High Pressure intermitent drops on CDTI
 

Hi guys, I'm experiencing some drops on the High pressure side each second more or less.

I first noted that on road, without accelerating, the car seemed to slightly oscillate on power, like I was stepping on and releasing the throttle slightly and not mantaining the speed.

Connected the laptop to see if there was any fault and nothing except the glow plug one, nothing related.


I make the reading for the low pressure pump and was consistent on 3.6 bar, but on the high side, there are drops of arround 50 bar or more each second at 800 rpm and more noticeable at upper revs.

I have had bypassed the fuel filter with the same results, so it's not from the filter or filter case.

Next suspect could be the fuel pressure regulator on the HP pump?

Also consumption increased slightly. This issue is active with full and near empty tank

Open to more ideas...

Carry out a leakback test on the injectors, and don't bypass the fuel filter ;)

If you suspect an issue with the HP regulator, then see what the current draw is at idle, the normal figures are circa 650mA.

Brian :D

I know that was a risk movement, but was only some seconds to discard problems from there.


Will try to make the current draw test, the injector readings were mormal, not much compensation or differences, arround 0,12 and 0,32 on best ans worst one, not appear bad figures.

Seems like the pressure regulator is not regulating the pressure.--:shrug:

Worth checking & indeed changing the regulator O-rings cheap fix link below.

https://www.ebay.co.uk/itm/BMW-530d-...1/333148956531

Just dismantled the fuel high pressure regulator and not seemed quite clean:


https://i558.photobucket.com/albums/...pscrt5n3fa.jpg



Also, there is some wear on the down side, perhaps by resonance?


https://i558.photobucket.com/albums/...psspvcgtdz.jpg




Also expected a big o-ring in the insert, and was empty, should not be one?

HI Javier.
Yes it looks like the nylon O-ring is damaged, some do not have the large black O-ring, the replacements do and I always fit them, as above purchase the O-rings to fix ;)