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  • Fuel Pressure reg

    Tested my pres reg today,not sure if it duff. I thought when the pump primes the pressure reg should be closed? When I primed mine fuel came out of the spill port pipe,not a huge amount but im concerned its not seating correctly. Also when I removed the fuel rail I put a vac pump on it but it did not release a huge amount of fuel.

    I have a brand new montego one the one from the later cars which sits on the end of the round cast bus rail located by two bolts.
    Has anyone got one that is known to work from a car with the square section bus rail where the reg is a push fit on the rail and a screw union to the spill pipe.

    Cheers

    A very hopeful Russ!
    07798 576081

  • #2
    Fuel pressure reg is designed to keep a certain pressure in the fuel rail (above the pressure of the inlet manifold). Its normal for some fuel to come out when you prime the pump. The pump pressurises the rail and then the excess pressure is returned back to the pump. If you turned the pump on continuously then you've get a continuous stream out of the spill port (which would return to the tank). I'm not saying that it isn't faulty but the behavious observed is normal so far. Is the air pipe connecting it to the manifold intact and not leaking? If it leaks then it'll produce the wrong fuel pressure even if the reg itself is perfectly ok.
    www.maestroturbo.org.uk - The Tickford Maestro Turbo Register
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    • #3
      The vac pipe is fine, as you may have realised the flat spot is back Ive set the pot,had my injectors cleaned the onlt thing i havnt changed is the pres reg. I have a felling it sticking as when I had the rail off I held it over a container and operated the vac pump a bit of fuel came out but not a lot ,when I took the injectors out there was alot still in. Also if you crack the inlet union open there is not a lot of pressure. The pump is the second brand new one ,new filter ,fuel sprays out if you operate the pump with the pipe off. So other than the ecu the pres reg is all thats left.

      Cheers

      Russ

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      • #4
        Hi Russ if you just rely on the priming period 2-3 seconds to bring the rail up to full pressure then you will not get a large amount of fuel from the return because the regulator is there to allow pressure to build up in the rail to 2.5bar.

        If you run the pump constantly by turning the ignition on and earth the pink brown wire on the fuel pump relay you will find that the fuel pressure regulatator behaves more like you expect. But the trouble is in just seeing how much fuel is returned to the tank it does not tell you anything useful about fuel pressure, to test the fuel pressure regulator and pump is working correctly you need a suitable pressure gauge.


        With the gauge installed you can easily see what the pressure is at idle (2.0bar later model) (2.5 bar early) and with the vac pipe removed(2.5bar later models) (3 bar early). If you briefly clamp the return hose the pressure should rise to approx 5 bar and no more than 6.5bar.

        You can also check that the pressure is holding in the rail when the engine is turned off. If it is not holding then clamp the return hose, if the pressure then holds then the regulator is faulty.

        If the pressure still does not hold with engine off, then clamp the fuel feed pipe before the gauge, if it then holds the fuel pump non return valve is faulty. If the pressure still drops with both feed & return pipes clamped off, you must have an injector leak.


        Gary

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        • #5
          On the subject of the flat spot I would still be suspicious of water in the tank as it did improve for a while when you fit a new filter.

          You could pump out a few litres and let the fuel stand overnight in a glass vase to see if anything seperates.

          You could also check the throttle pot multiplug connections are clean and tight, sometimes just pulling the plug apart and reconnecting it can effect a cure.

          Gary

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          • #6
            Blanked off the the fuel pres reg today as it was stuck open, took it out for a quick test run. What a difference,no flat spot at all. Ive ordered a new reg and should pick it up tomorrow,84 + vat so not to cheap and no joy with a secondhand one ,but if it sorts the car out its worth it. I'll now have to reset the CO and base idle. At least the pot is ok they are 115+vat Thanks again for your suggestions chaps.

            Russ

            PS Still got the dash to sort....

            Comment


            • #7
              Hopefully Russ you have found the culprit and a regulator will sort out your flat spot.

              It might be me just looking on the black side but blanking the fuel return puts the fuel pressure up to above 60psi, and in doing so can mask a whole lot of other problems. But with any luck I will be wrong and you can then concentrate on converting your dash.

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              • #8
                Its virtually sorted 99% better but not perfect still slight flat spot when driven hard ,I have another idea. When the pump was fitted the union to the pump (its a volvo bosch pump with a different fitting but same spec) it had a pipe that was slightly smaller than the hose. So im going to get a hose with the right fitting on it as it may be restricting pressure.
                Found a very helpful rover parts man this morn. The speed sensor i need for dash is either ybe10037 or drc8154 both of which look like the 820 one i have but without the earth, so if i cant get one of those i may try the 820 one.

