Hardwiring that pump will overrun the FPR at idle. It needs to have a dual voltage rewire, not a hard wire. Redo that and go from there.

 

I'll get that going and see if it helps. Do you think you could pm me more info about that rewiring? Not sure exactly how to go about a dual voltage rewire.

 

I'll post it here so people can find it.



1. Return your fuel pump wiring to stock.
2. Obtain a hobbs switch. Anything from 0-7psi will be fine.
3. Wire up the rewire kit you bought so that the hobbs switch activates the relay. Preferrably the hobbs switch will control the ground (pin 85).
4. Plumb the Hobbs switch into an intake manifold reference line.
5. Wire pin 30 to the battery.
6. Run a wire from pin 87 and splice it into the fuel pump power wire as close to the plug as possible.
7. Wire pin 86 to a power source controlled by the ignition switch.
8. Cut the fuel pump ground wire from the factory harness close to the plug at the fuel pump sending unit and run a new 10ga ground wire for the fuel pump.


What this does is maintains the OEM dual voltage setup. The factory wiring even goes to high voltage at the same point it would as if it were stock. Then when the hobbs switch activate, the pump is able to draw directly from the battery through 10ga wire, so it has plenty of juice as the load on the pump goes up.


And you will want to drill the siphon out to 7/64 or 9/64 so that the return line can flow more.

 

Post #121 from mrfred also explains it. Makes it a bit more simple...lol


https://www.evolutionm.net/forums/ev...l#post11183124

 

Just an update for anyone who may experience this issue in the future and finds this thread: The misfire instantly went away and the car is running fine on a base tune after I rewired the fuel pump. I don't even think the wiring diagram is necessary, just don't over complicate it. My new fuel pump is installed but is wired in the same way as the stock one was, just install it, and crimp the new power wire to the factory wire. No need for any of the extra wiring, fuse or relay (unless you want it hooked up to 14v constantly, that's for very high horsepower cars, in which case you probably already know what your'e doing.)

 

The OEM wiring will not support the walbro 450. You need to add in an additional circuit as described in mrfred's thread.

 

Will it not work even with the 400? It seems to be running fine but I have yet to really push the car.

 

I'm still confused on the wiring then, I,ve seen so many examples of Evos here without mention of this switch, but have seen that the rewire allows for more power to be made. I've also seen things such as the fuel lines being upgraded. From where I am now, what else should I do to make the most power from my setup? I'm headed to the dyno to get tuned a week from today.

 

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