The fuel pump controller is a bit like an electronic speed controller for a RC car.

If you diagnose the problem and is a ST part only(not std Focus) and you need parts, Athol Park Ford wreckers(Adelaide) have 2x ST170s, including my smashed 1, which was going great at time of the stack! 
 Good luck 

Hi Marty,
 
I called them and unfortunately the fuel rail pressure sensors are gone. I thought I was in luck.
 
Stevie, that is worth checking and I have looked into it somewhat.

Needs some good thorough diagnostic checks...fuel pressure and oscilloscope logging carefully selected voltages and signals to either prove or disprove correct operation of sensors and circuits. Sounds like it's been thrown in the too hard basket by the local guys. It would probably be cheaper to ship it down to me for a week or two!!! These things arent built on rocket science...basic principals still apply!!

I'd first want to prove the fuel pressure issue with a guage, then look at the voltage to the pump during the faulting sequence, if voltage is still good then chase a pump/tank issue, if voltage is dropping, causing fuel pressure to drop, then use the oscilloscope to check the fuel pump controller +ve and -ve in and out as well as the duty signal from the ecu. Once you know all these facts during the faulting sequence the answer will be in front of you. It is possible that the ecu is dropping its duty output to the controller, either deliberately due to one of the fuel metering calc sensors telling it to do so, or the controller output from the ecu is playing up. If the ecu is dropping the output deliberately, you will see the duty signal reduce gradually, if the output disappears all together the transistor contolling this output in the ecu is playing up.
 
Very easy to prove the basics on this one.
1. Connect mech fuel pressure guage at rail.
2. Connect multimeter at fuel pump.
3. Drive the car and produce fault, note the fuel pressure and voltage at the pump during fault.
4. Does fuel pressure drop? yes. Does voltage at pump drop? yes...test controller/ecu output circuits. no...look for fuel pressure loss at tank fuel pump module.
 
Do these tests, let me know the results and we will go from there. Sounds like your dealer doesnt have much talent in the workshop as this is really basic stuff for a good modern technician.
Cheers,
Phil.

Oh...and dont trust the OBD data when diagnosing these type off issues, as it is possible to be spitting out the targetted signal rather than the actual signal. This issue can arrise if a output controller in the ecu is playing up, and also depends on where the ecu manufacturer has elected to deliver the data from...either befor or after the output controller device, whether it be a transistor, var resistor, etc.
 
Only trust OBD data if you know it is correct through your own independent readings with an oscilloscope.

Hi Mickas, I am not ruling anything out... but I am fairly certain it is a fuel system issue. When I have had issues with crank angles sensors in the past it has caused the car to cut out. This issue is as if the car is not upping the fuel pressure from the base line idle fuel pressure.
 
Hi Phil, cheers for all of the information. I have ordered a pressure gauge, so hopefully it will come later in the week. I will try some tests with the multi-meter this week and let you know how I go.
 
I was trying to remove the ECU, but unfortunately there seems to be a child-proof bolt preventing me from removing it.. I might have to drill it out.
 
Thanks,
 
Damion
 
 

If it was a Holden, I would have burnt it by now