because its an electronic mechanical hybrid pump. and as far as the 4 different injection systems you can get for a B cummins. its by far the poorest setup/ having the electronic modue right on top of the hot pump, useing fuel to TRY and cool and lubricate the thing. even with a FASS or good aftermarket pump and fuel pressure guage. they can fail with no warning or reason. there were no less than 5 different injection pumps on my '98.5 24v with 180,000km on it.
the P7100, the CP3 HPCR are superior fuel systems, even the VE rotary is known for great fuel economy and longevity.