On Sat, Jun 27, 1998 at 09:05:50AM +1000, David Peterson wrote:

> Another thought, is the return line really nesessary or can it be blocked,
> early model vehicals didn't have them. Maybe the flow pressure wasn't as
> high ? My old jalopy has an electric fuel pump with no reticulation.

It is necessary; the fuel pumps used on injected engines are different
to those used on carburetted engines. The pump for an injection system operates
at a high pressure (it provides the injection pressure). The electric pumps
used on carburettors basically provide a low pressure via a spring-loaded
diaphragm with a solenoid to reload the spring as required; with no flow the
pump simply stops. An injection type pump is quite different and the return
line is required so that the pressure can be regulated (the injectors depend on
a constant pressure).

I suspect that cars with injection systems and trip computers get the fuel
flow data from the engine controller, which calculates it from the injection
parameters. To measure this externally would require monitoring of the pulse
rate and duration to the injectors and knowing the parameters to convert this
to flow rate.


--
Clyde Smith-Stubbs               |            HI-TECH Software
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