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Old 05-31-2012, 12:52 AM   #1
Sapote
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Fuel pump or no gas?

Wife called saying the car -- 2000 323i 110k miles -- lost power slowly and died. Got to car and checked the fuel pump the first thing. Honestly I have never been able to tell how the normal working pump humming before for the reference since when turned on the key there are so many other humming noise i.e. cabin fan, heater valve...etc. So after removed the back seat and listen to the pump at close range while my wife turned the key on, I heard no hum at all. Next I popped the pump's elec connector and check the voltage: I got momentary 12v to pump for ~3 seconds, which is normal. Next I tapped on the pump with an object and this time I heard the humming for 3 seconds with ignition on. Wonderful!! i hoped I could nurse the car home (0.5 miles from home) with the injured pump. It cranked but still not running!!! Could the pump be humming but still no fuel pressure??? I squeezed the soft fuel hose on top of the pump while wife turned on the key: not felt any pressure built up at all while pump was humming. Is this possible that pump humming but not working? Or maybe empty gas tank on the pass side? The fuel gauge shows one mark above empty -- there are two tanks and the fuel level sensor on the pass side? If it is then this rules out the possibility of the siphon pump moving L tank to R tank issue.

It's after 9:30pm on street. I called a quit. I did try to remove the pump to check if there was gas in the tank but was unable to turn the locking ring tapping the end of a screwdriver. Tomorrow will try with screwdriver and hammer.
Question: should I feel the fuel line on top of the pump building up pressure (for 3 seconds) if I squeeze it while the turning on the ignition?
Any idea of my car problem?

Thanks,
Sapote

Last edited by Sapote; 05-31-2012 at 12:59 AM.
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Old 05-31-2012, 04:45 AM   #2
jfoj
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Pumps are known problem areas on these cars, they can also soft fail where there is not enough return fuel volume to transfer enough fuel from the drivers side to the passenger side.

You can check my signature below for the Hidden OBC menu to access the fuel level in each tank to check. Once car is below 1/2 tank the driver side should empty.

If it was my wife's car, I would replace the fuel pump, fuel pump relay and fuel filter. Even if the pump is not dead now, it WILL die sometime soon and leave her stranded.

If you do no have time, a fuel pump will cost you about $230 best price from the dealer if they give you a good price. BMAParts.com the pump is about $125 shipped, but you will need to wait a bit. You might find a local import parts store that has them in stock for somewhere between these prices?

At times, you can add a few gallons of fuel and get pump running to get you home, but if the problem is really the pump, you are asking for trouble if you put the wife back in the car until the pump it replaced.

See this post about BMAParts - http://forum.e46fanatics.com/showthr...848&highlight=
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Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temps, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

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Lower hose fan switch O-ring - BMW #13621743299
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Old 05-31-2012, 09:35 AM   #3
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since it's original pump, I had already ordered the pump and filter lastnight from BMA and pick them up at 9am this morning.
My question is that does the fuel hose on top of the pump have high pressure (~50psi) with normal running condition? If it is then one should be able to squeeze the soft rubber hose and test for fuel pressure to rule out if pump failed.

Exactly how the fuel tank level being balanced from L to R tank? If the L has fuel and R is low fuel, what component failed? (I'm just preparing for the case.)

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Old 05-31-2012, 09:55 AM   #4
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Apparently the unused fuel going back to the tank goes through a syphon gadget that moves fuel from the left side to the right side, where the pump is. So normally the left side empties first while the right side stays full.
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Old 05-31-2012, 10:18 AM   #5
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If you have a failing pump, it can be so weak that the syphon action of the sucking jet pump will not move fuel from the driver side tank to the passenger side tank. And as we know, the passenger side tank is where the pickup is.
Replacing the pump with a strong new one will cure the transfer problem.

Probably have high fuel pressure directly out of the pump, but I have no experience to tell by squeezing the fuel line. You are making the correct move by just replacing the pump to eliminate this possibility.

When you are writing about technical things and asking questions, please try to be more precise. It prevents us from knowing exactly what you mean, and it can make a difference in our answers.

Let us know how you make out please!
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Old 05-31-2012, 10:56 AM   #6
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The exact same thing happened to me. The right side was empty due to poor syphon action. Even though it showed approx 1/4 tank on the gage it wouldn't start. So, adding fuel worked for a short time. But I noticed reduced performance I assume from low fuel pressure due to a failing pump. Two days later the pump quit altogether. You will need a new pump and a hammer and big screw driver or drift to knock the ring loose. I cleaned the rust off the ring and used anti seize to help it tighten easier.
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Old 05-31-2012, 11:56 AM   #7
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Your symptoms remind me of exactly what I experienced last week with my fuel pump failure.
When you do hook up the new pump and turn the key on...you'll hear that sound you've been trying to hear. Good luck with the install.
It was pretty easy actually. I'm sure you'll be up and running today.
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Old 05-31-2012, 08:30 PM   #8
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As I said that I heard the pump was humming when ignition on but no fuel pressure (squeeze the pump hose by hand). I used the hidden OBC display to read the L and R tank level: R tank was empty. I topped up the tank with 5 gallons from portable container. Cycle the ignition sw a few times before starting (tried to save the batt since it's on street far from home). It fired up and I nursed it home. I will replace the pump tonight before handing the key to the wife.
I was so worry when wife called saying the car slowly loose power and then OIL light and BATT light came on then she shut the engine down. I thought she drove on low OIL. As it turned out, the car ran on low fuel for about 300 ft then died, then the dask light came on, then she turned the key off when seeing the OIL light, without knowing the engine was already quit.

I still not understand how the system control the amount of fuel transfered from L to R tank to maintain the balance between the two tanks and when to empty the L to the R tank. I think the computer must output a signal to control (open/close) a valve on the L tank suction line. Otherwise the L will be transfered to the R too soon.

