re: GTV L-jet System/Fuel Pump shut-off

[James Montebello <jamesm@domain.elided>]

I think Kurt is misinterpreting the function of the throttle switch.
The switch simply informs the ECU that the throttle is fully closed,
or fully open (i.e., there are actually two switches).  When closed,
the fuel is cut if engine speed is above a set point (decel fuel cut,
which prevents backfiring, and helps emissions).  It is NOT cut at idle.
The fuel cut is not accomplished by shutting off the fuel pump, but by
leaving the injectors closed.   

The fuel pump on L-Jet runs whenever the engine is running or cranking.
It never shuts off until the engine itself stops running.  The system
is a full-return system, so fuel is continually pumped from the tank
to the fuel rail and back to the tank, some of it being drawn off to go
through the injectors.

Anyone who really wants to understand how any Bosch injection system
works is encouraged to buy a copy of Probst's book on the subject.
It covers L-Jet very well.  All L-Jet systems are basically the same,
with only minor variations other than the "major" versions (L, L w/
lambda, LH, LU, etc).  

james montebello

On Tue, 19 Mar 2002, Joe Elliott wrote:

> I don't have my wiring diagrams here, but I dare say that's 
> impossible.  If for no other reason than because the engine wouldn't 
> run if you shut off the fuel pump.  And I'm pretty sure that the 
> throttle switch wires go straight to the ECU, which has no say as to 
> whether the pump runs, IIRC.
> 
> Joe Elliott
> '82 GTV6 (L-Jet)
> 
> (parents):
> '86 Volvo 240 (L-Jet)
> '87 Jaguar XJ6 (pseudo L-Jet)
> (buddies):
> '85 SAAB 900T (LH-Jet)
> '87 Milano (L-Jet)
> 
> At 1:02 PM -0500 3/19/02, alfa-digest wrote:
> >Date: Tue, 19 Mar 2002 07:30:24 -0800
> >From: "Kurt Incledon" <kurt6507@domain.elided>
> >Subject: GTV L-jet System/Fuel Pump shut-off
> >
> >Group and especially Curtis,
> >I think all of you in this discussion should carefully examine the operation
> >of the throttle switch mounted on the Plenum Throttle Body in the schematic
> >diagram of the late model GTV-6 and Milano manuals, (note I say late model
> >GTV-6 as I am not familiar with the inertia switch operation) you will find
> >that at idle with the throttle body closed this switch will shut off the
> >fuel pump.
> >Replies and comments welcome.
> >Kurt
> >AROSC
> >kurt6507@domain.elided
> >87 Milano w/L-jet injection
> >86 Spider w/L-jet injection
> >71 Volvo P-1800 w/D-jet injection
> >All with throttle switch to control unnecessary fuel flow at idle.
> 
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