2001 Mazda Tribute 3.0 Dura tec....Ford Escape (same thing for the most part)


I had a sudden drop in mileage from 20 city 25 highway to 11 city and 16 highway, and no,... a drop like this is not winter blend fuel. Truck runs great, great power. I've checked output from sensors, looked for a brake hanging up, tire pressure. I had a few times with a ever so slight odor of gas in the cabin, and I did get a CEL for gas cap p0457 a while back. Anyway questions I can't seem to get a firm answer from the Ford Repair CD.


1.) fuel pressure cd states a range 35-65 psi then some place else it says 65. I have 65psi.

2.) The cd says the fuel system utililized is a mechanical non feedback type as opposed to electronic non feedback or feedback types. a.) whats the difference between mechanical and electronic non feedback types?

3.) being the the cd is written for 3 types of fuel systems its a little hard to follow dianostic routines. For example on test says fuel pressure should remain constant (flux no more than 3 psi in driving situations) yet in another test they have you hook a pressure gauge into the fuel rail, drop vacuum by opening the throttle and you should be able to note a difference in Fuel pressure from idle. Which is it? does it stay steady, or should it increase? I know for the feedback type with a rail mounted regulator it should increase from idle.

4.) how is fuel pressure regulated in this system?

is it a fixed pressure from the tank module? (65psi)

is it a variable pressure with a regulator in the fuel tank module?
if so what kind of signal is used to adjust fuel pressure, vacuum, electronic, other? is that the difference between mechanical and electronic?


I have a fixed 65 psi (at the rail), it doesn't change with engine vacuum. This doesn't seem right to me. I think the EEC is trimming it out damn close to its max without tripping a CEL.

What should the FP range be?

 

For anyone watching this thread this is what I found.


mechanical non feedback have a fixed output from the fuel module and do not flux with engine vacuum. In my case 65 psi.

electronic non feedback systems adjust fuel pressure by increasing or decreasing voltage to the fuel pump and operate in a span of 35 to 65 psi. a sensor on the fuel rail detects pressure and also has a vacuum line to check for manifold pressure/vacuum. It in turn relays a signal to a control module which varies voltage output to the fuel pump.

I'm thinking maybe ECT sensor bad and EEC not going closed loop.