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Fuel Injectors Replacement
 
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Pelican Technical Article:

Fuel Injectors Replacement

Steve Vernon

Time:

2 hours2 hrs

Tab:

$7 to $1,400

Talent:

**

Tools:

24mm, 19mm, 17mm wrench, 10mm socket, extension, flathead screwdriver, rags

Applicable Models:

Porsche 944 Turbo (1986-89)

Parts Required:

New injectors, white lithium grease

Hot Tip:

Check for flooded cylinders

Performance Gain:

Better-running engine, improved fuel mileage

Complementary Modification:

Replace worn out hoses

If your car is starting to run rough, getting horrible gas mileage or has an error code, there is a good chance it is time to replace the fuel injectors. Modern fuel injectors are made of plastic. For this reason I do not recommend having them serviced or rebuilt. Older mechanical injectors opened by fuel pressure alone and were easier to service; newer injectors are made of plastic, need an electronic pulse from the ECU to open and are better replaced than sending them out for service.

A properly working injector will send a precise amount of atomized fuel into the induction system at a designated time. A weak or improperly working injector can do everything from send no fuel, to leak raw, non-atomized fuel into your engine.

Have a fire extinguisher handy and know how to use it. There will be some spillage of fuel as it's nearly impossible to prevent. Also, wear chemical resistant and proper eye protection. Make sure that you have plenty of paper towels or rags to help you clean up and dispose of them in accordance with your local regulations. Never store fuel soaked rags, as they can self-combust. Perform the injector removal in a clear, open, and well-ventilated space. In addition, it wouldn't hurt to have an assistant around in case there are any problems.

You are going to be opening holes that go into the engine. This being the case, before you begin, get a can of compressed air and blow all the dust and debris away from the injector ports.

Open the gas cap to relieve any residual pressure.

The fuel rail and injectors (red arrow) sits on top of the engine between the head and intake manifold.
Figure 1

The fuel rail and injectors (red arrow) sits on top of the engine between the head and intake manifold. There is a fuel supply line (green arrow) going to the fuel dampener on the front of the rail and a fuel return line (yellow arrow) coming out from the fuel pressure regulator on the rear of the rail.

To help decrease the pressure in the fuel rail, you will want to remove the fuel pump relay and turn the engine over a couple of times until it runs out of fuel.
Figure 2

To help decrease the pressure in the fuel rail, you will want to remove the fuel pump relay and turn the engine over a couple of times until it runs out of fuel. Begin by locating the relay panel. In earlier cars it will be up under the dash. For later cars it will be in the rear left side of the engine bay by the base of the windshield. Remove the cover (red arrow).

Check with your manual.
Figure 3

Check with your manual. Locate the fuel pump relay and remove it (red arrow). Crank the ignition over a few times until the car runs out of fuel. Fuel will still escape while performing this job, but this will help relieve some of the pressure.

The pressure regulator bolts to the rear of the fuel rail where the fuel enters the regulator (red arrow, hidden by bracket).
Figure 4

The pressure regulator bolts to the rear of the fuel rail where the fuel enters the regulator (red arrow, hidden by bracket). There is also a vacuum line (yellow arrow) and the fuel return line attached to it (green arrow). There is no need to remove the regulator from the rail as it will come off with the rail, but the lines must be separated.

Pull the vacuum line from the regulator (red arrow).
Figure 5

Pull the vacuum line from the regulator (red arrow).

Use a flathead screwdriver and remove the clamp from the return fuel line and slip the line off the regulator (red arrow).
Figure 6

Use a flathead screwdriver and remove the clamp from the return fuel line and slip the line off the regulator (red arrow).

Move to the front of the fuel rail.
Figure 7

Move to the front of the fuel rail. The pressure dampener mounts to the front of the fuel rail; on one end is the fuel supply line (red arrow), a vacuum line (yellow arrow) and a line out to the fuel rail (green arrow). The line out to the fuel rail actually has a fitting on the bottom of the dampener. There is no need to remove these, as they will stay on the rail when you remove it.

Remove the vacuum line by pulling it off (red arrow).
Figure 8

Remove the vacuum line by pulling it off (red arrow). These lines get old and brittle so use care when you remove it. Replace the vacuum line if necessary.

Support the 24mm nut on the dampener (red arrow) and use a 19mm wrench to loosen the fuel supply line (yellow arrow).
Figure 9

Support the 24mm nut on the dampener (red arrow) and use a 19mm wrench to loosen the fuel supply line (yellow arrow). Fuel will escape so be prepared to catch it and dispose of it properly. You can leave the 24mm nut holding the dampener to the bracket.

Move the supply and return line out of the way and cut any clips or zip ties holding the injector wiring harness to the fuel rail (red arrows).
Figure 10

Move the supply and return line out of the way and cut any clips or zip ties holding the injector wiring harness to the fuel rail (red arrows). Disconnect any plug wires or anything else someone might have attached to the fuel rail.

Use a small flathead screwdriver or pick and release the wire clips on the wiring harness (red arrow).
Figure 11

Use a small flathead screwdriver or pick and release the wire clips on the wiring harness (red arrow). Pull the connections off the injectors (yellow arrow).

Remove the four 10mm bolts holding the fuel rail to the head (red arrows).
Figure 12

Remove the four 10mm bolts holding the fuel rail to the head (red arrows).

Pull the fuel rail and injectors straight up and out from the intake manifold.
Figure 13

Pull the fuel rail and injectors straight up and out from the intake manifold.

The injector ports are open right into the engine so make sure to put some paper towel or rags in them (red arrows).
Figure 14

The injector ports are open right into the engine so make sure to put some paper towel or rags in them (red arrows). You DO NOT want anything falling in there, as it may mean removing the head to get it out. Be smart and plug them up fast.

The injectors and rail will come out as one piece.
Figure 15

The injectors and rail will come out as one piece. Take it to your bench or workspace. Be prepared because some fuel will still leak out when removing the injectors.

The injectors are held to the rail by a small clip (red arrow) that sits in a groove in the injector port on the rail (yellow arrow).
Figure 16

The injectors are held to the rail by a small clip (red arrow) that sits in a groove in the injector port on the rail (yellow arrow). You can slip the clip off with a small screwdriver or sometimes just your fingers.

The injector will pull out from the rail with the clip removed.
Figure 17

The injector will pull out from the rail with the clip removed. There are two O-rings on each injector where they seat in the rail or manifold (red arrows). These O-rings must be replaced every time you remove the injectors. When installing the injectors, it is a good idea to put a little white lithium grease on each O-ring to help slip them into place. Installation is the reverse of removal.



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