2000 528i Hard to start

[jonathan1985]

2000 528i 5-speed 120k miles.

Issue: Very hard start, cranks fine.

This problem started with me having to crank the engine multiple times to get it to start but once started for the first time for the day would run perfectly and start up again with no issues. If left overnight it would become hard to start again.


Actions Taken: Replaced Fuel Pump and filter with BOSCH, New Fuel Pump Relay, New Fuel Pressure Regulator, Rebuilt Vanos, Smoke test that found cracked valve cover, Replaced Cracked Valve Cover and gaskets, New Spark Plugs (NGK), Verified all coils are functioning properly (getting spark), Another smoke test that showed nothing.
I checked the fuel pressure at the rail and was getting roughly 10-15PSI after trying to "prime" the fuel lines by turning the key to accessory position and waiting for ~10-20 seconds multiple times.

I already changed the fuel pump and filter with new BOSCH so to see if I had a faulty new pump I tested the pressure just after the fuel filter and before the 3/2 valve and was getting (if I remember correctly) 80+ PSI. Thinking it might be a faulty fuel pressure regulator I purchased and installed a new one. I tested the fuel pressure at the rail and had ~10 PSI after "priming" the system multiple times.

Since I had plenty of pressure going to the Running Losses (3/2) valve or Fuel Control Valve (Part# 13311740281) but little to none after, I replaced it and the car started the first time for about a week or so. Then I started having the hard to start issue again. Checked the fuel rail and I was at ~10 PSI again, but if I “primed” the fuel system by turning the key to accessory for 10 seconds or so, back off, then back to accessory mode again it would climb up ~10 PSI per cycle to the needed ~52 PSI. Even with proper pressure, it was hard to start requiring 10+ attempts to get it started.

This weekend, thinking I may have gotten a faulty 3/2 valve assembly, I replaced it again and ran into the same ~10 pounds of pressure at the fuel rail as the previous one.
This morning I ended up draining the battery trying to start it with no luck. I checked with the Peake code reader and have no codes showing at all.

Am I missing something obvious? Any idea of what I should do moving forward?

[effduration]

Any smell of fuel?

typically poor fuel pressure is due to:
1. failed return check valve (in the fuel pump)
2. leak in fuel hose at pump or filter
3. Leaky fuel injectors

since you have replaced several components, I don’t think it is 1 or 2.

I suggest you do this. By a hose pinch clamp or use vice grips with tape on jaws to pinch fuel inlet hose ( I think there are two fuel hoses on the M52TU engine you have), and AFTER you have 50 psi in the system pinch off the fuel inlet hose.
See how quick it bleeds off. If it is quick, I would check fuel injectors

The way to check fuel injectors is to pull all of them off the intake, but keep them attached to fuel rail as one unit. Then prime the fuel line with the ignition and see if any are leaking. My guess is that one or more fuel injectors are leaking. Get th3 ones that leak repaired and replace all injector o-rings on reinstallation.

[amancuso]

My vote was also 3. Leaky fuel injectors.