Mercedes-Benz Parts Catalog Mercedes-Benz Accessories Catalog Mercedes-Benz Technical Articles Mercedes-Benz Tech Forums
 
Follow Pelican Parts on Facebook Follow Pelican Parts on Twitter Follow Pelican Parts on Instagram Follow Pelican Parts on YouTube Follow Pelican Parts on Pinterest Follow Pelican Parts on Tumblr
  Search our site:    
View Recent Cars  |   Cart  | Project List | Order Status | Help    
 >  >
Fuel Injector Replacement
 
Bookmark and Share

Pelican Technical Article:

Fuel Injector Replacement

Tom Morr

Time:

2 hours2 hrs

Tab:

$100

Talent:

***

Tools:

E12 Torx, 5mm Allen, 15mm, 17mm wrench, flathead screwdriver, rags

Applicable Models:

Mercedes-Benz SLK230 (1998-04)

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 and we 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.

If you are going to be replacing your injectors, the first step is to prep the car. I like to tell people to pull out the fuse for the fuel pump and then try to start the car. The car will turn over and then die. Do this about 2-3 times - it will help drain excess fuel out of your system, also open the gas cap to help depressurize the system. Then, make sure that the car has cooled down; you don't want to be working with gasoline when the car is hot.

Have a fire extinguisher handy, 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.

You are going to be opening holes that go into the engine so 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.

At the front of the fuel rail is a Schrader valve that you can use to release any pressure. Use a 15mm wrench on the cap and a 17mm wrench on the base of the valve and remove the Schrader valve cap.

Use a rag and a small flat head screwdriver and release the gas from the rail into the rag

Use two 17mm wrenches and break loose the fuel line on the rear of the rail. Be prepared to catch any gas that will leak out and remove the line form the rail. This will give you access to the E12 bolt.

Move to the front connection for the fuel line and using a 17mm wrench remove the line from the pressure regulator. With the line free remove the 5mm Allen holding the line to the rail. Note: there is a small nut underneath the bracket that will fall into the engine if you are not prepared for it.

Remove the two E12 blots holding the fuel rail in place.

With everything removed pull the injectors from their ports. They pull straight out on the angle they are inserted in. There are only held in by friction at this point and you will feel them "pop" when they release. Set the injectors and wiring harness on the top of the engine.

Be sure to put a few rags in the open holes in the manifold to prevent anything from falling into the engine. If you drop something into this hole you must get it out before going any further, this hole goes directly into the cylinder head and will cause catastrophic damage if left in!

Remove the electrical connector on the injector. It is a simple push (in the two clips) and pull up the connector. These can get stuck so take your time. If you are having trouble removing the injector harness, remove the wire safety and the harness will come straight off. As Andrew Riordan at Pelican says when you get frustrated working on a car "try and be smarter than the piece you are working on".

Take the fuel rail and injectors to your bench.

The injectors are held on by metal clips; they can be pried or pulled off the rail. Next, you can remove the injector from the rail by wiggling it out, it is just held in by the O-ring at this point.

Sometimes the O-ring stays in the rail; make sure to remove it.

New injectors come complete with new O-rings. Apply a small amount of White Lithium grease and reinstall.

If you have had an injector that has been leaking heavily it can be a good idea to remove the coils and plugs to drain the combustion area of the extra fuel. While most of the fuel will drain out pass the piston rings, a severely leaking injector can cause hydro lock. It is easy to remove the plugs and can be cheap insurance.

You are going to be opening holes that go into the engine so before you begin get a can of compressed air (yellow arrow) and blow all the dust and debris away from the injector ports.
Figure 1

You are going to be opening holes that go into the engine so before you begin get a can of compressed air (yellow arrow) and blow all the dust and debris away from the injector ports.

Open the gas cap (red arrow) to relieve any residual pressure.
Figure 2

Open the gas cap (red arrow) to relieve any residual pressure.

At the front of the fuel rail is a Schrader valve (yellow arrow) that you can use to release any pressure in the fuel rail.
Figure 3

At the front of the fuel rail is a Schrader valve (yellow arrow) that you can use to release any pressure in the fuel rail. Use a 15mm wrench on the cap and a 17mm wrench on the base of the valve and remove the Schrader valve cap.

Figure 4

Use a rag and a small flat head screwdriver and release the gas (yellow arrow) from the rail into the rag

Use two 17mm wrenches and break loose the fuel line on the rear of the rail (red arrow).
Figure 5

Use two 17mm wrenches and break loose the fuel line on the rear of the rail (red arrow). Be prepared to catch any gas that will leak out and remove the line form the rail.

