23 replies to this topic

[icklemini]

yeah... measured where?

[Cian 'the pain' MPI]

Im not exactly sure, all i remember him saying is that the pump is not giving enough pressure, or else there is a blockadge but im not convinced its a blockage

[icklemini]

thats why:
- suggest changing the filter...
and
- measure the pressure as it comes straight out the tank..

will know for sure then if the problem is with the pump or not!!!

[Sprocket]

Page 1 in the general data/fuel system section of the Rover MPI/SPI factory workshop manual 5th edition,
fuel pump maximum pressure = 2.7 bar
regulated injection pressure = 1 to 3 bar

Yoru answer is in the text above

SPi = 1bar
MPi = 3 bar

The pump you reffer to is an MPi pump, which will work perfectly OK on an SPi system at 1bar, or the MPi at 3bar, but the SPi pump on an MPi system will eventually struggle at 3bar

[Sprocket]

Could you please explain the last bit sprocket.

Unfortunately your picture does not show which line is the flow or the return?

If you are still using the original MPi fuel flow and return lines, the regulator should be plumbed in after the fuel rail in the return line, with the pump feeding the fuel rail on the flow line.

The in tank pump pushes fuel through the fuel filter, along the underside of the car up to the fuel rail, out of the fuel rail into the fuel pressure regulator, out of the regulator, back along under the car and straight back into the tank. The pressure regulator needs to be the last device in the system after the fuel rail, before the tank. The regulator creates a resistance against fuel flow from the pump, and is what raises the fuel pressure. Adjust the regulator, and the fuel pressure will rise or fall. everything from the pump outlet in the tank to the pressure regulator, including the fuel rail and fuel line inbetween will be at the set pressure of the regulator. The return line (depending on regulator) is usually connected to the bottom outlet of the fuel pressure regulator.

Question. Is this an MPi or an SPi pump? if it is an SPi pump, they don't get along well with a 3bar fuel pressure.

If you have the fuel regulator before the fuel rail on the feed line, this will be your issue, as there will be little or no pressure in the fuel rail, but the pump pressure will be at whatever the regulator is set to.

As for the comments above about workshop manuals and fuel pressures. The part number suggested is an MPi pump which, can be used in the SPi at 1bar fuel pressure, or the MPi at 3bar fuel pressure. It pretty much superceded the SPi pump. That does not change the fact that the fuel regulator in the MPi is a 3 bar set pressure, therefore the fuel pressure is 3bar (differential), not 1 bar.

[Cian 'the pain' MPI]

So i need to have the feed from the tank going directly into the fuel rail and have the regulator after that???

[icklemini]

yes. - as per the standard setup...

[R1minimagic]

The standard MPi regulator is controlled by inlet manifold vacuum i.e. fuel pressure changes according to engine demand. If you just use a normal regulator it will always be a set pressure..

[Cian 'the pain' MPI]

Got it sorted was the fuel pump! So just a few niggles to sort and should be finished on wednesday, thanks for all your input! :)