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CSFI to MPFI - Vortec Engine Fueling Fix

Posted in How To on December 1, 2010 Comment (0)
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In 1996, Chevrolet added Vortec heads to their 5.0L and 5.7L V-8 engines. This top end makeover also brought a redesigned fuel delivery system known as a Central Sequential Fuel Injection (CSFI) system. With a single injector for each cylinder, the CSFI system has a much more efficient design than its predecessor. By only delivering fuel to individual cylinders sequentially, at the proper times during the engine's cycle, the system produced considerable performance improvements within the Vortec motors. Unfortunately, this system created many problems and forced Chevrolet to issue several Technical Service Bulletins (See: GM TSB# 00-06-04-003B).

In the CSFI system, injectors are located centrally in the upper intake manifold and send pressurized fuel into tubes that run into each cylinder. This central body and long, leg-like tubes gives the system an emblematic shape, leading many to refer to it as the "spider injector system." It is the tiny poppet valve assemblies at the end of the pressurized tubes that cause the most trouble within the system.

This poppet valve is controlled by a mechanical spring, making it is very sensitive to fluctuations in the fuel pressure. Not enough pressure and the valve won't open enough, while too high of a pressure will unintentionally keep the valve open too long, leaking fuel into the cylinder. The other issue is that the end of a poppet valve is positioned just above the intake valve to each cylinder. This puts the valve very close to the hottest part of the engine; the combustion chamber. After every spray, the poppet valve is coated with residual fuel. The latent heat of combustion bakes the fuel, creating minute amounts of varnish. With roughly a few million combustions occurring in each cylinder for every thousand miles driven, this fuel varnish can quickly build up enough to partially block or completely clog a poppet valve. The best way to solve these problems is to get rid of the poppet valve altogether.

There are several aftermarket companies that sell a direct replacement for the problematic CSFI system. These aftermarket kits can be found for $400 to $500, and use a simple Multi Port Fuel Injection (MPFI) system. The major difference between the two systems is that the aftermarket system removes the faulty poppet valves and replaces them with electronic injectors located at the end of each fuel tube. These new injectors have a much larger opening making it very difficult to clog an injector. In addition, the injector is now opened electronically instead of mechanically. This maximizes the performance of the engine's stock settings by precisely controlling when then fuel injection begins, as well as the duration of the fuel spray (pulse width). This will translate into a quick, crisp response during acceleration.

The MPFI system is still subject to some of the same concerns as the CSFI system, such as low fuel pressure. However, the aftermarket kit eliminates the most flawed and troublesome parts of the CFSI system, the poppet valves. These reasonably priced MPFI kits are an advised upgrade by Chevrolet because, in a single afternoon, they bring definitive performance and reliability to your '96-to-'03 Vortec V-6 or V-8 engine.

When one of the poppet valves completely clogged our engine with 180,000 miles on the odometer, we thought our Vortec V-8 may have seen its last days. Our '96 Chevy truck was beginning to fall on its face when hitting the throttle. But it felt more like a fueling problem than worn-out engine. Once we diagnosed the problem and swapped in the new fuel injection retrofit kit, the '96 Tahoe felt more powerful than the day it was driven off the lot.

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