Yes, the serpentine belt runs the peripheral components on the engine. The timing chain is inside of the engine.
it is in the block behind the timing cover. the timing belt drives the water pump so you have to remove the timing components to install the water pump.
The Jeep 2.5 ltr engine ran a timing chain in all years from 1983 to 2002. It is CLOYES TIMING COMPONENTS part #9-4023.
It is on the front of the crankshaft, under the timing components.
It's all electronic and controlled by the DME unit. There is no distributor and threfore no manually adjustable timing components.
R (resistance) and C (capacitance).
It's very likely difficult considering the fact that the oil pump is located inside where the timing belt and components are. To access these, the front right wheel must be removed along with the drivebelt, most of their pulleys, the timing belt cover, and timing belt. It is an awkward procedure because when reinstalling the timing components, certain steps must be taken to maintain proper ignition timing.
A timing chain is not the same as a timing belt. Timing chains do not generally need replacement unless you are rebuilding the engine. While a timing belt is simply a ribbed, flat fanbelt that wears and can become weakened with age, a timing chain is oiled constantly and should be expected to last the life of the engine. Like other internal engine components, a timing belt is affected by the condition and quality of your engine oil, and as such, should last as long as the other internal engine components.
The rotor is not adjustable on 99.9% of distributors. The timing is adjusted by loosening the distributor body and turning it in relation to the rotor and other driven timing/ignition components.
A BMW 320d has a timing chain located in the top of the engine. It links the cam and crankshaft together. This ensures that the engine components rotate in sync.
Yes, the timing chain can and does eventually develop wear/fatigue after so many years and miles. Other components of the timing system (such as the tensioner and guides) also wear out (and in fact are more likely to wear out sooner than the timing chain itself). The OE timing guides are made of plastic, so they tend to wear out relatively quickly compared to the metal components. There also are gears as part of the system. If the truck has over 200,000 miles, and the timing components have never been replaced, I would recommend buying a timing kit which comes with all the necessary parts (chain, guides, tensioner, gears, seal, gaskets). You can get a good quality kit for about $100.
If the timing belt snaps on a 2.5 Transit diesel, a secondary issue may be valve damage. When the timing of the engine is off, it throws the internal components out of whack.