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Discussion Starter · #1 ·
I had a very weird issue with my 03 M5 the other day. While driving home, the car sputtered and died... WTF, I checked the cluster, no lights, gas gauge showed 1/3 tank, all looked A-OK. I tried to restart, but the car just stumbled and died... very strange. I figured either I got a tank of gas with water in it, or something was very bad and going to be very expensive. I called my father in law for a ride and asked that he bring down a tank of gas, just in case. He graceously came to save me. We poured 4 gallons into the tank, and vroooom the car started right up. Very odd, then I happened to check my trip odometer. 323 miles, that's an awful lot on 2/3 of a tank of gas. I drove to the nearest gas station and pumped in 16.5 gallons of gas. Obviously the gauge wasn't accurate.

Since then, I've put a few tanks in and the gauge and range seem to act fine for at least the first half a tank. As it gets closer to the empty half of the tank, the gauge seems to stop decreasing around 1/4, but I haven't gone past 220 miles on a tank of gas since I got stranded, so I'm not sure if it is still misreading or not. I just had a new cluster put in to fix the pixel issue a month ago. I did some searching tonight, and it looks like I need to check the secret menu tests 6 and 14 and suspect a fuel sender unit (looks like the left side is usually the culprit), although most of the errors I saw were the opposite of mine (gauge showed too little).

Is there anything else I should check out? Thanks in advance for any suggestions, this board is extremely helpful.
 

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You've done your homework, Josh.

The ONLY way to make sure you have (or haven't) got a failing (could be intermittent) siphon pump, is to check the Conosle Test # 6. (assuming the console is correct.)

The right hand tank should be full, until you are approximately at 1/2 tank. The left tank will drop to completely empty as you drive up to around a half a tank. Then the right hand tank will begin to drop. (obviously, sloshing gas from cornering with allow some gas to go back to the left hand tank, which when you are back on the straight and level will go empty again.)

If Test # 14 shows a "D7," your siphon pump has failed or is failing. The odd part, is that you put 16.5 gallons in ... that would allow for 2 to 2.5 gallons of gas from your Dad's gas can. And, at that point your gas gauge should have the Reserve light on.

Our fuel tanks will only hold a max of around 19 gallons (the manual says 18.5 gallons or 70 liters officially). The Reserve light normally comes on at around 16 to 15.5 gallons of use.

Your gas gauge will not show the correct amount of gas, if you add LESS and a quarter of a tank, or you forget to remove the key while refueling. It will slowly correct itself, however.

I suspect you had deduced as much. I would fill your Dad's gas can, put it in the trunk and drive until the car stalls again. Examine Test # 6, your Range, and your gauge.

By the way, do you have any idea of what kind of gas mileage you were getting the time you ran out of gas?

UPDATE: Thinking here. (I smell smoke) I suppose you could have a loose, or corroded connection, on either the gauge (not sure if the gauge can be removed separately from the console), or the fuel float coverS under the rear seat.
 

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Discussion Starter · #4 · (Edited)
You've done your homework, Josh.

The ONLY way to make sure you have (or haven't) got a failing (could be intermittent) siphon pump, is to check the Conosle Test # 6. (assuming the console is correct.)

The right hand tank should be full, until you are approximately at 1/2 tank. The left tank will drop to completely empty as you drive up to around a half a tank. Then the right hand tank will begin to drop. (obviously, sloshing gas from cornering with allow some gas to go back to the left hand tank, which when you are back on the straight and level will go empty again.)

If Test # 14 shows a "D7," your siphon pump has failed or is failing. The odd part, is that you put 16.5 gallons in ... that would allow for 2 to 2.5 gallons of gas from your Dad's gas can. And, at that point your gas gauge should have the Reserve light on.

Our fuel tanks will only hold a max of around 19 gallons (the manual says 18.5 gallons or 70 liters officially). The Reserve light normally comes on at around 16 to 15.5 gallons of use.

Your gas gauge will not show the correct amount of gas, if you add LESS and a quarter of a tank, or you forget to remove the key while refueling. It will slowly correct itself, however.

I suspect you had deduced as much. I would fill your Dad's gas can, put it in the trunk and drive until the car stalls again. Examine Test # 6, your Range, and your gauge.

