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Discussion Starter #1
Hello folks,


To start this off I have searched through older fuel pump threads but alas they were not having the same issue as I am. I have replaced three fuel pumps on my M5 this year, with almost zero run time on each of them. A short and frustrating story is to follow, on the steps I have taken to attempt to fix my 00' M5's fueling woes.

So I bought this M5 five years ago, daily drove it for two faultless years, then came to realise that it needed a good amount of work as I learned more and more about these cars. I am currently going through the entire car, mechanically restoring it to it's former glory.

Earlier this year the fuel pump died, it was replaced in 2010, and I replaced it with a genuine BMW pump and a hengst fuel filter. It ran fantastic, but in the process I damaged the blue fuel feed line connection, with seemingly no leak and or other issue. Two weeks later, I went to start the car and low and behold the fuel pump was dead...again. I order a new fuel line, replaced the pump (this time with an FCP Delphi pump) and the fuel feed line. However upon moving the car and letting it sit for two weeks.....the fuel pump was dead again (very glad I have an FCP euro at this point).

At this point I began to sniff around at other areas of concern, (fast forward to this month) ended up replacing the fuel pressure regulator, fuel filter, FPR vacuum line and last but not least the fuel pump relay. It ran fantastic on the test drive, no fuel **** off, no misfires, nothing out of the ordinary at all. It sat for a week as I played around with other bits and....the fuel pump was dead again (this happened today.)

So to recap:
  • I have checked power to the pump while cranking and while running on the new at the time pump, all good.
  • I have replaced the fuel filter x2, the fuel pump relay, the fuel feed line (blue), 3x fuel pumps ( 2x Delphi, one genuine BMW) and the evap purge valve solenoid.
  • the car runs excellent when the new fuel pump has been put in, every test drive has been thorough and successful, however when left to sit the pump seems to die.
At this point I am completely baffled....and not sure where to look next. Any help would be greatly appreciated. Sorry for the jumbled story but..it's alot to recall.

Thanks in advance!
 

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The car will crank over at this point, right? Just isn't firing?

Do you have power at both the relay and electrical connector to the pump currently. There's no way that pumps are failing that fast on their own. You can test the fuel pressure at the filter, there's a Schrader valve where you can connect a gauge.

If you have INPA/DIS/PASoft, I'd also scan all the body modules and see if anything stands out.
 

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I would concur, there is no way you lost 3 pumps in a row something else is going on. What tests did you do to know the pump had failed? Some of your tests don't make sense, like the pump having voltage while cranking, if your car is a Canadian car it might run through cranking but only under very rare situations. Are you sure you were testing the correct leads and what sort of voltages were you seeing. Have you looked at the codes? Are you getting the 01 code?
Seems electrical to me but your test would prove that not correct.
 

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Discussion Starter #4
The car will crank over at this point, right? Just isn't firing?

Do you have power at both the relay and electrical connector to the pump currently. There's no way that pumps are failing that fast on their own. You can test the fuel pressure at the filter, there's a Schrader valve where you can connect a gauge.

If you have INPA/DIS/PASoft, I'd also scan all the body modules and see if anything stands out.

Yes the car cranks just fine, no firing though. I have power at the relay, and before replacing the old one I jumped it and there was no changed. I replaced the relay as a extra "just incase" measure.

I have not tested the fuel pressure yet, however wouldn't the car run rough or stutter at WOT? I do have a scan tool with BMW software (foxwell) and the code I have gotten when the fuel pump has died is 01 DME Driver/Fuel Pump Relay which in my research points to many things.
 

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Just throwing out ideas with the previous comment

Sounds like an issue between the relay and pump perhaps? I don't recall which driver(s) on the DME control that aspect, but you'd be able to find it in WDS if you hunted through it. It's... a long slog at best though if you aren't into schematics...
 

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Discussion Starter #6
I would concur, there is no way you lost 3 pumps in a row something else is going on. What tests did you do to know the pump had failed? Some of your tests don't make sense, like the pump having voltage while cranking, if your car is a Canadian car it might run through cranking but only under very rare situations. Are you sure you were testing the correct leads and what sort of voltages were you seeing. Have you looked at the codes? Are you getting the 01 code?
Seems electrical to me but your test would prove that not correct.

There is most certainly something fishy going on lol. So I tested power at the plug I am positive I tested the correct leads and got 10.5V. I also had a second person turn the key to ignition "on" and listen for the relay click. I jumped the old relay before replacing and it didn't make a difference.

I am getting a 01 DME Driver/Fuel Pump Relay code on my foxwell. With basically an entirely new fuel prep system I would have thought the problem was electrical but...nothing seems to point to that. Plus this problem just started when I started replacing these pump, it never had an issue before.
 

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Discussion Starter #7
Just throwing out ideas with the previous comment

Sounds like an issue between the relay and pump perhaps? I don't recall which driver(s) on the DME control that aspect, but you'd be able to find it in WDS if you hunted through it. It's... a long slog at best though if you aren't into schematics...

Well any idea is a good idea at this point. Could bad gas be a suspect? The gas in the tank isn't exactly fresh...is it possible moisture could be in the mix? Or maybe an unusual amount of ethanol?
 

