Can anyone point me to, or offer a decent decription of how the 'L' fuel system actually works. I've searched several different forums and I've seen a few differing concepts.

There's 2 pumps - at what point does the 2nd pump kick in and what actually governs it?

What pressures should I see with the factory pumps under idle, normal driving and WOT conditions.


Thanks in advance for any help you can give me.............

Bird

 

Nobody has a clue ????

 

I think they both run at the same time. Your pressures should be in the low to mid 30's at idle and in the mid to high 50's at WOT.

 

there are two pumps, they run at the same time all the time. under part throttle they recive power through the lowspeed realy with a voltage of around 7 volts. this just keeps the pumps cool and keeps them from recirculating unecessary fuel.

at WOT, the high speed realy switches on, and the pumps receive a full 12 volts.

on the fuel rails there is a fuel pressure regulator. it is set to 39 psi from the factory (with the vacuum line off), and is boost referenced in a 1:1 ratio. so for every psi of boost in the manifold after the blower, there is a 1 psi increase of fuel pressure. excess fuel is sent back to the fuel tank in a return line.

the regulator is sensitive to vacuum also. so at idle the psi should be around 33 psi(with the vacuum line on). at wot, the fuel pressure should be 39 plus the amount of boost you run. so if you run 15 psi of boost, the fuel pressure should be around 54 psi. the point of the increase in pressutre is so that the injectors see the same pressure drop across them as if the engine were natuirally aspirated, so they will flow the same amount of fuel they are rated for.

 

Brain - that's EXACTLY what I was looking for -thanks

 

no problem,

sorry for the typos, i was in a bit of a rush