Longer start and engine died once. No check engine light.

fernando306 · Post by **fernando306** » Fri May 13, 2022 5:02 pm

Hello my friends,

Recently the car is taking twice as long to start. Fine at first start, but if I park, get a haircut and come back out, I have to crank it like and old beater to get it going.

Yesterday I noticed that the idle wasn't very happy, it was dipping a bit below the set point. If I blipped the throttle, it would dip and recover before dying. But once, coming to a stop on a traffic light, it just died. This never happened before, and hasn't happened today.

Scanned, no fault codes. Runs just fine, no loss of power. New MAF and spark plugs put 18 months ago. Disa valve rebuilt and VANOS seals replaced too. Fuel pump pressure is >50 psi running, and 48 psi with ignition on and engine not running. Fuel pressure drops to 20 psi in 45 minutes, so the check valve had better days.

What are the possible issues? ICV, check valve, fuel pump, fuel pump relay... what else? What is more likely to be?

Thanks guys!!!

Scooba_Steve · Post by **Scooba_Steve** » Fri May 13, 2022 5:12 pm

fernando306 wrote: ↑Fri May 13, 2022 5:02 pm What are the possible issues?

Battery.

fernando306 · Post by **fernando306** » Fri May 13, 2022 5:23 pm

Thanks Scooba_Steve!

I'm a bit hesitant though. It is turning over the engine just fine. How does that make sense that the problem presents itself with the second-start, after parking for minutes? That's when the battery had just been charged. Shouldn't it then happen on the first start, after sitting overnight?

Rockhopper · Post by **Rockhopper** » Fri May 13, 2022 5:31 pm

Sounds more like a fuel pressure problem to me.

zriha · Post by **zriha** » Fri May 13, 2022 5:35 pm

I would go with the fuel pump! Sounds like a fuel pump.

fernando306 · Post by **fernando306** » Fri May 13, 2022 5:47 pm

Just measured the fuel pressure. It's a bit over 50 psi when running, and about 48 PSI with engine off and ignition on. So that looks correct.

fernando306 · Post by **fernando306** » Fri May 13, 2022 6:38 pm

Now is at 20 psi after 45 minutes...

I want to put a check valve in line, like this. What would be the best way to do it? The fuel pump access is tricky, so what is the next best spot to tap and put the check valve?
https://www.youtube.com/watch?v=6ezt4M1NZDk

fernando306 · Post by **fernando306** » Fri May 13, 2022 11:21 pm

I'm replacing the camshaft sensors. Will see...

colb · Post by **colb** » Sun May 15, 2022 11:17 pm

Could well be the camshaft sensor failing, after doing some work on mine that required the sensor to be disconnected I forgot to plug it back in and noticed it took longer to crank, as soon as I reconnected the sensor immediate starting was restored.

Old-Duckman · Post by **Old-Duckman** » Tue May 17, 2022 12:16 am

My issue was similar. Start after sitting over night...starts right up. Start after sitting 10 minutes...starts right up. Sits for 1 hour plus (up to several hours) have to run the starter for a while and when it started it would stumble for a while before it would smooth out and take some gas pedal.

Replaced all injectors, started good for awhile then started doing the same thing again. diagnosed a leaking injector, replaced that and it started OK for a shorter while, replaced another suspect injector, started good twice before acting up again. Replaced all O-rings on all injectors and the air distribution "thing" (rail?). Made no difference at all.

Found a video on the Net where a guy complained about similar issues (I think his was in a Volvo). Anyway the mechanic on the video suggested replacing the engine coolant temperature sensor. The M54 has two I was told (Thanks Rockhopper for that info). I replaced the one in the lower rad hose housing ($41 USD) with an OE BMW part...Cured my problem!

The computer was telling the engine that it was cold and needed to richen up the fuel mixture...makes sense how that would cause my issue. maybe yours is the same?

fernando306 · Post by **fernando306** » Thu May 19, 2022 10:29 pm

Gentlemen...

I replaced both Intake and Exhaust camshaft sensors. Pretty easy DIY job. Problem gone.

Z4-forum.com

Z4-forum.com