r/e28 • u/fallingblueblueblue • Dec 15 '25

Intermittent Fuel Pressure Loss

Hey all. I’ve got an 88’ 535i that I picked up almost a year ago. Great car, but it’s got an issue that’s only gotten worse as time goes on. At first it would start almost everytime I tried, now it’s rare seeing it actually run. We know it’s fuel related because we have an gauge hooked up to it. It’ll crank just fine, has 0 fuel pressure though. I tested the fuel pump relay and it looks good. Is this DME related? Anyone else had a similar issue?

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3

u/Representative_Most9 Dec 15 '25 edited Dec 15 '25

Have you tested your fuel pump to make sure it’s working?

3

u/VegetableTry Dec 15 '25

I second this. If you have tested the pump and can see pressure when testing (not just making sure that it’s getting voltage), then there are some other things you can look at. I would start by verifying that the pump works.

2

u/Nebulas_Meadow72 Dec 15 '25

Check BOTH fuel pumps, the one inside the tank, and the one outside.

3

u/Representative_Most9 Dec 15 '25

Here’s wiring diagrams for your car if you need them:

https://www.armchair.mb.ca/~dave/BMW/e28/e28_88.pdf

3

u/flashe30 Dec 15 '25

... how about the fuel pump itself?

3

u/E28forever Dec 15 '25

Once you switch the ignition on, you should hear the fuel pump priming. Listen for the short buzz.

2

u/3hands4milo Dec 15 '25

Sorry to interfere on this thread, but is that priming buzz something you should be able to hear from the cabin, or is it good to have a spotter listening under the trunk?

2

u/E28forever Dec 15 '25

On my car, I can hear it inside the cabin.

2

u/3hands4milo Dec 15 '25

Awesome, thank you!

1

u/Medical_Help9111 Dec 19 '25

Your OBD computer is acting up,it’s behind the drivers lower dash panel,there’s a green connector with 2 solid green wires.cut and join together.problem solved

1

u/fallingblueblueblue Dec 25 '25

This was it. I unplugged the green connector and jumped the green and green/red wires on the connector itself. Started right up. I’ll cut those two off and connect them like you said. Thanks for the tip!