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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 11-26-2012, 07:31 PM
pcrossley pcrossley is offline
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Low Voltage at Fuel pump

I've been having an issue where my '02 525i turns over continuously, but doesn't crank. I checked the fuel pu,p relay and could feel it clicking, so I assumed the fuel pump was bad. I pulled the fuel pump and checked it by putting 12V across it and it ran like a dishwasher. Plugged back in (with the pump out of the tank) it does nothing when I turn the key.

I found where some had suggested to jump out the relay between pins 2 and 6. I gave this a try (even though the relay appeared to be working) and no change. At that point I disconnected the fuel pump and put my meter across the connections and turned the key and got exactly 3.64V at the pump. I get the same reading if I am trying to crank the car or if i just turn the key to the start position (of course I only get voltage for about 3 seconds with the key in start).

I have 12V on the battery (a little low.....this appears to be a separate battery drain problem) but still only get 3.64V at the fuel pump. I not sure where to go from here. Any help would be much appreciated.
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  #2  
Old 11-26-2012, 08:54 PM
edjack edjack is online now
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Measure the voltage between chassis ground and the low side of the pump power. If not zero, you have a ground problem.
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  #3  
Old 11-26-2012, 09:53 PM
pcrossley pcrossley is offline
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Thanks edjack. Sorry for being an idiot, but please describe what you mean by "low side of pump power." is this just checking voltage from the negative pump terminal to the chassis?
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  #4  
Old 11-27-2012, 12:14 AM
edjack edjack is online now
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Yes. This can help to determine if you have a grounding problem.
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  #5  
Old 11-27-2012, 06:42 AM
vavet5308 vavet5308 is offline
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I like edjack's advice there. I've never done it, but it's certainly relevant.
As far as the 3.64 volts, 2 thing jump to mind.

1. Battery voltage is low, but I think you should still get more than 3.64V. You might have a problem with the electrical portion of the ignition switch. Are there any other strange electrical behaviors? If you put down the visor and turn on the vanity light with the radio on, does the radio stay on or cut off? If it cuts off, that's usually an indicator of a bad ignition switch. There might be other quirky things.