This will give you access to the E12 bolt (red arrow).
Figure 6

This will give you access to the E12 bolt (red arrow).

Move to the front connection for the fuel line and using a 17mm wrench remove the line from the pressure regulator (red arrow).
Figure 7

Move to the front connection for the fuel line and using a 17mm wrench remove the line from the pressure regulator (red arrow). With the line free remove the 5mm Allen holding the line to the rail (blue arrow). Note: there is a small nut underneath the bracket that will fall into the engine if you are not prepared for it.

Remove the two E12 blots holding the fuel rail in place (yellow arrows).
Figure 8

Remove the two E12 blots holding the fuel rail in place (yellow arrows).

With everything removed pull the injectors from their ports.
Figure 9

With everything removed pull the injectors from their ports. They pull straight out on the angle they are inserted in. There are only held in by friction at this point and you will feel them "pop" when they release. Set the injectors and wiring harness on the top of the engine (yellow arrows).

Be sure to put a few rags in the open holes in the manifold to prevent anything from falling into the engine (yellow arrows).
Figure 10

Be sure to put a few rags in the open holes in the manifold to prevent anything from falling into the engine (yellow arrows). If you drop something into this hole you must get it out before going any further, this hole goes directly into the cylinder head and will cause catastrophic damage if left in!

Remove the electrical connector on the injector.
Figure 11

Remove the electrical connector on the injector. It is a simple push (in the two clips) and pull up the connector (yellow arrows). These can get stuck so take your time. If you are having trouble removing the injector harness, remove the wire safety and the harness will come straight off. As Andrew Riordan at Pelican says when you get frustrated working on a car "try and be smarter than the piece you are working on".

Take the fuel rail and injectors to your bench.
Figure 12

Take the fuel rail and injectors to your bench. The injectors are held on by metal clips; they can be pried or pulled off the rail (red arrow).

Next, you can remove the injector from the rail by wiggling it out, it is just held in by the O-ring at this point (red arrow).
Figure 13

Next, you can remove the injector from the rail by wiggling it out, it is just held in by the O-ring at this point (red arrow).

Sometimes the O-ring stays in the rail; make sure to remove it (red arrow).
Figure 14

Sometimes the O-ring stays in the rail; make sure to remove it (red arrow).

New injectors come complete with new O-rings.
Figure 15

New injectors come complete with new O-rings. Apply a small amount of White Lithium grease (yellow arrow) and reinstall.

Bookmark and Share
Comments and Suggestions:
Leoo Comments: I have a 2002 Mercedes Benz slk turbo 4 cylinder. Heads been serviced/repaired but injectors no. 2 &3 doesn't pulse.benched test 4 injectors found to have good spray pattern. Has good compression at 150 psi average, passed leak test, secondary ignition working.then ohm out #2 and 3 injector circuit harness leading to ecm module/relay found to be continuous.need help. Thanx
September 3, 2016
  Followup from the Pelican Staff: if the injectors have power and no trigger, the DME may be faulty. - Nick at Pelican Parts  
pepe Comments: Hello sir today i disconnect the MAF sensor and the car work fine again , so can i conclude this MAF sensor need to be replaced , Regards
August 22, 2016
  Followup from the Pelican Staff: No, disconnecting it is not a good test. You could have an air leak, faulty wiring, etc. - Nick at Pelican Parts  
peter de clerq Comments: Hello sir
I have a 230 slk kompressor 1997
After storing it 2 years at the garage
Now he start and run terrible engine shake like grazy at the begin it sounds like only 2 cilynders work after a while 3 . Fuel pressure seems ok.i guess 1 of more injectors are blocked by old fuel? Can i try to drain the old fuel , replace fuelfilter , add new fuel with injector cleaner ? Best regards , verry nice website !
August 20, 2016
  Followup from the Pelican Staff: I would remove the fuel from the tank and replace it to start. That may be the only issue. If it still misfire, I would check spark, fuel and compression on all cylinders. - Nick at Pelican Parts  

  Search our site:    

View Cart & CheckOut | Project List | Order Status |  Help    

 

[Home] [Customer Service] [Shopping Cart] [Project/Wish List]
  [Privacy Statement]  [Contact Us] [About Us] [Shipping] [Careers]

Copyright © Pelican Parts Inc. -    DMCA Registered Agent Contact Page

Page last updated: Wed 12/7/2016 02:26:35 AM