Long start after short sitting

pysical

Sergeant
Jun 16, 2017
345
73
0
Ride
2009 335xi E90
Currently on 100% E85. If my car sits for a short period of time (2 hours), it gives me a 4-5 second long crank. If the car sits over night, it fires up no problem.

I have been doing some research and it could be anything from a leaky injector, a failing HPFP, and just how E85 works with heat soak?

I checked my rail pressure and lpfp pressure after the car sat overnight. both was at about 70ish. Then I drove to work today, and checked it 4.5 hours later and it was also at 70ish. It did the long start then.

My next step was to let the car sit a couple hours and then pull the plugs and see if any of them are wet or smell like E85. If so, then I was going to test that injector. This also didn't start happening until I replaced injector #4 with a new one from FCP Euro. I did code it properly. But it also just may be a coincidence. I might not have started the car within a few hours prior to the injector install since it was just my second tank of E85.

Anyone got some feedback or ways to test?

Thanks.
 

dyezak

Major
May 4, 2017
1,768
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Plano TX
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335is
Leaky injector(s). When you have a short period that particular cylinder is way to rich to light off and it takes a few cranks to get the extra fuel out.

When you have a long period the fuel in the cylinder evaporates and there isn't a rich condition to cause issue.
 

dyezak

Major
May 4, 2017
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Plano TX
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335is
Take a log on full decelleration. Log your O2 and STFT's. You should see the injectors cut all fuel and the O2's flatline. If you see one bank that is not flatlined you found the bank with the leaky injector.

If it is E85 the problem would be more pervasive in a cold start situation. The vapor pressure of e85 is significantly lower than gasoline so in cold starts it doesn't atomize as well. In a hot engine this wouldn't be a problem.

HPFP problems show themselves by losing rail pressure after sitting...you checked that and it was fine so that's not the issue.

My money is on injectors.
 
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pysical

Sergeant
Jun 16, 2017
345
73
0
Ride
2009 335xi E90
Take a log on full decelleration. Log your O2 and STFT's. You should see the injectors cut all fuel and the O2's flatline. If you see one bank that is not flatlined you found the bank with the leaky injector.

If it is E85 the problem would be more pervasive in a cold start situation. The vapor pressure of e85 is significantly lower than gasoline so in cold starts it doesn't atomize as well. In a hot engine this wouldn't be a problem.

HPFP problems show themselves by losing rail pressure after sitting...you checked that and it was fine so that's not the issue.

My money is on injectors.

What type of declleration would be the best? Like 6k down to 1k? What gear?

Thanks for your help.
 

NoQuarter

Major
Nov 24, 2017
1,534
955
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Indiana, USA
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Z4 35is, 535xi, X5 35i
What type of declleration would be the best? Like 6k down to 1k? What gear?

Thanks for your help.
No fuel is no fuel. Anything that matches the conditions for slowing down with no foot on the gas should do it I would think?
 

NoQuarter

Major
Nov 24, 2017
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Indiana, USA
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Z4 35is, 535xi, X5 35i
Is that the top of the Piston? Hard to make out on my phone.

Ha.. nevermind. I read the post again.
 

pysical

Sergeant
Jun 16, 2017
345
73
0
Ride
2009 335xi E90
Yeah that's too of piston. I just started it up and let it for a a second then checked cylinder one and had same amount.
 

pysical

Sergeant
Jun 16, 2017
345
73
0
Ride
2009 335xi E90
Do you think the next step would be to rotate all the injectors 180 degrees and crank the car over with the coils and injector connector unhooked? See if any of them spit out any fuel?
 

pysical

Sergeant
Jun 16, 2017
345
73
0
Ride
2009 335xi E90
Update... I was talking to someone on e90post and he mentioned to get in the car and push the button to start twice. So not starting the car but turning everything on. Leave it like that for 15-30 seconds and then start. I did that and the car started no problem.
 

pysical

Sergeant
Jun 16, 2017
345
73
0
Ride
2009 335xi E90
Low pressure fuel line losing pressure?
From the regulator to the pump? My brother said he thought it was bleeding off as well. But I did just do some logs with my car. 3rd gear pulls. And the AFR is a bit different in these compared to the ones last night.


I also tried the 30 second start trick before I left and it didn't work this time.
 

AK135i

Corporal
Dec 13, 2016
117
32
0
27
Anchorage, Alaska
Ride
2010 135i
If you have a msd80 dme, the older units don't prime the lpfp when you open the door or unlock it, like the newer mds81 dme does. Just my 2 cents, especially if you turn on the ignition and let it prime and you're not having any other issues, id bet on that. Unless you have a 09 model or newer, or the dme was already upgraded.
 

NoQuarter

Major
Nov 24, 2017
1,534
955
0
Indiana, USA
Ride
Z4 35is, 535xi, X5 35i
If you have a msd80 dme, the older units don't prime the lpfp when you open the door or unlock it, like the newer mds81 dme does. Just my 2 cents, especially if you turn on the ignition and let it prime and you're not having any other issues, id bet on that. Unless you have a 09 model or newer, or the dme was already upgraded.

I'm pretty sure our 07's and 08's prime the pump.
 

AK135i

Corporal
Dec 13, 2016
117
32
0
27
Anchorage, Alaska
Ride
2010 135i
I'm pretty sure our 07's and 08's prime the pump.

My personal 2008 135i had a msd80 dme, replaced it after mosfet and misfire issues. Before with dme upgrade it never primed the fuel pump for me, and i thought i had read somewhere about it. It would explain why op's problem is solved with cycling the ignition before starting. Now that im thinking about it, what i remember from the past might just be a part up a factory dme update.
 
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pysical

Sergeant
Jun 16, 2017
345
73
0
Ride
2009 335xi E90
I am MSD81. But it doesn't always prime the pump. In fact now that I am thinking about it, I don't think it has primed since I had a issue with one of my Walbro 450's drawing to much amps. I wonder if it burnt out..