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Fuel pressure regulator

Posted: Thu Jun 13, 2019 5:58 pm
by Tamos
Am almost ready to start engine so put some petrol in tanker and ran pump to check for leaks. All seemed ok but a bit later I noticed wet patch on floor. Inspection revealed a very slow drip coming from the breather pipe attached to the top of the pressure regulator. Maybe it will sort itself out when the engine is fired up, it has also been suggested that the regulator is faulty but that I can simply plug pipe without affecting running. Any thoughts?
Attach pic that was taken before engine installed to show type and positioning of regulator.
F8401B86-BDDF-4838-A81A-3365285B7E0E.jpeg

Re: Fuel pressure regulator

Posted: Thu Jun 13, 2019 6:55 pm
by Richard and Pat
Well that is well tucked in there Tony, I don't recognise that pressure switch at all. Needs someone with more experience than me.

Re: Fuel pressure regulator

Posted: Fri Jun 14, 2019 7:31 am
by jtdesign
For fuel injection systems the port on the top of a regulator is to provide the reference pressure for its operation. Often connected to the inlet manifold (on a car) for the Guzzis it just goes to atmosphere. If there is petrol coming out of it then there is a fault in the regulator, probably a perforated diaphragm.

John

Re: Fuel pressure regulator

Posted: Sat Jun 15, 2019 1:57 pm
by Tamos
John, thanks for info. There is very slow drip from “breather pipe” but if it only goes to atmosphere would it still work if I simply plugged the pipe?
Cheers, Tony

Re: Fuel pressure regulator

Posted: Sat Jun 15, 2019 10:31 pm
by jtdesign
Hi Tony.
If the regulator is leaking then plugging the reference port will lead to a build-up of pressure wth the result that the fuel pressure will increase above the required 3 bar value.
Looking at your photograph I can't make out the port arrangement on the regulator but if it has only two main ports (plus the reference port) then the pipe that comes up the bulkhead towards the camera should be the fuel return to the tank, and the feed to the engine should be tee'd off between the filter and the regulator. These regulators work by releasing excess pressure fuel (above 3 bar) back to the tank. If there is no tank return then the pump pressure will be very high and all sorts of things will start to leak.
Apologies if this doesn't make sense as I don't recognise the regulator model and can't clearly see where all of the piping goes, but it does look as though you've configured the regulator in line with the feed to the engine rather than in the return to the tank.

Hope this helps a bit, John

Re: Fuel pressure regulator

Posted: Sat Jun 15, 2019 10:33 pm
by jtdesign
Forgot to say that if you're running a low pressure, carb system then please ignore all of the above.
John.

Re: Fuel pressure regulator

Posted: Sun Jun 16, 2019 8:28 am
by Tamos
Hi John,
Really appreciate your info. The regulator is std type fitted to Cali EV between 1997 - 2000. It has 3 main ports (plus the breather on the top), the one on the underside being the return to the tank with the horizontal ones being the supply from the filter and the feed to the injectors.
As I have the return to the tank the pump pressure should be ok so hopefully won’t do any damage if I try starting engine with the breather pipe plugged. If this fails will have to source suitable aftermarket regulator - will then regret fitting existing regulator in such a “clever” position.
Thanks again, Tony

Re: Fuel pressure regulator

Posted: Sun Jun 16, 2019 9:20 pm
by jtdesign
Hi Tony,
it sounds as if you have got it all plumbed correctly. The two ports on the regulator for filter and engine will be connected together in the regulator.
I really think you will struggle if the breather is plugged - the fuel pressure will rise and the engine will run rich. Will be OK for a trial run (leave the breather open and catch the drips) but look for a replacement before finishing the car.
I think replacement Cali regulators are hard to find but there are generic fuel injection regulators on ebay for not very much - you will need a pressure guage to set the 3 bar fuel pressure.

Good luck with your build, John

Re: Fuel pressure regulator

Posted: Tue Jun 18, 2019 6:03 pm
by Tamos
Hi John,
Will try starting with “plug” out. Will then buy aftermarket regulator. There is one called a PR159 which is similar to existing with same ports and costs about £80. Most others don’t seem to have a return to the tank so are presumably not suitable.
If anyone can recommend a type that will work, would be appreciated.
Cheers, Tony

Re: Fuel pressure regulator

Posted: Tue Jun 18, 2019 8:56 pm
by EricStarmer
Hi, Tony - you may find this link of some help

https://wildguzzi.com/forum/index.php?topic=70628.0


Good luck

Eric