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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Wed, Apr-24-2019, 09:03:05 PM   #1
wolffbimmer
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Angry Warm Start Problem

(FINAL UPDATE: A new fuel pump seemed to have fixed the issue at hand) I have this intermittent problem when the car/temps outside are warm. The first start will just crank and crank, I stop and crank again and it starts every time without any stumbles/issues. This mostly happens when I am leaving work after 7-8 hours of sitting when it's warm outside or when I leave my girlfriend's place after it's been sitting for 3-4 hours. I've read threads where people claim leaky fuel injectors cause this but if mine were leaking why does it do this only sometimes and not every morning for the very first start (which it always fires up first time) I have replaced the fuel injector relay under the hood (blue) and the ignition relay (light green) and the fuel pump relay in the trunk (green) with no luck. The reason I don't think this is a fuel issue is because one time I cranked it for a good 30 seconds or more when it did this one time and started it the second crank and it stunk of fuel. Leads me to think this is an ignition/spark issue but no idea where to turn. I have a new crankshaft position sensor, intake cam sensor, new starter, fuel filter. I'm guessing the next best thing is to hook up a fuel pressure gauge on the under side of the car and see what the pressure does after sitting for a while but I feel this isn't fuel pressure related (even if it was losing fuel pressure via the injectors wouldn't it fire up after cranking so long and building pressure or a few cylinders just fire even if one was flooded?) Any other ideas?

Update at end of thread (replaced pump no luck, replaced fuel pressure regulator and no luck, trying fuel filter next as it's 3 years old; update didn't fix problem, I even had a test light into the fuel pump connector to ensure I have getting power during a non start event and it was) Hooked up a gauge and saw pressure was dropping a good bit. The gauge is a POS but showing over 10 psi of drop even when I had the return line pinched off. Leads me to believe injectors have to be leaking as regulator is new. Update will come after injectors replaced this week) Update: Injectors did not fix issue, replacement pump died on me and left me stranded: put old one in to get it running again. No resolution.

Last edited by wolffbimmer; Tue, Jun-18-2019 at 02:34:22 PM. Reason: updates
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Old Wed, Apr-24-2019, 09:19:04 PM   #2
ZiMMie
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Default Re: Warm Start Problem

Change the fuel pump.

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Old Wed, Apr-24-2019, 11:44:30 PM   #3
wolffbimmer
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Default Re: Warm Start Problem

That’s a hefty 400 bucks to throw at this problem when I don’t expect fuel delivery to be the problem since it smelt of fuel after the one 30 second crank I did as described above. Any reason why you believe it is? I had the rear seat and fuel pump cover off for a while and I heard the pump prime every time I turned to position 2.
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Old Thu, Apr-25-2019, 12:39:20 AM   #4
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Default Re: Warm Start Problem

Mine does this all the time. Never starts the first try... turn the key and it cranks but never starts. Take the key out and try again and it will starts right up. I thought fuel pump or pressure regulator but my BWM dealer said it was probably the starter switch after they looked at it...
no codes either... let me know if you figure anything out.
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Old Thu, Apr-25-2019, 03:50:52 AM   #5
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Default Re: Warm Start Problem

My guess: not fuel pressure issue. Possible proble
1) injectors leaked causing too rich mixture which fired up ok with cold engine but not when warm. Check fuel pressure for drop after key off 30 minutes
2) no ignition signal due to ignition key recognition issue. Check: get the condition when this will happen and remove plug to check for spark
3) verify if injectors triggered: after a long crank but failed to fire up, quickly remove a plug and for sign of fuel or not
4) could be a bad temperature sensor causing bad fuel mixture
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Old Thu, Apr-25-2019, 05:42:45 AM   #6
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Default Re: Warm Start Problem

Change the fuel pump.

The one way check valve(built in the fuel pump) that makes the primary line holds pressure is defective causing it to loose pressure when the car is warm. When the car is cold the ecu primes the fuel pump much harder.



