Big Top Gt

I just loaded a canned tune from JDM Engineering to support my 05 Saleen (05-0538) with a 3.2 pulley, 39# injectors, JDM GT500 Fuel pump setup.

When I get into boost anywhere near WOT, the fuel pressure falls off. It starts at 30 on the gauge and as RPM climbs, the fuel pressure falls off.

It got as low as 20 pounds on the gauge before the gauge flashed red and I got out of it. (That's a GREAT feature of the Nexus gauges, by the way.)

Does anyone have any idea as to what could be causing this issue?

Thanks,
Alan

hammeron

it appears to be tune related.

i say this because the hardware
(fuel pump) is working, but the
injector pressure does not rise
along with the manifold pressure.

rkozola

I remember reading about someone having a similar problem with the gt500 setup. It ended up being that one of the fuel pumps/fpdm was not working. You can try unpluging both fuel pumps for the fpdms and just turn the key to on which would normally prime the system. Turn the key off and plug the fuel pump in to stock fpdm turn the key to on and ensure you are getting pressure. Turn the key off and unplug the pump from the stock fpdm and plug in the second pump to the fpdm that was added with the gt500 kit. Turn the key to on and ensure you are getting pressure. This procedure will at least let you know you have no problems with the fuel pumps and fpdms.

Big Top Gt

Thanks guys.

RK: do you mean I have to physically pull the fuel pumps or do I just pull one of the plugs off the second FPDM and switch the stock one from one to the other?

The FPDM is less than 5000 miles old. I installed it after I installed my Vortech. Then I pulled the Vortech and stepped up to the Saleen blower on the car now. I stayed out of boost up until I uploaded the tune. The few times I got frisky with the car, I don't remember the fuel pressure ever falling off like this.

I sent a PM to my contact at JDM to see what they have to say. I'd love for it to be as simple as them tweaking the tune.

explict

That was me it happened to.
The harness going from one module to the other had a loose data wire.
the wire was simply not turning on the second fuel pump.
The single pump could easily handle up to 5psi ish, but then would start dropping off.

Big Top Gt

Here's a picture of my wires.

One seems to be either pulled out, or I left it out for some reason or another.

In the picture below, you'll see the white wire loose. It was originally connected to the blurry end of the white wire the instructions tell you to wire into the green with yellow stripe wires.

Is that wire supposed to be part of the white wire to the connector/green and yellow wire junction?

The wires pointed to by the red arrows were, at some point, all attached. The left wire was cut from the top wire. Now the top wire (part of the plastic connector that plugs into the FPDM) is only connected to the green with yellow stripe wires.

hammeron

ok i take back what i said earlier,
this really doesn't look tune related
at all anymore....

here's the wiring diagram for the dual
pumps, maybe it will help you figure
out which wires need to go where.

Big Top Gt

My wiring from the factory isn't showing the same as the diagram above.

If you look at the pins in mine you'll see what I mean.

hammeron

yeah i figured the wire colors might be
different, but i suspect your wires
should route the same way.

explict

Your wires are different from mine.
I had a yellow data wire going from one module to the other. This wire was loose on the second fuel pumps connector shell.

Whipple gives you a whole new harness, plug and play. Did the Saleen kit tell you to wire it yourself? That is probably the difference between our harnesses.