Engine/Transmission (1998.5 - 2002) Help with WOT (full fuel) response.

[moparguy]

A friend has a 2000 5 speed we've enhanced a bit; 4" exhaust, FASS fuel system, EdgeEZ, full gauges, 275 RV injectors, and BHAF.



It runs great with one exception, if you give it full fuel, it's kinda "blah", let up on the pedal a bit and it pulls great. No egt problems and great power... . once you back out of the fuel a bit.



It's kinda like a gas burner with a carb that's a little big or the accelerator pump isn't working.



The following has been tried in an effort to identify and eliminate the problem; different VP44, clean MAP sensor, replace crank (or was it cam) position sensor and last of all, change out the Edge EZ.



Fuel pressure does not go below 13 psi, or above 17.



So, anyone have any ideas?



Thanks, RJR

 

[fox]

I think you need to check the APPS. (throttle posision sensor. )

I bet its got a flat spot.

 

[moparguy]

Fox, in rereading my post I see that I failed to mention it, but that was my first thought as well. I don't recall if he did a swap with another truck or just bought a new APPS, but that wasn't the culprit.



Thanks, RJR

 

[moparguy]

ttt

 

[CEkstam]

moparguy,



If you will look at the dyno results posted by Hammer on the "FASS dyno results" post, page 1, you may see why you are experiencing "blah" performance at WOT. Because the FASS, as admitted in state court, was designed by altering the blue prints to the Fuel Preporator (Note: old style Preporator), I, as the registered inventor and patent owner of the Preporator, have personally inspected and tested the FASS to see the variations in design and to understand the performance variations of that system as compared to the Preporator. Given the pressure flows that you are operating under and the higher operating pressures at 'WOT', the pressure regulator/return flow check valve is probably closed to the point that most, if not all, flow from the FASS is passing to your engine and little if nothing is returning (air/vapor included) to your tank through the return line. The pump on the FASS has a higher flow rate than your original LP and therefore cavitates at a greater rate producing more vapor than your original LP. This potentially increases vapor flow going to your VP44 at the 'WOT'. The increased level of retarded injection timing that follows could be the source of the "blah" performance you are seeing at 'WOT'.



Hope this helps,



Charlie

 

[pgleavitt]

Question for the preporator

I have close to the same set up as Moparguy. I run the Fass at 9psi and at wot it only drops to 8psi. I don't have the problem he has. Mash the pedal and full power. Would the lower operating pressure be the cure?I was just getting ready to install a 17psi bypass spring. Thanks in advance.



Pete

 

[CEkstam]

PLeavitt,



Probably, yes. However (I hate it when somebody answers a question and then says however, don't you?), anyway as the fuel filter plugs the return valve pressure regulator will begin to close and the problem can/may again show up. Unfortunately, this can happen so slowly you may not even notice it.



Good luck,



Charlie

 

[Murle]

I have about the same setup and at WOT she justs wants to climb and climb. No drop in power. Could it be the quality in your fuel.