SOLVED : Hard start issue

[acarr6]

Just wanted to address a hard start issue I had, in case anyone else is searching for a solution

Symptoms : hard start problem after car has been sitting for 24+ hours. Very long crank (5-6 seconds, barely starts). On second start, no issues, rest of day no issues.

Cause : loss in fuel pressure, caused by failing/failed fuel pressure regulator located in the fuel sender unit

Diagnosis procedure I used : prime the fuel pump 4 times before starting - if starts with no issues, fuel pressure loss is the cause of the hard start issue.

Solution : replace fuel sender unit (also includes fuel filter). P/N 16112283495

[Camnyc]

Just to confirm, you replaced the fuel pump assembly completely correct?

[acarr6]

Originally Posted by Camnyc

Just to confirm, you replaced the fuel pump assembly completely correct?

That is correct, it’s all in one. The part number I gave is a complete repair kit from bmw. Basically the guts of the sender unit.

[amrazM]

i hated changing that thing by myself with those long ass lines on them. it was such a mess.

[acarr6]

Update : not solved! Issue is still present. I pulled out the injectors and primed to see if they drip - no leaks!!

[Redd]

Any codes? I remember there's a separate control module for the fuel pump (aka EKP) mounted at the rear parcel shelf. Maybe that one is going faulty?

[acarr6]

Originally Posted by Redd

Any codes? I remember there's a separate control module for the fuel pump (aka EKP) mounted at the rear parcel shelf. Maybe that one is going faulty?

No codes, but you’re the second person to mention this - which I didn’t know! I should check.

[ZachE90M3]

Originally Posted by acarr6

No codes, but you’re the second person to mention this - which I didn’t know! I should check.

I found you on here lol. I thought someone solved the problem 😭

[acarr6]

So, I changed the fuel pressure sensor to the new one.. during the change when I popped it off no fuel came out, which tells me there was no pressure. I installed the new updated style sensor, opened the door, started the car. Fired up instantly. That’s after sitting for 3 weeks as well! Good news.

[Helmsman]

Originally Posted by acarr6

So, I changed the fuel pressure sensor to the new one.. during the change when I popped it off no fuel came out, which tells me there was no pressure. I installed the new updated style sensor, opened the door, started the car. Fired up instantly. That’s after sitting for 3 weeks as well! Good news.

Must be soo nice to get it sorted after hard work - congrats!

[RocketyMan]

Originally Posted by acarr6

Just wanted to address a hard start issue I had, in case anyone else is searching for a solution

Symptoms : hard start problem after car has been sitting for 24+ hours. Very long crank (5-6 seconds, barely starts). On second start, no issues, rest of day no issues.

Cause : loss in fuel pressure, caused by failing/failed fuel pressure regulator located in the fuel sender unit

Diagnosis procedure I used : prime the fuel pump 4 times before starting - if starts with no issues, fuel pressure loss is the cause of the hard start issue.

Solution : replace fuel sender unit (also includes fuel filter). P/N 16112283495

I'm following this thread as well trying to chase a "delayed start after sitting longer than 24hrs" issue. The P/N listed is for the "Repair kit conveyor unit" as 16112283495. To my understanding, this just the pump that kicks over to the main one.

So shouldn't the main fuel pump P/N be 16112283497?

https://www.realoem.com/bmw/enUS/sho...diagId=16_0601

[chicagob5]

Just adding that replacing the sensor fixed my long start after sitting overnight issue as well. Did the updated sensor with adapter yesterday and had a identical experience to OP. No fuel came out when I took the old copper sensor off. This morning it started right up.

[acarr6]

Originally Posted by RocketyMan

I'm following this thread as well trying to chase a "delayed start after sitting longer than 24hrs" issue. The P/N listed is for the "Repair kit conveyor unit" as 16112283495. To my understanding, this just the pump that kicks over to the main one.

So shouldn't the main fuel pump P/N be 16112283497?

https://www.realoem.com/bmw/enUS/sho...diagId=16_0601

The regulator is in the conveyor unit - which is what would be causing the pressure loss. Unless you have codes for fuel pump issue.

[RocketyMan]

Originally Posted by acarr6

The regulator is in the conveyor unit - which is what would be causing the pressure loss. Unless you have codes for fuel pump issue.

Ohh! Gotcha! I guess I had a difficult time understanding that part because the first post said SOLVED, then later said not SOLVED.

And then realizing its because the actual regulator is in that part! Makes sense now! So then yeah, if the regular leaks--which probably does after circa 10 years, then fixing it would help maintain fuel pressure.

I too replaced the fuel pressure sensor with the updated one with adapter. Didn't notice too much of any improvement with anything. Maybe mileage?

[chenium]

My car was doing this so I had the injectors, fuel pressure sensor, and fuel breather valve all replaced. It still did this immediately after replacement but stopped for a bit afterwards. The issue has returned since and I'm unsure what to try next. I currently have the updated sensor installed with the adapter. I'm considering ordering the original brass version without the adapter.

[acarr6]

Originally Posted by chenium

My car was doing this so I had the injectors, fuel pressure sensor, and fuel breather valve all replaced. It still did this immediately after replacement but stopped for a bit afterwards. The issue has returned since and I'm unsure what to try next. I currently have the updated sensor installed with the adapter. I'm considering ordering the original brass version without the adapter.

That won’t solve your issue. Plenty of cars run the update sensor with no problems, why wouldn’t yours work?

Sounds like you haven’t replaced the fuel conveyor (regulator) yet. That’s the solve for most people.