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Discussion Starter #1
Hello. I've spent a few days reading through the forums before posting. I just want to get some ideas if I'm diagnosing this problem correctly.
My 2000 M5 with 170k on it was sitting for about 6 months at 1/4+ tank. I take it out during quarantine for a drive and all is fine. A few days later I take it out for a drive to work (im an essential worker) and it runs fine, but when I leave work, 1/4 tank, the car starts, then dies after 2 seconds. Then everytime I start it, it starts for a second, then dies.
I unplugged both MAF's but the still does not start.
I'm thinking that PDK / black fuel relay in the right side of trunk. I use a paper clip to jump the 12V to fuel pump (bypassing the relay). I dont hear the pump at all and car still wont start.
With the key on 2, and relay in, the fuel power line is about 4v.
I checked some fuses. DME fuse under passenger cabin filter. All 5 fuses are in tact.
I checked the 25A fuse near the relay. It is good.
I also called AAA. they brought me 2 gallons of fuel. ( I thought the gas was stuck on one side of the tank) still no luck. Car now wont start at all now, when before it starts for a second before dying.
I go to the secret menu and I see TNK: 6.8 / 8.5 / 15.3 L.
Fuel filter and pump service history is unknown, I can assume they have not been done in the past 3-5 years.
I have the fuel filter TBInstalled. I dont have the fuel pump yet.

My conclusion is the fuel pump is toast. May I have some feedback on my conclusion before I purchase from FCP. ($223) They have the Delphi brand w / lifetime warranty. Is there anything else I can test?

Thank you!
 

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I had a similar problem. I put about two gallons and still no luck. Read online did more research, the next added about two more gallons and it started perfectly fine. Start there first

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Do you have a code reader? That is always the best thing to do first, but I agree it sounds like your fuel pump got a virus and died. Extremely common scenario.
 

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Discussion Starter #4
Do you have a code reader? That is always the best thing to do first, but I agree it sounds like your fuel pump got a virus and died. Extremely common scenario.
Yes the reader gave me MAF codes, (because I unplugged) and it gave me

code #1 DME: Driver / Fuel-pump relay

Any idea what that means?
 

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Discussion Starter #5
I had a similar problem. I put about two gallons and still no luck. Read online did more research, the next added about two more gallons and it started perfectly fine. Start there first

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Couldnt hurt. I'll try and add another 2 gallons.
 

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Yes the reader gave me MAF codes, (because I unplugged) and it gave me

code #1 DME: Driver / Fuel-pump relay

Any idea what that means?
I had the same fuel pump relay code along with many other codes. When I read your description my car had the exact symptoms. Give it a solid 4-5 gallons. I am confident that's your problem. Was your car sitting for a while?

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Discussion Starter #7
thank you! yes sitting for 6 months or so. so probably bad fuel too. it made it to work, (20 miles) then I couldn't start it. I will add more fuel and report back.
 

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Discussion Starter #8
Just a thought. If adding fuel allows me to drive it home, I should probably still change out the fuel pump / filter right?
 

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yes. If you don't hear the pump after jumping the relay, the pump is dead. You can get a Pierburg (OEM) from FCP for ~200, and iirc FCPEuro sells a Delphi unit with sender for not too much more (sub 300, iirc)
 

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Wouldn't hurt to change the relay either, not sure what the new ones run, but @Clemster can probably hook you up with a good deal on a used one...
 

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Discussion Starter #11
yes. If you don't hear the pump after jumping the relay, the pump is dead. You can get a Pierburg (OEM) from FCP for ~200, and iirc FCPEuro sells a Delphi unit with sender for not too much more (sub 300, iirc)
Is the fuel pump pretty loud with the seat covering it? I cant remember. I have a 740i would the sound be similar?
 

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You'd hear it if it was running, but if you pull the rear bench out you'd be able to tell w/o question
 

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Discussion Starter #13
OK. should I even bother adding more fuel? would the pump know that there is no fuel and NOT power on? and about the relay. It's about 130. I can get that after if fuel pump doesnt fix it.
 

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Not worth adding fuel. And honestly, just pick up a used lower mileage relay from Clemster, it's not worth shelling out for new here...
 

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Discussion Starter #15
Not worth adding fuel. And honestly, just pick up a used lower mileage relay from Clemster, it's not worth shelling out for new here...
thank you and everyone else for your input! Much appreciated. I'll order the pump.
 

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If you don't hear the fuel pump it could be several issues. But you can test the whole system with a voltmeter at the fuel pump connector. If you get 12V then you know it's the pump and not the relay or fuses.
The error code wording is confusing.
 

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Discussion Starter #17
I've ordered the fuel pump and relay plus clams
I've been reading that the fuel pump is one of those things that will eventually fail. at 170K and little history, I have to assume its either original or replaced a while ago.
I may check fuel pressure, but im almost certain I wont have pressure because I cant even hear the pump.
 

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Discussion Starter #18
I already have a fuel filter at home to replace. Is the fuel regulator something I should replace too? or only if needed?
 

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Shouldn't, thery're pretty reliable. If you really wanted to, you could hook up a gauge to the FPR (it's a Schrader valve) and see what it is
 

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Discussion Starter #20
Did the fuel pump, relay, regulator, and filter yesterday. Car fired right up. I ran 12 v to the Old fuel pump and nothing happened. The pump was toast. Fuel filter was bad. The dirty side had black fuel coming out.
by the way, I had the seat off when I fired up the car. The pump is very quiet. It’s a very faint buzz. Def not the same in other cars. I may tear open the old fuel pump to see where it failed. Prob the brushes if I were to guess.
Thanks everyone for the help.
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