By the way, do you have any idea of what kind of gas mileage you were getting the time you ran out of gas?

UPDATE: Thinking here. (I smell smoke) I suppose you could have a loose, or corroded connection, on either the gauge (not sure if the gauge can be removed separately from the console), or the fuel float coverS under the rear seat.
Thanks for the reply jclyman.

I've been averaging 16 to 17mpg per tank. The nearest gas station in my story was about 18 miles away (I had just passed through the toll booth on the turnpike when the car died), so the 16.5 gallons + 3 - 4 from the portable tank - 1.5gal of consumption sounds about right for completely empty. The low gas light never came on and the gauge never showed less than 1/4 even after the portable tank worth of gas was added. (Fun math fact: 323 miles onthe trip odo/16.5mpg = 19.57 gallons)

I'll check the secret tests tomorrow and report back. Interestingly, prior to my issue, I did fill the tank with the car on and noted that the gas gauge didn't show my updated tank level. I quickly shut the car off and restarted before leaving the station and the guage spiked to full.

Chowdah, when yours failed, was it the sender as well or something else?

Thanks guys.
 

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From your latest description, it does sound like a sensor (one of 2), or the gauge. I should mention, in 700,000 miles of driving BMWs (one had 320,000 miles), I have never had a GAUGE go bad. Sensors ... a couple. (My current 318ti DD has a sensor that sticks at the point where the Reserve light goes on. Sometimes, it never moves at all, until shortly after it is REFILLED the next time, but it isn't terribly important to me, as I always reset my trip mileage when fueling. One day I will change it.)

So you witnessed the fuel gauge issue and the key. Again, it will happen, even with the engine OFF. You have to take the key completely out of the ignition, for it to work properly (and, oddly, sometimes it works fine when leaving the key in). When it doesn't reset, it can take 50 miles or so to correct.

If it is a sensor, they are NOT terribly expensive (at least, not a while ago), and they can be fixed by a competent DIYer.
 

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Discussion Starter · #6 ·
From your latest description, it does sound like a sensor (one of 2), or the gauge. I should mention, in 700,000 miles of driving BMWs (one had 320,000 miles), I have never had a GAUGE go bad. Sensors ... a couple. (My current 318ti DD has a sensor that sticks at the point where the Reserve light goes on. Sometimes, it never moves at all, until shortly after it is REFILLED the next time, but it isn't terribly important to me, as I always reset my trip mileage when fueling. One day I will change it.)

So you witnessed the fuel gauge issue and the key. Again, it will happen, even with the engine OFF. You have to take the key completely out of the ignition, for it to work properly (and, oddly, sometimes it works fine when leaving the key in). When it doesn't reset, it can take 50 miles or so to correct.

If it is a sensor, they are NOT terribly expensive (at least, not a while ago), and they can be fixed by a competent DIYer.
This morning when I got in, the gas gauge showed near empty, the light was on and the range showed 27 miles. When I parked it last night it was firmly on a 1/4 tank at a trip odo of 259. My wife did drive it for a few miles after I got home, but not enough to suck up a 1/4 of a tank (well at least not without A LOT of explaining on her part... she better not be doing extracuricular activities on her "milk run").
I went into the secret menu and first checked test 6. the left tank showed 0.0, and the right showed 11L. As I drove the right side fluctuated wildly from 0.0 to 20L (is this normal)? So I went to the gas station and filled up and topped off. Tanks showed 34/31/65 and stayed there for the rest of my 8 mile commute to work.

I pulled the codes in Test 14 and got the following:
Test 1: D7 81 125
Test 2: BF 88 000
Test 3: 90 84 000
Tests 4/5 all 0s

So I'm guessing the D7 means left sensor? What does the BF mean? I'd do it myself, but the car is still under extended warranty, so I might as well get my moneys worth while I'm still covered.
 

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This morning when I got in, the gas gauge showed near empty, the light was on and the range showed 27 miles. When I parked it last night it was firmly on a 1/4 tank at a trip odo of 259. My wife did drive it for a few miles after I got home, but not enough to suck up a 1/4 of a tank (well at least not without A LOT of explaining on her part... she better not be doing extracuricular activities on her "milk run").
I went into the secret menu and first checked test 6. the left tank showed 0.0, and the right showed 11L. As I drove the right side fluctuated wildly from 0.0 to 20L (is this normal)? So I went to the gas station and filled up and topped off. Tanks showed 34/31/65 and stayed there for the rest of my 8 mile commute to work.

