Right peeps,
Has anyone come across this wierd problem
concerning the original Weber FPR fitted to
cosworths,i've always found that they loose fuel pressure
within a a short time.i've changed three on my car and when
i connect my mech. fuel press. gauge the initial fuel pump prime pressure
shoots to 3Bar but 2 minits later,zero pressure!.
The only way i've cured this is by squashing the return line briefly
and sending the fuel pressure into orbit,off the gauge's scale so that when i release the pipe,hey presto the fuel pressure stays for hours on end.
Anyone had similuer problems???.

 

If you've done 3 then its probably time to look elsewhere... you checked pump voltage?

Dan

 

And you find that odd ?
They are NOT a pressure accumulator, they control pressure when being faced with a higher pressure they let the excess go so maintaining what they are set to.
They will not, AND DO NOT NEED TO hold pressure for hours, unless you want to run a engine with no fuel pressure ?
I have a brand new RS500 one on mine, and that acts the same, the ecu primes first thing in the morning it would not need to if they held pressure, presumably they do this as the makers know they don't hold presssure ?
The prressure will subside back into the tank through the pump when off due to thie pump design, same as they can run backwards, do this to clear them out as well.
tabetha

 

Is that right?,
Then why if i've changed all three and after blocking the return they ALL work,i.e hold pressure
That would also be true with other fpr's,not only Webers,such as Bosch units such as those fitted to Jetronic equipped cars,the fpr fitted on those cars work in the same way as the Weber units.
The fuel pump is fitted with a non-return valve that should stop fuel returning to the
fuel tank for a while
The pump prime timing on Weber injected cars will no way be enough to fill the empty lines,rail etc you'd need to turn the ign. switch at least 3/4 times to prime the system.
And i still don't understand how the hell after closing the fuel return line on all 3
fpr's they suddenly all work after various attempts.
The same thing happened on my mates Toyota mr2 turbo that had a Weber fpr temp.
fitted in place of the original unit,on the Toyota the fpr is fitted on the Return circuit
and the Weber unit did the EXACT same thing,at first the unit would not hold pressure for nowt,after crushing the outlet returning to the fuel tank it worked,holding pressure for two days...
Faulty non return valve?,maybe,but the chances of having BOTH cars with faulty fuel non return valves seems a little remote.

 

If they had a NON return valve, the NON return of the fuel would mean the pressure had to be there.
It's a bit accedemic when engines are using running pumps anyway, although it has an initial prime, the pump also engages upon rotation of the engine.
tabetha