>Lawrence writes:
>>However, this simplicity does have a high price. These systems run at a
>>very high fuel pressure to actuate the mechanical injectors; 70psi
>>coming off the pump, 50psi in the system. If you break a fuel hose,
> I thought most all fuel injection systems ran at high fuel pressures
>all the way from the tank (where the pumps are located) to the injector rails.
> I know that injection systems are required to have a cutoff valve that
>stops the fuel pump when the engine quits. Perhaps you could modify this
>switch
>to shut off in the case of extremely high mass flow - like a broken fuel line.
>You could measure the difference between the mass leaving the tank versus that
>returning.
I've had several '70s BMWs, mechanical and electronic fuel injection. They all
run at high pressure, hence the need for electric fuel pumps, special fuel
filters and high pressure tubing & clamps. They route the fuel pump power
through a relay controlled by an oil pressure switch. The engine dies and the
fuel pump shuts off. Any rubber hoses in a fuel injected system should be
replaced at the first sign of cracking or wear to prevent ruptures. To control
fuel delivery to each cylinder, the mechanicals used a fuel distributor and the
electronics use solenoid like valves at each injector. Both use a cold start
injector that injects extra fuel into the intake until the car warms up. Note
that the mechanical fuel distributors are very susceptible to water damage,
especially if the vehicle sits for a long time (beware of junk yard spares).
They are not rebuildable and are $$$$ new. The injectors can be kind of pricey
too. However, both systems are very reliable, I never had to repair or adjust
any I've had.
Mike G.
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