Cold no start

[stewart in slc]

I have a 528i 3.5 that won't start in the cold. If the outside temperature is below 40 degrees it won't start but above it will. It will turn over and occasionally fire. The exhaust smells of gasoline. Starting when the temperature is above it will run rough and rich until it gets up to temp. I recently cleaned up/replaced the grounds & that didn't help. Any help or ideas would be greatly appreciated

[Peter Florance]

I have a 528i 3.5 that won't start in the cold. If the outside temperature is below 40 degrees it won't start but above it will. It will turn over and occasionally fire. The exhaust smells of gasoline. Starting when the temperature is above it will run rough and rich until it gets up to temp. I recently cleaned up/replaced the grounds & that didn't help. Any help or ideas would be greatly appreciated

check the coolant temp sensor (beige connector) for corrosion.

Also try pulling the fuel pump fuse next time it happens. If it starts easier, it's over-fueling for some reason.

But mostly I'm thinking weak spark. Carry a spare plug so you can check spark easily.

[Mike W.]

I had a FPR one time that seemed to adjust pressure almost inverse with the temp. Shouldn't work that way even in failure mode, but it did. It would starve for gas when it was hot and I got it miserably flooded in Reno one time in a snowstorm.

So, check your fuel pressure, no fun when it's cold, but that's when it has to be. And to get it started when it's cold if you flood it, shut the key off, then pull the plug to the ECU in the glove box. Crank it and it will briefly start, run, then die again. Plug the ECU back in and away you should go. You just burned off the excess gas and warmed it up just a tiny bit so it will start easier.

Oh, perhaps more likely, check your thermo time switch and CSV for an always on situation.