its first good run of the season
>> -- 75 miles of southern Oregon backroads -- with our local Rogue Euro Car
>> Group. Everything was terrific from start to finish. Car started on the
>> first push of the button after sitting for six weeks, ran smoothly from
>> start to finish, never faltered in restarts, everything nominal.
>>
>> Except that, towards the end of the run on a pretty hot day (in mid 90s
>> though the car never ran warm all day) as I was cruising along about 40
>> mph, the fuel pump started tapping at a high rate of speed and pretty
>> continuously -- certain enough so I could hear it behind me. I have a
>> standard original-spec points-style fuel pump, purchased new from Moss
>> about 10 years ago and running without any issues every since.
>>
>> Any thoughts from anyone -- could it just have been the heat? As noted,
>> the car never missed a beat, so fuel was getting through the carbs smoothly
>> at all times.
>>
>> Anyone?
>>
>> Gary Anderson
>>
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