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Fuel pressure regulator not sending fuel back

Tiny
KMOGOROSI
  • MEMBER
  • 2007 BMW 323
  • 2.5L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 127,000 MILES
My car shuts off when I start it, I realized when I opened the fuel tank to check there was no fuel-on-fuel pump side and the fuel is full on the fuel pressure regulator side, and it doesn't start unless I put some more fuel. And it will shut off as soon as the fuel is finished on the fuel pump side. What could be the problem? I have tried to replace the fuel pressure regulator, the same problem persists.
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Friday, February 4th, 2022 AT 11:53 AM

8 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,117 POSTS
Hi,

When you say no fuel on the fuel pump side, you are referring to the return line, correct? Also, how are you adding fuel to the fuel pump side?

As far as the regulator is concerned, is anything preventing it from getting fuel? I ask because if you are getting fuel on the return side, where is it coming from if there is nothing on the supply side.

I attached a pic below of the fuel pump sending unit. It shows the return lines and the supply line. Which ones have fuel, and which don't? Also, let me know if that is what you are seeing. That is the US version. I just need to be sure we are on the same vehicle. LOL They change things based on destination.

I will watch for your reply.

Take care,

joe
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Friday, February 4th, 2022 AT 9:09 PM
Tiny
KMOGOROSI
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Hello Joe, thanks for the response.
Yes, there is no fuel on the side where the fuel pump sits, and there is lots of fuel on the side where the sending unit sits. When I put in some petrol it will start for a while and it will shut off, and when I open the tank I find all the fuel has been transferred to when the side where the sending unit sits. Yes, the picture you have shown is the right one, it is similar to the one I am talking about.

Form the little knowledge I have, I know the fuel pump pumps the fuel to the sending unit via fuel line (2) as you have shown and then to the injectors, but when it is supposed to return the excess fuel back to the other side it doesn’t do that, I don't know what causes that.
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Saturday, February 5th, 2022 AT 12:40 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,117 POSTS
Hi,

Okay, it sounds like an issue with the high-pressure fuel pump. If you remove the engine cover, locate the HPFP. See pic below. That is what you are looking for.

Is that where fuel makes it to and then stops?

Let me know.

Joe
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Saturday, February 5th, 2022 AT 4:34 PM
Tiny
KMOGOROSI
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  • 5 POSTS
Hi Joe,

That looks like a different engine than this one (e90 323), I can’t see where it’s located. I read someone say it’s under the manifold. But is it safe to drive it for a few kilometers to the garage with malfunctioning HPFP.
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Sunday, February 6th, 2022 AT 7:47 AM
Tiny
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  • 5 POSTS
Hello Joe,

As a follow up, do 323 e90 has hpfp? Because am reading somewhere that only 335i has it.
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Sunday, February 6th, 2022 AT 10:01 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,117 POSTS
Hi,

As far as I'm seeing, it should have a high-pressure fuel pump. By chance, are you located in Canada? I ask because the 323 isn't offered in the US, so I am much more familiar with the 335. If you look below, you'll see why I assumed it has one.

Let me know.

Joe
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Sunday, February 6th, 2022 AT 8:09 PM
Tiny
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Hi Joe,

No, I am in Botswana, Africa, but the car comes from Singapore.
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Monday, February 7th, 2022 AT 1:32 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,117 POSTS
Hi,

That is where the issue is likely coming into play. The manuals I have indicate this model is for Canada. It's likely because I am close to that area.

I apologize, but the manuals I have may not be the same as what you have.
.
Do me a favor. Locate the fuel supply line to the fuel injectors and follow it as far as you can in the engine compartment. If the vehicle does have an HPFP, it will be mounted on the engine. It will be a mechanically operated pump. It will have electric connectors to it, but the pump itself is actuated off cam lobes.

Let me know. Also, if you don't find one, take as many pics as you can and upload them for me. Hopefully, I'll be able to help you determine the issue and what to check.

Take care,

Joe
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Monday, February 7th, 2022 AT 6:18 PM

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