fuel rail pressure

[parkin10]

how long should the pressure stay in the fuel rail for?

i have mpg of around 13-14 miles was thinking that it may be leaking fuel some were very slightly
fuel rail pressure is 3bar and lasts for 20-30 mins
the car is 325 89

and the blue temp sensor works
thanks

[Grrrmachine]

Fuel pressure should last and last and last. If you park up overnight, fuel pressure should still be there the next morning.

On most it isn't because of a weeping or dribbly injector, but if you're losing it in 20 mins, there's definitely a leak somewhere in the system:

http://www.e30zone.net/e30zonewiki/index.php/Fuel

[parkin10]

funny thing is i cannot smell any fuel though

[Grrrmachine]

That probably supports the dribbly injector situation; it's leaking into the cylinders.

The other thing is the rubber fuel hoses might have perished, and the fuel vapour is escaping through the whole pipe, not as a single-point leak, so check them out too.

Normally I'd look at the FPR, but if your mileage is that bad you must have a spillage somewhere.

[parkin10]

i changed the injectors for a new recon set about august time last year
bad starting they cured it

[Brianmoooore]

Clamp off the fuel lines and see what effect that has.

[parkin10]

clamped the line to the rail got 5 bar fell to 4bar in 20mins
cannot see any fuel leaks
its taken me along time to get this motor to run well and now it does it really drinks it

i am only using the car on the school run though
so i not getting the motor hot really may be that does not help my mpg

[clipper]

I only found my petrol line leak after running my fingers along ALL of the fuel lines until I found a wet bit, it was only a hose clip that had jumped a thread from being over-tightened and it couldn't be seen or smelled.

[parkin10]

what size are the fuel pipes?
guess i will have to change all the pipes

[kman82]

How much pressure are you loosing? I think I read somewhere that it is within spec if it looses something like 1bar of pressure after 30 minutes - someone else should be able to confirm that though.

you should be able to work out where you are loosing pressure from by clamping off the pipes at various points rather than replacing them - they are very expensive from bmw!

I had this problem recently and Brian helped no end with this post:

Connect up your pressure gauge, run the engine and switch off to confirm that residual fuel pressure is your problem, then repeat, but immediately after switching off, clamp off the fuel hose that runs from the FPR., and see if this maintains pressure. Repeat again, but this time clamp the hose that goes directly to the fuel rail, before where you've teed the gauge in.
If first test maintains pressure, it points towards a duff FPR; if the second test maintains pressure, the non return valve in the pump is the problem.
If neither test maintains pressure, then one or more injectors are the problem.
All assume that there are no simple leaks.

[Grrrmachine]

http://www.e30zone.net/e30zonewiki/inde ... Fuel_Hoses

[kman82]

the two fuel hoses within the engine bay cost me £50 to replace recently.

I couldn't find that size from a motor factors so had to go to bmw

[Grrrmachine]

I bought mine on ebay for a tenner Genuine BMW stuff, still used in brand new Minis.

[rrs]

Sytec make a fuel injection hose with the correct I/D and O/D, I bought 6m for about £15.

[parkin10]

the two fuel hoses within the engine bay cost me £50 to replace recently.

I couldn't find that size from a motor factors so had to go to bmw

i have to say that every part from bmw costs a mint
i wanted to change the vacuum hose on the servo bmw wanted £22 plus vat i got mine from hoselines for £4 it is exactly the same as what came off

http://www.hoselines-catalogue.co.uk/default.aspx

i am planing to use hoselines for the fuel pipe too