Fuel pump recommendations

[andrewwynn]

To be clear: the pump needs to be submersed fully at all times. That is clearly part of the design and spelled out in some of the BMW technical reports. I'm sure that's why the gauges are designed to report approximately 4L less than the tank actually contains:

When the fuel gauge reads zero you will have approximately 1G or 3.5L of gas: double what is necessary to submerge the entire fuel pump which is at the bottom of the 5L surge tank.




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[andrewwynn]

Originally Posted by Crowz;

As in what does it have that makes it special for offroading angles and such?

The little "bump" on the bottom of the tank is where the fuel pump resides. The pump is so low in the little bump that with 5L of gas the pump will be completely submerged at a 30° nose up or nose down attitude. (or left or right but I wouldn't attempt that one I don't know at what angle the x5 will tip but I've had mine at 37° down 12° list before and it was awesome.

The design is great! I couldn't start my Ford explorer with 1/4 tank of gas when parked in an angle driveway and that was only maybe 8° angle. I had to put in neutral, coast to the road then when close to horizontal the car will start what a moronic design for supposedly an off road vehicle.

The diagram you showed is one of the hundreds of incorrect resources I mentioned when researching the fuel system of the x5.

100% of the existing resources referenced similar designs implying or explicitly declaring that the x5 fuel pump had two equal lobes which can not be more innacurate!

If you break the x5 tank into three virtual tanks it makes more sense:

Tank A is used first, holds about 60L
Tank B holds about 28L and holds the spill over from tank C
Tank C holds 5L and is where ALL the fuel is actually pumped.

When tank A is empty, tank B continually pours fuel into C to the point of overflow to keep it completely filled to 5L up until tank B is empty. This keeps the pump submerged even at extreme angles and down to 0.0 gallons remaining since there is almost 4L more in the tank than reported by the instruments.

It's an absolutely brilliant system but leads to some confusion during trouble shooting that will have people draw the wrong conclusions such as "keeping more than 1/4 tank will help something" or "a defect in the siphon jet will wear out the electric pump" neither of which applies to an x5 .

(The fuel pump is fully submerged by recirculating fuel down to 1/18th of a tank well below the low fuel light)

(In the EXTREME rare case of a siphon jet failure you will fuel starve having run for no more than ten or 15 miles with the pump not submerged it will not likely cause any significant harm unless you follow the "fill at 1/4 tank rule in which case you can cause damage by running the pump uncovered without realizing it because once below 1/3 tank the ONLY thing keeping the pump covered is the siphon jet).

These are just facts based on research and first hand measurements and tests (and a few mouthfuls of 93 octane).

There is no more accurate resource for the e53 fuel pump online. (Than mine). My digrams are based on my measurements and photos of an actual e53 tank I took apart not supposition upon speculation upon myth based on 1950s gas without ethanol. It's cold hard facts.

[Crowz]

So just for the record it makes no difference how much fuel is in the tank as long as the amount need to cover the pump in the depression is there right?

So if there is 5L of fuel then the pump will not run cooler by adding more fuel right?

[andrewwynn]

That is basically correct. When there is a little more maybe up to 10 L the recirculation of fuel will help a little bit but basically until the low light comes on the pump will get no increase in cooling. Again a brilliant design needing the bare minimum of fuel to run the engine and to cool the pump.

When the fuel is more than 5L, the excess goes in circles.

The fuel pump sends fuel to the filler/regulator, what is not used goes back to left side, that collects fuel from the left side and dumps into the right side which spills like a waterfall back to the left side. Any time the left side of the tank is cooler than the right side, some chilling will occur but since the turnover is limited and slow, it's not a significant factor so the reality is the fuel pump will be completely submerged by fuel that is cooled by conduction to the very large plastic fuel tank, you will have effective fuel pump cooling down to 0.0 on the gauge.

Also, it's important for the reasons above to test the siphon system periodically so you know the pump isn't worn and the seals are working.

Test Six should report about 1.3-1.4L right side on level ground driving steady state. If you learn what your particular car shows you can verify the system is working. If the right side ever drops below your baseline most likely the pump is worn out but also a good chance the stupid no o-ring seam on the siphon jet has failed. That can be fixed for free don't replace with the identical flawed design.

[80stech]

Excellent info Andrewwynn! I have read your thread on how the E53 fuel system works and appreciate all the effort you put into posting your findings! Do you have a part number for the O-ring you added to the syphon jet fitting? Maybe that could be repaired differently ?