                Cheers
                Russ

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                • #9
                  Changed the pipe on the pump today,no difference at all
                  Im really fed up with this now,ive got my ZR booked in at a rover specialist tomorrow, so im going to see if he can sort it as he has some fastcheck gear but hes not sure what.
                  Could the fuel ecu be at fault? The only time in the past ive experienced knackered fuel ecu was one that running far too rich cos someone had sparked the batt pos on the airflow meter.
                  Ive set the throttle pot up perfect but can these fail and give flat spots?

                  Russ

                  Comment


                  • #10
                    Originally posted by Russ
                    Could the fuel ecu be at fault?

                    Ive set the throttle pot up perfect but can these fail and give flat spots?
                    Hi the ECU could be faulty but on the whole they are reasonably reliable, I have never changed an ECU for your type of fault, but you can't rule it out totally.

                    The throttle pot can cause flat spots if faulty but again they are pretty reliable. If the throttle pot is faulty it will show up with your multi meter. Once you have set the initial output setting to 325mv as you slowly open the throttle the voltage output should rise smoothly and steadily to around 5v at full throttle. Bad connections from the throttle pot to the ECU are far more common than actual throttle pot failures.

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                    • #11
                      I got a pot off a V8 rangerover,looked the same except for colour coding but the bloody thing is the opposite hand! Ive just spent the last 2 hours removing another one from a mates scrap XJ40 that fits and works but needs the slots filing out to get the right setting but cant be far out, flat spot is still there
                      on the plus side i got a full set of fast check gear for the efi today so setting the pot is now very easy,im not sure how the ignition one works and I think there is some adaptors missing from the injection one but the pot set up one is there.
                      The only thing I havnt changed on this car is fuel ecu which fast check cant test,im wondering if its worth buying one anyway to keep in the boot as a spare,does anyone know if the one from the early digi dash one is the same as later ones as it may be worth getting one of those. incidently one of the fast check modules i got today is for digi dashes.

                      Cheers

                      Russ

                      Comment


                      • #12
                        Originally posted by Russ
                        on the plus side i got a full set of fast check gear for the efi today so setting the pot is now very easy,im not sure how the ignition one works and I think there is some adaptors missing from the injection one but the pot set up one is there.
                        It is more accurate and gives better results if you use the multimeter to set the throttle pot setting.

                        There should be a lead for the EFI fast check that connects to the ECU harness. Note it has to be the Electronic Fuel injection Fast Check and Not the Fuel Injection fast check.

                        The programmed ignition fast check is simple to use, Plug the fast check lead into the Programmed ignition ECU harness and turn the switch on the fast check to static. With the ignition on the correct response is ign & coil LED's illuminated and all 3 left hand LED'S extinguished, ignore the 3 right hand LED'S at this point. Any different response indicates a fault on that particular circuit.

                        Next turn the switch to dynamic and crank the engine. The correct response is ign & coil and all 3 right hand LED'S illuminated, ignore the 3 left hand LED'S at this point. Any different response indicates a fault on that particular circuit.


                        Originally posted by Russ
                        The only thing I havnt changed on this car is fuel ecu which fast check cant test,im wondering if its worth buying one anyway to keep in the boot as a spare,does anyone know if the one from the early digi dash one is the same as later ones as it may be worth getting one of those.
                        The early EFI ECU is different to the later ecu and won't run your car properly because the injection duration is different, but the later ECU is OK to use with the Digi dash.

                        Gary

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                        • #13
                          Im now 99% certain its electrical, disconected the pot and ran it exactly the same as with it connected. Ive tested the wires from the multiplug upto the main engine multiplug and are all ok, the pot is getting the correct voltage but the ecu is doing nothing with the return information.
                          So ive taken the plunge and ordered another ecu,if its not this at least ill have a spare in the boot.

                          Cheers

                          Russ

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                          • #14
                            Originally posted by Russ
                            . Ive tested the wires from the multiplug upto the main engine multiplug and are all ok, the pot is getting the correct voltage but the ecu is doing nothing with the return information.
                            Have you checked the wires to the ECU plug or just the engine bay multi plug?

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                            • #15
                              Checked both,there seems to be something rattling in the ecu which is not a good sign
                              New one should be here in morning

                              Russ

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