Question on vortec 'poppet' style fuel injection system

Good day,

I was wondering if anyone could confirm or deny this for me... Regarding
GM¹s poppet injection Œspider¹ system on the 4.3L vortecs, etc., do any of
you know if all cylinders receive fuel at the same time? In other words, is
it possible to mix up the poppets or if they¹re all working properly, will
it make no difference? I didn¹t know if there was actually individual
pulsing control from the central injector or if they simply Œfired¹ when
they exceed the pressure of the poppet spring itself.

Thanks!
Andrew.

On Jun 11, 8:18Â*pm, AWN > wrote:
> Good day,
>
> Â* Â*I was wondering if anyone could confirm or deny this for me.... Â*Regarding
> GM¹s poppet injection Œspider¹ system on the 4.3L vortecs, etc., do any of
> you know if all cylinders receive fuel at the same time? Â*In other words, is
> it possible to mix up the poppets or if they¹re all working properly, will
> it make no difference? Â*I didn¹t know if there was actually individual
> pulsing control from the central injector or if they simply Œfired¹ when
> they exceed the pressure of the poppet spring itself.
>
> Thanks!
> Andrew.

They get fuel at the same time.

Central port injection (CPI)
General Motors developed an "in-between" technique called "central
port injection" (CPI) or "central port fuel injection" (CPFI). It uses
tubes with poppet valves from a central injector to spray fuel at each
intake port rather than the central throttle-body. However, fuel is
continuously injected to all ports simultaneously, which is less than
optimal. This system tends to have a high failure rate and repair is
fairly easy. The 2 models used were CPFI from 1992 to 1995, and CSFI
from 1996 and on.

Thanks! I thought so but I wanted to be sure. I put replacement clips on
some of the poppets and was curious as to whether or not I'd be up the creek
without numbering them. It ended up being a moot point as I decided to do
the job properly and put a new Delco unit in to be sure. Yes - I did the
nut kit also.

Thanks again!
Andrew.





in article , dahpater
at wrote on 6/11/07 9:49 PM:


> They get fuel at the same time.
>
> Central port injection (CPI)
> General Motors developed an "in-between" technique called "central
> port injection" (CPI) or "central port fuel injection" (CPFI). It uses
> tubes with poppet valves from a central injector to spray fuel at each
> intake port rather than the central throttle-body. However, fuel is
> continuously injected to all ports simultaneously, which is less than
> optimal. This system tends to have a high failure rate and repair is
> fairly easy. The 2 models used were CPFI from 1992 to 1995, and CSFI
> from 1996 and on.
>
>

On Jun 11, 11:01 pm, AWN > wrote:
> Thanks! I thought so but I wanted to be sure. I put replacement clips on
> some of the poppets and was curious as to whether or not I'd be up the creek
> without numbering them. It ended up being a moot point as I decided to do
> the job properly and put a new Delco unit in to be sure. Yes - I did the
> nut kit also.
>
> Thanks again!
> Andrew.
>
> in article . com, dahpater
> at wrote on 6/11/07 9:49 PM:
>
>
>
>
>
> > They get fuel at the same time.
>
> > Central port injection (CPI)
> > General Motors developed an "in-between" technique called "central
> > port injection" (CPI) or "central port fuel injection" (CPFI). It uses
> > tubes with poppet valves from a central injector to spray fuel at each
> > intake port rather than the central throttle-body. However, fuel is
> > continuously injected to all ports simultaneously, which is less than
> > optimal. This system tends to have a high failure rate and repair is
> > fairly easy. The 2 models used were CPFI from 1992 to 1995, and CSFI
> > from 1996 and on.

Andrew-did putting in the delco injector unit help your fuel trim
issue? Jp

Jerry,

My short term fuel trim is dead flat now at idle but I am still running
+20-25 on the long term fuel trim readings. I am starting to think that
this might be normal as it idles perfectly, and has it's full power band
back. The fuel economy is sooo much nicer when you aren't boiling off the
gas under the plenum... For what it's worth, I can now pull the plenum,
clean the ports, protect the cylinders, replace the spider unit and slap it
all back together with proper torque specs (I think 144in lbs/12ft lbs) in
under 40min. The first time I pulled the plenum it took me about 3 hours
total. All I can say is that a deep-well 10mm socket and a 3/8" torque
wrench make the job a snap. Thanks for all your help previously - I
couldn't have done it without the help and encouragement. It sickens me to
think that with an hour labour and approx $300 USD I was able to do the same
repair that my dealer charges $1500 for....

Thanks.
Andrew.

>
> Andrew-did putting in the delco injector unit help your fuel trim
> issue? Jp
>

On Jun 14, 3:31 pm, AWN > wrote:
> Jerry,
>
> My short term fuel trim is dead flat now at idle but I am still running
> +20-25 on the long term fuel trim readings. I am starting to think that
> this might be normal as it idles perfectly, and has it's full power band
> back. The fuel economy is sooo much nicer when you aren't boiling off the
> gas under the plenum... For what it's worth, I can now pull the plenum,
> clean the ports, protect the cylinders, replace the spider unit and slap it
> all back together with proper torque specs (I think 144in lbs/12ft lbs) in
> under 40min. The first time I pulled the plenum it took me about 3 hours
> total. All I can say is that a deep-well 10mm socket and a 3/8" torque
> wrench make the job a snap. Thanks for all your help previously - I
> couldn't have done it without the help and encouragement. It sickens me to
> think that with an hour labour and approx $300 USD I was able to do the same
> repair that my dealer charges $1500 for....
>
> Thanks.
> Andrew.
>
>
>
> > Andrew-did putting in the delco injector unit help your fuel trim
> > issue? Jp


WOW! The dealer charges $1500 for this???? You probably get 'free'
clams, steak and all the booze you can drink while at this stealer
err..I mean dealer. later jp

Jerry,

The part alone with the nut kit is over $900 here as I recall.... Clams and
steak sounds good...

Andrew.






in article , blazerman
at wrote on 6/14/07 10:48 PM:

> WOW! The dealer charges $1500 for this???? You probably get 'free'
> clams, steak and all the booze you can drink while at this stealer
> err..I mean dealer. later jp

Jerry,

Although it seems all my issues have been resolved - I can smell unburned
gas when I park. Could it be that if I really 'get' on the pedal, it
partially floods and some unburned gas gets through? Is this just
ridiculous to imagine? The other question - if my oil has been thinning due
to the gas leaking under the plenum, would that cause the same 'unburned
gas' smell? I know the thinned oil is very bad for the rings and
compression, etc but I al curious about the gas smell. I also thought
perhaps the evap cyl might be faulty or leaking... Otherwise I am thrilled
now with the performance of this vehicle - night and day difference.


Thanks.
Andrew.

>>
>>> Andrew-did putting in the delco injector unit help your fuel trim
>>> issue? Jp
>
>
> WOW! The dealer charges $1500 for this???? You probably get 'free'
> clams, steak and all the booze you can drink while at this stealer
> err..I mean dealer. later jp
>