Converting to 318i Electronic Fuel Injection

Original Author: Mike Kubani

Mike's 318i Electronic Fuel Injection setup including his custom cold-air box

Introduction:

This conversion is not recommended for anyone who is not mechanically knowledgeable and ready for a challenge. There are many steps involved and several places where fabrication skills will be required. If you feel that you are not ready for this, it would be best to leave the conversion to a professional.

When considering this conversion, it is advisable to do significant research to familiarize yourself with the theory, parts and workings of both your 2002 and the 318i fuel injection system. There are several valuable resources available, namely ‘Bosch Fuel Injection & Engine Management’ by Charles O. Probst, SAE, ‘BMW 3-Series Service Manual’ published by Robert Bentley, and ‘BMW Coupes and Sedans, 1970-88 Repair Manual’ by Chilton’s. Other sources of valuable information may be obtained by locating the Electronic Diagnostic manuals for the 1984-85 BMW 318i. I found access to them from a local repair facility.

The more you know about all of the systems involved when doing this conversion, the better. Once can never have too much knowledge when it comes to tackling this type of project.

There are many systems involved in the conversion and many of them interact with one another. The systems involved are the fuel system, electrical system, vacuum system, ignition system, starting system, intake system, etc.

Parts Required:

Below is a list of the components required to complete this conversion. This is only a guide. Some conversions will require more parts, others will require less, depending on your decisions regarding some critical questions.

From a 1984-85 BMW 318i:

• Intake manifold w/ cold start sensor
  
• Throttle body with throttle switch
  
• Water inlet with sensors
  
• Fuel injection rail with injectors and fuel pressure regulator
  
• Complete engine harness with relays and ECU (make sure that the harness and ECU are from the same vehicle since they changed from 84 to early 85 and again in late 85)
  
• Air flow meter
  
• Main Fuel pump
  
• Throttle connector for cable
  
• As many hoses as you can get and don’t forget the hose clamps!
  
• Intake air boot
  
• Rear starter bracket from a tii, 318i or 320i or modify yours
  

From a late 320i:

• In tank fuel pump/level sender and harness (measure your tank and get the correct length pump) I used 16 14 1 179 423 on an early ’72.
  
• Aux air valve (0-280-140-126)
  

Misc. parts:

• Throttle cable (custom made or from Honda)
  
• Intake gaskets
  
• Gasket for throttle body
  
• 8mm fuel injection fuel hose (the expensive stuff)
  
• 3/8 fuel hose
  
• 5/16 fuel hose
  
• 4 bay fuse holder
  
• Fuses for fuse holder (7.5A, 15A & 20A)
  
• Plug for water port in engine block
  
• Blank off plate for fuel pump on head
  
• Miscellaneous terminals and wire
  
• Miscellaneous hose clamps
  

Battery relocation parts:

Battery cable (highly suggest getting one from an E30 with trunk mounted battery), battery mount, battery Air cleaner (cone style or stock) ECU mounting standoffs/bolts/screws Manual idle valve Miscellaneous hoses for pluming idle valve and aux air valve

Optional parts: (1984-85 BMW 318i):

• Idle control module
  
• O2 sensor (heated) (11-78-1-715-263)
  
• O2 sensor mounting bung
  
• Idle control motor
  
• 318i Distributor & camshaft
  
• Ignition control module
  
• Head gasket set
  
• 002 or 008 distributor
  
• Metal fuel return line from mid’72 and newer 2002
  

There are some questions that you need to answer prior to delving into the conversion. This is by no means all of them either, there may well be many more, but this is a good start.

Are you going to use all the stock 318i systems? Such as idle air circuit, fuel pump relay, ignition (including distributor and ignition control module), O2 sensor, etc.

Will you be using your stock distributor or a 002/008?

See the list of optional parts above and add or subtract parts as required.

The Conversion:

Battery Relocation:

The first step in the conversion is to make room for the EFI fuel meter and other parts of the system by moving the battery from the engine compartment to the trunk (or under the back seat, if you get a sealed battery). This is easily done with a kit available from any number of aftermarket suppliers, welding supply stores, or you can use a cable from a junked e30. Check out the FAQ article on this procedure.

I suggest using the cable from an E30 with the battery in the trunk. This will allow you to have all the power sources you will need already available in the engine compartment without having to overload the starter terminal or the alternator. Approximate time to complete this step: 6 hours

Fuel System:

Starting with the basics, you need a way to get highly pressurized fuel from the gas tank to the injectors on the engine. In my case, I had to install a steel fuel line (normally the fuel return line on newer cars) from a newer 2002 (later than mid-’72). I used cushion clamps available from a hardware store along with large-head aluminum pop rivets and silicone to install the fuel line. It is very easy to install, but takes some time lying on your back unless you are fortunate enough to have a lift. Approximate time to complete this step: 2 hours, or zero if your car already has the steel return line that you can convert to a feed line.

The next step is to install the fuel pump/s. There are a couple of ways to do this, but probably the best is to simply use the single in-tank pump from a 1991 318i. This is a high-pressure feed pump that eliminates the need to use an in-tank pre-pump and the seperate external high-pressure pump.

