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Injector, O-rings and Sleeve Replacement
 
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Pelican Technical Article:

Injector, O-rings and Sleeve Replacement

Time:

2 hours2 hrs

Tab:

$2 to $275

Talent:

**

Tools:

14mm, 12mm wrench, screwdriver

Applicable Models:

 
Porsche 911 (1974)
Porsche 911 Carrera (1974-89)
Porsche 911E (1973)
Porsche 911S (1973-77)
Porsche 911SC (1978-83)
Porsche 911T (1973)
Porsche 930 Turbo (1976-77, 1986-89)
Porsche 964 Carrera 4 (1989)

Parts Required:

New injectors, O-rings, sleeves

Hot Tip:

Depressurize the fuel system first

Performance Gain:

Proper running motor

Complementary Modification:

Change fuel filter

If your car is starting to run rough, getting horrible gas mileage there is a chance it is time to replace the fuel injectors. While the injectors on the CIS system are not known to be a problem area they should be checked and or replaced. A properly working injector will send a precise amount of atomized fuel into the induction system. An improperly working injector can do everything from send no fuel, to leak raw, non-atomized fuel into your engine. While the injectors themselves are not know to be a trouble area the O-rings around the injectors and sleeves are known to be a cause of vacuum leaks causing all kinds of trouble including a rough running engine..

The 911 uses a CIS or Continuous Injection System which consists of metal injectors that can be serviced, bench tested and flow matched. Unfortunately like most things now it is getting harder to find shops willing to perform this work and it can actually be cheaper just to by new injectors.

You're going to be working on the fuel system so 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 gloves if you don't want to get any gasoline on your hands, and make sure that you have plenty of paper towels or rags to help you clean up. Perform the injector removal in a clear, open, and well-ventilated space, and it may not hurt to have an assistant around in case there are any problems.

Before you open the fuel system up it is a good idea to relieve the pressure in the system.
Figure 1

Before you open the fuel system up it is a good idea to relieve the pressure in the system. The best way to do this is to remove the fuel pump relay (red arrow) and crank the engine over a few times. This will draw the fuel already in the system out and relieve some of the pressure. The fuel pump relay is located in the fuse panel under the hood on the left side.

There are six injectors on the 911 motor; three on each side.
Figure 2

There are six injectors on the 911 motor; three on each side. Depending on the year of the car you may have to remove several components to get access to the injectors. If you remove the heater fan you will have much easier access to the three injectors on the left side of the motor (yellow arrows).

The fuel line (yellow arrow) attaches to the top of the injector (red arrow).
Figure 3

The fuel line (yellow arrow) attaches to the top of the injector (red arrow). There are two types of fuel lines; plastic and metal. The injector sits in an O-ring inside of a plastic sleeve. Some of the intake runners are notched to keep the injector sleeve in place and on some motors we have seen they are not. You can see in this picture how the O-ring around the injector is old, dried out and starting to crack.

If you have the metal lines it is OK to use the connection point to gently pull the injector out; if you have the plastic lines do not attempt this as they get brittle over the years and can crack.
Figure 4

If you have the metal lines it is OK to use the connection point to gently pull the injector out; if you have the plastic lines do not attempt this as they get brittle over the years and can crack. Use a 14mm wrench (yellow arrow) on the line and 12mm wrench on the injector and separate them.

Most of the time you can simply pull the injector out from the sleeve.
Figure 5

Most of the time you can simply pull the injector out from the sleeve. On really old injectors you may need to use a small screwdriver and pry the injector from below the knuckle up and out. On this injector the sleeve came out with the injector red arrow).

This photo illustrates the injector and sleeve together out of the intake runner.
Figure 6

This photo illustrates the injector and sleeve together out of the intake runner. You can see the O-ring to sleeve (red arrow) and the amount of build up on the sleeve and injector (yellow arrow).

Push the injector out from the sleeve.
Figure 7

Push the injector out from the sleeve. You can see the sad condition of the old O-ring (yellow arrow).

Slide the old O-ring (red arrow) out of the groove in the injector (yellow arrow) and off.
Figure 8

Slide the old O-ring (red arrow) out of the groove in the injector (yellow arrow) and off.

Clean up the injector with carb cleaner.
Figure 9

Clean up the injector with carb cleaner. Use a little gas or white lithium grease and slide a new O-ring on the injector, then the injector into the sleeve. Install a new O-ring on the sleeve.

Stuff a rag into the injector port and clean the opening in the intake runner (yellow arrow) using care to make sure nothing falls into the runner.
Figure 10

Stuff a rag into the injector port and clean the opening in the intake runner (yellow arrow) using care to make sure nothing falls into the runner. If you drop anything down the runner you must get it out before proceeding as it leads to the intake valve and combustion camber and will do serious damage if left in. There are no factory notches in this intake runner as the O-rings and vacuum from the motor are enough to keep the sleeve snuggly in place.

Insert the new injector, O-rings and sleeve into the runner (red arrow).
Figure 11

Insert the new injector, O-rings and sleeve into the runner (red arrow). The sleeve should pop into place as the O-ring seats. There will be a little wiggle to the injector that is fine as it is just the rubber in the two O-rings. Reattach the fuel line.

Some injectors will pull out leaving the sleeve in place (red arrow).
Figure 12

Some injectors will pull out leaving the sleeve in place (red arrow).

Be sure to remove the old O-ring (yellow arrow).
Figure 13

Be sure to remove the old O-ring (yellow arrow). If the intake is notched you will need to stuff a rag in the hole and gentle file back the notch to remove the sleeve.

The number six cylinder is the most difficult to remove (red arrow) because of all the engine accessories around it.
Figure 14

The number six cylinder is the most difficult to remove (red arrow) because of all the engine accessories around it.

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