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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / June 2007Question 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 spider¹ 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 fired¹ when they exceed the pressure of the poppet spring itself. Thanks! Andrew. > Good day, > [quoted text clipped - 8 lines] > 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. > They get fuel at the same time. > [quoted text clipped - 7 lines] > 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 [quoted text clipped - 19 lines] > > 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 > Jerry, > [quoted text clipped - 17 lines] > > 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. > 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 |
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