Jump to content

Cranking Fuel injection delay? BMW M50


Recommended Posts


Im running a BMW M50 Plug-in ECU on my Drift car and Ive noticed something thats a little annoying.

When I turn on my ignition, wait for my Fuel Pump to prime fully, and go to crank my car, there is a small delay as to when the fuel injection actually starts.

I have tried adding more Cranking enrichment, but form looking at the Runtime Values list while cranking, I can see the Fuel injector duty cycle doesn't ramp up for a few seconds. Once it does, everything works great. Its just a little annoying that every time I start my car, I have to stay on the starter for 2-3 seconds.

Ive tried finding a setting for this in PC Link. Maybe i'm looking in the wrong place?

Im also running 92 Octane fuel ( Not E85)

Any help is appreciated.


Link to comment
Share on other sites

In our E36 base map the pre-crank prime happens at key-on, before the engine starts cranking.  This may not be captured in the logging as it potentially is all over before the logging is working.  Cranking enrichment will initiate as soon as the trigger syncs, so worst case scenario is one full engine revolution.

Can you attach a log and your map.

Link to comment
Share on other sites

That would make sense! I actually turned off my Pre-crank prime because I didn't want any fuel getting in there unless i'm trying to crank the motor.

It does make sense to build up a small fuel film on the intake manifold before cranking. I just don't like the idea of the fuel injectors running every time I turn the key on, to put up/down a window, to upload a tune. etc. I will try logging the trigger parameters in Runtime values and see if maybe it takes that long for the triggers to be Sync'd, but I honestly think something is holding up the injectors for a few sec. My old VEMS ecu used to start this same motor instantly!

I took a log today datalogging the Injector Duty cycle and Engine speed and noticed that the engine speed isn't reconized while cranking. The RPM on the log read 0 until the Injector duty cycle jumped up. ( I also forgot to save this log, not that it was very useful)

I will attach my tune so you can check out my settings to see if maybe anything is conflicting with this.

M52 2.8 NA.pclr

Link to comment
Share on other sites

Disconnect coils or turn ignition off (so it doesnt start) and do a triggerscope while cranking.  It may be that something is wrong with the arming threshold or something similar causing it to be slow to sync.

If you dont like the precrank prime to occur at key-on, you could wire a start signal to a DI, then you can set the pre-crank to occur only when start signal is seen.   I've never seen a problem with the more common "key on" prime though.  Even with multiple on/off cycles I dont remember causing flooding or fouling type symptoms.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...