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Discussion Starter · #1 ·
A few months ago I started a thread regarding the problems I had with my 91 535i. It wouldn't start in the morning (cooler weather) but it would start and run great in the afternoon once the weather warmed up. In the mornings it would crank but that was it.

So I received a lot of good advice here on what to look for.

But what it turned out to be was the fuel pump. I started another thread a few days ago with pictures of my cracked fuel pump. It was like someone took a can opener to the top of it. So my guess is when it was cooler outside, it caused something in the pump to contract and affected the electrical connections. When it warmed up - it expanded and made the connection. - Just a theory on my part.

While I was replacing my fuel filter, I had someone crank the engine with the filter off and no fuel came out of the fuel line. I tested the electrical connection and saw that I was getting power but the pump was not drawing any current.

But thanks to everyone’s advice on this forum and giving me ideas on what to look for I did discover I had some bad cells in my battery and had to get it replaced.

I replaced the pump last week and so far it has started up every morning.

So I thought I should let everyone know that their help is appreciated and definitely helped in fixing the problem.

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