What pressure must you measure from the fuel pump before the fuel regulator of a sierra cosworth 4x4 at idle and when driving?

And if you want to install a fuel pressure gauge for in-car reading, which fuel pressure is better to monitor, that one from the fuel pump before the fuel regulator or the fuel pressure at the injector rail after the fuel regulator? And why one or the other?

 

Sure it's 3.5 bar with the pipe off and 3 bar with it on.

 

Thanks, but that's after the fuel regulator at the injector rail. I like to know what the pressure should be before the fuel regulator directly from the fuel pump.

 

if you mesure it should be 3,5 bar without vakuum at the fuelrail BEFORE the regulator.

 

Horlicks, the pressure will be higher by quite a margin, the regiis there ot ensure that enough pressure is ther when you suddenly boot it and also to give a known pressure so that the relevant injector phase opening time can occur to deliver enough fuel.
If it was 3.5 bar from pump it would drop a lot upon WOT, albeit maybe breifly but enough to do damage, the reason they use a regulator and not do without, which they could if it just ran at 3.5 bar alll the time !!.
You need to measure at the rail as this is the one that matters for your engine, it it was 1,000000 bar before it would not tell you anything or matter, as it is regulated to 3.5 bar , so long as you see correct amount you KNOW PUMP IS WORKING OK, and that the reg is working ok.
tabetha

 

Well said tabetha great explanation, i had it on my mind but sadly couldnt word it

 

I don't say a lot but when I do - it's usually shit, ha ha know what you mean though!!
tabetha

 

Thanks for this very clear answer!

Now I know how to install the fuel pressure gauge the right way!!