Noticed this last time at the track. Had a very cold night and a ton of rain all night as well. When we got to the track I had a hard time trying to start car and chalked it up to moisture and the cold that morning, but it ran fine and was the fastest it ever ran.
So now every morning it is tough to start and sounds like it is starving for fuel and want's to start .Fuel pressure s right on the money.. Takes 3-4 times and than fires up clean. never a problem after that and even if I shut it off right after it does start...it will restart instantly and every time and even through out the day even if it sits all day at work..
IAT and Engine Temp sensors are reading correctly when monitored. Temps here are around 40* and in my garage will be 50-60*. Car runs perfect other than that.
Any thoughts ??

 

Did you check your fuel pressure before starting first thing in the morning??? Not too familiar with the E55 just yet but sounds like a check valve leaking back and youre losing your fuel prime overnight.

 

Yea I do have to cycle the key for a second or two to build pressure due to the fact that I have a return style fuel system so when sitting a long time just have to spend a couple extra seconds or so to before starting. But yes fuel is at it's normal 65psi when starting.

 

try pressing that shrader valve on the fuel rail before the cold start and see if there is line pressure - gas should spray out

 

Dont have one....this car is way past that and does not have a stock fuel system.

 

Bump

 

Swap the cam sensor if you’ve got a spare sitting around.

 

Interesting.....Would never thought of that sensor for any reason. It's probably the only original part I never changed as well LOL. I will throw a new one in and let you know. Thanks

 

Also what role does a cam sensor play for cold starts ?

 

The cam sensor helps facilitate quicker starts.
The ECUs RPM signal comes exclusively from the crank reluctor, but since the crank rotates at 2x the speed of the valvetrain, the cam sensor indicates either TDC compression or TDC exhaust.

 

Since you have the return system on now, the pre-start pressure after a lengthy sit will be affected by any pressure valve that may (or in your case) may not be in the system. With older return systems there was always a valve that would be at the output of the pump that would keep pressure in the system (Post pump) before the (closed) injectors.

Additionally, all ICE cars still need a "prime" that should happen between you opening the door and the first turn of the starter motor.

I am very sure you know all this. Good to review though. And I am going to do return as well, so...

Further down the rabbit hole, a pressure sensor or physical analog gauge on the rail while cranking is good.

 

I have a digital live gauge and always cycle the key a couple times when it has been sitting for a long time. Waiting for sensor to come in...old one already out.
Real cold with snow here so spending the down time with an NOS digital gauge and bottle warmer install for next season/race. Time"s a tickin !!!!

 

Is the pump priming on the key cycle?

 

Yes it will. first key cycle 50 psi , second 65 psi than I start it. Again car has to sit for a few days in very cold weather. As soon as the sensor is in will see where its at for starting.

 

Hmm. I suppose it could be not compensating for the colder temps due to an IAT or Coolant temp sensor. Below say, 45 degrees, some more "serious" changes have to happen to normal start PWs and timing to make a car start. Hence why batteries in MN get dead earlier than they do where I live (SoCal).

 

No go on the cam sensor. Still hard to start cold but again when it fires...it will fire every time instantly. Even when it finally will start if I shut it down , it will instantly restart.
Iat and engine temp readings before and after start are reading correctly. May put my spare IAT sensor in for the hell of it but doubt it will do anything.
Very strange

 

This just sounds so much like a fuel backfill issue.

Is 50psi enough for starting? That is 50 at the rail?

 

I remember hearing about an ambient temperature sensor in the ECU. Kind of a long shot, but maybe the car doesn't know it's cold. Hoofbeats and zebras I know, but it's all I got.

 

Hey guys....yes 50 psi it will start but it sits around 60-65 psi. I did crank it up to 75psi and it made no difference.
Interesting on the ECU sensor....never heard that before but.....Why when it finally starts will I be able to shut the engine off and than it will restart every time instantly.
The temperature is still the same in those few seconds.

The car clearly does not know it is cold even though the sensors are reading correctly and that's what I am thinking.
This all started after a COLD HEAVY RAIN night before a race at the hotel so am going to poke around at anything that could have taken on water near the cowl. My hood vent cover is removed so I know water got in there. { It's out since I never drive in the rain really } but so much for that idea LOL.