Fuel Pump or Relay?

[Pierre]

There seems to be 3 pumps that BMW used on the E36. (The z3s use a different pump 16 14 6 756 323. It fits most z3s regardless of engine. M44, M52, M54, S52. The S54 had yet another pump 16 14 2 229 672.)

The M44 ti uses 16 14 6 758 735
The M42, (including the ti up to 2-95) M50 and S50 uses 16 14 1 182 842
The M44 non-ti cars, M52, S52 use 16 14 6 758 736.

There seems to be a little overlap between engines and pumps but for the most part, these are differences.

The interesting thing is that the same pump that fits the M42 ti fits the sedans and coupes. All ti tanks are the same through the years which means the physical fit is the same which explains Rock Auto's interchangeability of the pumps.

The fuel pressure regulator can reduce fuel pressure but not increase it beyond the maximum pressure of the pump. If the S52 pumps goes up to 51psi and the ti pump goes up to 43.5 psi, the ti pump will not deliver pressure over 43.5 psi that the S52 may need under certain conditions.

I have learned not to doubt BMW engineers. They know by far more than I do. And if they choose a different pump for different engines, I have a difficult time accepting that it's not important. At least, I would like to hear a plausible technical explanation that would convince me that a ti pump will work just the same on the S52 motor.

The tii crowd also have quite a debate about fuel pumps. tii electric pumps are VERY EXPENSIVE. Some people are using E28 pumps with "good" results but the pressure and fuel volume are not the same. Does it work? Absolutely!!! It's less than half the price at $200. Is it as good as the original? The tii gurus seem not to think so.