E46 M3 Cold Start Hesitation, Cant Find The Solution?

[Tomba]

I do a lot of ECU modifications to racing cars with S54B32 with stock ECUs and this starting behavior on the first video is not normal. All cars that I work on fire up within a blink and idle perfectly, even with large duration camshafts. I can only suggest that the amount of fuel to prime the intake and cylinders isn't enough to make the engine idle smoothly upon start up. I would check injector flow (static & dynamic) and spray pattern first. Also observe the coolant and air intake temperature before starting. Large deviations can indicate a problem with these sensors and might results in less or too much fuel during start up. Fuel adaptations would be welcome to.

[SliM3]

Wonder if this could also be attributed to slow VANOS response on start-up, particularly the exhaust cam since it has to travel to full advance.


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[S54B32]

Wonder if this could also be attributed to slow VANOS response on start-up, particularly the exhaust cam since it has to travel to full advance.


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Now that’s a nice input, I will perform a vanos test this weekend.
Maybe the seals are hardened (leaking) or the vanos pressure tank can not store long enough pressurized oil for the startup.

And I try to log vanos positions due startup.

[SliM3]

Now that’s a nice input, I will perform a vanos test this weekend.
Maybe the seals are hardened (leaking) or the vanos pressure tank can not store long enough pressurized oil for the startup.

And I try to log vanos positions due startup.

S54B32,
Might also be beneficial to inspect/clean the CPV valve. If it's bleeding oil from the cylinder head back down to the pan, you'll most likely get a momentary delay as it has to refill to provide any meaningful supply to VANOS.

[S54B32]

S54B32,
Might also be beneficial to inspect/clean the CPV valve. If it's bleeding oil from the cylinder head back down to the pan, you'll most likely get a momentary delay as it has to refill to provide any meaningful supply to VANOS.

On my previous M346 I had to replace the CPV, it leaked very bad (but no startup problem). And on this M3 with the start issue, the CPV looks very clean, no leak.

i also have a Vanos pressure gauge. I will also check this during startup. Only problem is, that only one „unsuccessful“ try per day is possible.

@sliM3: I found it very strange, regardless how long i crank during the first crank, I would not fire up. Do you know if the mss54(hp) lock the injectors that they not flood the chamber after some cycles? Or prevent from injection/ignition if vanostarget is not reached? I really need to log during startup some data!!

[Christian_M3]

M3S54E46 is your car doing the same thing as mine?

Absolutely the same on my 57k mile M3.

it wasn't like that before.

We should leave the topic open to new insights.

[Dakarvert]

I don't think that cold start is normal, back in October 2006 I leased a brand new ZCP and it never started like that. Last year I bought an 04 (my current M3) and the cold start is exactly like I remember from my 06.

[terra]

I wonder if this map might be part of the issue:

US 2701:



Euro 2001 / CSL 0401:


This function describes the amount of torque the DME tries to generate at the specified coolant temp and RPM during the engine start. The columns are RPM, the rows are coolant temperature (in ºC), and the actual table entries are torque (in Nm).

Euro / CSL goes 40-25-15-7-0 regardless of temperature. US does 25-25-25 etc at temperatures between 32 and 68 F. Then between 68 and 178 F it will generate something between that 25 and 10 Nm. Maybe that 25 at 240 RPM just isn't cutting it for some motors (There are probably minor variations in friction from engine to engine).

My car is running CSL management

[eljay]

On cold start, sometimes on mine rpm jumps up normally and it drops from 1200 to 1000 rpm a couple of times and then stabilizes at around 1100-1200 and finally drops to normal idle as expected. My indy shop said that it may be time for VANOS work and I agree. I am at 98k miles.

[S54B32]

To all with this problem: Check your fuel pressure and make a leak down test! A compatible gauge is very cheap.





I have found my issue! The pipe from the fuel pump (the internal one in the tank) had a pinhole where the clamp sits, that was not visible without pressure, but enough to bleed the whole fuel system over night. The pipe was very stiff and hardened from the years, not like it should be.

Because while i was there, i installed along the new pipe a 400l/h Walbro just for future possibilities.
Runs great, Very fast start, even with drained battery.

[DropTopKingM3]

To all with this problem: Check your fuel pressure and make a leak down test! A compatible gauge is very cheap.





I have found my issue! The pipe from the fuel pump (the internal one in the tank) had a pinhole where the clamp sits, that was not visible without pressure, but enough to bleed the whole fuel system over night. The pipe was very stiff and hardened from the years, not like it should be.

Because while i was there, i installed along the new pipe a 400l/h Walbro just for future possibilities.
Runs great, Very fast start, even with drained battery.

Thank you for this. You may have helped a few of us who have been plagued with this problem. Do you know the part number for the pipe that had the pinhole leak?

[Christian_M3]

To all with this problem: Check your fuel pressure and make a leak down test! A compatible gauge is very cheap.





I have found my issue! The pipe from the fuel pump (the internal one in the tank) had a pinhole where the clamp sits, that was not visible without pressure, but enough to bleed the whole fuel system over night. The pipe was very stiff and hardened from the years, not like it should be.

Because while i was there, i installed along the new pipe a 400l/h Walbro just for future possibilities.
Runs great, Very fast start, even with drained battery.

Which Walbro do you used? Is it Plug and Play?

[jet_dogg]

Thank you for this. You may have helped a few of us who have been plagued with this problem. Do you know the part number for the pipe that had the pinhole leak?

He's probably referring to #4 https://www.realoem.com/bmw/enUS/sho...diagId=16_0484

https://www.fcpeuro.com/products/bmw-fuel-line-16112283288

[pnvhome]

Have issue very similar to that, also there was a problem with start on warm after 20-30 minutes, it starts during 3-4 seconds, engine was rebuilded, new fuel pump filters, sparks. The only solution was new fuel injectors, i bought bosh on sale for 47$, and now engine starts in second at any time, cold, warm, after month of standing.

[S54B32]

The strange thing was since I had the car, even after priming for minutes manual, I need at least 2 cranks. So only thing I can imagine is, that there was air trapped in the injectors/fuel rail, where priming not help without triggering the injectors.

Thank you for this. You may have helped a few of us who have been plagued with this problem. Do you know the part number for the pipe that had the pinhole leak?

Sadly this part is only sold with the complete fuel pump assembly.

i ordered a walbro kit for e46, it arrived with a similar to oem looking tube, soft sleeve, filter etc. But this tube did also leaked after shrinking, so I replaced it with a standard 8mm black fuel line. It‘s stiffer that the original one and but i know some people used this successfully in the past with aftermarket intank fuel pumps.

My walbro was sold as GST400. But take you time, mounting without a solid sleeve like the expensive radium one is a little bit tricky so take your time that it sits secure and as low as the original pump.
It‘s also helpful to have less that 1/4 tank prior this work.


But before you even think of lifting the pump out of the tank, check you full pressure/leak test!!