If you use seperate lo-pressure in-tank, and an external high-pressure external pump (which is what I did), the external pump must be mounted so it can be easily installed and be relatively out of the way of things like exhaust and suspension components. I installed mine using an old coil mounting bracket with a couple of rubber air cleaner mounting studs that are rubber mounted. (13-71-1-272-495) This way, it is out of the way, up near the differential, allows easy access and is relatively in line with the metal fuel line. Approximate time to complete this step: 2 hours with wiring, which we will get to in a bit.

Installing the in-tank pump and sender assembly is relatively straightforward. It is installed in the same fashion as the stock '02 sender with the exception that it is 2 pieces. If you have the one-piece 320 version, throw it away and get a 2 piece one. The one-piece version was replaced with the 2-piece version a few years after the 320 was first produced. Also remember to get the harness connectors that go with the pump and sender. The pump is a 2 prong and the sender is 3 prong. They are special connectors and are hard to find by themselves. Approximate time to complete this step: 1.5 hours with wiring

Next install the fuel filter. I got a stock 318i fuel filter and mounted it using a hose clamp. I drilled holes in a piece of strip aluminum and using pop rivets, fixed the hose clamp to the bottom of the car, near the fuel pump. Then I just tightened the clamp around the filter and installed fuel line between the pump and filter and from the filter to the metal fuel line. Remember to use high-pressure fuel injection hose because the fuel is under ~45psi at this point. Approximate time to complete this step: 1 hour

Once the in-tank low-pressure pump is installed, you can run your car with it (if it is still carbureted), just hook up the stock fuel hose to the outlet, wire up the pump and away you go. I ran my car with the stock engine-mounted pump until later in the conversion, but the fuel was drawn through the in-tank pump without any problem. Remember that there are two fuel connections to this pump, a feed and a return.

Fuel System Wiring:

Wiring the fuel pump/s can be a little tricky. If you decide to run the fuel pump relay, it would be wise to wait until later in the conversion to make the final wiring hookups in the engine compartment.

The connector for the in-tank pump has two terminals in it. One is green/purple and the other is brown. Brown is ground and the green/purple is power (+12V) The in-tank pump requires a 7.5A fuse.

The main pump has two connectors on it. One is power and the other is ground. If it was removed with the wires attached, power is green/purple and ground is brown. This pump requires a 15A fuse. The stock 318 system used one wire for both pumps and used a 15A fuse for both, but I wired them independently and used separate fuses for each. The fuel level sender has 3 terminals. One is signal, one ground and the other is low fuel. The brown wire is ground, one of the brown/gray wires is for level and the other is for low fuel. You may have to do some testing with a VOM meter to be sure you hook up to the correct wires. I installed a low fuel warning LED at the lower end of the fuel gauge. It works well and tells you when you are within 1 gallon of being empty. It is a grounding circuit, so hook power to your light and use the connection on the sender assembly for the ground.

Next was to install the 4-position fuse block under the hood. I chose a location close to the original fuse block on the firewall. The 4 fuses are for: one each for the fuel pumps (7.5A & 15A) one for +12V key switched (15A) and one for +12V key switch/crank (20A). Approximate time to complete this step: 1 hour

ECU and Engine Wiring Harness:

I installed the ECU in the glove compartment using standoffs from the bottom of the box to the ECU. I mounted it so that it moved with the glove box, since it would take more effort to install above the box similar to the 318i and there was limited space. Approximate time to complete this step: 2 hours

The next large step involves the main wiring harness. This harness is large and bulky. If there are systems that you will not be using, I would suggest that you remove all unnecessary wires from it prior to installing it in your car. It will be necessary to drill a large hole through the firewall on the passenger side of the car for the connection to the ECU. Retain the stock rubber grommet and use it to seal the hole. The hole is approximately 2” in diameter and can be made easily with a hole saw.

I would recommend that you acquire a complete wiring diagram for the specific year 318i you are using. The 318i changed from 1984 to early ‘85 and again in late ‘85, so finding the correct diagram is critical for the harness that you have. If you are going to use an O2 sensor and are not using a stock 318i exhaust manifold, it is recommended to use the late 1985 harness and ECU. This will allow you to remove all unnecessary wiring and be able to connect to the correct wires for power.

Click here for a larger version of this great wiring diagram provided by Ed Weimar. Ed got Mike's help on his own 318i injection conversion and created this diagram. Be aware that wiring colors do vary between the '84 and '85 EFI systems, so you should still get the appropriate-year electrical manual for the injection system you are using.

Wiring the harness into the 2002 is the hardest step in the process. I recommended that you check and recheck the wiring carefully. I removed the ignition wiring (ignition control module and vacuum advance solenoid), idle speed control unit (with the idle air motor), but retained the stock fuel pump relay. If you plan to use the ignition system, I would highly recommend you change the cam to use the 318i unit. It will give you the best control of ignition short of replacing the whole thing with and aftermarket adjustable version. Short of that, use a 002 or 008 distributor from a tii. It has a curve close to what the 318i has and will be the best stock approximation.

