Review of New OEM Low Pressure Fuel Pump

E28 technical advice asked and given! Troubleshooting, modifications and more.
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matreyia
Posts: 46
Joined: Dec 22, 2021 1:05 AM
Location: Houston

Review of New OEM Low Pressure Fuel Pump

Post by matreyia »

Hello Everyone,
I just installed a brand new LPFP (in tank unit) along with a new fuel level sending unit and wanted to report my observations after test driving. Both units were OE BMW brand.

Reason for replacement:
I noticed the external HPFP was too noisy so I replaced it, but the new unit was just as loud.
I also noticed that the car took long to start and throttle response was very delayed as well as acceleration itself.
I knew that the car had the original LPFP and sending unit - 35 yrs. old now.
So I suspected that the car needed the refresh. I was correct in my suspicions. The old pump was rusted, corroded, filter was totally clogged and the metal electrical contacts were totally dissolved such that there was a huge gap .5 inches between the contact and the connection bridge.
Also, when I went to get it inspected I saw the fuel level go erratically up and down then totally go empty as if it died. No amount of tapping on the instrument panel would even vibrate the needle.

Results after replacement:
Car starts in less than a second.
Acceleration and throttle response is instantaneous.
Upon releasing the pedal in park position, the RPM do not go way down then delay coming back to normal 600-700 RPM, no more stuttering when releasing the pedal in park position.
There is no detectible sound from the HPFP area any more. Only a tiny hum in the trunk from the LPFP in tank unit.
And, of course, fuel levels are now correctly shown in the fuel level needle area.

If your e28 shows similar symptoms, I recommend you check your LPFP first to see the state of the unit. And if the fuel level is at empty and won't budge no matter what you try...I recommend you also replace that device. Even if it were still working, I feel it is good as preventive maintenance in the fuel supply area.

The sending unit and the LPFP will be VERY expensive for what they are due to the scarcity of both items - don't think they are being made anymore and stock is running very low. Expect to shell out over $400 for the LPFP and $250-300 for the sending unit itself.

Do I recommend this work? Yes absolutely. It makes the car feel like it just came out of the dealership even at 127hp at the crank. Puts a smile on my face every time I drive the car.
Blue Shadow
Posts: 9748
Joined: Feb 12, 2006 12:00 PM
Location: SE PA

Re: Review of New OEM Low Pressure Fuel Pump

Post by Blue Shadow »

Nice report. Apparently a late 528e automatic.

The in tank pump can be diagnosed by an accelerating right turn onto an on ramp. Getting on it and the car stumbles when there is less than a quarter tank of fuel in the car. The right turn moves the limited amount of fuel away from the pick up and with a dead in tank pump the main pump doesn't have enough net positive suction head to pull in enough fuel for the demand and you get stumbles. Back off and the main pump can keep up but time to do something about the in tank pump.
Shawn D.
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Beamter
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Joined: Feb 12, 2006 12:00 PM
Location: Alpharetta, GA
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Re: Review of New OEM Low Pressure Fuel Pump

Post by Shawn D. »

Thanks for writing this up!
BDKawey
Posts: 1234
Joined: Sep 15, 2011 11:05 PM
Location: New Albany, Ohio.

Re: Review of New OEM Low Pressure Fuel Pump

Post by BDKawey »

Blue Shadow wrote: Jun 24, 2022 9:22 PM Nice report. Apparently a late 528e automatic.

The in tank pump can be diagnosed by an accelerating right turn onto an on ramp. Getting on it and the car stumbles when there is less than a quarter tank of fuel in the car. The right turn moves the limited amount of fuel away from the pick up and with a dead in tank pump the main pump doesn't have enough net positive suction head to pull in enough fuel for the demand and you get stumbles. Back off and the main pump can keep up but time to do something about the in tank pump.
this may be my hiccup cause. will have to give it an intentional try next time I'm low.
RetiredDoc
Posts: 1266
Joined: Feb 12, 2006 12:00 PM
Location: Aiken SC

Re: Review of New OEM Low Pressure Fuel Pump

Post by RetiredDoc »

You got me worried about the scarcity of the in tank fuel pump, so I decided to look for one to buy and save, just in case I need one in the future. You were correct about them being pricey, but I had no problem finding one.

Having just been through looking for a replacement driver’s side power window motor, I expected the fuel pumps to be even harder to find than this almost non-existent motor. Fortunately I was wrong, as almost every web site I went to at least claimed the new fuel pumps were in stock. So I am now the owner of a new, spare, in tank OEM fuel pump.
Blue Shadow
Posts: 9748
Joined: Feb 12, 2006 12:00 PM
Location: SE PA

Re: Review of New OEM Low Pressure Fuel Pump

Post by Blue Shadow »

Anyone tried the Herko intank pump for 75 bucks? You can buy a small pile of them for the going price on the BMW part, 466 (discounted a bit) as of this writing.
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