2. Is the fuel pump pulse-width modulated? I don't remember when they started doing this and I'm not sure a relay is fast enough to support PWM. Not to insult anyone, but pulse width modulation (PWM) is a "strategy" where an electrical device can run at reduced output by supplying it with the full voltage, but having on and off pulses instead of a constant voltage. Unlike alternating current (AC), it's not sinusoidal and it never goes negative. It's either full 12V or 0V. If it switches fast enough, your meter might "perceive" it to be a lower voltage. PWM is how the interior lights fade on and off. 3.64 volts might not be an unreasonable voltage.
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  #6  
Old 11-27-2012, 08:08 AM
cn90 cn90 is offline
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Check the connector!
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  #7  
Old 11-27-2012, 11:16 AM
pcrossley pcrossley is offline
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As far as strange electrical occurences....yes there have been many of them. The battery voltage is low because something keeps sucking it down. I'm going to let the battery sit disconnected over night to see if it holds voltage on it's own. If so, I have something that is not going to sleep, or a leak to ground as Ed suggested.
As of right now, all power appears normal with the exception that the radio has no power, so I can't check the ignition as you recommend. A few days ago (before it completely stopped cranking) the radio turned off while I was driving. I turned it back on and it seemed fine. When I got home and shut the car off, the radio stayed on with no key in the ignition. I know some models have that feature, but this car has never done that before.
The PWM concept makes sense, but I don't know if I have that or how to find out. I have a feeling I'm going to have to go over every component in the electrical system to see if I have a bad connector or ground issue, but I can't seem to find wiring diagrams for this system anywhere. I have searched BMW planet, spaghetticoder, and looked for a download-able Bentley Volume 2 with no luck. If anyone could help me out in finding the diagrams for the fuel delivery system, I would greatly appreciate it.
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  #8  
Old 11-27-2012, 11:41 AM
cn90 cn90 is offline
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Make sure you study the fuel relay pinout properly.
85-86
30-87
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  #9  
Old 11-27-2012, 12:44 PM
pcrossley pcrossley is offline
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Thanks CN....If I understand correctly, 30 is on the hot side from the ignition and 87 goes to the pump. That's why I wanted to look at the wiring diagram to confirm all the connections.
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  #10  
Old 11-27-2012, 02:09 PM
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bluebee bluebee is offline
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Typing /fuel pump F3 comes up with the following references which may help:
- How does the E39 fuel injection work (1) & what are the most often recommended fuel pump & fuel filter brands (1) (2) & a quick test for fuel pump operation (1) (2) and a DIY for replacing the fuel pump (1) (2) (3) (4) (5) & the location of the K96 fuel pump relay (1) & where is the fuel system pressure test Schrader valve for the I6 (1) & where is the fuel pressure test point for the V8 (1) (2) (3)
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Please read the suggested threads, where the best always add value to those threads, either by pictures or by descriptions, so the next person with the same problem stands on your shoulders.
See also: E39 Bestlinks & How to easily find what you need
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  #11  
Old 11-27-2012, 02:24 PM
pcrossley pcrossley is offline
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Thanks for the information bluebee....I did review most of those posts prior to working, but didn't really find anything to answer my questions. I located the fuel pump relay behind the dash and can feel it click, so it appears to be drawing in. I have checked the fuel pump and it is good. My problem is electrical in nature, so I'm just trying to find a wiring diagram for the fuel pump so I can see where my voltage is starting to drop and see if I've got an ignition problem or just a shorted wire. If it is anywhere on the forum, I apologize, but I can't find it. When I tried bmw-planet, for whatever reason, I couldn't get any diagrams to come up (I am running IE9). I may have a long night of wire chasing ahead of me, but as my old college professor said "Where the voltage dies, the problem lies."
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  #12  
Old 11-27-2012, 02:49 PM
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bluebee bluebee is offline
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Quote:
Originally Posted by pcrossley View Post
I'm just trying to find a wiring diagram for the fuel pump"
I didn't look but this might have what you need:
BMW_E39_E38_Fuel_Supply_System_Description.pdf

Otherwise, a /wiring diagram F3 in the bestlinks nets this:
- Where to find an E39 wiring diagram specific to your model (1) (2) (3) (4) & understanding European wiring diagrams (pdf)
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Please read the suggested threads, where the best always add value to those threads, either by pictures or by descriptions, so the next person with the same problem stands on your shoulders.
See also: E39 Bestlinks & How to easily find what you need
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  #13  
Old 11-28-2012, 06:25 AM
pcrossley pcrossley is offline
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Update from Last Night's Troubleshooting

So after some additional checking last night, I found that the problem lies somewhere between power distribution, and the fuel pump fuse, F22. The low voltage of 3V that I'm seeing at the pump is also present at the hot side of the fuse. If all was working well, this should be a constant 12V supply to the fuse. I have attached a sketch to help illustrate this. Now I have two options:

1.) Try to gain access to this wire to see what the issue is and replace it.....I can't see any way to do this other than pulling the dash, which I'm sure is something I'd like to avoid if possible. I can't locate a wiring diagram that shows the power distribution to this fuse, so I'm not even sure where the other end of the wire terminates.

2.) Run a new hot wire to the fuse and cap/abandon the 3V wire in place. This should totally fix the fuel pump problem and should not change the operation (the DME will still control when the fuel pump relay is engaged).

Option 2 is attractive because it is the easy, quick way to get me going, but whatever is causing the low voltage at the wire could be related to my other electrical gremlins. Any opinions on what is best? Is there any safety reason I should not run a new hot wire to the fuel pump fuse? Thanks in advance
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  #14  
Old 11-28-2012, 07:57 AM
pcrossley pcrossley is offline
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FOUND THE WIRING DIAGRAMS!!! I was finally able to find a browser that could get the WDS to run without issue (believe it or not, it was safari on my ipad). Now I can pretty easily see where the wires go and should be able to find the issue. My only question is some of the notations on the wiring diagram. I ALREADY READ THE DOCUMENT ON HOW TO UNDERSTAND EUROPEAN WIRING DIAGRAMS, so please don't send me a link to that again. It does not answer my question. All of the wires have three notations on them, two of which I don't understand:

1.) The first notation is something like "31U<5", or "30<22". Is this some notation for the wire gauge? I can't find anything on this online.
2.) The second notation on each line is a number like 2.5 or 4.0. I would guess this is amp rating.
3.) The third line is the DIN code for the wire color. No problems with any of these.

