AWR-fix: e53 Fuel pump / siphon pump details

[andrewwynn]

A couple days ago, driving about 75 miles home from chicago, got 3 miles from home and engine shut off no warning. no stutter, no warning lights, (no DTC even after it stalled).

I have a knock-off fuel pump that is the under-warranty replacement of the one that failed after 10 months, so I was pretty darn sure that had to be it, i actually didn't even look at the test-6 or open up the tank before i ordered a new Bosch unit (the pierburg are too hard to find quick shipping). I also liked the verbiage on the Bosch unit regarding new improvements in the design in the past TWENTY YEARS since mine original was made.

Anyhow, imagine my surprise when yesterday i go to take out the old sending unit (where i'll transplant the new motor), and see a bone dry tank (i mean BONE dry; it would take less than 3 paper towels to remove every bit of remaining fuel; clearly the pump was working at the time).

So; siphon jet? at nearly 1/2 tank registered; well that's not laws-of-physics possible if the senders are reporting properly, so i pull up test 6 and it shows 330000 ; 33L left 0L right; well i can visually confirm right is 0.0000, but the left when you look from the right port hole, you see reflections and you really can't tell..

So, 5-8 minutes later, the left side port open and what do you know it's BONE DRY ALSO; so the sender was reporting the wrong #; by 33L. Well that will throw a big monkey wrench into the system for sure.

So, i hook both senders back up (careful to point the fuel pump down into the tank in case any fuel might spurt out), and get test 6 up and running; and both will do a proper sweep from 0 to 27 and 0 to 55L.

I go to fill up the tank and something odd happened; when the left tank got to about 28L, it stopped climbing while the right side ramped up properly to 27L or so.

Then i started driving and the left side popped up to 55L as it's supposed to read and the right stayed pinned to 27L like it's supposed to.

I get 6.0 reading of 550270 as it supposed to, 6.1 reads 82.0 and 6.2 reads like 62.5L; wtf?

So i knew i had to reset the IKE but didn't know that was what I had to look for.

That worked like a charm, instantly my fuel gauge now went from 2/3 to 1/1.

I still have to figure out what is going on with the left side sender that is 'sticking' at 33L; it's either somehow a dirty sweep (btw has a TIS how to fix by increasing the spring tension) or a physical blockage, like the float is getting caught up on the discharge hose from the siphon jet pump.

I have to drive about 180 miles tomorrow so after that drive i should have the fuel low enough to send in the 'rectal probe' (fiber optic inspection camera) and see if there is a physical obstruction causing the hang-up.

Soooooo. since I already bought the new Bosch pump, and my wife is still using the original pump from my car, i'm going to put that pump in her car and put her pump in my car in the trunk as a spare, with just enough tools to swap on the side of the road if necessary when my china pump actually fails. That will be enough to get me home where i'll order another bosch/pierburg pump.

[SlickGT1]

Subscribed. Excellent thread.

[cn90]

For fuel pump, stick to Pierburg.
About $150 at FCPEuro or on ebay.

The aftermarket pump quality is questionable.

The Pierburg should last some 150K.

[Bucephalus]

Crazy thing happened today; guage read 1/2 tank, but the tank ran dry, right next to a gas station.

The car took 25 gallons and started right up. I think there was 427 miles on the trip meter.


I installed a new fuel pump a few months ago, then I changed the O ring on the syphon side.


I did page2 of test 6 a couple days ago, it showed phase 1.


So after I filled up, I ran the instrument test; no faults.
I ran test 21 and effected a reset.


Gonna do some research to find out why the guage showed 1/2; perhaps the fuel level,sending unit

[cn90]

Fuel sending unit fails either:
1. Mechanical: stuck in one position: I doubt it.
2. The rheostat fails "electronically", i.e., it sends the signal to the cluster saying the tank is 1/2 full, even the float is down to 1/8.

Try a few bottles of FI cleaner such as Techron and report back. This should be easy fix. If Techron does not fix it, then get new sending unit from dealer.

If you are very short of budget, then use the odometer as your fuel gauge!

[andrewwynn]

Originally Posted by Bucephalus

Crazy thing happened today; guage read 1/2 tank, but the tank ran dry, right next to a gas station.

The car took 25 gallons and started right up. I think there was 427 miles on the trip meter.


I installed a new fuel pump a few months ago, then I changed the O ring on the syphon side.


I did page2 of test 6 a couple days ago, it showed phase 1.


So after I filled up, I ran the instrument test; no faults.
I ran test 21 and effected a reset.


Gonna do some research to find out why the guage showed 1/2; perhaps the fuel level,sending unit

That's almost verbatim what I wrote above I thought you quoted me.

I checked test six after I took the pump out to look and it read 33L left side.

I took out left side and plugged it back in so I could run the sweep and it went the full range.

When I filled the tank it got stuck at like 28L left until I drove away then it popped right to 55L as it's supposed to.

I still have 39L left and about 5L right so I can't tell if the suspected physical hang up on the float is the issue but as soon as it gets closer to 33L left and especially if the number stops dropping I will be sending the "rectal probe" (snake camera) in from the right side into the left and figure out for sure if the float is caught.

I can't figure out how it could possibly be a case where the resistance is stuck in the middle electrically but BMW does have a TIS about how to fix the resistor sweep by adding more spring pressure so that might be required.


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[Bucephalus]

Starting guage reading was 1/2.


Did some work on the truck's fuel tanks this weekend; I pumped-out 12 gal from the fuel tank; from the R/S, then peered into the L/S with an Ames camera. The L/S float was in fact suspended on a fuel line (my foul up from oring change out).



Opened the L/S, insp. the new o ring, and re-installed the syphon. Put it all back together and started the truck; the guage read 1/8th tank and ran fine. 18.2L, 0.0L, 18.2L. So, I'm fairly-confident the syphon system works.


Replaced the 12 gal of fuel and guage read at 1/2. 41.0, 0.0, 41.0.


This thread (as I've shared before) is the most benificial thread I've ever seen on the web; thanks!


Eneded up with a new 12v pump assem. and a new camera (@$184.00).



Did more work on the trk today, will post in proper place.


G

[andrewwynn]

41 left 0 right not plausible. Right should never be below about 1.5L.


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[Bucephalus]

Originally Posted by andrewwynn

41 left 0 right not plausible. Right should never be below about 1.5L.


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10-4. Bugs me too. I did pump the R/S dry to clean it. I'll evaluate after my next fill up. I could of messed up the float placement on the R/S this time...lol


Thx!

[andrewwynn]

Right level should swing from 1.5 to 27L. The key is that the left joins the right at approximately 28.5/1.5/30

It's tragic that some STUPID simple programming would stop a lot of stranded situations.

If left > 29 and right drops to zero flag an immediate pull over fault.

If right > 2 and left < 28, flag low fuel light.

You can not have left > 29 and right < 2 it's impossible when working.

You can't have left lower than 29 unless right is "bottomed out" at flood stage (usually 1.4L)


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