trouble starting

[rh71]

Well you guys will be happy to know that it happened again 3 days after I got it back - failed to start in the morning, but only once (1 time too many). The rough-feeling start I just mentioned, that's happening pretty much every morning. Wasn't likely a symptom of the new solenoids... probably that whatever the real problem is, it's just getting progressively worse. Dealer taking a 2nd look...

 

[rh71]

verdict #2: fuel pump relay (sensor?) intermittently failing to detect fuel

god how many parts are in these things? 😀

 

[PricklyPete]

verdict #2: fuel pump relay (sensor?) intermittently failing to detect fuel

god how many parts are in these things? 😀

Believe me...you haven't even scratched the surface. German manufacturers stick more sensors in their cars that NASA ever used in the space program. The problem with sensors is that they are only good if they work...and when you have eleventy billion of them in a car, a few are bound to go bad.

 

[DivideBYZero]

Did this get sorted RH? I'd say coil packs, the dealer can use the diagnostics to check the missfire counts on each cylinder. If it's the CPs then one or two of them will have higher than normal counts (some missfire counts are normal, you never have an ECU show zero).

 

[exdeath]

You need an electrical engineer, not a mechanic. Someone who can use the right tools like an o-scope.

PS: It is nearly impossible now days for ignition to cause a complete no start condition with individual coils on multi cylinder engines, each with their own internal amplifier, etc, unless something on the much larger picture like PCM ignition controller or crank position sensor is faulty.

 

[rh71]

2 days and so far so good, though right at the point of start it is still not as smooth-sounding as it was.

 

[DivideBYZero]

Believe me...you haven't even scratched the surface. German manufacturers stick more sensors in their cars that NASA ever used in the space program. The problem with sensors is that they are only good if they work...and when you have eleventy billion of them in a car, a few are bound to go bad.

For realz. Look up things like the secondary air pump. It's an air pump that pushes extra fresh air into the exhaust before the secondary cats and it's only used during the cold cycle at start up to heat up the cats faster. 😛

 

[PricklyPete]

For realz. Look up things like the secondary air pump. It's an air pump that pushes extra fresh air into the exhaust before the secondary cats and it's only used during the cold cycle at start up to heat up the cats faster. 😛

Oh...I know the secondary air pump very, very well. It is causing a nice "Service Engine" light on my dash as we speak. It is on my to do list...it is just a pain to diagnose, because the engine has to be cold to do it and you need a helper.

 

[Howard]

Oh...I know the secondary air pump very, very well. It is causing a nice "Service Engine" light on my dash as we speak. It is on my to do list...it is just a pain to diagnose, because the engine has to be cold to do it and you need a helper.

Can you not jump the relay for it?

 

[PricklyPete]

Can you not jump the relay for it?

Yes, I can do that to ensure that the pump is working (which I'm pretty sure it is). But I have to also test whether the rest of the system is working including the sensor, the vacuum lines, and the one way valve. I think only the sensor test needs to be done when the engine is cold if I recall correctly.