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944 S: Removing the Fuel Rail and Intake System (Read 2614 times)
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944 S: Removing the Fuel Rail and Intake System
Sep 7th, 2011 at 8:33pm
The 16v and the 8v engines differ in the respect that the fuel rails and intake manifolds are arranged differently.  This causes confusion when someone tries to remove these systems on a 16v following instructions for an 8v engine.  

Below is a write-up that you can use as a reference to remove both the fuel rail and the intake manifold on a 16v engine. 

This procedure is necessary to repair/replace MANY things on a Super Variant engine.  The Throttle Position Switch, for instance, CAN NOT be reached without undergoing this procedure.

If you work at my pace, this should take you a day or so to do.  I like to take my time, and clean and document each part.  Because you will be dealing with a lot of different bolts, washers, etc. it's important to bag and label all fasteners during this project.  

Also, realize that I am not a professional mechanic; this is a write-up written by a home mechanic to other home mechanics. You alone are responsible for any work you preform on your car.

Okay, let's get started...    

-Fuel Rail and Intake Manifold Removal: 16 Valve 2.5 Liter Engine-

Tools Needed:
-10mm socket
-10mm wrench
-13mm socket
-13mm wrench
-6mm allen head socket
-ratchet (socket wrench)
-ratchet extension
-ratchet u-joint adapter
-19mm open wrench
-24mm open wrench
-medium flat-tip screwdriver
-inspection light
-zip-lock baggies
-permanent marker
-catch rags

1. Start by disconnecting the battery.  You can just disconnect the positive lead, but I prefer to disconnect both leads for safety.

2. Position catch rags beneath the fuel supply and return lines connected to the fuel rail and pressure regulator.

3. Use the 24mm wrench to hold the fuel rail steady, and disconnect the main fuel supply line with the 19mm wrench.  Also, disconnect the fuel return line from the pressure regulator using the flat-tip screwdriver.  Be sure to clean up spilled fuel with the catch rags.

4. Disconnect the pressure dampener bracket from the intake manifold.  It is held in place by two 10mm bolts.

5. The fuel rail should be held in place now by three 10mm bolts.  use a 10mm socket, an u-joint adapter, and a ratchet extension to loosen the two lower bolts, the third bolt on top is much easier to remove.

6. Disconnect the electrical connections from the fuel injectors and the idle control valve.  If necessary, loosen the wiring harness from the fuel rail by cutting any zip-ties that bind it.

7. Disconnect the vacuum lines attached to the fuel pressure dampener AND the fuel pressure regulator.

8. Now you can pull the fuel rail off of the engine.  Position yourself above the fuel rail and pull directly up.  Be patient and apply steady upward pressure because it can be tough to remove those injectors.  If it helps, rock the rail gently from side to side to loosen the injectors.  NOTE:  if it is too difficult to remove the rail, you can remove the rail by itself and remove the injectors one by one.  The only downside to this method is that it spills fuel all over the place.  If you take this route, pull the injector clips off of the fuel rail, position catch rags around the injectors, and loosen them from the fuel rail one at a time.  Once the fuel rail is free from the injectors, you can pull the injectors out of the engine one by one.

9. With the fuel rail removed, proceed to removing the air filter housing.  The air filter housing is secured by two 10mm bolts on the front and one 10mm bolt on the side.  Remove the bolts and lift the air filter housing out of the engine bay.  Bag the bolts.

10. Next, you must remove the air flow meter (AFM).  Loosen the hose clamp on the back of the AFM.  The AFM is secured in the engine bay by an overhanging bracket.  Disconnect the AFM from the overhanging bracket by removing the three 10mm bolts and washers on the top of the bracket.  Support the AFM with your hand as you loosen the bolts.  After the AFM is free from the bracket, pull it free of the rubber boot and disconnect the AFM's electrical connector.


-Jacob&&&&1987 Porsche 944 Super Variant, zermatt gray&&&&"Buying a car because it's reliable is like marrying someone because they are punctual." -Jeremy Clarkson &&&&
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Re: 944 S: Removing the Fuel Rail and Intake Syste
Reply #1 - Sep 7th, 2011 at 8:38pm
At this point, we have disconnected the fuel rail, removed the air filter housing, and we have removed the AFM from the engine bay.  

Next, we will begin to remove the intake manifold from the vehicle.  This write-up will guide you through removing the intake manifold as a unit from your car.  

Write-ups specific to 8v cars will direct you to remove components of the intake system piece by piece.  While possible, this approach is very difficult on 16v cars. I found that it was far easier and faster to remove and install the intake system as a unit.  

10. We will begin by disconnecting all vacuum lines.  Disconnect the vacuum line at the electric tank breather valve.

11. Disconnect the brake unit vacuum line with your flat-tip screwdriver.

12. Disconnect the larger vacuum line from the electric tank breather valve at the manifold.  My finger is touching it in the picture.

13. Disconnect the Air Oil Separator (AOS) to intake manifold vacuum line.

14. Now that the vacuum lines are taken care of, we can deal with the intake manifolds hard attachment points.  Start by disconnecting the oil dipstick tube bracket from the intake manifold.  It is held in place by a 10mm bolt.  Once free, the oil dipstick tube can be removed from the engine by gently pulling it up.  Be sure to cover the hole in the crankcase with a clean rag to prevent contamination.

15. Next, loosen -BUT DO NOT REMOVE- the 13mm intake manifold support bolt.  Simply loosen it a few turns so that it is not torqued on the support bracket anymore.

16. Now we can disconnect the throttle cable assembly from the intake manifold.  Start by releasing the throttle cable from the throttle body cam.  Do this by pulling back on the throttle cam to release tension on the cable, and gently pulling the cable off of the throttle cam.

17. Remove the throttle cable assembly from the intake manifold.  It is secured by two 10mm bolt on the top of the manifold and two 10mm bolts on the side of the manifold.

-The next step of the procedure involves a risk of stripping threads if you do not slow down and take the necessary precautions-

18. Remove the seven intake manifold retaining bolts using a 6mm allen head socket.  They are the bolts that secure the intake manifold to the cylinder head.

Over time, these bolts can bond to the aluminum and become difficult to remove.  Before trying to remove them, first "wake the bolts up".  Attach your 6mm allen socket and extension to the heads of the bolts, and tap the end of the extension gently several times with a hammer.

This should make the bolts easier to remove. However, keep in mind that these cars are very old and-even with the best preparation- bolts get stripped.  Worst case scenario is that your weekend job takes more time to repair the stripped thread holes with thread inserts.  

19. Reach under the throttle body and disconnect the throttle position switch electrical connection.  It might require you to shift the intake manifold around a bit to reach the connection.  

20. Inspect the intake assembly to make sure it is detached from the engine.  Once you are satisfied that all connections are severed, lift the whole intake assembly out of the car: intake manifold, throttle body, j-boot, and all of the vacuum lines below the manifold.  Take your time and slowly pull the assembly out of the vehicle.  A buddy could make this part much easier, but it is doable by one person.  After the assembly is out you should end up with something that looks like this...

22. Be sure to cover the intake holes on the cylinder head with clean rags to prevent things from falling into the engine.

The intake manifold assembly is now removed and can be further disassembled into smaller pieces off of the vehicle. 


-Jacob&&&&1987 Porsche 944 Super Variant, zermatt gray&&&&"Buying a car because it's reliable is like marrying someone because they are punctual." -Jeremy Clarkson &&&&
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