Hi i just thought id share some information. ..i have a 2004 rx8 with a fresh rebuilt engine
had a lot of problems with the omp pump..
i emptied a can of contact sprayin behind the position sensor as it seemed to be seized..
it helped for a few months but gave problems again. .
so i decided to strip it down as im a trained electrician/engineer speacilising with motors.
so upon strip down i found that the pump itself is perfect. .theres nothing to break really in it..
The sensor also is not an issue.
The stepper motor is the problem i stripped the motor down and found that the bearings inside were half seized its a bad design. ..The front bearing in the motoris protected by a crappy little o ring that obviously doesn't work. .there's a pipe right above the pump and in my case a small amount of coolant leaked into the pump and got past the o ring and ruined the bearings in the stepper motor..seizing up the motor and throwing up a p1688
i looked high and low for a replacement stator for the motor. But its a very bespoke unit. .not off the shelf.i decided to replace the bearings..i gave it to a specialist motor refurbishment business because I thought they would have better tools than mine..but they ended up braking the internal magnet in the motor...donkeys. .i should have done it myself.
but in summary. .its the bearings in the stepper motor seizing up that is causing the problems with the omp pump
anyone with a bit of technical know how can save them selves money. .
The measurements of the bearings are 8mm accros to fit the internal shaft diameter 22 mm
and 7mm thick
i would have been able to fix it..shouldn't have subied out the last bit
be careful not to break the magnet its right up against the bearings...some creative engineering needed to get the old bearings off.
I've a 2nd hand unit ordered off flea bay..
I can take pictures if anyone is interested