Fuel Pump?

[Ranger_Vet68]

I have a 2003 BMW Z4, and I think I have a fuel pump issue. When I start the car in the morning (0430-0630), the vehicle will not turn over, and when it does catch, it sputters and dies. But, if I go out and start the car between 0900-1900, the car starts up with no issues and no sputtering. Also, I have begun to hear behind the passenger side seat that some electric motor or something starts to run when I start the ignition or leave the key in that position. Thoughts/Suggestions?

Thank you.

[pungo]

Originally Posted by Ranger_Vet68

hen I start the car in the morning (0430-0630), the vehicle will not turn over, and when it does catch, it sputters and dies.

First, I think you're using the wrong terminology to describe the problem.
will not turn over = the starter is NOT spinning the engine
catch (a.k.a. fires) = the spark explodes the fuel (meaning you have both spark and fuel)

Use INPA to test the fuel pressure both when the engine fires/sputters/dies as well as when it starts normally, compare the values and report the results here.

[JAS1169]

Hey

1st, I'm guessing the starter is working and the engine generally won't start but, if it does start, it will then sputter out and die. Right?

Although I've never been in LA I'm guessing it's cooler in the early morning and then hotter for the balance of the day until nightfall. If so, then your issues really tie's into the car not starting when there are cooler temp's. In that, the car starts the balance of the day when it's warm?

Your going to have to trust me here, the time of day, in it's self, has nothing to do with a car starting. It would have to relate to the temp's when the car would start, as well as, not start.

Generally, no starts caused by colder temp's swings are caused by electrical contact issues. You have a car that's pushing 20 years old (as do I) and heavily tarnish electrical contacts should not be a surprise. You might want to try and clean, the contact points for the plugs, the coils(both sides) and the harness contacts with Electrical Contact Cleaner (about $5.00) a can. When doing this look for cracks and lose connections.

I totally agree with the recommendation that you use a code reader.

Ok, let's say you cleaned the contacts and your code reader comes up blank and you still have the issue. Then check your ignition switch. A failing ignition switch can cause your exact issue and because it's the correct on/off location for the car it will not cause a code.

[Ranger_Vet68]

The code reader was clean. No issues. When the car starts in the afternoon, it starts right up with no sputtering. It's only in the early morning when it does startup. After trying for 5-10 mins, it would start and then sputter. Also, I have found that when driving, the car cuts out and then back on again as if it was chocked off of its fuel supply. One more thing. What would be that electric motor sound behind the passenger seat? Also, to answer pungo, I have had it on the reader when the car starts fine, but there's no one to start that process around 0300-0430 to check it when I have the issue.

[Steeler]

Originally Posted by Ranger_Vet68

The code reader was clean. No issues. When the car does start in the afternoon, it starts right up with no sputtering at all. It's only in the early morning when it does startup. After trying for 5-10 mins, it would start and then sputter. Also, I have found that when driving, the car cuts out and then back on again as if it was chocked off of its fuel supply. One more thing. What would be that electric motor sound behind the passenger seat?

Sorry can't help with the difficult start and sputtering in the AM(0430-0630), but the noise behind you is the pump running when you turn the key to position 2.

Does the pump noise go away once started in the colder air(0430-0630)and does the noise from the pump occur in the afternoon(0900-1900) when the air is warmer?

[pungo]

Originally Posted by Ranger_Vet68

Also, to answer pungo, I have had it on the reader when the car starts fine, but there's no one to start that process around 0300-0430 to check it when I have the issue.

Checking for errors with a code reader and using INPA to measure actual fuel pressure are not the same thing

[JAS1169]

Given your update of info, I'd center on the Ignition switch. Please read: https://www.yourmechanic.com/article...9362aeea79e132

After reading this google, BMW problems caused by failing ignition switch.

[pokeybritches]

I would also look at your MAF readings on startup. You should see around 20 kg/hr, +/-5.

[GuidoK]

I can't imagine that the difference in functioning for that fuel pump is so far apart with the two temperatures.

My guess is either a problem with your maf (that also houses the IAT), or maybe some vacuum leak that's opening when the rubber is more stiff/brittle (cold).

The weird thing is no codes, especially if the car cuts out....