This article is one in a series that have been released in conjunction with Wayne's new book, 101 Performance Projects for Your BMW 3 Series. The book contains 272 pages of full color projects detailing everything from performance mods to timing the camshafts. With more than 650+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any 3 Series owner's collection. The book was released in August 2006, and is available for ordering now. See The Official Book Website for more details.
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I was planning on writing a technical article on the fuel pump replacement, but was unfortunately "forced" into it when the pump in my E36 3-Series died on us in Las Vegas last year. We spent all night trying to figure out why the car wasn't starting, checking ignition, electrical components, etc. Then we decided to check the fuel pump. We pulled out the rear seat, and pulled off the fuel pump cover. Surprise - the pump was not making any noise or vibration when we tried starting the car. Disconnecting the electrical harness and checking the voltage supplied to the pump revealed a healthy 12 volts - the problem was definitely with the pump.
Luckily for us, one of Pelican Parts' suppliers had a warehouse a mere two miles away, and we were able to obtain a new pump the next morning. We then set out to perform the arduous procedure of a fuel pump replacement in the parking lot of our hotel! Needless to say these weren't ideal circumstances for performing this repair, but I thought I would document what we did, as you may find yourself in a similar predicament if your fuel pump fails on you.
A little background is in order here. This particular car had been sitting for an entire year, as I slowly performed a head gasket replacement on it. I had put about 500 or so miles on it since the head gasket replacement, but the gas that was sitting in the tank probably still had some old gas mixed in there. While we were tooling around in Vegas, I let the gas level get really, really low in the tank. Then I filled up and let the car sit for about an hour. When we came back to the car to get some dinner, the car would not start and (as we found out later on) the fuel pump wasn't working. My conclusion here (and also after looking at the pump as it came out of the car) was that running the car very low on gas was a bad thing, as it allows a lot of dirt and debris to be sucked up into the pump mechanism. So the moral of this story is to make sure that you don't run your car very low on gas.
Now, let's talk about fuel tank senders. On the E36 BMW there are two of them (I still haven't completely figured out why), one on the left side and one on the right side, which is integrated into the fuel pump. The procedure for the replacement of the fuel sender on the left side is identical to the procedure for replacement of the fuel pump on the right side.
Okay, onto the replacement procedure. The first thing to do is to prep the car. Remove as much gasoline out of the car as possible. The way I like to accomplish this is to get some long fuel hose, a small battery operated carburetor fuel pump, and pump from one car to another. An alternative approach would be a gasoline hand pump available at most local auto parts stores. The bottom line is to get as much gasoline out of the tank as possible. Unfortunately in the parking lot of the hotel, we were not able to get as much gasoline out as we hoped - under ideal circumstances, the tank would almost be completely empty.
Another important thing to remember - always disconnect the battery when working near the tank - you don't want any accidental sparks from any electrical connections.
Some additional warnings too:
- Always have a fire extinguisher handy in case an emergency arises.
- Gasoline is highly flammable. When working around fuel and fuel line connections, don't disconnect any wires or electrical connections that may cause electrical sparks.
- Always remove the gas cap to relieve any pressure in the tank prior to working on the fuel system.
- Do not use a work lamp when working near fuel or fuel tanks.
- Gasoline vapors are strong, harmful, and can cause you to become drowsy and not think straight. Always perform work in a well-ventilated area with plenty of fresh air blowing through.
- Always disconnect the batter when working on the fuel system. Leave it disconnected for at least 30 minutes to allow any residual electrical charge in components to dissipate.
- Keep plenty of paper towels on hand, and wear rubber gloves to prevent spilling gasoline on your hands
- Be well grounded - don't do anything that will create static electricity. Keep all cell phones and pagers a safe distance away.
The first step is to remove the back seat from your car. It's simply clipped in place. Move both the driver and passenger seat all the way forward, crawl in the back of the car, and simply tug up on the rear seat from the bottom edge. It should pop up with a minimal amount of force. BMW seems to have smartly designed the car so that the fuel tank senders and the fuel pump were very easy to get to - on some cars you need to drop the fuel tank to do the replacement.
With the back seat removed, you will see some sound deadening material (Figure 1) with two flaps, one on the right side and one on the left. The fuel pump is located on the right side of the car - lift up the right side flap. You will see a circular cover with some wires exiting out of it (Figure 2). Remove this cover, and the thin foam seal underneath it (Figure 3). Underneath, you will see the top of the fuel pump. Disconnect the two connectors that mate with the pump (Figure 4). Now, disconnect the fuel lines that feed into the top of the pump. There will be some gas spillage here - have a roll of absorbent paper towels on hand. Plug the lines quickly with a bolt or a pen and use a hose clamp to prevent further leaks.
The pump is held in place by the big circular disc with the risers on it. There is a special BMW tool that is used to remove and tighten this black plastic ring. However, with a large flathead screwdriver and a small hammer, you can easily tap the plastic ring loose. Carefully remove the ring from the top of the pump.
Now comes the fun part. Make sure that you are prepared at this stage, with a heavily ventilated garage, plenty of paper towels, and rubber gloves (we didn't have any gloves with us in Vegas). Pull up on the pump, and the entire assembly should come right out of the tank (Figure 5). There is a big, thick o-ring that seals the pump to the tank - it will probably fall to the bottom of the pump, as shown in Figure 6. Don't let it fall into the tank - you'll then have to fish it out somehow later on. Figure 7 shows this big o-ring from a different angle, having fallen down to the bottom of the fuel pump screen. Notice in this photo how brown the bottom filter of the pump looks. For reference, the new pump's screen was completely white.
Now, you have an open tank of gas in your backseat (Figure 8). Needless to say, you don't want to leave the car like this for any length of time. However, you also don't want to work too quickly, as you don't want to make any big mistakes.
You could probably reuse your old sealing o-ring, but I opted for a new one (Figure 9). If you do use the old one, and it doesn't seal well, you will be plagued with a fuel smell in the interior of your car from that point on. Figure 10 shows the brand new pump (placed in my laptop bag, as I didn't have anything else to use as a backdrop in the hotel parking lot). Notice how white and clean the pump looks compared to the old one.
Insertion of the pump into the tank is the reverse of removal (Figure 11). Make sure that the big o-ring is properly sealed around the outside of the pump and will seal with the opening of the tank (Figure 12). The new pump sits snuggly on the top of the tank, as is shown in Figure 13. Spin on the large circular ring and use the hammer/screwdriver tap procedure to tighten it. I tightened mine about as tight as I could get it without feeling that I would break the ring. Reconnect the fuel hoses as is shown in Figure 14. Use new hose clamps.
Plug in the new fuel pump, and reconnect the battery after all fumes have subsided. Then crank the car over and see if it starts. If the car starts and runs for any length of time then the pump is working fine. Replace the top cover and foam seal. Then reinstall the back seat simply by pushing it down into its home position.
Well, there you have it. Really not that difficult - just a bit unnerving if you don't have all the info - but we provide that here. If you would like to see more technical articles like this one, please continue to support Pelican Parts with all your parts needs. If you like what you see here, then please visit our online BMW catalog and help support the collection and creating of new and informative technical articles like this one. Your continued support directly affects the expansion and existence of this site and technical articles like this one. As always, if you have any questions or comments about this helpful article, please drop us a line.