davecosworth

just checked the fuel pressure in my s2 and noticed it is down a bit was just wondering which way i have got to turn the smal allen key on the back of the blck sensor on the metering unit to turn it up, also the car does not like starting from cold some time you have to turn it over and pump the throttle pedal its as if there isnt enough fuel but then other times it will fire up straight away but miss for about 20 second the run great.

MattyRST

How did you check your fuel pressure ??

SafeChav

IS the system retaining pressure over night?

And how did you check it as said?

davecosworth

checked the fuel pressure via a fuel pressure gauage, no it dont i thought maybe it was the one way valve in the pump also i get a missfire some times when its been boosted about abit the engine was rebuilt 600 miles ago

SafeChav

If it doesn't hold the pressure the 1 way valve must be gone

Either that or you have a leak in the main fuel line.

vroooom ptssssh

Suerly the accumulator would go before the one way valve?

If it doesnt hold pressure when the fuel pump is turned off thats what i'd look at.

SafeChav

Accumulator is after the valve.

And the accumulator is only used for the MFI systems because of the opening pressures of the injectors etc, and also works in sequence with the fuel pressure regulator when you switch off to achieve a specific pressure in the line.

vroooom ptssssh

His car is MFI is it not?

It has 2 jobs, one to flatten out any pulses in the fuel and the 2nd to hold pressure after shut off. When you shut off the engine all of the nonreturn valves close & the spring pressure against the diaphragm holds residual pressure.

What do you mean it works in sequence? they both have different jobs, apart from when you shut off, the primary pressure regulator closes and holds the pressure in the metering unit?

SafeChav

Indeed it is there to help reduce fluctuations, its not all about retaining pressure though, EFI cars don't have accumulators but retain pressure.

Read the Bosch manual and you will see about the shut off sequence of the accumulator and fuel pressure regulator.

davecosworth

thanks guys i am going to put a cosworth pump on it now and see if that helps but its weird as i started it todau ater not starting it for two weeks and it fired up straight away, but then other times i will have to hold the pedal down to get it to start the emisions is on 2% has had new plugs new dizzy cap rotor arm all new gaskets when it was rebuilt and it has only done 600 miles since then

SafeChav

Before you splash out on a pump remove the one way valve from the pump and see if you can blow through it, should take a few minutes to do.

I doubt very much it needs a pump if it started today.........

vroooom ptssssh

No, but it is its 2nd most important job and stop talkin EFI were talkin MFI here

SafeChav

Im not talking EFI, all im saying is the accumulator isnt there to keep prssure in the fuel line. You can do that without an accumulator.

Its there because its a pressure operated MFI system and is needed to control the fuel shut off when you turn the engine off, which works together with the pressure regulator.............

davecosworth

what do i need to blow threw the pump. i am still thinking of getting a new one any way as the last engine melted a piston due to leaning out but when the engine was checked after it had been rebuilt and set up the fueling was ok, just dont want to blow another engine.

SafeChav

Well when i took my valve out i could blow through it in both directions, which obviously it should never do! IF you can blow through it its fucked for sure.......