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Old Thu, Apr-25-2019, 01:47:56 PM   #7
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Default Re: Warm Start Problem

Quote:
Originally Posted by Cbouts View Post
Mine does this all the time. Never starts the first try... turn the key and it cranks but never starts. Take the key out and try again and it will starts right up. I thought fuel pump or pressure regulator but my BWM dealer said it was probably the starter switch after they looked at it...
no codes either... let me know if you figure anything out.
I doubt it's the starter switch/ignition switch. I've actually changed that out on the column.
Quote:
Originally Posted by sapote View Post
My guess: not fuel pressure issue. Possible proble
1) injectors leaked causing too rich mixture which fired up ok with cold engine but not when warm. Check fuel pressure for drop after key off 30 minutes
2) no ignition signal due to ignition key recognition issue. Check: get the condition when this will happen and remove plug to check for spark
3) verify if injectors triggered: after a long crank but failed to fire up, quickly remove a plug and for sign of fuel or not
4) could be a bad temperature sensor causing bad fuel mixture
I'm going to do a fuel pressure test and make sure. I may change the engine coolant sensor (under the manifold) for good measure since it's cheap enough. The key thing I believe wouldn't allow any crank at all if it wasn't recognizing it. Correct me if I'm wrong though.
Quote:
Originally Posted by ZiMMie View Post
Change the fuel pump.

The one way check valve(built in the fuel pump) that makes the primary line holds pressure is defective causing it to loose pressure when the car is warm. When the car is cold the ecu primes the fuel pump much harder.



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I have had several shops go over this with me and the warm weather they seem to get a lot that go up. I'll hook up a fuel pressure gauge and monitor it when this issue happens and make darn sure. I have a inclination it could be that but why wouldn't it start even the first time after cranking for 30 seconds, surely it would build enough pressure then? Are you 100% sure about the system priming harder when it's colder. I feel like I should have this issue in the morning on first start as well if the check valve is leaking down unless at a certain point it seals again and I'm able to get start up in the morning and build pressure.
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Old Thu, Apr-25-2019, 01:53:44 PM   #8
ZiMMie
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Default Re: Warm Start Problem

Fuel Priming times are different between cold engine and warm engine.
You don't need to crank it 30 seconds. It won't start.

You can just crank for 3 seconds for the first time, it should start right away on the 2nd try.

Don't waste ur time with fuel pressure gauge.

Just change the fuel pump.

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Last edited by ZiMMie; Thu, Apr-25-2019 at 02:08:04 PM.
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Old Thu, Apr-25-2019, 03:15:49 PM   #9
sapote
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Default Re: Warm Start Problem

Quote:
Originally Posted by ZiMMie View Post
Fuel Priming times are different between cold engine and warm engine.
Technically there is no need for fuel priming. It’s the fuel pump shut off safety feature in case the car involved in an accident— pump must be turned off after x seconds delay with rpm = o. The shutdown delay time has nothing to do with engine or ambient temperature.

If OP can confirm fuel pressure around 60psi consistently then no reason to blame the bad pump.
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Old Thu, Apr-25-2019, 03:23:20 PM   #10
Toxic0n
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Default Re: Warm Start Problem

Quote:
Originally Posted by ZiMMie View Post
Fuel Priming times are different between cold engine and warm engine.
You don't need to crank it 30 seconds. It won't start.

You can just crank for 3 seconds for the first time, it should start right away on the 2nd try.

Don't waste ur time with fuel pressure gauge.

Just change the fuel pump.

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This.
I had the same issue for many years. Sometimes it would not start on first crank after it's been sitting a while. It started immediately on the 2nd crank. Summer gas, winter gas, fuel filter, pressure regulator, I heard it all here.

Then my fuel pump died. I replaced it and haven't had the issue since. Something about the pump check valve losing the fuel pressure after it's been sitting?
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Discussing Warm Start Problem in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)