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Unlikely, I'm still going with electrical here... I've fired a M5 with ~2 year old gas and it was 'fine' - car had other issues, but it started and ran
 

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I am getting a 01 DME Driver/Fuel Pump Relay code on my foxwell. With basically an entirely new fuel prep system I would have thought the problem was electrical but...nothing seems to point to that.
On the contrary that absolutely points to an electrical issue. I would bet dollars to donuts it is a rusty ground. Not a great bet since I just payed over a dollar for a doughnut the other day.
That code is an electrical continuity check from the power wire output at the relay through the pump to ground, so if you get the code you know there is a break in continuity. Take a volt meter set it to ohms pull the relay and from pin 2 at the relay place the red probe and ground the black probe with the ohms set to the smallest setting, what does it read?
I will give your the relay wiring diagram. Red wire with a white stripe runs to pin 2.
941038
Your relay is big and black, just checking never know what could happen. I will give you the wire colors for future use because in the WDS they are German and can throw people off.
941039
 

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Discussion Starter #10
On the contrary that absolutely points to an electrical issue. I would bet dollars to donuts it is a rusty ground. Not a great bet since I just payed over a dollar for a doughnut the other day.
That code is an electrical continuity check from the power wire output at the relay through the pump to ground, so if you get the code you know there is a break in continuity. Take a volt meter set it to ohms pull the relay and from pin 2 at the relay place the red probe and ground the black probe with the ohms set to the smallest setting, what does it read?
I will give your the relay wiring diagram. Red wire with a white stripe runs to pin 2. View attachment 941038 Your relay is big and black, just checking never know what could happen. I will give you the wire colors for future use because in the WDS they are German and can throw people off. View attachment 941039

Thanks alot! I will redo some of my testing tomorrow morning and hopefully return with some results.
 

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Discussion Starter #11
Alright, so I finally got around to re running tests. For the fuel pump relay, 2 pin to ground I got a reading of 1.2ohm with a fluctuation to 1.3ohm...howevee I do not know what that means really as I don't know how much resistance there is supposed to be?

I tested power at the pump plug again and got 8.16V (old relay) with key out of the ignition and 10.27 (new relay). When turned to ignition 2, it spikes to 12.3V which I assume is battery voltage?

Turning wrenches is one thing, wires scare me. Lol
 

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I tested power at the pump plug again and got 8.16V (old relay) with key out of the ignition and 10.27 (new relay). When turned to ignition 2, it spikes to 12.3V which I assume is battery voltage?
That seems strange but I don't have a car close to test. It might be very low amperage and of little consequence. Referring to the key out tests I would have expected it to be 0 volts but sometimes when electronics are involved readings like that are returned. Need more tests but not to solve your issue.
Unplug the pump set the meter to ohms now check the pump itself and any others you have by placing the probes in 1 and 4 at the pump. Then check 4 at the pump plug to 2 at the relay( you will likely need to run a wire to reach) then do pump plug 1 to ground. Next bench test the old pumps by connecting them to 12V and see if they run. Don't test the one in your tank by just connecting 12V at the plug sparks and stuff, but do the tests in this thread.
 

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Discussion Starter #13
I redid the "jump" test for the relay, pump won't run. I cycles the key with both the new and old relay, both of them "clicked".

Resistance at the pump (assuming you meant the male connector on the top of the fuel level sensor, as I only have the pump in the tank) was a similar 1.1-1.2ohm. I also tested the resistance at the pump plug in the 1/4, which I got no ohm reading what so ever.

Going from pump plug 4 to 2 at the relay and then 1 to ground, I got no reading however I must clarify, am I supposed to be running the wire between the two plugs, then reading the resistance off the wire?
 

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The fuel pump "relay" is actually a MOSFET + a capacitor. It takes a bit of time for the cap to discharge, so reading some voltage with the key out is normal.
 

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Discussion Starter #15
The fuel pump "relay" is actually a MOSFET + a capacitor. It takes a bit of time for the cap to discharge, so reading some voltage with the key out is normal.
That makes sense, thank you for the clarification! Although at this point I think it is safe to say the "relay" itself (or the new one at the very least) is not my issue.
 

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Resistance at the pump (assuming you meant the male connector on the top of the fuel level sensor, as I only have the pump in the tank) was a similar 1.1-1.2ohm. I also tested the resistance at the pump plug in the 1/4, which I got no ohm reading what so ever.

