E46 M3 Cold Start Hesitation, Cant Find The Solution?

[heinzboehmer]

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

Radium sells fuel tubing that's very similar to what comes with the OE pump assembly and is safe for E85: radiumauto.com/Submersible-Fuel-Tubing-P672.aspx

I bought the "20-0175 Submersible Fuel Tubing, 5/16in x 12.8in" for use with an AEM pump that I installed in the original pump carrier and it's been working fine. Can't comment on whether that size will work with the stock pump though

[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.

[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.

[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.

[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.

[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?

[Icecream]

never mind

[jet_dogg]

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

[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.

[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.

[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.

[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]

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

[Will]

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

How old was the fuel?

[E46 M3]

How old was the fuel?

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