I pulled the codes in Test 14 and got the following:
Test 1: D7 81 125
Test 2: BF 88 000
Test 3: 90 84 000
Tests 4/5 all 0s

So I'm guessing the D7 means left sensor? What does the BF mean? I'd do it myself, but the car is still under extended warranty, so I might as well get my moneys worth while I'm still covered.
Believe it or not, your Fuel Gauge is sounding MORE normal. The "D7" IS the "signal" of a failed or failing LEFT tank sensor. There are a few write-ups here that discuss the part change in more (and, important) detail. Like how to hook up the hose from the left tank to the fuel pump (right tank) properly. Search.

The 81 seems to be unimportant. The 125 decrements by 1 each time you start the car (it seems to indicate how long the siphon has been faulty ... or inversly so).

The "BF 88 000." He!!, I don't know. I have it, as well (exactly the same numbers). It came on for the first time at around 82,000 miles. The best I have been able to find out, so far, is that it has something to do with an incomplete" loading of a specific computer.

No idea on a "90," either.

Relative to your "cold start" low Range condition. I have written about that, too. Short answer. The gas "free" siphons back into the left tank overnight, and the tanks are both equal in the morning. Since there is NO need for a reserve sensor in the left tank (no gas, if it is working), the reserve reads JUST the level in the right tank. Drive (the Owner's Manual states, "Do not warm up your engine at an idle ..." on page 57) and you may see the Reserve light go out.
 

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this just happened to me last nite in the middle of no where! gauge read 1/4 w/ approx 80mi of range. The kicker is that the left side fuel sender, part 16141183179, was replaced just 7 months ago! This should be covered under the part warranty right?
Also, how does one run a console "secret" test????
 

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M5 e39 running out of fuel but guage said 1/4 tank.

This happened to me last night in my e39 M5 2001 which left me stranded on Putney Bridge in London waiting for the AA. He checked a few things and towed me to the Shell garage. It started straight back up and once the air was out of the lines was 100% fine. The guage was reading 1/4 tank. No lights were on or the range warning. The computer range suggested roughly 100 miles.

What sensors will need to be changed and how much would anyone expected this to cost?
 

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Mine did it on the autoroute, 2 miles short of a servie station (but uphill all the way - jeez these things are heavy to push) and with 34 miles showing on the range display.

I'll be checking that secret menu when I finish work...

YG
 

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If I may share what happened with mine before:

I still have 1/4 gas but car died. I checked test #6, left tank has gas, while right has 0. (which was weird - since left should always run out of gas first - especially when you are at 20 liters left and engine is running.)

My issue was - either change the fuel sensor or fuel pump is weak - (when you are running out of fuel, it can't produce enough pressure/psi to "feed" the remaining fuel (which is on the left tank) to the right tank.

Changed the fuel pump and I'm good. (apparantly, previous owner tried to hide this issue by chipping + retuning) He installed the wrong fuel pump (wtf - 525 fuel pump)

forgot to note: at idle, in cold start, my m5 sounded like a honda or evo engine with aftermarket cams.

Hope this helps.
 

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I've had the same issue, starnded on the road with 60 miles left according to OBC my level sensor was faulty and replaced, after that once i hit a min of 75 miles left I fill up not worth trusting.
 

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I still have 1/4 gas but car died. I checked test #6, left tank has gas, while right has 0. (which was weird - since left should always run out of gas first - especially when you are at 20 liters left and engine is running.)
This is the classic symptom of the lift pump failing. Both level sensors are working fine, so there is 20L + left in the tank. The problem is that the fuel is all in the left side and the lift pump is inoperative, so the right side runs dry while the Range is still 100 miles or so and the gauge says 1/3 full.
 

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Discussion Starter · #19 ·
My car has been flawless since this happened a few months ago. The tank that it ocurred on was the last time I left the car "on" when I filled up. From posts at different places, it seems like the car doesn't like to be filled up while the engine is running or even if the engine is off but the ignition switch is on. So far, so good for me.
 

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If you tried to fill up with the engine running in this country, the cashier would shoot you stone dead ;)
 
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