In a message dated 8/4/99 12:47:22 PM Eastern Daylight Time,
kehrlich@dyax.com writes:
> A number of folks at VTR suggested I replace my mechanical fuel pump
> with a low pressure electric pump to better feed the Webers. In the
> interest of safety, how could the electric pump be wired to guarantee
> its shutoff in the event of a collision? I heard one concept about
> routing the wiring through the oil pressure sensor, which sounded nifty.
> Any other suggestions?
Keith,
I'm a little bit late, but for whatever it's worth, here's how I'd wire it.
I'd run a wire from a convenient green wire to one side of an inertia switch
(if you use 14 gauge or larger, there is no need to add a fuse, as the green
wires are already fused). From the other side of the inertia switch, I'd run
a wire to one side of a hidden on-off switch. From the other side of the
on-off switch, I'd run a wire to one side of a single pole, double throw
(SPDT) relay coil. The other side of the relay coil I'd wire to ground.
Next, I'd run a fused 12 gauge wire from one of the white wires, either at
the ignition switch or the fuse box, to the common terminal of the SPDT
relay. Place the fuse (10 amp) as close to the white wire as you can. From
the NO relay contact, I would run another 12 gauge wire to the fuel pump.
>From the NC relay contact, run a 14 gauge wire to a buzzer.
Mount the inertia switch inside the cockpit where it can be reached while
driving to reset it if it should trigger from hitting a pothole or similar.
It would be a nuisance to have to stop the car and raise the hood to reset
it.
Mount the on-off switch in a very hidden location, as it will serve as a
theft deterent. With the switch off and the fuel pump not running, the car
will only run for about a block before it runs out of gas to the carbs. Place
it where you can operate it in a casual manner, such that a would-be thief
will not notice you operating it.
Mount the buzzer inside the cockpit where you can easily hear it. This buzzer
serves two purposes: First, if you forget to turn the switch back on when you
return to your car, it will buzz when you turn on the key to remind you. It
is embarrassing to have your car stall in the middle of the road. Secondly,
if you do hit a pothole, you won't have to wonder if the inertia switch was
triggered, as the buzzer will sound if it was. You can then just reach over
and reset it before you run out of gas.
Mount the relay in an accessable location, and carry a spare. If the relay
should ever fail, just pop in a new one and be on your way.
I don't recomend using an oil pressure switch to interlock with the pump for
two reasons: One, it isn't necessary. If the pump puts out enough pressure to
flood the carbs if the engine should stall, it is putting out enough pressure
to flood the carbs when you are setting at a stoplight and idling, and you
will have to add a pressure regulator. Two, if you don't drive the car on a
regular basis, the fuel in the carb float bowls can evaporate, making the car
hard to start till the fuel pump refills them. With an electric pump, you can
turn the key on and wait a few seconds while the float bowls are refilled.
Others may disagree with me, but that's my feelings on the subject.
If any one is interested, I'd be glad to post wiring diagrams on the internet
for your use.
Dan Masters,
Alcoa, TN
'71 TR6---------3000mile/year driver, fully restored
'71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion - see:
http://members.aol.com/danmas/
'74 MGBGT---3000mile/year driver, original condition - slated for a V8 soon
'68 MGBGT---organ donor for the '74
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