There have been a couple of recent autocross events where long and sweeping right turns have been part of the course. This is when an E36 is susceptible to fuel starvation due to the fuel pump being located on the passenger side of the car. Centrifugal forces send all the fuel to the driver side of the car during hard right turns which starves the pump and thus starves the engine (causing bogging, hesitation and very high air-fuel ratios). I’ve experienced this issue with my E36 a couple of times during events.
Luckily, there’s already a provision on the driver side of the fuel tank to install a secondary fuel pump to eliminate fuel starvation in turns. I’ll go into the install and impressions of the VAC Motorsports E36 Fuel Starvation Kit in this post.
The picture above illustrates the irregularly shaped fuel tank in the BMW E36 that’s located under the rear seat area. The design clearly has two main tank areas separated by a crossover section. Thus fuel can get concentrated on one side or the other when the car drives through a sustained turn at high G loads. In a stock BMW E36, there’s only a fuel pump in the Primary location. We’re going to add a Secondary fuel pump with the necessary lines for the two pumps to work together to provide fuel to the engine.
After researching the few different E36 fuel starvation correction kits on the market, I decided to go with the one from VAC Motorsports. The kit looked pretty complete, included high quality components and appeared to be a relatively straight forward install.
The picture above illustrates the complete kit that I received from VAC Motorsports. I already had a new VDO OEM Fuel Pump Assembly that I’d purchased separately. With the kit you basically get the required electrical connectors, fuel lines, fuel line adaptor fittings, and clamps.
First, you’ll need to remove the stock fuel tank sending unit from the driver side. The sending unit is not a fuel pump, it only returns fuel to the tank from the engine and provides a fuel level signal to the computer. To remove the sending unit simply unscrew the black ribbed ring (a large screwdriver and mallet help), disconnect the electrical and fuel lines, and then pull the unit straight out.
In the picture above, I’ve already installed the secondary fuel pump assembly in the driver side and started to push in one of the fuel line adaptor fittings. I believe this will be the best orientation of the secondary fuel pump in the tank to allow for best fit with the lines.
You can see in the picture above where the the adaptors go for proper operation. What you can’t see in the picture is the new high pressure large diameter crossover fuel line that’s running into the primary fuel pump from the secondary pump. Note that the high pressure line is not kinked like shown in the picture above. I did that just to illustrate where the other adaptor is located.
The last thing to do is splice in the power connector for the pump. I just located the wiring running to the primary pump and spliced into it for the secondary pump. I then wrapped the splices in electrical tape for safety.
One final thing to note is that I didn’t start out initially with installing a brand new VDO fuel pump in the secondary location. I tried to reuse an old fuel pump that I already had and thought to be working well. I actually installed that pump into the primary fuel pump location and put my normal fuel pump into the secondary pump location.
The old fuel pump (in the primary pump location) started to have issues and wasn’t able to pump enough fuel to the engine to maintain proper air fuel ratios (making a whining noise as well). Interestingly, the secondary pump wasn’t able to make up for the failing primary pump. The primary pump actually was an impedance as the fuel pumping from the secondary pump has to flow through the primary pump first before going to the engine. So, in summary, you can still have major AFR issues even in a dual pump setup if your primary pump fails. I never knew this! So obviously the new VDO OEM fuel pump assembly went into the primary pump location.
I no longer need to keep my E36 filled at 3/4 of a tank of fuel before a race in order to alleviate fuel starvation during runs. I’ve heard you can run only 1/4 or less with a fuel starvation kit installed and not experience starvation issues. I probably won’t go that low initially but I may work down to that in the future. When trying to remove weight in my car, it’s important to note that each gallon of gas weighs a little over 6 lbs. Every little bit helps!
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VAC Motorsports BMW E36 Fuel Starvation Kit (note that you can buy the kit w/o a pump like I did)