| Fuel Pressure Test |
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When swaping your heads or for some other reason you may run into lean conditions. Here is what you NEED to do to diagnose the lean
condition:
Purchase a fuel pressure test gauge (ACTRON, p.n. CP7818 from Pep Boys) and install it on the Schrader fuel pressure relief/test port.
Make your notes with the KEY-ON/ENGINE OFF, then at idle.
Finally, run some extra fuel line so you can mount the gauge on the cowl to view during a part/full throttle run.
Key-on/engine off: 4.6L should read, 35 psi
Idle: 4.6L should read, 30-35 psi
WOT: 40-45 psi
If you see a dip in the needle or it is below 39 psi @ WOT, then you are running out of fuel. This is caused by few things:
- You have maxed out the air meter (MAF). Let us know the voltage/rpm from the Autotap data. At a certain point, the air flow
across the MAF will max out the meter and the EEC-V will stop adding
fuel. This is very common on supercharged applications (the fmu fixes this).
- The 19 lb./hr. fuel injectors are maxed out, meaning they are at 100% capacity (duty cycle) at WOT (wide open thottle). You will see a drop in fuel pressure with this.
- The stock fuel pump is maxed out creating a lean condition during
load.
- The fuel filter is clogged. I doubt this since others are
experiencing this dilemma as well
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