E46 M3 Cold Start Hesitation, Cant Find The Solution?

[Will]

12+ months, lost track of time... won't happen again!

Your penance shall be two hail mary's and 5 redline pulls with fresh fuel. Lol.

[E46 M3]

How old was the fuel?

12+ months, lost track of time... won't happen again!

[Will]

Just an update to my issue for future reference, it was stale gas...

How old was the fuel?

[E46 M3]

Just an update to my issue for future reference, it was stale gas...

[Lee_Enfield]

My M3 has had this problem of hesitant starts that seems to be getting worse. Seems like every start it idles rough with varying rpm, and now it regularly stalls after a second or two, but starts right up second crank.

I have a new filter I have been meaning to throw at it, but if that does not fix it what is the procedure for pressure checking the system?

[E46 M3]

Would stale gas cause this too?

I haven't found a pattern to mine

New sparkplugs/ignition coils (had a misfire)
New fuel filter
Just did rod bearings and everything else around it.
68k miles so I dont think the injectors should be that bad yet or fuel pump
Battery tested okay and lifes on a ctek trickle

Like I said earlier I have found no pattern, sometimes it fires up on on the first time but most of the time I'll have to crank it a second time.

The only thing I have tried yet is fresh fuel but I want to run the tank lower before filling with fresh gas.

[BigLooga]

Nothing really to offer but after storing the car for the winter, i put it back on the road on May 1st and since taking it out of storage the issue is mysteriously gone. My intermittent issues only happened last year for a couple of months and i had noticed it was very hot and humid at the time my issue was present. It cranks and starts on first turn now, just like the past 8 years.

[MTiz]

I did a fuel filter and reset my adaptions and this problem completely went away. My car would start rough like yours and occasionally stall out on the first crank.

[jet_dogg]

How does one determine what an abnormal fuel injector looks like without flow testing?

[Icecream]

never mind

[Arith2]

OP here, I put in brand new fuel injectors(Bosch) and it solved the cold start issue. So far 3 perfect starts, one where the car was sitting for a month.

That's good to know. Did the old ones have anything abnormal about them?

[sapote]

OP here, I put in brand new fuel injectors(Bosch) and it solved the cold start issue. So far 3 perfect starts, one where the car was sitting for a month.

Take a video so we can compare before and after. I still think these cars take about 1sec cranking -- crankshaft turning a few turns -- to fire up. Post #19 Terra's car took about the same time to fire up also. although his engine fired up smoother. The non-M cars fired up quicker for some reasons.

[M3S54E46]

OP here, I put in brand new fuel injectors(Bosch) and it solved the cold start issue. So far 3 perfect starts, one where the car was sitting for a month.

[Christian_M3]

He means the Pressure Hose, from Pump exit to the Pumo Cover (where you connect your outlines). But you can save you money, and replace it by youself.

[DropTopKingM3]

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.




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!!

I purchased a new oem fuel pump and it didn't come with any tubes.. Just the actual pump itself.