Thread: Fuel Filter
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Old 05-02-2010, 05:43 PM   #3
6th Gear Member
Join Date: Apr 2010
Location: Toronto
Posts: 1,892
Maybe your correct. I'm wondering then, what is at the top of the fuel tank that has many hoses coming from it. (It looks to be pretty rusted also). Did some searching and found this. So it's the fuel transfer pump that under the seat =\ Can you find cheap ones around the Oshawa area?

Taken from BMW Winnipeg.

If you look under the car just forward of the left rear tire you will see the main fuel pump. It is held in place with four rubber mounts. Each rubber cylindrical mount has bolts coming out of either end. The bolts are attached to the pump bracket and to the car's body.

I tried to remove the nuts for these bolts but they were rusted solidly to the bolts. I didn't want to try the usual trick of putting a propane torch on the nuts to loosen them up. My favorite rust eater, PB Blaster, didn't seem to help all that much. I got impatient and ended up twisting the rubber mounts apart, then drilling out the bolts.

Carefully pry the rubber boots off of the two electrical connections. Remove the electrical connections. The electrical terminals are different sizes so you won't be able to mix them up later.

The fuel pump gets fuel from the transfer pump, located under the back seat, and sends the fuel under high pressure to the fuel filter, which is located in the engine compartment. Remove the two hoses from the fuel pump, but be careful and wear eye protection. About cup of gas will spill out of the hoses when you remove them.

There is a small can located between the output side of the fuel pump and the tube which delivers fuel to the fuel filter. The intention of this device is to absorb pulses created by the fuel pump. This small can started leaking on me about two months before I replaced the main fuel pump. The E30 Service Manual didn't mention this part.

I asked a mechanic friend of mine about this part's function. He told me that it wasn't needed, and so I removed it. I replaced the two short lengths of fuel hose which were left with one piece which was about 9 inches long. You can buy a length of fuel hose from your neighborhood auto parts store. Take one of the short pieces with you so that you can get approximately the same inside diameter. Remember to only buy high pressure hose which is intended for fuel injection applications.

Replacement of the pump is easy. Since I neglected to purchase the rubber mounts, I decided just to use long bolts with a 10mm head. I took four short sections of high pressure fuel hose to isolate the pump bracket from the body. I was willing to sacrifice some noise isolation for the ability to remove the nuts at some future time.

Replace the electrical connections, making sure the nuts are tight and you use the lockwashers, but don't overtighten them. Replace the rubber boots, making sure that they completely seal the electrical connections from the ravages of water, dirt, and salt under the car. Replace the hoses, making sure to use new hose clamps. Mount the pump using the hardware of your choice.
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