How to Install Mustang Cobra #39 Injectors

Member Credit: Unklejoe

I’ve decided to make a quick guide detailing how I installed Mustang Cobra 39# Injectors in my 2002 Maxima.

There was very little information on this topic, other than “it could be done”.

These injectors are rated at 39# at 39 psi, so this equates to roughly 470cc/min when used in the 2002+ Maxima’s 51psi fuel system.

You can find these injectors for around $100 if you look on the SVT forums. This is FAR cheaper than buying the RC 440’s or another similar aftermarket injector. And because these are for the 2003/2004 Mustang Cobra, you will get 8 injectors, leaving you with two spares.

These injectors use an EV6/USCAR connector.

This is the best route for someone who is going to boost or run a large dry shot of nitrous, and doesn’t want to spend a ton of money on new injectors.

PARTS REQUIRED:

(4) M8-1.25 x 40mm Allen Key Screws
(3) FEL-PRO Part # ES70599 (O-Rings, Set of 4) (Got these from Rockauto)
(6) EV6/USCAR Injector Pigtails
(6) 2003/2004 Mustang Cobra “Blue Giant” 39# Fuel Injectors
(20) 5/8″ Washers

PROCESS:

1. Start the car. While the car is running, pull the fuse for the fuel pump (located inside the car; under the steering wheel). The car will eventually stall out. Try to start the car a couple times. This allows the pressure in the fuel rail to be relieved.

2. Remove the upper intake manifold, exposing the lower intake manifold and the rear fuel rail. Place paper towels in the holes of the lower intake manifold to prevent debris from falling in there.

3. Remove the bolts holding in the fuel rails.

4. Rock the fuel rails back and forth (towards the windshield and the front of the car) while pulling up. Eventually the injectors should pop out. They are only held in by the fuel rail. If you can’t get them out this way, remove the clips holding the injectors in the fuel rail, and remove the fuel rails. This will leave the injectors suck in the manifold, but you can then use pliers to yank them out.

5. Grab one of the new injectors and two O-rings. Gently lube the O-Rings with motor oil and slip them on to the new injector. One goes on the top and one goes on the bottom. (DUH)

6. Pop the injector into the fuel rail, then slide the clip over it in the same fashion that it popped off. Repeat this for the 5 remaining injectors.

7. Maneuver the fuel rail back into its position on the LIM.

8. These injectors are about a half inch taller than the stock ones, so the washers must be used to shim the fuel rail up. Use 5 washers per bolt. This also forces us to use allen key bolts, because you won’t be able to get a wrench or a socket in there once the rail is shimmed up, as it would interfere with the top of the lower intake manifold.

9. Now the tricky part. Line up all of the bolt holes and position the washers, then slide the bolt down the hole. This is tricky because it is hard to hold the washers due to the space constraint. Also, the fuel rail has to be slightly bent into place, as the upward spacing changes the angle between the cylinder banks. It’s nothing big, just requires some force to line up the holes.

10. Cut off all of the stock injector plugs. Prepare the EV6/USCAR plugs. I bought a whole pigtail, so I had to solder mine. Crimp on plugs are available though. Each stock injector plug has a solid red wire. This is the ground. Connect the new plugs in such a way that the GROUND CONNECTS TO THE + SIGN ON THE NEW INJECTOR. I’m not sure why Bosch decided to put a + sign on the injector, but ignore it, trust me. The + sign is located inside the injector plug, on the injector itself.

11. Reinstall everything.

NOTES:

Your car will run perfectly fine in closed loop with these injectors without tuning; you will just have a far negative long term fuel trim. This is confirmed by my wide band readings right after the injectors were installed. I do however, have an E-Manage Ultimate, and this allows me to scale the injectors, for easier tuning.

If you do not have a way to tune for these injectors, you will run extremely rich at WOT. If you are installing these in the first place, you already know this.

The drivability has changed slightly with these injectors. The RPM’s seem to fall faster when the clutch is pressed in, causing me to have to shift “faster”. This is not a problem, it will just take some getting used to. I can only attribute this to the Mustang injectors have a faster response than the stock injectors.

PICTURES:

Picture of the bolts required.

Picture showing the length difference between the stock and the Mustang injector.

Picture of the lower intake manifold, showing the fuel rails. The injectors are already installed in this picture, and the plugs are soldered, but not taped yet.