Going from pump plug 4 to 2 at the relay and then 1 to ground, I got no reading however I must clarify, am I supposed to be running the wire between the two plugs, then reading the resistance off the wire?
Not sure you did it right so I will be a little more clear. You seem to have tested the pump correctly but there is a slight difference in reading to your first test, this may mean something, but it may not. If you did not zero the tester before the tests that could account for the little difference. Read your meter manual for the way you zero the specific meter. You touch the two leads together and do something but most my meters are a bit different on what that is but when you do it the meter will read 0 ohms. A lot of digitals are automatic and all you have to do is set the dial then touch the probes together and it will zero itself, but read what it says when you touch them together and make a note. A meter must be zeroed each time it is turned on.
Don't worry too much about that yet. I suspect we will see some resistance in one of the wire tests and that will point you in the right direction.
Unplug the relay and unplug the pump. Now you are going to test the wires, so your probes need to be on the wire side of the plugs.
So for the first test 4 to 2 you will be testing at the plug where the red white wire is, both ends, not the plug that is part of the pump, but the side that plugs into that. On ohms the volt meter applies power so it will run out of one probe down the wire to the other probe and the meter will tell if there is any resistance which might indicate a part break or corrosion. I know they are not completely broken, because your first test you got a reading of 1.3 which means the power left the meter went down the wire through the pump, out the ground wire to the body and then flowed through the body back to your meter. Things not completely broken are harder to figure out.
The second test is to test the wire that takes the power from the pump to the body, so one probe goes to the plug with the brown wire that runs to the body, not the pump, the part that plugs into that.
In the first test from 4 to 2 you may need to add a wire. This wire is only required if your probe wires are not long enough to reach from 4 to 2. So if they will not reach the wire you add is basically an extension of one of the probes.
It is a long way from the trunk to the back seat. So put something stuck into 2, a paper clip, a small screw driver anything conductive the fits tight wrap a wire to it and take that wire to the back seat area so you can touch it with your probe.
 

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Discussion Starter #17
Not sure you did it right so I will be a little more clear. You seem to have tested the pump correctly but there is a slight difference in reading to your first test, this may mean something, but it may not. If you did not zero the tester before the tests that could account for the little difference. Read your meter manual for the way you zero the specific meter. You touch the two leads together and do something but most my meters are a bit different on what that is but when you do it the meter will read 0 ohms. A lot of digitals are automatic and all you have to do is set the dial then touch the probes together and it will zero itself, but read what it says when you touch them together and make a note. A meter must be zeroed each time it is turned on.
Don't worry too much about that yet. I suspect we will see some resistance in one of the wire tests and that will point you in the right direction.
Unplug the relay and unplug the pump. Now you are going to test the wires, so your probes need to be on the wire side of the plugs.
So for the first test 4 to 2 you will be testing at the plug where the red white wire is, both ends, not the plug that is part of the pump, but the side that plugs into that. On ohms the volt meter applies power so it will run out of one probe down the wire to the other probe and the meter will tell if there is any resistance which might indicate a part break or corrosion. I know they are not completely broken, because your first test you got a reading of 1.3 which means the power left the meter went down the wire through the pump, out the ground wire to the body and then flowed through the body back to your meter. Things not completely broken are harder to figure out.
The second test is to test the wire that takes the power from the pump to the body, so one probe goes to the plug with the brown wire that runs to the body, not the pump, the part that plugs into that.
In the first test from 4 to 2 you may need to add a wire. This wire is only required if your probe wires are not long enough to reach from 4 to 2. So if they will not reach the wire you add is basically an extension of one of the probes.
It is a long way from the trunk to the back seat. So put something stuck into 2, a paper clip, a small screw driver anything conductive the fits tight wrap a wire to it and take that wire to the back seat area so you can touch it with your probe.
Okay so I did go about the ohm reading on the 2/4 incorrectly, tonight after work I will retest correctly and get back with results.

I do have two things I forgot to mention, my first drive on the last fuel pump (the one before this current failure), I had a dead speedo/tach, abs light and TC light. I chalked those up to a wacky happening but...it now seems more possible that whatever issue I am faced with this fuel pump could also cause some weirdness in other systems.

Also, I have replaced the fuel level sender with a genuine part, but lastnight I popped the lid to the tank before calling it and noticed once of the leads that plugs into the pump in the tank, it's plastic protective case was split. Upon inspection the spade and wire seemed okay, but is it possible that that may be causing this?
 

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Voltage drop testing is much more accurate that ohm testing when looking for a bad electrical connection.
Are you sure you aren't just running out of gas and your fuel gauge/senders are bad? Just happened to me and it's pretty common.
 

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Voltage drop testing is much more accurate that ohm testing when looking for a bad electrical connection.
Are you sure you aren't just running out of gas and your fuel gauge/senders are bad? Just happened to me and it's pretty common.

I am 100%, I have changed the fuel pump 3 times in 4 months now, so I have been in the tank alot....half a tank of fuel is what has been in there. My hands agree with what my eyes see. :LOL:
 

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Now that it is not really late at night I read through the posts again and found some stuff.
The 4 to 1 test is at the plug to the pump but on the side that the pump is on, you are testing the pump. You will get no reading if you test the wire side of the plug. There was no mention of the ground wire test which is the wire side of the plug to ground, this is the most likely spot for the fault so make sure you test it correctly. From 1 at the pump plug on the wire side to ground on the body.
While you are there follow that wire and inspect closely there is a joint in that wire. I don't remember where it is and don't have a copy of WDS to look it up. It is marked in the diagram as X13379. You could be getting a path to ground through it. That joint is the ground from another device so real power will not likely run correctly through that joint which will be why your pump does not run but you have a path to ground with the volt meter.
I need my other computer to look at the WDS and it is a long way away.
If someone else has access to WDS maybe they can look it up and give some screen shots. I would love to know what it goes to.
 
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