When I started in on my Lexus/Riemer
air/fuel upgrade, one of the items I would be installing was an adjustable
fuel pressure regulator. Since fuel pressure was now going to be one of
my adjustable parameters, I wanted to be able to measure the fuel pressure
of the system to know where I was and what the magnitude of the adjustment
I was making was. i.e., if I felt that the fuel pressure needed to be raised
a little, I wanted to know where it was now, and then be able to raise
it a given amount. This would allow me to eliminate all guesswork about
how much I was changing the pressure, and whether it was high or low. Along
with the air screw measurements, I could write down my settings in my log
book and make notes of which settings were better than others.
The key to the fuel pressure gauge
installation was to find a way to tap into the fuel rail without doing
too much custom work. One day, when I was at the Toyota dealer's garage,
talking to my mechanic, I was asking him what the threads and pitch were
for the banjo bolt attaching the cold start injector to the fuel rail.
To determine this, he pulled out an SST fitting designed to allow fitting
of a gauge or injector cleaner to be mounted to the rail along with the
cold start injector, to measure the size and thread pitch. Well, I didn't
even know this fitting existed!! I thought, damn! That's exactly what I
want. All the sudden, the job got a lot easier. The fitting had a standard
12mm banjo bolt on one side and an AN-4 fitting on the other. I went to
a local hose and fitting supply house and had an 18" hose assembly
made up. AN-4 fittings on each end and Teflon hose with stainless steel
braided sheathing. I also bought a 45 degree adapter which was AN-4 to
AN-4 and a female 1/8 NPT to male AN-4 adapter. The latter was to adapt
to a standard gauge, which had male 1/8 NPT threads on it. Finally, I went
to a local speed shop and bought a fuel pressure gauge made by Marshall, which
was oil filled (almost).
The Toyota part number for the SST
fitting is 000TG-01252
Installation was very easy. The 1/8
NPT pipe threads require Teflon tape to seal them. The rest of the AN fittings
just get tightened, not too tight or they will distort and leak. I replaced
the banjo bolt attaching the cold start injector with the new fitting,
mounted the 45 degree adapter and then mounted the gauge assembly. The
gauge itself is mounted to the fenderwell with a couple of large black
wire ties. Nice and simple.
Now I know what the fuel pressure is
and can tell if it is still in adjustment. It should never change, but
since it is now a variable in my system, I can always tell what it is.
