BMW E46 is generally revered as one of the most reliable BMW 3 series ever made. Aside from the few known issues, E46 was solid. That being said, reliable doesn’t mean invulnerable to wear and tear. Today we’ll show you what to do if that wear and tear gets to your fuel system. Our BMW E46 fuel pump replacement guide is simple to follow and as straightforward as possible. By the time you’re done reading, you should know precisely how to fix it on your car and get it back on the road.
Why do Fuel Pumps Fail?
If you consider that your average submerged fuel pump assembly is essentially an electric motor converted to deliver pressurized gasoline through the lines, it’s not so hard to see why one might fail. If there’s one dominant reason, it’s the lack of cooling.
Here’s the deal, submerged units use the gasoline as a coolant of sorts to keep the temp down and keep everything lubricated. This mutually beneficial relationship goes south when there’s no more fuel to cool and lubricate the system.
One of the main reasons submerged fuel pumps fail is driving on an empty or near-empty gas tank way too often. To prevent any of this from happening, it’s generally recommended that you always have half a tank of gas in your car. An overkill? Maybe, but it’s a surefire and easy way to keep the trouble away.
Other Causes of Fuel Pump Failure
Aside from what is arguably one of the main causes of burnt fuel pumps, there’s also the minor stuff. For example, water getting into the gas thank can corrode the pump, rendering it ineffective at doing its job. Water is heavier than gas and will sink, settling around the pump.
Debris can also find its way into the pump. Most, if not all, modern submerged pumps have a filter that sits on the system’s intake side. However, those can get damaged over time, and let all kinds of debris through.
How to Recognize a Failing Pump in Your BMW E46?
Signs that you’re about to lose all fuel pressure to the engine can be sudden or intermittent. It mainly depends on the type of damage the pump has suffered. It’s not uncommon to have the whole system work one day, then not work the next, and then miraculously spring back into action the following day.
This malfunction is caused by a ‘sticky’ rotor that sticks to the static part of the electric motor and gains a temper of its own.
Troubleshooting fuel feed issues is relatively easy. Here are some steps you can take to do so:
- Check the relay and fuse before going any further – Do yourself a favor and follow the Occam’s razor when diagnosing any automotive issues, fuel pump included. Check the relevant fuse and relay first. If both are good, proceed with the other steps.
- Listen for the Pump – One of the sure-fire ways to know if your pump is dead is to listen for it. When you turn your ignition to accessory, the pump receives power and preloads the fuel lines in preparation for the engine start. You can actually hear it in the back if you pay attention. It’s a humming sound that lasts a few seconds and then cuts out. If you don’t hear anything, chances are the pump is either dead or not getting power.
- Unhook the Gas Line and Power the Pump – This method less subtle, but that might be the only way to figure out what you’re dealing with in some instances. Find the main gasoline line, unhook it, crank the engine, and see if anything is coming out your end. Just a tip – use an old rag or a bunch of paper towels to catch any fuel that might come out.
BMW E46 Fuel Pump Replacement
Let’s assume that you’re 100% sure that the pump is the problem. Now what? Fuel pumps are almost never fixed or repaired. Replacement is the go-to choice. Let’s see what you’ll need in terms of parts and tools to do the replacement.
- 1 x Fuel Pump – We offer a wide range of fuel pumps for the E46. We have the affordable URO, the OEM VDO, and the aftermarket, high-quality Bosch. Pick the one that best fits your budget. Bosch may be on the expensive side, but their products are pure quality. If you’re looking to never deal with fuel pump issues again, Bosch might be the way to go.
- 1 x Small Hose Clamp – Although it’s essential, it’s good form to replace the fuel line clamp that leads to the whole assembly when you’re already in there.
- 1 x Fuel Pump Seal – Last but not least, you’ll want to get a replacement pump assembly unit seal. Even thigh this rubber seal sits high on the gas tank, it can deteriorate over time. Replacing it now is an excellent way to reduce the risk of any further issues.
Tools Required for the Job
Accessing the fuel pump assembly unit on most cars is quite easy and requires very few tools. This particular job will need the following:
- 1 x flathead screwdriver
- 1 x hammer or a mallet
- 1 x 10mm socket with a wrench
- 1 x bucket
- 1 x latex or nitrile gloves
Additionally, you could go out and get a fuel pump removal tool, although that’s not necessary. With everything laid out, we’re ready to get to it.
Fuel Pump Replacement Guide
Step 1 – Get to the Pump
The gas tank on E46 is partially located under the back seat. That’s also where the fuel pump assembly access point is located. To reach the access point, remove the rear seat by undoing two clips holding it in place. Once you feel them release, slide the seat out. Make sure not to catch any trim panels while doing so since you can damage them.
Step 2 – Locate and Remove the Fuel Pump Cover
Next, find the fuel pump cover. It’s located under the softcover. This is where that 10mm socket wrench comes handy. Once you lift the softcover, you’ll find a metal cover held in place by 4 10mm nuts. Pop the grommet that covers the nuts and remove them.
Step 3 – Unhook the Fuel Pump Assembly
With the cover off, we can now access the power connector that feeds power to the pump. Unhook the connector by sliding the housing to the left.
Step 4 – Unhook the Gasoline Line
Next on our list is to remove the gas line from the pump assembly unit. The line is held in place by a pinch style clamp that has to be replaced once you remove it. These clamps are one-time-use only and can’t be used again. Pack the surrounding area with a cloth of some sort as there’s going to be some spillage. Additionally, use a bolt to plug the gas line.
Step 5 – Remove the Lock Ring
Here comes the hardest part of the process. The fuel pump assembly is held in place by a large lock ring. To undo it, you’ll have to take your flathead screwdriver, anchor it against one of the extruded points on the ring, and whack it with a hammer. Be prepared for it to be completely seized up. There’s a small chance you’ll have to go ham on this thing for it to let go.
Step 6 – Remove the Entire Assembly Unit
With the ring successfully removed, wiggle the entire pump assembly unit out of the gas tank. Grab yourself that bucket we’ve mentioned before and put the whole assembly inside. The bucket makes everything easier as you’re guaranteed to find gasoline inside the assembly. At this point, proceed to replace the pump with your new unit.
Step 7 – Replace the Rubber Seal and Reinstall the Fuel Pump Assembly Unit
Next up, remove the old rubber seal and replace it with the new one. Make sure it’s seated properly, as it might take some effort. Once you’re absolutely sure that the seal is seated, wiggle the new pump assembly unit back into the tank.
Step 8 – Reverse the Rest of the Process
With the pump back in the tank and the locking ring installed, the rest of the job comes down to retracing your steps. Just make sure to use that new clamp on the fuel line since the old one definitely won’t hold.
Replacing the fuel pump means that you’ll be working with an open tank. Make sure that your work area is well ventilated and that there are no sources of open flame around. If you’re a smoker, put out your cigarette before coming near the car. Better safe than sorry.
If you’re unsure which fuel pump to go with, you can always give us a call, and we’ll do our best to help you with any information you might need. You can reach us via phone or email. Our customer support reps are standing by to offer assistance!