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Sorry for another cold start thread but after searching and trying the other fixes I am still stuck. 2011 R56 with N18 and 110k miles. Car sputters and fails to start after sitting overnight. Usually it will only fail to start once and then start up fine the second time but randomly it will take multiple tires before it will start. Here is what I have done so far:
- Replaced low pressure fuel pump
- Replaced HPFP with brand new one from FCP euro
- Replaced both vanos solonoids with Febi ones from FCP euro. (rear one was sludged up despite 3k oil change intervals)
- Replaced thermostat housing with the sensors due to it being cracked.
- Replaced Valve cover with metal one from ecs tuning which finally stopped an oil leak after a new plastic one didn't work.
- Replaced Coils and spark plugs.
Any more Ideas for the parts cannon? I noticed the last time I changed the oil that there was a lot of sludge in the oil filter despite 3k intervals. Could there be something else in the oiling system that could be malfunctioning due to sludge other than the vanos solenoids? Or could it be injector related. The only codes I have gotten were for the vanos solenoids which cleared up after changing them. Could there be hidden codes? Thanks!
Last edited by 65calinete; Feb 11, 2026 at 09:46 AM.
The next time you do a cold start, cycle ignition ON (w/o cranking) several times for 10-15 seconds before trying to crank and start the engine. If the cold engine starts fine, then there may be a fuel pressure issue.
The next time you do a cold start, cycle ignition ON (w/o cranking) several times for 10-15 seconds before trying to crank and start the engine. If the cold engine starts fine, then there may be a fuel pressure issue.
I will give it a shot tomorrow morning, thank you!
65, connect a scan tool (live data) and see what your long term fuel trim (LTFT); is. STFT dumps when the engine computer powers down; the car used LTFT to restart. If the LTFT is highly negative ... say -20, the DME is pulling fuel away. The LTFT number will give you a direction you need to travel next. Post your LTFT number and your MAF grams/sec number (at idle) here.
65, connect a scan tool (live data) and see what your long term fuel trim (LTFT); is. STFT dumps when the engine computer powers down; the car used LTFT to restart. If the LTFT is highly negative ... say -20, the DME is pulling fuel away. The LTFT number will give you a direction you need to travel next. Post your LTFT number and your MAF grams/sec number (at idle) here.
The next time you do a cold start, cycle ignition ON (w/o cranking) several times for 10-15 seconds before trying to crank and start the engine. If the cold engine starts fine, then there may be a fuel pressure issue.
Originally Posted by ECSTuning
+1 check that and use this as a guide. At least it will tell you whats working on fuel side.
So update, I did the cycling and it started right up. The fuel rail pressure on the first press was 63.8 psi and it stayed there on each additional press. Since the cycling worked what does that mean?
65, connect a scan tool (live data) and see what your long term fuel trim (LTFT); is. STFT dumps when the engine computer powers down; the car used LTFT to restart. If the LTFT is highly negative ... say -20, the DME is pulling fuel away. The LTFT number will give you a direction you need to travel next. Post your LTFT number and your MAF grams/sec number (at idle) here.
Possibilities - (1) Fuel system losing fuel pressure while parked (e.g., bad fuel pump check valve); (2) weak HPFP; (3) fuel injector leaking.
Any pending fault codes?
No pending codes. Is the check valve in the high pressure or low pressure fuel pump? I am skeptical that it is the hpfp as last week I replaced it with a brand new non-chinese one from FCP euro for $900 and the symptoms didn't change at all. What is the best way to check for leaking injectors?
MAF looks low, but let me check my records when I get back to the house. Remember, if the MAF is giving a false low airflow that means less air going into the engine, and the DME will pull away fuel (negative fuel trim number). Now warm up the engine and see what the short term and long term fuel trims are. Add the two numbers. This is your total fuel trim (TFT). A perfectly running engine will be at 0 TFT.
MAF looks low, but let me check my records when I get back to the house. Remember, if the MAF is giving a false low airflow that means less air going into the engine, and the DME will pull away fuel (negative fuel trim number). Now warm up the engine and see what the short term and long term fuel trims are. Add the two numbers. This is your total fuel trim (TFT). A perfectly running engine will be at 0 TFT.
After letting it run 20 min the fuel trim is a net negative 10 at idle. Coolant temp is 167.
+1 Yep, my guess is something is not hold pressure. Like a slight dip.
Replaced low pressure fuel pump and filter? - this gasket on the top likes to leak, but most of the time it throw a code. Maybe small tear or leak from the gasket?
Do you know what the pressure should be at the rail after sitting overnight?
Not sure.
Did you check the fuel pressure with a gauge or scan tool? Can you measure the pressure after the car sits overnight?
With engine running, you should read 72.5 PSI. The service manual states that, after turning off the engine, the pressure should not drop by more than 10% in 20 minutes (65.25 PSI).
Last edited by Maybe, maybe not; Feb 12, 2026 at 03:24 PM.
Not sure.
Did you check the fuel pressure with a gauge or scan tool? Can you measure the pressure after the car sits overnight?
With engine running, you should read 72.5 PSI. The service manual states that, after turning off the engine, the pressure should not drop by more than 10% in 20 minutes (65.25 PSI).
Looks like I would need a manual gauge to check that as the only pressure sensor that I know of is on the fuel rail and I would need to measure it pre fuel rail.
Your engine is running rich and cold. Does the coolant temperature get higher after a 20 minute drive?
Did you bleed the cooling system after replacing the thermostat housing?
I used a vacuum fill system to replace the coolant in the system so it was bled properly. It does get higher after driving. I may check the purge solenoid. I also need to clean the MAF to rule it out.