[Crowz]

Originally Posted by andrewwynn

That is basically correct. When there is a little more maybe up to 10 L the recirculation of fuel will help a little bit but basically until the low light comes on the pump will get no increase in cooling. Again a brilliant design needing the bare minimum of fuel to run the engine and to cool the pump.

When the fuel is more than 5L, the excess goes in circles.

The fuel pump sends fuel to the filler/regulator, what is not used goes back to left side, that collects fuel from the left side and dumps into the right side which spills like a waterfall back to the left side. Any time the left side of the tank is cooler than the right side, some chilling will occur but since the turnover is limited and slow, it's not a significant factor so the reality is the fuel pump will be completely submerged by fuel that is cooled by conduction to the very large plastic fuel tank, you will have effective fuel pump cooling down to 0.0 on the gauge.

Also, it's important for the reasons above to test the siphon system periodically so you know the pump isn't worn and the seals are working.

Test Six should report about 1.3-1.4L right side on level ground driving steady state. If you learn what your particular car shows you can verify the system is working. If the right side ever drops below your baseline most likely the pump is worn out but also a good chance the stupid no o-ring seam on the siphon jet has failed. That can be fixed for free don't replace with the identical flawed design.

Actually our test showed the plastic tank didn't provide any measurable cooling effect for the pump in our test. Volume of fuel did but sitting directly on the tank bottom or suspended in the plastic bucket the tank came with didn't help with pump temperatures.

Free floating without the bucket provided the most cooling of the pump.

[Crowz]

One thing we found strange was that without a pressure regulator the pump ran much hotter than with the regulator but a dead head system aka no return got the hottest.

[jdstrickland]

Originally Posted by 80stech

I wanted to order a spare fuel pump to have on hand and was wondering what experience anyone has had with the aftermarket ones and if there is any good reason to order complete w/sending unit ? Thanks!

I just replaced the fuel pump in my '05 3.0L. I see absolutely no reason to replace the entire assembly, you can replace the pump separately. I was sitting at a traffic light at the exit from Sam's Club, the light turned green and I stepped on the gas, the engine stalled as if it was sucking air. I had come from the gas station in the last 25 miles so the tank was filled. I pulled the old pump and did a continuity test, it was open. The new pump had resistance. It could have taken as little as 30 minutes to replace the fuel pump, but I had trouble with the seal -- which is actually easy to not have trouble with -- that slowed me down. I would not recommend changing the fuel pump on a full tank of gas, but sometimes you can't always get what you want.

Personally, in all of my years owning cars, this is the second fuel pump that failed me. I would not bother stocking a pump for the next time.

[andrewwynn]

The seal must be installed onto the pump assembly before installing into the tank. Was that the problem.

It's not a difficult process to swap the pump and you can likely end up with a better pump doing that. I swapped the whole assembly because I found one with a year warranty that was a price too good to pass


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[terminx]

Originally Posted by oldskewel

The OE supplier for the fuel pump that came in my 2001 3.0i was Pierburg. Made in USA. I replaced it with the same when mine went out a year or so ago.

Pierburg was bought about 10 years ago by TI Automotive. So my new pump actually came in a hologrammed box saying Pierburg, etc., but stamped into the Aluminum shell on the pump was "TI Automotive." Taking a quick look on that RockAuto link, and looking at the photo they have with the Bosch unit (not the Delphi one), I see that it looks the same as mine (from memory) and that it also says TI Automotive on it. If you know what to look for, you might be able to read that too.

So I will guess that if you buy the Bosch one there, you might get one made by Pierburg / TI Automotive.

Weird stuff going on now with buying parts online. I recently bought a Gates-branded alternator pulley from RockAuto, and it came in a Gates box, Gates instructions, Gates warranty, but had a Litens part inside it, with Litens name and part number stamped on the part. Checking up with both RockAuto and Gates, and yes, that is how they do it. Gates puts a Litens part in a Gates box and sells it.

I had no problems swapping the new pump into the original plastic assembly. Would do it again.

Also, regarding buying the part before it fails, I agree - good idea. It will wear out just like tires do. I took mine apart when it failed at 173k miles, and the brushes had simply worn out. Everything else looked great in there, but brushes are a wear item and they were done.

I can confirm that the TI Automotive pump is what came in the box when I bought this on Amazon: https://smile.amazon.com/gp/product/B00PQXAWQI

I got lucky and found one open box on Amazon Warehouse Deals for $109. Guessing somebody bought it and thought they were getting the whole assembly, or couldn't figure out how to get the old pump out of their existing assembly without breaking it.