Slow crank when warmed up, doesn't seem to be a ground problem, other ideas?

S4NoMore · 03-30-2021, 02:19 PM

My '11 335i with now ~100k miles has turned over more slowly when it's warmed up, ever since I got it two years ago with a little over 70k miles.

Initially I figured it was an ailing battery, but earlier this year I put a new battery in, coded/registered, and the cranking is a little better but still exhibits this same behavior.

Last summer I replaced the plugs and coils, no change there either.

When cold, the car cranks "normally" although maybe not like a <2yr old car would. It starts up without any issue and no one would notice or suggest a problem.

When "cool" it still cranks normally. I haven't pinpointed the temperature range, but I can start the car and move it in the driveway or maybe even drive for a couple minutes and then the next startup is fine too.

But if I stop for gas, or get groceries, or am somewhere for less than say an hour or so, when I go to start it up again it will crank more slowly and take more than 1 second to fire up (sounds like not much, but watch 2 seconds elapse... it's noticeable). My dad had a 2009 335i at one point years back and I know "long crank" - this is not long crank. It's noticeable, and to the point of being awkward/embarrassing

Even my wife has said "is your car ok?"

On my drive home from work, though, it's totally fine again with the engine fully "cold."

I came across the success stories of grounding the engine with jumper cables to determine if it's a failure of the ground strap, but I tried that and I have to say it really didn't improve things. The strap will get replaced but I don't expect that to be my smoking gun here.

Could it be that the starter is going bad, or the grounding at the starter itself is failing? I'm not sure what else to check... but I definitely don't want to replace the starter unless I know it'll help. No codes are being stored, no MIL.

Soden82 · 03-30-2021, 08:06 PM

Could be fuel related. Wondering if when the car is warm the lpfp isn't priming correctly. Can you run a log and check LPFP and rail pressure? At least that would rule out a fueling issue

lurker14 · 03-31-2021, 05:54 PM

i would put money on its the ground or the starter I have had to do both on my car over the last year symptoms exactly as you describe for both of them.
same year car and same climate as you

S4NoMore · 04-01-2021, 10:02 AM

Quote:

Originally Posted by Soden82

Could be fuel related. Wondering if when the car is warm the lpfp isn't priming correctly. Can you run a log and check LPFP and rail pressure? At least that would rule out a fueling issue

I attached a jpg showing two starts with fuel rail pressure and flow. Admittedly this is the first time I've logged anything and tried to make use of it, via BimmerLink. It looks like the warm pre-start (left side graphs) rail pressure is close but 10 psi lower than cold start rail pressure. When cranking, the cold pressure is much higher (490 vs 260 psi). Is that an issue? I don't know.

Quote:

Originally Posted by lurker14

i would put money on its the ground or the starter I have had to do both on my car over the last year symptoms exactly as you describe for both of them.
same year car and same climate as you

I'll have to just put a new strap on there and then see how it goes. Ugh, starter replacement... stuff of nightmares.

whyzee125 · 04-01-2021, 10:20 AM

Is it taking a longer time to fire up or is it turning more slowly until it fires up?

If the latter, I'd be pretty strongly convinced it's just your starter getting weaker. I had a 4runner that was like that. It would crank so slowly you'd think it wouldn't start but the battery was fine. It was this way for 2 years until I sold it and never once did it not start. The starter actually looked newer but I think it was just an aftermarket one.

S4NoMore · 04-01-2021, 01:13 PM

Quote:

Originally Posted by whyzee125

Is it taking a longer time to fire up or is it turning more slowly until it fires up?

If the latter, I'd be pretty strongly convinced it's just your starter getting weaker. I had a 4runner that was like that. It would crank so slowly you'd think it wouldn't start but the battery was fine. It was this way for 2 years until I sold it and never once did it not start. The starter actually looked newer but I think it was just an aftermarket one.

It's turning more slowly until it fires up. When it's warmed up, that is.

skippybonez · Yesterday, 07:29 PM

Quote:

Originally Posted by S4NoMore

It's turning more slowly until it fires up. When it's warmed up, that is.

Dude! Did u ever fix this?!?! I have done starter and battery no luck. Can find the issue

03-30-2021, 02:19 PM	#1
S4NoMore Major 258 Rep 1,003 Posts Drives: 16 340i, 15 X3d, 91 318i Join Date: Aug 2008 Location: Philly suburbs iTrader: (2) Garage List 2016 BMW 340i [0.00] 2015 BMW X3 28d [0.00] 1991 BMW 318i [8.66]	Slow crank when warmed up, doesn't seem to be a ground problem, other ideas? My '11 335i with now ~100k miles has turned over more slowly when it's warmed up, ever since I got it two years ago with a little over 70k miles. Initially I figured it was an ailing battery, but earlier this year I put a new battery in, coded/registered, and the cranking is a little better but still exhibits this same behavior. Last summer I replaced the plugs and coils, no change there either. When cold, the car cranks "normally" although maybe not like a <2yr old car would. It starts up without any issue and no one would notice or suggest a problem. When "cool" it still cranks normally. I haven't pinpointed the temperature range, but I can start the car and move it in the driveway or maybe even drive for a couple minutes and then the next startup is fine too. But if I stop for gas, or get groceries, or am somewhere for less than say an hour or so, when I go to start it up again it will crank more slowly and take more than 1 second to fire up (sounds like not much, but watch 2 seconds elapse... it's noticeable). My dad had a 2009 335i at one point years back and I know "long crank" - this is not long crank. It's noticeable, and to the point of being awkward/embarrassing Even my wife has said "is your car ok?" On my drive home from work, though, it's totally fine again with the engine fully "cold." I came across the success stories of grounding the engine with jumper cables to determine if it's a failure of the ground strap, but I tried that and I have to say it really didn't improve things. The strap will get replaced but I don't expect that to be my smoking gun here. Could it be that the starter is going bad, or the grounding at the starter itself is failing? I'm not sure what else to check... but I definitely don't want to replace the starter unless I know it'll help. No codes are being stored, no MIL.
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03-30-2021, 08:06 PM	#2
Soden82 Major 491 Rep 1,218 Posts Drives: 2011 BMW M3 Join Date: Jun 2017 Location: Boston iTrader: (1) Garage List 2011 BMW M3 [0.00]	Could be fuel related. Wondering if when the car is warm the lpfp isn't priming correctly. Can you run a log and check LPFP and rail pressure? At least that would rule out a fueling issue __________________ 2009 BMW 335i 6MT big single (eventually) For now... MHD tuned VRSF Race IC DCI ATM exhaust
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03-31-2021, 05:54 PM	#3
lurker14 Private 8 Rep 65 Posts Drives: e92/g82 Join Date: Jul 2015 Location: OH iTrader: (0)	i would put money on its the ground or the starter I have had to do both on my car over the last year symptoms exactly as you describe for both of them. same year car and same climate as you
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04-01-2021, 10:20 AM	#5
whyzee125 Brigadier General 1927 Rep 3,955 Posts Drives: Dinan stage 2 335i Join Date: Jul 2014 Location: Chattanooga Tn iTrader: (0)	Is it taking a longer time to fire up or is it turning more slowly until it fires up? If the latter, I'd be pretty strongly convinced it's just your starter getting weaker. I had a 4runner that was like that. It would crank so slowly you'd think it wouldn't start but the battery was fine. It was this way for 2 years until I sold it and never once did it not start. The starter actually looked newer but I think it was just an aftermarket one.
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