Check Twisted Gear: Diagnose & Repair

Hello.

I'm interested in learning how to easily check what's going on when there's a suspicion of a misaligned crankshaft pulley (the old 1Z problem).
Okay, here's the translation:

"So, without any interpretations of fuel injection start measurements (which can also be affected by the NBF), removing the valve cover, etc."

If the pump alignment pin doesn't fit properly in the overhead (OT) position, it could theoretically also be due to a belt that was incorrectly installed (you never know who was working on it last).

If the timing belt is already loose, with the timing belt cover removed and the gear engaged, you should be able to see how the camshaft and crankshaft pulleys move back and forth, initially with a delayed movement, and then how they are driven by the valve springs and camshaft, causing them to jump back and forth.

If the wheel is still difficult to move on the transmission shaft, the engine control unit might still be functioning correctly, even though it is already shifting around during operation.
Then, one should be able to carefully turn the pump wheel with, for example, a ring wrench and check if there is any excessive play, without the crankshaft rotating – or is this not possible in practice, due to the risk of overloading the belt or the pump bearing?

Hi,

...perhaps we could expand on this topic a little more.

Which types of dental procedures are generally associated with the problem of quadrant-worn gears?
Was ist die Übersetzung von 'Wurde das Problem im Laufe der Bauzeit des jeweiligen MKB irgendwann behoben (andere Schraube, etc.)? Wenn ja, wann?' ins Englische?

This question is not new, but it has never been clarified in a clear and systematic manner.

There are some experts here, like Michael II, who seem to be able to dissect and answer even the most detailed and complex questions!

(I am specifically interested in the AAT model, manufactured in November 1993.)

Hi everyone,

I don't think you can detect such issues with these tests (like pushing the car in gear, moving the timing belt, etc.).

Force = mass x acceleration.

When calculating the force transmitted from the crankshaft to the crankshaft pulley, especially when the engine rapidly increases in speed from 850 to 2000 rpm during clutch engagement, this is not comparable to simple back-and-forth movement. If the gear were able to shift during these tests, the engine would immediately stall with even the slightest increase in speed. I also find it hard to imagine that the pulley would simply wobble back and forth, even in neutral, given that the masses are unevenly distributed in the vibration dampers and flywheel (which would likely cause it to fail quickly).

Normally, the force is not transmitted through the screw, but through the contact surfaces between the wheel and the crankshaft. However, if the screw is not tightened to the required torque for some reason (e.g., due to expansion), then, in my opinion, only an acceleration caused by a sudden increase in speed (the camshaft, intermediate shaft, ESP, generator, etc. are accelerated -> forces) can generate a force large enough that the contact area is not sufficient, and the screw must transmit a portion of the force. The contact area between the screw and the crankshaft wheel is extremely small, which results in an infinitesimally small movement of the crankshaft wheel on the crankshaft in a counter-clockwise direction. If this play persists for a while and the screw does not break, then the start of injection slowly shifts from early to late with each significant engine acceleration.

Now, the question arises as to why the installation area is being damaged. A slight rotation would certainly not be a problem! So, the uneven mass distribution on the crankshaft will cause a "jerky" movement during acceleration, which puts stress on the crankshaft stub.

This is a theoretical consideration!! Please correct me if I have a flaw in my reasoning .

Best regards, Christian.

ulf wrote:

Then, one should be able to carefully turn the impeller with, for example, a ring wrench and check if there is any excessive play, without the crankshaft rotating – or is this not possible in practice, due to the risk of overloading the belt or the pump bearing?

Hi Ulf,

Okay, so the pump bearing isn't a problem, but the timing belt! While it can withstand considerable tensile forces, the force required to move the crankshaft a small distance using a timing belt is enormous! The "lever" created by the small crankshaft pulley is almost negligible, which would require immense forces for even a tiny movement. I once tried this on my old TD before replacing the timing belt -> it made a lot of noise... I wouldn't have been able to drive much further with the timing belt like that .

Best regards, Christian.