Re: Crossfire injectors.

["Fran and Bud" <quest100@gte.net>]

This is what an old GM training manual says about the Model 400, Crossfire.
Quote:
"----through a fuel filter and the fuel inlet line to the nozzle end of the
injector assy.-------
--Incoming fuel flow greatly exceeds injector flow, so excess fuel passes
through the accumulator, which compensates for a momentary fuel pressure
drop in the front unit fuel meter body due to injector openings.  Fuel from
the accumulator passes through the connecting fuel tube to the rear unit,
where the rear unit injector operates the same as the front unit injector. 
Again, incoming fuel flow exceeds injector flow, and the excess fuel passes
to a pressure regulator assembly.  Fuel pressure is regulated by the
balancing of the circulating fuel flow on one side of a diaphragm assembly
and the calibrated spring on the other side, providing desired fuel pressure
at both injector nozzles. Fuel in excess of injector needs is returned
through the fuel return line to the fuel tank.  Neither the fuel pressure
regulator nor the accumulator is serviced separately from its related fuel
meter cover assembly." End quote

While a regulator has spring and diaphragm, an accumulator needs only a
diaphragm that can stretch under pressure and maintain pressure as it
returns.  Some types of accumulators have a free floating piston that
compresses trapped air and then maintains pressure as the compressed air
pushes it back against a reduced inlet.  I suspect that the small metal
spider is designed to "manage/control" the amount of stretch that the
diaphragm is allowed and its corresponding recovery rate.

PS:
Carl,
If you ever plan to go to Muroc or El Mirage this coming season, contact me
offline ahead of time.
We don't live too far apart, but not really close either.  Would enjoy
meeting you.
Bud (Surge Tank)
 
----------
>From: Carl Summers <InTech@writeme.com>
>To: gmecm@diy-efi.org
>Subject: RE: Crossfire injectors.
>Date: Tue, Feb 8, 2000, 7:29 PM
>

>I've got a couple of pairs of crossfire setups here and can take them apart
>to see, but I would have to agree, one is probably a dampener..hth's
>-Carl Summers
>
>-----Original Message-----
>From: owner-gmecm@diy-efi.org [mailto:owner-gmecm@diy-efi.org]On Behalf
>Of Ken Kelly
>Sent: Thursday, February 03, 2000 4:19 PM
>To: gmecm@diy-efi.org
>Subject: RE: Crossfire injectors.
>
>
>> I may be way off base on this(happens alot), but I thought the Idea of
>>accumulator had to with keeping the firing of each injector from effecting
>>the other since they are in series.
>>i.e. the front injector firing wouldn't affect FP to the rear when it
>fired,
>>especially under higher demand times.
>
>I was under the same impression until I took it apart. There's no regulation
>of any kind going on here. Just a rubber diaphragm with a hard metal piece
>in the middle. On the body, there's a small metal "spider" that keeps the
>metal piece from going anywhere. If you think about it; they don't have two
>FPR's for the 2bbl throttle bodies, either.
>
>Ken
>
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