From: noel shelley (noel@shelley1722.freeserve.co.uk)
Date: Mon Sep 22 2003 - 15:31:33 PDT
Hi List,
Although designed as a failsafe engine shut down system for a
diesel genset it also stops the engine from starting until oil pressure
comes up. Using a water temp switch in the system if the water overheats or
the oil pressure fails the engine stops .
It works like this!
The oil switch is normally closed with the engine stopped , switching to
ground .
The temp switch is normally open when cold , switching to ground at about
105 C {220F }.
Both switches are wired in parallel to the coil of a relay , the coil being
fed from the ignition switch . The contacts are normally closed and the
fuel shutoff is fed from the ignition switch through the contacts .
On turning on the ignition the oil switch being closed pulls the relay in
and fuel valve is kept shut , on cranking the engine only when the oil
pressure comes up does the switch open allowing the relay to close , making
the fuel valve circuit and the engine is fed with fuel to start .
Once running if either switch closes , the relay goes open circuit , the
fuel valve closes and the engine stops .
The same circuit could be used for a gasoline or gas engine but instead of
the fuel valve the ignition coil would be wired through the relay contacts .
The relay used can be any small normally closed one with contacts rated at
10 Amps or more and a coil voltage to suit the electrical system of the
engine . The temp switch if used should be fitted in the thermostat housing
and can be sourced locally as described in the text { I used a Peugeot/
Citroen 1.9 D one }It`s not very sophisticated but it works .
for more details Email me Noel
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