Anyone tell me if one of these two specs will fit between fuel line and pressure regulator coupling for a fuel pressure gauge install? 6AN or 8AN male/female, coupler/adapter. 1997 XJ6R x300.

To quote my post July 2012 -
I have had a fuel pressure gauge fitted for many years as shown in the attachment with no leaks/problems at all.
You require -
: Suitable gauge with 1/8 npt port connection ( common & easily obtained)
: inline barb connector with 1/8 npt port
You then cut the rubber fuel line leading up to the fuel rail and insert together with the gauge.
You can leave it in place at all times, it allows instant reference when experiencing engine problems.

John Herbert
1996 XJR

whats the PSI reading we should be looking for on a guage?
no idea what pressure this system runs at

The fuel line fasteners are NOT AN (Army Navy) fittings, they are METRIC.

Got it Motorcarman

So tired of sweating an adapter pressure fitting install so . . . one question. Can I fit the barbed T with gauge into the return line (post regulator and after end of rail) and still be accurate?
For peace of mind I'll use multiple EFI clamps.

The return line is not a good idea. The return only contains the excess fuel over and above what the engine has consumed from the feed line. You need to know the pressure available to the injectors, ie the feed line pressure.

this is def on my list of things to do.
especially now after just swapping my fuel pressure regulator.
car had stalled a couple times when stopping. led me to believe the regulator might be at fault.

Thanks all, I post when it's in.

PSI is 43 at idle and goes to 46 - 47 on throttle up , this has to do with the vacuum line attached to the FPR

There was a Australian sourced fitting some time back on an old computer

You have to place the gauge upstream of the FPR ( fwd position ) and not aft ( dumping / return pressure very low back returning to tank )

I drilled a hole to tap into on the FPR fwd fitting but then you sacrifice the FPR

Spud Maat you might consider changing the fuel pump relay as it may have a limiting current ( burnt internal power contacts ) effecting pump performance

The fuel pump motor pins / sockets can be burnt on the motor connector itself be sure to closely examine the sockets

There is an IAC control valve reset / exercise that someone had

EGR valve clean and reads 0 % EGR_ERROR ( EGR valve true position vs. ECU command signal ) as a PID on a live data reader , 0 % is the target but there is some time lag as you throttle around

With your live data reader you may see whole car voltage drop on deceleration ( voltage regulator not responding and maintaining quick enough ) , seen it once before , this can effect ECU precise 5.0 dc feed voltage to the engine sensors if the reference voltage is not stable throwing your sensor values off

No EGR here, iacv reset, swapped out with another, maf replaced, ecu swapped, fuel pressure regulator now also swapped.
will swap the fuel pump relay if problem persists.
hopefully tho no more issues.

voltage regulator may make sense.
I have been thinking that may be on its way out as recently i have begin to get voltage fluctuations with at times the car dipping under 13v.

With the voltage regulator dropping all the way out you will read fully charged battery voltage of 12.75 abouts

You can just change the VR and keep your existing alternator , new alternator issues

The VR is part # IN435

I had issues sourcing a VR from E - Bay vendors more than once and got one from a brick and mortar business that had more skin in the game or reputation to maintain

I had a live data graph ( on a old computer ) of someone's X300 alternator response on engine spool down that does show the proof , The IN435 is supposed to be a fast response to not do this ( stereo bass note draw as another example )

The same behavior can come from a slipping belt or slipping harmonic balancer under different conditions

I got a search engine hijacker in my new computer that prevents me from searching for it on the web