I now have about 30hrs on my 350i engine.   On every engine start, I crank engine for about 5  to 8 seconds and nothing happens.  However, after I wait 15 seconds and crank it again it immediately  starts.  I have tried starting on different fuel tanks, different fuel pumps, different throttle positions and cranking engine for 15secs all of which have no effect on starting engine on first try.   I did talk to Ray at UL and he gave me some things to try but none of them had any effect on getting engine to start on the first attempt either.  I am ok with engine performance and have experienced no other engine related problems.  Just curious if anyone else has experienced this. 

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Larry,

As long as I remember to turn on both ECU and fuel pumps before cranking my 350i starts quickly and easily. My fuel pressure is in the 40 psi range before I start cranking the engine. The basics of all engine issues tend to trace back to air, fuel, and spark.  I suspect that air can be crossed out. That leaves fuel and spark. Spark on UL Power is beyond me to even think about. Do you have a pressure gauge on fuel line that tells you that the system is up to pressure before you start cranking? The lag you are experiencing reminds me of the loss of power I experience when switching fuel pumps and the second pump has to run for a moment before fuel pressure comes back-up. When switching pumps in flight I have experienced a few moments of silence before engine gets enough fuel from new pump to start running again. I really dislike silent airplane engines.

I have puzzled over this since I first read your post and other than the above thoughts I am drawing a blank. From the few clues it appears to be a pressure lag.

Let us know what you discover.

Ralph

N750RP

Ralph,  I have tried starting with secondary fuel pump running continuously with fuel pressure reading 43# and engine still will not start on first attempt.  Ray is going to discuss this with UL Power folks and let me know what they say.  Thanks.

Larry, I am curious as to the suggestions made by Ray.  He is quite knowledgable and I'm thinking that you all will eventually figure this out.  My only thought which comes to mind is whether you running the fuel pump(s) long enough prior to start to  purge the fuel lines.  Do you have the integrated fuel bypass mod  (SB 2019-02) installed?

Also be mindful of the starter engagement time limitation of 5 seconds...

Good luck, let us know if you meet with sucess and what the fix was!

Dave

Larry,

My 350i does the same thing most starts.

I always run secondary pump in preflight to verify pressure buildup and then primary pump by ECU prior to turning the key .Starts immediately on second attempt. I only use starter 3 -5 seconds first attempt.

Fuel related? After first attempt, you can hear ECU pump run to pressurize system again.

Ralph,

By running the secondary pump on the ground in preflight, I do not have engine hesitation when switching pumps in air. I learned this by switching pumps in air as you described, without running secondary on ground during preflight and having instant "pucker moment" when sweet running 350i stopped, but started again immediately ,but seemed like a long time.

Silent. Yes!!!!

Just my experience.

Jerry 

David, I do not have integrated bypass installed.  I have tried starting with secondary fuel pump running continuously with no success.  I have not timed how long I run pumps prior to start but I will try this next time and see if it makes any difference.  Ray is going to discuss this with UL Power folks.  Thanks 

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