On/off cycles are minimal for most pumps compared to the total number of hours of operation. And start/stop cycles do little to cause wear to the pump. Consistently, pumps fail when the copper contacts on the armature wear through. IME the MTBF is directly related to the amount of fuel pumped vs the amount of run time. IOW running the pump dry or with low fuel level will take it out of service much faster than ensuring fuel is available to cool and lubricate the armature and the brush/armature interface. I have also noticed that almost all manufacturers except GM tend to have large intervals between failures. I have Ford and Dodge vehicles with 300k miles which have never received pumps, while most of the GM's have used as many as four pumps in the same time.I wonder if MTBF for tbi fuel pumps is in on/off cycles, or total run time?
MSD?? or maybe Holley? has a pump control module which steps up voltage to the fuel pump to create higher than stock pressure and volume. I've worked with vehicles using this system although ultimately I always try to remove it and use proper tuning to make the engine run correctly. There are quite a few stories around about these modules causing premature pump failure but I haven't left one in place long enough to know.
Brushed DC motor controllers aren't new, of course. There are quite a few guys using PWM controllers on brushed motors in Power Wheels type vehicles (yes, the kids toy). Soft starts as well as variable speed control are usually the goals here. These motors usually get abused once Dad is done "fixing up" the toy and if they burned out quickly after modifications I'd be willing to bet there would be a lot of discussion on the forums.
You know, there is another option that might cause less worry and effort. The vacuum regulator is a very nice analog pressure control device. Why not PWM the signal to the regulator? This allows you to use the stock fuel system without worry about purging the vapors which will inevetably form, or purging air after a filter change or extended storage, or worry about deadheading the pump. A small vacuum pump and reservoir could ensure a constant supply of vacuum. An EGR control solenoid already designed to PWM a vacuum signal would be a perfect match for the control system, and the existing EGR control code and ecm output could be repurposed for the FPR. And really, the system could even be connected to pressure rather than vacuum, which would allow increases in pressure above base regulator settings vs reductions below max. Just a thought.
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