Title:92-95 CPI Repair
Author:IRCMaxell
For all trucks with a 4.3L vin W engine. This applies to the Central Port Injection (CPI) engines from 1992 to 1995. The CPI Unit is located inside the upper intake plenum. It consists of the cpi which is connected (integrated) into the fuel pressure regulator. To see the system, you must first take off the upper plenum. The unit is located in the center of the intake, with 6 poppet lines/nozzles branching off of it. There are 2 things that tend to break with this system over time. They are
1. Fuel pressure regulator: this is the most common thing that breaks. There is a diaphragm inside the fuel pressure regulator that breaks and will leak gas into the plenum. The fuel pressure regulator is in the center of the intake on the passenger side. It looks like a gold cylinder.
2. Inlet/Return fuel lines: There are 2 fuel lines that connect to the cpi unit. They are on the drivers side. They will weaken over time and can get pin size holes in them that will leak gas into the intake. These are also called the "Nut Kit".
Common systems of these failing are: Bad idle, hard to start, shaky revs, low gas mileage, and most important I think is bad smell from the exhaust. The best way to check for a failure is to remove the upper plenum. The plenum is the huge piece under the "vortec" plastic piece. Looks like there are 3 tubes going down on each side. There are about 9 or 10 10mm bolts that you need to take out. You will also need to remove the throttle linkage and all electrical connectors and vacuum hoses that attach to the manifold. I would suggest buying a Haynes manual or Chilton’s manual, as well as photo documenting your way through the process. It really isn’t that hard if you take your time and remember each step. If you do this, and get the intake off, look at it from the front. If one side of the intake appears clean, this will be where the leak is coming from. If it is passenger side, it is probably the fuel pressure regulator, if it is on the drivers side, it is probably the fuel lines. There is also other ways to check for a leak, but aren’t as effective. One way is to disconnect the brake booster line and smell for gas. It comes out the back of the plenum and goes to the brake booster at the back right of the engine on the firewall, (if looking from the front.). One other common, but not as effective method is to remove the Manifold Tuning Valve on the top of the plenum. First, remove the plastic "Vortec" cover. The MTV looks like a big round plastic disc held in by two torx bolts, and has an electrical connector. If you remove this, you should be able to see into the manifold and look for clean spots. If you determine your regulator to be bad, you have two options. You can replace the Regulator assembly, or the entire injector. Replacing the entire injector is a little bit more expensive, but also replaces the injector poppet nozzles, which commonly get stuck or dirty. The other common problem is the "nut kit", or the two fuel lines that connect to the injector. If they leak, they MUST be replaced. This is a good time to mention that if you are replacing the Injector or regulator, that you should definitely replace the nut kit as well. This will save a lot of headaches in the future. Lindertech offers rebuilt injectors, regulator kits, and the nut kit as well.. HELP (Check your local supply store) has the regulator kit available also. If you want to go to the dealer, expect to pay $473, and $63. I've checked. If you want them to do the install, expect $700-900+. This is a total rip off. INSTALL SECTION TOOLS NEEDED
Open Ended Wrenches
10mm Deep Neck Socket
Various other smaller sockets
T15 Torx bit (MUST BE A SOCKET TYPE)
Torx set (can be folding or socket)
Flat head screwdriver
Pair of needle nose pliers
Fuel pressure gauge
Step One - Remove the upper intake manifold
DISCONNECT THE NEGATIVE BATTERY CABLE!!! The plenum is the huge piece under the "vortec" plastic piece. Looks like there are 3 tubes going down on each side. There are about 9 or 10 10mm bolts that you need to take out. You will also need to remove the throttle linkage and all electrical connectors and vacuum hoses that attach to the manifold. Once you have the upper manifold off the stage is set. Step Two - Nut Kit Removal
At the rear of the manifold, there are 2 steel fuel lines. On the drivers side one you will see a Schrader valve. Attach the Fuel Pressure Gauge to this valve and release the pressure in the lines. Now, using an open ended wrench, remove both lines, and CAREFULLY move them out of the way. Be careful not to go too far, and bend them out of position. Now, using the T15 Torx bit, remove the screw that holds the nut kit in position. This is on the rear of the manifold and is VERY difficult to see. I suggest feeling around until you find it. Now, there is a spring clip attaching the nut kit to the injector, remove that using the screwdriver or pliers. Now the nut kit should just slide right out of the manifold. Step Three - Injector Removal
This is simple. There is an electrical connector on top of the injector. Now, CAREFULLY remove each of the 6 poppet nozzles by GENTLY squeezing the plastic clips. With all that done, the injector unit should lift right out. The Installation is simply the reverse of the removal. A couple of notes.
You are dealing with fuel here. NO SMOKING!!! Taking pictures of every step will greatly help remembering where everything goes. The T15 screw that holds the nut kit in WILL strip if forced. Be VERY careful, and make sure everything is aligned when inserting and removing this screw. While you have everything apart, now would be a good time to clean the EGR valve, as well as replace any old, worn vacuum lines. Written By: ircmaxell
Edited by : ircmaxell
Information Provided by: Jamesla30 |
