Long cranking when warm

[captain slowly]

Hi all,

I have a 2011 135i N55 DCT, if that matters. 7400 miles on it. Not a typo. Car was ordered by me and my father in law, and it spent most of its time in the garage being driven every couple of weeks, or, 1000 miles per year, roughly. Anyway, the car became officially mine about 6 months ago, and I've managed a grand total of 1400 miles. The car has had the oil changed annually at bmw, all recalls and such done, whatever maintenance came up on the display that was due on time, you name it, it was done at bmw. I just had the battery replaced at bmw as well. So to make a long story shorter, the car fires right up most of the time. Thats good, but, if you drive the car for lets say 40 min, turn it off, then come back and try to start it, say 15 min later, it will crank for 6-7 seconds and then start. Drives fine. No CEL. If you shut off and immediately crank again, it starts right up... So I'm at a loss. The car is stock with the exception of bmw power pack that was installed back in 2011. Anyone experience this before?

Thanks again,
Danny

[desertman123]

I've had similar before, nothing like 6-7s but definitely long cranks on hot start. I wouldn't worry about it if it runs fine. Maybe cleaning vanos solenoids, or checking spark plugs is worth a shot.

[captain slowly]

Originally Posted by desertman123

I've had similar before, nothing like 6-7s but definitely long cranks on hot start. I wouldn't worry about it if it runs fine. Maybe cleaning vanos solenoids, or checking spark plugs is worth a shot.

Interesting. I thought about the plugs, but again, only 7k on the car. How f'd up could they be? As for the vanos solenoids, how does one go about testing/cleaning them?

[desertman123]

Originally Posted by captain slowly

Interesting. I thought about the plugs, but again, only 7k on the car. How f'd up could they be? As for the vanos solenoids, how does one go about testing/cleaning them?

I mean, plugs shouldn't deteriorate, but I do know it's the first thing people replace when a cars been sitting for a while. They're cheap enough anyway. I would do the vanos solenoids first since it's free.

And the solenoids are super easy to clean

http://www.pelicanparts.com/BMW/tech..._Replacing.htm

I don't know about N55, but N52 you can remove them without removing anything else.

To clean them, just spray them with carb clean, inside and out, then spray with compressed air and let dry. Then just reinstall them.

[captain slowly]

that does look pretty simple. Guess I should see if they are in the same place and as accessible in the N55. I would imagine at some point it should manifest itself a bit more regularly, or at least throw a check engine light, no?

[desertman123]

Originally Posted by captain slowly

that does look pretty simple. Guess I should see if they are in the same place and as accessible in the N55. I would imagine at some point it should manifest itself a bit more regularly, or at least throw a check engine light, no?

Yeah you're right, dirty solenoids are usually more consistent and do throw codes. I don't know if cleaning will help, but it's cheap and easy so it's a starting point.

When it wasn't really been used how long did the gas sit in the tank? I've seen ethanol gum up fuel systems (especially carbs) like no other. Maybe it just needs some fuel system cleaner and an Italian tune-up

[captain slowly]

yea, who knows. Its just an annoyance really. If there is a problem, it will eventually throw a code and I'll deal with it. Thanks for your help!

[mr.fabulous]

Does your LPFP prime the system after the car has been sitting (you should hear a whir from the back of the car when you open a door)

[captain slowly]

it does. I hear it every morning in the garage

[desertman123]

Originally Posted by captain slowly

it does. I hear it every morning in the garage

I put my car in the same scenario as you (unintentionally) and it triggered a rough start. Drove about 20-40min, let the car sit for like 10-20 then started it again and it started slowly and kept dipping rpm, had to give it a rev to level out but once it did nothing weird happened.

Not exactly the same symptoms, but those conditions did make a rough start.

[captain slowly]

Originally Posted by desertman123

I put my car in the same scenario as you (unintentionally) and it triggered a rough start. Drove about 20-40min, let the car sit for like 10-20 then started it again and it started slowly and kept dipping rpm, had to give it a rev to level out but once it did nothing weird happened.

Not exactly the same symptoms, but those conditions did make a rough start.

interesting. If I ever figure out what causes this, I'll let you know so you can fix yours too

[mr.fabulous]

6-7 seconds is an eternity. You have a fuel delivery problem. My first thought (above) was LPFP... but (said in relative ignorance) I suppose HPFP could cause this too? Do you have equipment that will read you shadow codes... that could tell you something.

[captain slowly]

Originally Posted by mr.fabulous

6-7 seconds is an eternity. You have a fuel delivery problem. My first thought (above) was LPFP... but (said in relative ignorance) I suppose HPFP could cause this too? Do you have equipment that will read you shadow codes... that could tell you something.

Next time it happens I'll actually time it, so I'm not guesstimating. Either way, its a good bit longer then normal. My scantool is a pretty cheap, so I doubt it could read "shadow" codes. Not sure if its worth paying a shop or the dealer to investigate this when a very specific circumstances need to occur, and I couldn't duplicate this at will.

[DarthFader]

I had this happen on one of my N52 cars. Long cranks when engine was warm or hot, but no codes thrown and car ran fine. Turns out it was a leaking injector.

[MightyMouseTech]

With that little mileage, how old is the gas in this thing?

Only takes about 3 months for gas to go bad. And if you use fuel with ethanol in it, that will really gum up the entire fuel system.

[Stewy_604]

Totally agree with the above, 6-7 seconds IS an eternity for cranking. Even 3 seconds would be too long IMO. Looks like no codes from what was said above? Definitely sounds like a fueling issue, either pump or pressure sensor related.

[mr.fabulous]

Originally Posted by MightyMouseTech

Only takes about 3 months for gas to go bad. And if you use fuel with ethanol in it, that will really gum up the entire fuel system.

It is next to impossible to find gas in the US that does not contain ethanol.

[MightyMouseTech]

Originally Posted by mr.fabulous

It is next to impossible to find gas in the US that does not contain ethanol.

Next to impossible, but not impossible I am sure.

http://www.pure-gas.org

[Dackelone]

I would also suspect the fuel(bad). Maybe start to use a fuel stabil additive. I would burn off that old fuel and get some fresh quality name brand fuel. Do you have some way to check for codes? Like using BMW Carley App ? Does the exhaust smell of gas when the car has this long cranking? A leaking fuel injector could cause that long crank too. You really just need to check for shadow codes first.

[Blown95ImpalaSS]

just replaced injectors on mine to fix this same issue

[captain slowly]

the fuel shouldn't be an issue, as the car has been driven regularly for about 6 months now. Interestingly, it hasn't done it in the past couple of days, despite me trying to time every start up...so we'll see. Maybe its normal, maybe not. Maybe 3 seconds feel like 6, but I'll know for a fact next time it happens. Also, my cheapo code reader says no codes, but I doubt its able to see everything like the carly app would.

[mr.fabulous]

Originally Posted by captain slowly

....Also, my cheapo code reader says no codes, but I doubt its able to see everything like the carly app would.

I recently bought a Carly, and it seems unable to read shadow codes. Find a reader that will show shadow codes (something the car has seen once or twice, but not often or frequently enough to latch a code and throw a CEL) and you might learn something.

(my car shows HPFP shadow codes, it latched codes and lit CEL once about a month ago, hasn't happened since, cranks normally)