What could be causing delayed starts in a 2005 BMW 325i after it sits for an hour?

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What could be causing delayed starts in a 2005 BMW 325i after it sits for an hour?

Hello!
I own a 2005 BMW 325i manual with 120,000 miles. The car starts up perfectly fine when the engine is cold, but if it sits for more than an hour after running, I have to crank it for a while to get it to start. I’ve checked for codes, but none have appeared. I suspect it might be due to a faulty sensor o r a leaky injector.

Aarav asked on 18 Feb 2025 16:01:41 pm

1 Answer

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Muhammad Yasir - on 18 Feb 2025 16:03:22 pm

Hi!
It seems like a faulty fuel pressure regulator could be the issue. If you have a fuel pressure gauge, you can check if the fuel pressure s after the car has been off for a while. Typically, it should only about 5 psi, but be sure to verify the specific specifications for your vehicle. The car starts easily when cold because the ECU runs in open loop mode, which means it pumps extra fuel into the engine until it reaches operating temperature. However, after the car sits for a while at operating temperature, the fuel pressure tends to , and it takes some time for the fuel pump to restore it. This is just a theory, but testing the fuel pressure should help pinpoint the issue.