AWR-fix: e53 Fuel pump / siphon pump details

[andrewwynn]

The tiny bump you describe would poke out of the bottom of the car.

They didn't anticipate the siphon jet o-ring failure hence my description as a "design defect". Your proposal would not be an improvement. The car would starve of fuel with 40% full tank when you go up or down a steep hill. that's the beauty of the design. By putting the pump in a dent in the raised part of the tank, the pump is submerged down to about 3L of fuel regardless of the pitch angle of the car.

Just like 100 other systems on the car there are required subsystems. Once we know about it though it's easy enough to keep on top of things.
By monitoring the fuel level with hidden menu 6, watch the right tank level and if it drops before the left tank goes to zero the siphon jet is leaking. You can prevent getting caught with fuel starvation with 1/4 of a tank remaining.

[80stech]

Having 2 fuel pumps or even a separate pump for the syphon jet would solve a lot of issues.

[andrewwynn]

Oh hell no. Siphon jet has no moving parts in theory it woukd last indefinitely. An oversight in the design of the flexibility of the plastic causes this failure. An electrical/mechanical pump would be far less reliable. Also the beauty of this system is it's no more effort to pull fuel from the front and back of the main tank to account for up and down hill operating.


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[BMWguy206]

Hey guys!

I have a 2006 BMW X5 3.0i, with 128,000 miles, and have some fuel gauge issues. A couple of months ago, the X5 ran out of fuel when the fuel gauge needle was between the 1/4 and 1/2 hash mark. This all started after another shop replaced the fuel pump and they said it was nothing that they did. Last month, I added a full tank of gas and needle moved to 1/2 mark. I removed both fuel sending units and didn't find anything wrong. I reinstalled it and the needle went to full. I figured that maybe something got stuck and now it was fixed. A couple of weeks later, the car died again because it ran out of fuel and the needle was just under the 1/2 mark. I took it to a shop to read faults and they said I had the following:

Stored in the DME:
- (141) 8D PLAUSIBILITY, TANK FILL LEVEL, NOT PRESENT. OCCURRED 2 TIMES.

Stored in the Instrument Cluster:
- (199) C7 TANK SENSOR #1 (FUEL PUMP SIDE), NOT PRESENT. OCCURRED 0 TIMES.
- (215) D7 TANK SENSOR #2 (WITHOUT FUEL PUMP SIDE), NOT PRESENT. OCCURRED 0 TIMES.

I removed both fuel level sensors, checked the resistance when I did the sweep test and didn't find any opens in the resistor. I reinstalled it and the needle dropped to the 1/4 mark. I found out about the instrument cluster test and got the following:
Tank Sensor #1 = 21.8 liters
Tank sensor #2 = 8.1 liters
This is roughly 7.8 gallons which looked liked it did when I last checked it.

I then added 16.18 gallons of fuel and the needle went to the 3/4 mark. I did the cluster test again and got the following:
Tank Sensor #1 = 55 liters
Tank Sensor #2 = 27 liters
This is about 21.66 gallons so this should be a full tank right?

I am also getting" TNKANZ: 58.8L, Phase 1"
58.8L equals 15.53 gallons. Phase 1 means both sensors are OK but I don't know if I believe that or not.

To my knowledge, the drivers side fuel sending unit has never been replaced. I am starting to think that the drivers fuel sending unit or the instrument cluster itself could be faulty.

Any thoughts?

[andrewwynn]

The gauges only read to full minus ten liters. (The floats hit the top of the tank).

If it says phase one as your surmise, car is getting realistic values from the floats. If you are getting intermittent drops in value sounds like a bad connection somewhere.

Two things most likely cause of fuel starvation at 1/4 tank: leak on the siphon jet or a weak fuel pump. It's tedious so get measurements of the fuel pressure but I just crack the left sender open and turn the key to determine if the siphon jet is leaking


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[andrewwynn]

The last 5L will get you 15-20 miles it's not mere minutes.

Watching the test six once the tanks split left/right (about 30L total) the right tank will stay the same until you run out of gas. You can tell of there is a soft failure without running out of gas very easily:

The right tank number will stay the same on level ground. In my wife's case 1.4L (there is an additional 3.6 L not displayed).

You can drive for quite a long way while that number slowly drops, for example once the number drops to 1L there is still some gas coming from the left tank just not more than is being consumed. I've driven 40+ miles watching the level in the right go from 1.4 to 0.9L.

So: drive down to 1/3 of a tank and watch the right tank value. If the number drops, you have either a leak in the siphon jet or a weak electric fuel pump.

The flawed design of the siphon jet guarantees a failure at about 3-4000 hours. I recommend fixing the o-ring preventatively at 3000 hours. (100000 miles if you average 33mph.)


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[cn90]

- On the issue of preventive maintenance...

- If I open the LEFT tank to check the Siphon Pump, and let's say it is good with no issue, what can I do to prevent O-ring issue? Should I apply a hose clamp around the connection? Should I secure the Siphon Pump better?

[andrewwynn]

Zip tie will prevent the problem. See where I put in the thread on the diy fix for siphon jet


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[Bucephalus]

This is definitely the most beneficial thread I've ever seen on the www; makes my head hurt.


Knowing when the siphon pump is supposed to kick in (@32L?) is priceless.



I want to replace the entire siphon pump on my X5 3.0i; not comfortable with the task of separating the components without busting them. I'm wondering if any of today's siphon pumps being offered have been upgraded with the better O Rings, etc.


I read down to page 5 or 6 and haven't seen a part number for a siphon pump; any help would add to the pile of appreciation I have for this community.


Onto page 7



Thanks again for all the info. Salute!


G

[wpoll]

Originally Posted by Bucephalus

... I want to replace the entire siphon pump on my X5 3.0i; not comfortable with the task of separating the components without busting them. I'm wondering if any of today's siphon pumps being offered have been upgraded with the better O Rings, etc.


I read down to page 5 or 6 and haven't seen a part number for a siphon pump; any help would add to the pile of appreciation I have for this community.

...

The siphon pump assembly is not sold as a complete part - you will have to buy two major parts (plus the o-ring) and assemble them yourself...

BMW Part #16111184427



BMW Part #16116762044



Might as well simply replace the o-ring...

BMW Part #16116761645 (o-ring)