JNorris

iTrader: (4)

The fuel pressure drops with relation to the throttle position. If I go WOT it drops to 50psi instantly.

I am using the stock regulator in the tank and reading the fuel pressure on the fuel rail. I expect to see some drop but not this much.


Thanks

John

Crunch

I had the same problem, and it initially turned out to be that the hose that connects to the in-tank fuel pump came loose. But when we fixed that, the pressure STILL dropped to 50PSI at WOT. I think low fuel pressure is what did my stock motor in. I had a good tune with no detonation and no knock retard. After the rebuild we'll have to revisit this immediatley so this same problem doesn't burn up my brand new bottom end.

joecar

Consider this (is this a feasable explanation...?):

At higher RPM the injector duty cycle goes up
(the injectors are open for higher percentage of the time), and so the pressure will be less since there is less injector "restriction";

The regulator is at the pump and regulates the pressure there (at the pump), but there is nothing to regulate the pressure at the fuel rails (...9 feet away from the pump...);

JNorris

iTrader: (4)

Joecar,

That is something I did not think of! I guess that is possible. How could I test for that?

I have another idea as well. I cut an access hold to get the pump out. I tried to pull some slack the plastic/nylon fuel feed line and it would not budge. Maybe when the car was assembled the fuel tank was installed against this line causing a restriction.


Thanks

John