Your specialist subject: The life and times of the BMW EKP low pressure fuel pump controller

[B21]

This is probably going to be one of the least relevant posts to Z4 Forum E89 members..

The key point is that the EKP or EKPM or fuel pump controller is very reliable on the E89 and seldom causes issues.

This not the case on other BMWs where they frequently fail, the key failure mode is over heating of the main chips on the circuit board.

EKPs are fitted to all ICE BMWs from around 2000 onwards ..at least..

This appears to be in part caused by the EKP location, which is usually buried under the rear seat and suffers from a lack of ventilation and being effectively insulated.

The EKP manages the current to the low pressure fuel pump..it does this by using pulse width modulation if a dc power supply..a bit like rapidly switching the dc power on and off..it’s not alternating current is still direct current but the average voltage / current is reduced compared to being simply on.

The EKP receives its instructions from the DME and then alters the current flow to maintain an adequate pump pressure / flow but not excessive.

In the E89 the big aluminium heat sink on the EKP is bolted to the rear wheel arch ensuring good cooling by conduction.

In NA cars the EKP and LPFP are the main ways to get fuel to the port injectors into he inlet manifold.

In turbo cars the LPFP lifts fuel to the engine driven HPFP which then uses direct injection to deliver fuel.

For E89 owners the primary reason for interest is when folks start chasing more power via uprated turbos.

In the chain of demands ..bigger turbos, especially those using ethanol blends require more fuel than the standard LPFP can supply..so folks use uprated pumps..but the uprated pumps require more current to drive them..which then tends to overheat the EKP…it gets to the point where people have installed huge fans and heat sinks to try and cool it.

In my case at 550bhp crank on RON 98 my LPFP wasn’t good enough..I installed an uprated LPFP and now I’ve replaced the stock EKPM3 box with an ET3 version which uses a later design of power control IC from the same manufacturer that’s pin compatible with the original..

These guys have just reworked old boards, replaced some parts and market them in various uprated versions..mine is their entry level upgrade.

Swapping it out was easy once the trim in the boot was removed.

I put a bit of silicon heat transfer grease on the back for maximum thermal conductivity / cooling.

It may or may not need coding..I’ll look at that shortly.