Once the harness is stripped of all unnecessary wiring, it can be installed in the engine compartment. I welded the mount for the fuel pump relay on the inner drivers’ side fender similar to where the 318i had its mounted. It worked well for locating the harness. Approximate time to complete this step: 4 hours

You can now hook up the wiring from the harness to the 02. You will need two power sources, an ignition source (- side of the coil), a crank source (starter) and ground. Basically that is all. Although it sounds simple, it takes some time to find the correct wires and hook them up. Approximate time to complete this step: 2+ hours

I used an O2 sensor in my conversion and installed it in the lower "Y" of the stock exhaust collector. Initially I used a non-heated sensor and was getting poor results since it was not getting hot enough. I changed to a heated O2 sensor and the system worked great. If you use a stock 318i exhaust manifold and down-pipe, you can use a non-heated O2 sensor. Either way, I would recommend a heated O2 so you can be sure the signal is accurate. Approximate time to complete this step: 1 hour

Engine Compartment:

The throttle cable that I used was a custom cable made by Ireland Engineering in Southern California. I sent the stock 318i parts (at the throttle end) to them and had them fabricate a cable using those parts so it would fit the stock bracket. I had to fabricate an L bracket that I mounted to the brake booster mounting to hold the lower end of the cable housing above the pedal linkage. A simple rod end with a through bolt was used to attach the cable to the pedal linkage. I have also heard that a Honda cable will work, but do not know from what vehicle it is. Approximate time to complete this step: 1.5 hours

When I received my throttle body, it was not in great condition. I rebuilt it and made it work as new with only a two-hour investment of my time. I also rigged up a pump and tank assembly to test the fuel injectors. Since they were not mounted in the intake manifold, this was a simple arrangement of fuel source (gas jug), high-pressure pump and a battery. A simple momentary switch and 12V were required to power the injectors one by one. I verified that all the injectors were spraying a good pattern and that they all work. That was one thing that I did not want to be a stopping point in my conversion. If any of your components were from an unknown source, this is highly recommended.

I then installed the injectors in the intake manifold using new o-ring seals (13-64-1-286-708), two per injector. Approximate time to complete this step: 1.5 hours

As we approach completion, the intake manifold swap is next. It is a straightforward swap. Remember to use the new 318i water inlet. You will also need the 318i water pipe that runs under the intake manifold for the heater hookup. On a stock 318i there is a rod that supports the intake manifold above the starter. I was not able to make this fit even with a lot of bending and modification work. In the end, I left it off. It has been there since late ’99 without a problem. If it has not been done, it will also be necessary to use a starter bracket from a tii, a 318 or 320 which is different from the carbureted 2002. The extra tab for the manifold will get in the way of the throttle body. Approximate time to complete this step: 6 hours

Fabricate a bracket to mount the air flow meter to the drivers’ side fender well or the engine. I was able to make a simple bracket by bending some thin sheet metal and welding in a cross brace. I bolted it to the fender. This turned out to be a good move since it sits above the oil filter and needs to be removed to gain access to the oil filter. The installation of a K & N cone style filter completes the installation. I removed some of the radiator support to allow a direct line to cool outside air. Approximate time to complete this step: 2 hours

I utilized an auxiliary air valve and a manual idle valve in place of the stock idle air motor and controller. This is a very simplified way of removing the expensive electronic components (that are known failure items) and retaining the drivability and cold starting which makes the conversion desirable. It is, however, quite the plumbing nightmare. It took several tries and different configurations to make the two parts work together. It was not too difficult with the intake off the car, but it was a little cumbersome once it was installed on the engine. It does, however, work very well and is less expensive to replace than the stock 318i components. Approximate time to complete this step: 3 hours

Final steps are to hook up all the wiring and hoses to the new components. Once all the hookups are made, check over everything carefully. Now you are ready to take your fuel injected 2002 for a test drive assuming you have done everything correctly.

Conclusion:

After spending nearly 55 hours on the actual conversion and countless others on the internet, reading through manuals and books, searching for information from other sources, talking to numerous people and deciphering all the information, I am very pleased with the outcome of the conversion. It makes driving my 2002 daily a pleasure (not that driving one is anything but).

With the reliability and performance that I now have, I believe that I can drive this car for many years with few problems. There are also other things that can be done to boost the performance even more, namely turbo charging, but I will leave that to someone else. Other ideas are to use other throttle bodies, convert to LH-Jetronic, which uses a mass air sensor instead of the air flow meter used by the L-Jetronic. All of these and more are possible modifications of the existing system. I have not done any of them yet, but who knows, maybe in the future.

Further Tinkering:

Once I had gotten the basic system working well, I was initially impressed with the performance of the FI system. However I had heard pinging numerous times, specially at high RPM. I adjusted the timing (stock '02 distributor) until the pinging ceased, but noticed poor idling. This led to the installation of an Electromotive HPV-1 ignition system that is adjustable.

In hindsight, it would have been better to install the Electromotive TEC-II or SDS system which controls both ignition and injection or to have installed the stock 318i camshaft and distributor.

Both of these solutions would have provided better control of all the systems together, although both the Electromotive and SDS systems would be far superior in that they are fully adjustable.