If anyone can clarify items 1 and 2 for me, I would appreciate it.
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  #15  
Old 11-28-2012, 08:18 AM
JimLev JimLev is offline
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Quote:
Originally Posted by pcrossley View Post
1.) The first notation is something like "31U<5", or "30<22". Is this some notation for the wire gauge? I can't find anything on this online.
2.) The second notation on each line is a number like 2.5 or 4.0. I would guess this is amp rating.
3.) The third line is the DIN code for the wire color. No problems with any of these.

If anyone can clarify items 1 and 2 for me, I would appreciate it.
I'm not looking at a drawing so I don't know what #1 is, doubt you need it.
#2 is probably the wire gauge.

The pump fuse hot side is busses together with a copper strip that typically feeds more than one fuse.
If you pull the fuse rack above the glove box down (easy to do) you can pretty easily see what other fuses are bussed together. You probably just have a bad connection on the hot side of the connector that the fuse plugs into.
Yes, the quick fix would be add a new wire, this would not cause any problems as it would be in parallel with the bad wire connection.
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  #16  
Old 11-28-2012, 08:20 AM
cn90 cn90 is offline
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The design of the fuel system is as follows, when key is in position II:

1. #86 is 12V. When the DME shorts #85, it completes the primary circuit, closing the relay.

2. Now current flows from #30 ---> #87 in the secondary circuit.

-------
To test the system:

1. Remove the relay (if you can swap the relay and the problem is solved, then you know the relay is bad).

2. Key out of ignition.
Switch your DMM to Ohmmeter and black probe to good ground, red probe to pin #87.
It should read about 1 Ohms, which is the resistance of most fuel pumps out there.

2. Now with key in position II and DMM set to Voltmeter:
#86 should have 12V
#85 should have 2-3V from DME (I am going from memory here)

#30 should have 12V
#87 should have 0V

3. Make a jumper wire and jump directly from #30 ---> #87, the fuel pump should run.
If not, the problem is in either the wiring/connector or the fuel pump itself.


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  #17  
Old 11-28-2012, 11:55 AM
pcrossley pcrossley is offline
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Thanks CN. I had already done the troubleshooting that you recommend...that's how I found out the relay is not being supplied with sufficient voltage. There should be a constant 12V to pin30 as your illustration shows. At this point, I have a constant 3V instead. The wiring diagrams I found on WDS show different fuse numbers for my model (it's a 2002), so fuse F22 is actually feeding the relay, which is fed by an 80 amp fuse (F110) that is in a panel in the right footwell. I'm going to go back to this fuse panel and check for loose connectors. If the voltage to the inlet of this fuse panel is still low, then the problem lies upstream in the cable shoe output fuse (F100), which is in the right hand side of the trunk near the battery. Either I have a loose connector at one of these panels, a bad wire, or a bad wiring harness. I'm going to check it out tonight and I'll post results.
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  #18  
Old 11-28-2012, 12:26 PM
cn90 cn90 is offline
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Did your car ever get flooded?
Or sunroof leak that caused water to pool under passenger seat?

In any case, info on Fuses 107-114 are in the thread below. All you need are Torx #50 and piece of wood to prop the seat up while you work on the fuses.


DIY: Troubleshooting S.A.S. and How to Replace the Famous Fuse # 107!
http://www.bimmerfest.com/forums/sho...d.php?t=459397



------------
Photo of Fuses 107-114:


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  #19  
Old 11-28-2012, 01:37 PM
pcrossley pcrossley is offline
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Funny you mention that....I had a bad vapor barrier on the rear driver's side door that leaked a good amount of water into the back seat. I thought it was only in the back, but it's entirely possible that water got to this fuse panel. That will be my first check this evening! Thanks for the help.
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