I think I figured out why BEWs have long cranks and no start crank position sensor issues

[burn_your_money]

This is a working theory and I would appreciate some input from the electrically inclined people in the group. Specifically those with a silly scope.

This is related to the "16705 - Engine Speed Sensor (G28) P0321 - 000 - Implausible Signal - MIL ON" code but also long cranking.

When the starter draw is excessively high, it creates a stronger magnetic field. This field induces noise into the crank sensor wires (that run directly on top of the starter solenoid). Because the crank sensor sends a weak signal by design to the ECU (no 5v reference signal) it doesn't take much noise in the wires to confuse the ECU. I suspect that this is why BEWs are notorious for long cranks, especially compared to the BHW. When the starter first starts turning, the most power is needed, and therefore the magnetic field is the strongest. Once the engine is turning over faster, the field diminishes and the ECU is able to read the crank sensor signal and begin firing the injectors. I suspect that the ECU doesn't throw the crank sensor code until the crank sensor misses a certain amount of readings, which is why a code isn't immediately thrown. This may also explain why extended cranking can cause the G28 implausible signal code to get thrown. The simple solution would be to move the wiring harness further away from the starter and that should result in faster startups. Of course, having a good starter and battery will also help reduce cranking time.

Can anyone prove or disprove my theory?

 

[mittzlepick]

I have long crank time compared to the alh on one pd not the other. No codes but its old and sick as well bad head gasket and 371k miles with smoke on startup after sitting more than an hr. Valve seals i presume. Whats your torsion value?

 

[burn_your_money]

My torsion is 0.

Magnetic fields drop off exponentially right? So extending the metal arm/bracket that guides the wires about an inch (double the distance) should quarter the noise right?

The issue with the TSB is that the wires still all run right by the starter.

 

[PakProtector]

The real drop off is by the square of the distance. Since we are not dealing with monopoles( which fall off just by distance to first power ). The really simple way around this is to take a unity gain stable op amp and build a wee buffer module. Power is relatively easy; two isolated DC-Dc converters, probably about the size of a pack of gum; it is easier to take the battery and its grounds out of the equation and keep the resulting device running on the same signal ground.
cheers,
Douglas

 

[Stupendous60]

Although I am not familiar with BEW, I would think if there was EMF interference, the engineers would have shielded the wires to the sensor. If not you could wrap it in tin foil to see if it helps.

 

[turbocharged798]

I think the other problem is the BEW is the only TDI engine that has no other reference for the crank sensor. The ALH and AHU can use needle lift, the BRM uses cam position. On top of that its a magnetic pickup sensor with no active voltage going to it which makes it very susceptible to noise and weak signals. The slower the engine spins the smaller the amplitude of the signal. This issue can be compounded when rust builds up behind the sensor and pushes it every so slightly from the tone wheel.

I thought about building a little amplifier box that can plug inline and boost the signal if the amplitude is under a certain voltage.

IMHO its simply a bad design. The ECU should be using the cam sensor which believe is hall effect until the engine is running.

 

[holeintheice]

Ran into that on a Ford 6.0. Starter drew too many amps so the crank and cam sensors would not sync. No magnetic field issue though. I know wires twisted together are CAN lines. Twisted to help with magnetism. Probably drawing too many amps.

 

[Tdijarhead]

I steer clear of electrical problems when I can, but have you seen this?

How to: solve the 04 BEW hard starts and 16705 G28 fault code.

This TSB will fix the 04 BEW hard start issue. I was getting a "16705 - Engine Speed Sensor (G28): Implausible Signal" code almost all the time. I would clear it and it would come right back within a day or so. I was also getting a large cloud of smoke when starting when cold along with a rough...

forums.tdiclub.com

 

[JDSwan87]

I love this forum, good stuff right here.

 

[burn_your_money]

I steer clear of electrical problems when I can, but have you seen this?

How to: solve the 04 BEW hard starts and 16705 G28 fault code.

This TSB will fix the 04 BEW hard start issue. I was getting a "16705 - Engine Speed Sensor (G28): Implausible Signal" code almost all the time. I would clear it and it would come right back within a day or so. I was also getting a large cloud of smoke when starting when cold along with a rough...

forums.tdiclub.com

I have, thank you. I was under the impression that the 2006 BEW had that fix from the factory. Confirming it was completed was the next step in my troubleshooting.

 

[oilhammer]

The BHW uses the same signals, and they start instantly (usually as soon as the first power stroke comes around, and they are off and running). But they do not have the CKP wire anywhere near the starter, it just is sort of loose on its own up to the connector mounts on the firewall.

The TSB relates to if the car has the DTC. Plenty of these have long crank times on a hot soak restart without ever having any DTCs. The 2004s seem to be more prone to flag a fault than the 2005s. Curiously, I've never seen a 2006 BEW (the few that there are) do this.

I also thought the tuners had an improved hot start strategy that helps, too, similar to the 1998/99 ALHs that had a similar problem, despite not sharing any parts.

I've also seen a handful of BEWs have some pretty abysmal looking engine harnesses around the front of the engine that needed some cleaning up. Not sure if that has anything to do with this issue or not, but they do run the CKP subarness through that main engine harness.