Fuel level sender won't fit?

[jimbojames]

EFI conversion... I purchased what was supposedly a 318i replacement fuel pump on eBay and I can't seem to fit my level sending unit onto it. It lines up 95% of the way but I don't want to force too hard it since the sending units are expensive and seem a little fragile. It seems like the hole tolerances are just crappy. Any suggestions? Maybe I'm doing something stupid?

 

 

[02Les]

Open up the holes a "size up" with a drill?

[jimbojames]

I used a rotary tool to try and "open it open a little" and it seems hopeless.. If I open it up too far it's going to leak. I'll probably order a new fuel pump.

[jimk]

You don't have a 318i pump because it doesn't have a fuel return nozzle.  There are 3 pumps that look alike if you are not familiar with them.  A 325i low pressure pump, a 325is/ix pump and the 318i pump.  The 318i and 325i low pressure pumps have a return nozzle. The other 325 systems return fuel directly to the tank, 

So you might have a 318i level sensor.  The 325i pumps have level sensors that do interchange between the two pumps.  The 315i low pressure pump motor is only about 4 inches long and is plastic covered housing, the high pressure pump has a motor that is about 4.75 inches long and is metal housed.

Edited July 28, 2019 by jimk

[jimbojames]

That is hugely helpful, thank you; I wondered why there was no return. Based on your description, it sounds like I have the high-pressure pump since it has the metal housing. Here's two additional pictures. Unfortunately, that must mean my sender is not compatible

 

 

[jimk]

A high pressure pump is needed for a 3 bar fuel pressure system.

Early EFI pumps grew out of the concept used on the TII (2bar), and when the E30s appeared (non IS models) they used a low pressure in-tank pump plus a second inline pump to reach 3 bar pressure.  Maybe evolution of pumps hadn't reached a single 3 bar pump at that time

Later systems use a single high pressure 3 bar pump that was the norm up until direct injection systems (except for the GM throttle bodies that operated at 13 psig).

The 318is pump with a return connection is your best choice even if the tank is the later one with the small return nipple.  That nozzle doesn't meet proper design for the internal tube for anti-splash return.  The 318is pump has that feature built into the pump assembly where it returns the fuel at the suction screen level on the pump.  Without the anti-splash feature in the fuel return, a static charge can develop with unintended results.

If you intend to use the pump in hand, I can come up with a level sensor for it.  I have 3 pumps in the basement that i have no use for the sensors.  Drop me a pm if interested.