<VV> Oil Presure Inertia Switch (long)

[JVHRoberts at aol.com]

The Vega OP switch will shut the pump off if there's a loss of oil pressure, 
due to stalling, etc. And this makes it no less safe than a car with a 
mechanical pump, with better priming after sitting for a long time. 
The Vega OP switch will allow the pump to run with the key on ONLY if:
1. The starter is engaged. 
OR
2. The engine has sufficient oil pressure to turn off the idiot light. 

This should satisfy any reasonable safety needs, if you think the mechanical 
pump is safe enough. 


In a message dated 4/7/2005 6:09:46 AM Eastern Standard Time, 
emills5 at cfl.rr.com writes:
    Although it is true that the Vega OP switch will allow the fuel pump to 
run while cranking the engine, if it is the same one sold by one of the 
vendors, it creates another problem.  It does not contain what is needed to cut off 
the fuel pump in case of an accident and the engine  stops (due to loss of oil 
pressure). This creates an extreme fire hazard.  True...if one has also 
installed an inertia type switch in series with the fuel pump (and assuming it 
tripped as designed) the fuel pump would not keep running.  But what if the 
collision was not of sufficient force to cause the inertia switch to trip.

My advice is to install an OP switch that contains a set of N\O contacts that 
will keep the engine running when the engine has oil pressure, but will kill 
the circuit to the fuel pump if oil pressure is lost.  OP switches are 
available that have this set of N/O contacts, plus a set of N/C contacts that one can 
use to operate the idiot light on the dash. (A normal OP switch contains only 
one set of contacts, a N/C set that is used to operate the idiot light).  Use 
of the type switch that I suggest, (along with an inertia switch) does not 
alleviate the cold (or dry carb) problem, but this can be overcome by wiring a 
momentary switch to the fuel pump to prime the carbs before cranking, which 
allows the car to crank quickly.  Works for me on two cars with zero failures 
since installed, which is a better track record than I was having with manual 
fuel pumps.  Somewhat more elaborate but covers all the bases.

This was covered in detail in the December 2003 Issue of the Communiqué in a 
Tech Topic article that I authored.  I still have copies that I can supply if 
anyone is interested.  Since this is a very debatable subject, and it is not 
my intention to offend some that disagree with my thinking or to start a fuel 
pump flame war, please contact me off line if you are interested, and I will 
forward you a copy of the article.

Cecil Mills
Cocoa, Fl.