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Old 05-31-2012, 09:06 PM   #9
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The fuel transfer is really a stupid simple process.

Return fuel from the fuel rail under 50 PSI or so will siphon fuel from the left side of the tank and pump it the right tank. If the car is above about 1/2 tank the fuel just keeps spilling back into the left side of the tank.

Once the fuel level drop below about 1/2 tank, fuel is then transfer from the left to the right tank until the left side is empty.

What happens when the fuel pump is on the way out and/or the fuel filter is really clogged, the return line pressure to the left side tank is too low to properly siphon fuel and then you drain the right hand side of the tank and run out of fuel.

What BMW engineers forgot to do is have an algorithm that could compare tank levels and if the right side of the tank kept dropping and the left side di not to then readjust and monitor the fuel level only in the right tank and possibly throw a CEL with a trouble code that indicated that there is a problem with fuel transfer.
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Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temps, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose fan switch O-ring - BMW #13621743299
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Old 05-31-2012, 10:40 PM   #10
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Does anyone out there own a fuel pressure gauge?
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Old 05-31-2012, 10:42 PM   #11
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Originally Posted by nateloffe View Post
Does anyone out there own a fuel pressure gauge?
Your point being?
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Old 06-01-2012, 07:22 AM   #12
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Quote:
Originally Posted by Stinger9 View Post
Your point being?
My point being? Call me crazy, but it seems to me like having the correct tool to properly diagnose a fuel problem would make a lot of sense. Taking 30 seconds to check for fuel pressure at the rail instead of "listening for humming," and "squeezing fuel lines," to check for fuel pressure makes a little more sense to me.
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Old 06-01-2012, 08:05 AM   #13
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I have a fuel pressure gauge, but only use it when the car runs, but not correctly. For no start situations on most cars, especially on the E39, E38, E46 and older BMW's simplest diagnostic is if the fuel pump is original, replace it.

You are starting to see an epidemic of fuel pump failures as all of these models are of the age that the pumps are all failing like clockwork.

The VERY FEW smart owners are proactively replacing the original fuel pumps so they do not get stranded!

I just need to decide when I need to replace the pump in my wife's '06 E46 Vert. Its not quite in the danger window, but peach and harmony are well worth the time and money to replace the pump before it leaves her on the side of the road or best yet, in a parking lot!!
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Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temps, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose fan switch O-ring - BMW #13621743299
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Old 06-01-2012, 09:45 AM   #14
Stinger9
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Quote:
Originally Posted by nateloffe View Post
My point being? Call me crazy, but it seems to me like having the correct tool to properly diagnose a fuel problem would make a lot of sense. Taking 30 seconds to check for fuel pressure at the rail instead of "listening for humming," and "squeezing fuel lines," to check for fuel pressure makes a little more sense to me.
It's one valid approach for sure. And to indulge in tech correctness, you would do a volume test to be totally thorough. I like science too.
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Old 06-01-2012, 09:16 PM   #15
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Originally Posted by nateloffe View Post
Does anyone out there own a fuel pressure gauge?
The pressure gauge hooked to the engine fuel rail may not tell where is the bad component. Say you have a logged up filter and so low pressure at the gauge; does this mean a bad fuel pump, or empty tank, or clogged filter?

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Old 06-01-2012, 09:28 PM   #16
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Originally Posted by jfoj View Post
What BMW engineers forgot to do is have an algorithm that could compare tank levels and if the right side of the tank kept dropping and the left side di not to then readjust and monitor the fuel level only in the right tank and possibly throw a CEL with a trouble code that indicated that there is a problem with fuel transfer.
I total agree with you. Since the computer already measured the level on both tanks (as seen by using hidden OBC), then all it needs to do whenever it detects that the R tank is lower than the L tank (abnormal condition) it should display CEL and the fuel gauge should now show the R tank capacity only instead of the sum of both tanks. This should have saved many motorists.

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Old 06-01-2012, 09:50 PM   #17
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Quote:
Originally Posted by Sapote View Post
The pressure gauge hooked to the engine fuel rail may not tell where is the bad component. Say you have a logged up filter and so low pressure at the gauge; does this mean a bad fuel pump, or empty tank, or clogged filter?

Sapote
Clogged filter would probably not affect static pressure. That's why you might do a volume test.

Here is pressure test:
http://tis.spaghetticoder.org/s/view.pl?1/06/04/54
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Old 06-13-2012, 02:44 PM   #18
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Just an update. I replaced with a new pump from BMAautoparts two weeks ago and everythings is perfect since. After using a hammer and a screwdrive to turn loose and removed the metal locking ring, I have to say that I was still not quite sure how to pry the pump out since the pump module is white plastic and there is also other white plastic part below the pump. I watched the youtube video again carefully this time to make sure where to pry up the pump while pulling it up. It came out easyly. I noticed the pump's flat screen filter at the bottom was perfect clean after over 100k miles. Does this mean the main inline filter should be still in good shape in my case?

with the new pump, I believe the car mpg also noticable increases (from average of 31mpg to 35mpg on FWY). This makes sense since the old low pressure pump was not giving the engine a proper fuel pressure for a optimum combustion. So replace your old pump and save money on gas.


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Old 06-13-2012, 02:49 PM   #19
KSims1868
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Holy crap...do you really get 31-35 mpg? Seriously?
I'm getting 25 mpg on a good day in my 325i.
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Old 06-13-2012, 02:58 PM   #20
Stinger9
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I can get 32 if I'm only on the highway in my 330 manual six speed with OD.
Doubt anything higher than that is accurate if you did the actual calc.

My record is over 500 miles on a tank before I choose to refill. Didn't want to run the pump dry and risk burning it out.
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