Replacing Fuel Lines In An E36 M3: A Step-By-Step Guide

Replacing the fuel line in a BMW E36 M3 is a complex task that requires a range of tools and safety equipment. It is important to note that BMW E36 vehicles have had major problems with hose clamps on fuel lines, so owners should regularly check for leaks and replace clamps with screw-type ones if necessary. When replacing the fuel line, it is recommended to run the gas tank down to empty and remove the fuse to the fuel pump to bleed fuel pressure from the system. The fuel filter is located under the driver's seat and can be accessed by lifting the car and removing the four bolts from the cover. The fuel filter is secured by a saddle clamp and removing it involves loosening hose clamps and carefully detaching fuel lines.

Prepare your tools and safety equipment

To prepare for replacing the fuel line in your E36 M3, you'll need to gather the necessary tools and safety equipment. Here's a detailed list:

Tools:

• A full set of sockets and ratchets, including a 3/8" drive, 10mm six or twelve-point deep socket or 3" extension with a shallow socket, and a 3/8" drive, 8mm or 5/16" six or twelve-point deep socket or extension with a shallow socket.
• A flat-blade screwdriver with a tip roughly 1/4-3/8" wide.
• Cable ties (ty-wraps or similar).
• A jack to lift the car.
• Jack stands to securely support the car.

Safety Equipment:

• Full-coverage eye goggles to protect your eyes from any debris or fuel spray. Simple safety glasses won't be sufficient.
• Gasoline-resistant gloves (nitrile rubber or equivalent) that preferably cover your forearms as well.
• A Class B fire extinguisher specifically designed for flammable liquids.

Additionally, you may want to purchase the fuel hose and clamp kit (BMW part number 13311703490) to have on hand in case the fuel hose is damaged during the replacement process.

Before beginning any work, ensure you have a clear and well-lit workspace and that you are wearing appropriate clothing. Avoid wearing loose or baggy clothing that could get caught in moving parts or hang below your waist, and tie back long hair. It is also recommended to work on a cool engine and in a well-ventilated area to avoid the buildup of flammable fumes.

Depressurise the fuel system

Depressurising the fuel system is an important step in replacing the fuel line of an E36 M3. The M52 engine fuel injection runs at a pressure of about 50 PSI. Failing to depressurise the system before removing the fuel filter will result in fuel spraying everywhere.

To depressurise the system, start the engine and walk around to the fuse box. Pull the fuel pump fuse. You should notice a change in the character of the idle before the engine dies due to insufficient fuel pressure.

It is also recommended to run the gas tank down to nearly empty in case of a leak that cannot be stopped.

Remove the fuel filter cover

To remove the fuel filter cover, you will need to jack up your car. It is best to jack up all four corners of the car to give you optimum clearance, but if you only have access to one jack, raising the front will be sufficient. Just make sure that the car is raised high enough to allow you to work underneath.

Once the car is raised, you will need to identify the fuel pump fuse. Open the hood, remove the fuse box cover, and locate the fuel pump fuse. On some BMW models, this is fuse #18.

The next step is to depressurise the fuel system. The M52 engine fuel injection system runs at around 50 PSI, so failing to do this will result in fuel spraying everywhere when you remove the fuel filter. To depressurise the system, start the engine, then walk around to the fuse box and pull the fuel pump fuse. The engine idle should change almost immediately before dying completely after a few seconds due to insufficient fuel pressure.

Now you are ready to identify and remove the fuel filter cover. The fuel filter is located underneath the car, adjacent to the frame rail, under the driver's footwell. It is installed behind a metal cover to protect it from damage. This cover has four fasteners, all of which can be removed using an 8mm or 5/16" socket. Two of the fasteners are common 6-point hex head screws, while the other two are a strange type of nut that screws onto a stud in the body. All four are easily removable, but the forward-most fastener is located in an area that makes it difficult to swing the ratchet. Patience is required here, and a fine-toothed ratchet will help.

With the four fasteners removed, the fuel filter protective cover can now be removed.

Remove the fuel hoses from the filter

To remove the fuel hoses from the filter, you will need to loosen the clamps on the lines going to the fuel filter. You can then slowly work the lines off, using a flat-head screwdriver and a prying motion to push the hose off the end of the fuel filter. It may help to tug slightly on the hose while prying with the screwdriver. You can also use an open-end wrench to pry the hose off, but you will need to back the hose off enough to get the wrench inside.

Another method is to use diagonal cutters or equivalent to cut the hoses about half an inch from the end of the filter nipples. Then, grab the ends of the hose that remained with pliers and twist back and forth until they release from the hard lines.

As you remove the hoses, expect some fuel to pour out of the filter and the hoses. If you have depressurised the fuel system, you will not experience this.

The aft hose doesn't leak much, but the forward one does, so it is recommended to use a vise grip to gently hold the forward hose closed.

Unclamp and remove the fuel filter

To unclamp and remove the fuel filter, you will need to first jack up the car. It is preferable that the car be up on all four corners for optimum clearance, but jacking just the front will work as long as it's up sufficiently high. Once the car is jacked up, you will need to identify the fuel pump fuse. Open the hood, remove the fuse box cover, and identify the fuel pump fuse. On some cars, it is fuse #18, but you should check your individual model first.

Next, you will need to depressurize the fuel system. Start the engine, walk around to the fuse box, and pull the fuel pump fuse. You should notice an almost immediate change in the character of the idle before the engine dies completely in a few seconds due to insufficient fuel pressure.

Now, identify and remove the fuel filter cover. The fuel filter is installed underneath the car, adjacent to the frame rail, under the driver's footwell, and is installed behind a metal cover to protect it from foreign object damage. This cover has four fasteners, all of which may be removed using an 8mm or 5/16" socket. The forward-most fastener is located in an area that makes it difficult to swing the ratchet, so you will need to be patient.

At this point, put on your safety equipment. Put on your rubber gloves and full-coverage eye protection. From this point forward, you may come in contact with gasoline and you need to keep it off your skin and out of your eyes.

Now, remove the fuel hoses from the filter. Loosen the clamps sufficiently so they can be pushed back on the hose well clear of the flares built into the filter nipples, and then use a screwdriver to push the hoses off each nipple. This may take some time and can be aided by grabbing the hoses and trying to rotate them on the nipples. As the hoses release, expect some gas to pour out of the filter and the hoses.

Finally, unclamp and remove the fuel filter. The filter is held in place with a metal clamp and a 10mm nut. To gain access to this nut, you may need to unclip the fuel lines that run parallel to the filter and remove a few zip ties to get the oxygen sensor wiring out of the way. Some articles suggest it is possible to simply loosen the 10mm nut rather than remove it, but that may not work because the clamp seems to "stick" to the filter's protective foam rubber sleeve. Once the nut is removed, the filter should slide right out.

Frequently asked questions