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As part of my efforts to diagnose my non-running 1997 XJ6, I decided I really needed to get an accurate fuel pressure reading from the system. So After examining the situation and finding no good way to connect a pressure gauge into the system, I looked carefully at the fuel rail and decided to drill and tap a hole to a 1/8 NPT thread size. I will then install this modified fuel rail onto the car in place of the original one that is currently in place and then connect up my fuel pressure test gauge into this tapped hole.
See photos for the location and position of the tapped hole and installed pipe plug.
I drilled a hole in the FPR on the fuel rail fitting side on one of the hexnut flats . As the engine is running you should see 43 PSI and bumps up to 47 PSI on throttle up .
Last edited by Lady Penelope; 02-24-2018 at 12:27 PM.
Depends on the condition of the check valve in the tank in some versions of the X300 . Mine stays pressurized for days . You would probably want to soldier the fitting in your installation as you don't want to torque it down too much to ensure no fuel lake on top of the engine . That was a consideration as I made my tap off fitting . The seals on the injectors are V something and available on Ebay but they may not be the real thing . The seals come with basket filters for the inlet side of the injectors . You can thoroughly clean the injectors in the following Youtube video with some X chemical found in brake clean . The injector electrical connector is the same as the trunk dome lights so you can barrow them .
Tinkered with a setup other then the one in the video . My setup rig failed as the epoxy didn't hold it together and will get back to it later as I paint the fuel rail . MEK is what you are looking for , not sold in California .
I cleaned my injectors with a similar method and it worked very well. I used a length of clear tubing that fit over the upper end of the injector. Stepped down with a few more tubes until it was the size of the little red tube in the aerosol can of cleaner. They went from sloppy spray patterns to nice consistent well atomized patterns. none dribbled.
I actuated the injector with a wall charger with a barrel plug. Put the center on one prong and tap the side on the other prong and it fires.
You can get new screens for the injectors and pull the old ones with a sheet metal screw. My screens were gunky.
Its a shame Ric you never checked the forum initially, especially under the heading "Anyone fitted a fuel pressure take off point to their fuel rail" 2016.
My post 13/4/2016 especially gives you a much simpler & perhaps safer method off attaching a fuel pressure gauge.
Simply cut the rubber hose leading to the fuel rail, insert an easily obtained fitting with 5/16 barbs each end & a 1/8 npt fitting to screw the gauge into.
Leakproof & drama free on my XJR over 3yrs.
Its a shame Ric you never checked the forum initially, especially under the heading "Anyone fitted a fuel pressure take off point to their fuel rail" 2016.
My post 13/4/2016 especially gives you a much simpler & perhaps safer method off attaching a fuel pressure gauge.
Simply cut the rubber hose leading to the fuel rail, insert an easily obtained fitting with 5/16 barbs each end & a 1/8 npt fitting to screw the gauge into.
Leakproof & drama free on my XJR over 3yrs.
John Herbert
I didn't install that. I think it will leak and be an issue...thus the keep a fire extinguisher handy comment.
Jensen Healy I think your mod is potentially dangerous. I believe the method I used is much safer.
I fitted a tee between the feed hose and the fuel rail, with a hose leading to the pressure sender mounted off the engine where it was safe from vibration (actually used an existing bolt on the throttle cable servo). Unfortunately no photos of it fitted.
Using an electric gauge meant I could safely fit it where I could see it inside the car while the fuel under pressure was kept safely in the engine compartment.
The downside to this method is that the plastic fuel rail and injector cover did not fit over the tee without modification.
I admit it was difficult to find a tee with the correct threads and seal form.
I'm a really cheap guy so I used a $ 5 tire pressure gauge from the discount bin at the auto part store . Certainly not a permanent installation as the device may not be fuel resistant and leak but it gave me the information I needed . It didn't leak . Drilled into the FPR as those are easily available vs . a fuel rail . I never could find a T for professional hardline setup . John Herbert's setup I never thought of and looks promising as a permanent setup . Cleaned that nasty looking fuel rail with a scotch bright and painted it . Will need to find a replacement rail as the original rail has deep tooling marks and they installed it
pre bent .
The fuel rail is far more fragile than one might expect, as some have experienced here. I've removed several from wrecking yards and in my first attempts dented them without hardly trying.
I've thought about adding a fuel pressure gauge, or at least a port, and my preference would be to take a salvage supply line and fuel rail to a hose shop to either find the correct tee or make a hose with a port.
BTW, certainly can appreciate the DIY approach to cleaning the fuel injectors, but also keep in mind that most services only charge about $15-20 per injector for a cleaning, test, flow check and replacement of screens and o-rings. No doubt the DIY approach is still cheaper, but just something to consider.
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Last edited by al_roethlisberger; 02-26-2018 at 07:35 AM.
This is what you need guys -https://www.ebay.com/itm/BLack-Fuel-Pressure-Gauge-Fitting-5-16-Barb-to-Gauge-Port-to-5-16-Barb-/152887186986d
Makes the job very straightforward & a reliable outcome.
Why struggle with other avenues ? The gauge can be left installed in the engine bay & is always there & available when required.
Jensen Healy I think your mod is potentially dangerous. I believe the method I used is much safer.
I fitted a tee between the feed hose and the fuel rail, with a hose leading to the pressure sender mounted off the engine where it was safe from vibration (actually used an existing bolt on the throttle cable servo). Unfortunately no photos of it fitted.
I admit it was difficult to find a tee with the correct threads and seal form.
YES! This was the exact problem. I was NOT able to find any match for the ball & socket type of connection on the fuel rail. If you can tell me where you found this T with the right connections then I would gladly change over to that instead. Also I did not intend to leave a gauge connected all of the time. My intention was to only have a gauge attached when I am troubleshooting. When not in use for troubleshooting my intention was to have the 1/8 pipe plug installed with appropriate sealant.
To be clear I drilled this hole in a spare fuel rail I had lying about. I still have the original unmodified fuel rail that does not have a hole drilled into it.
Looked to be a round ball toilet plumbing fitting I could never find and has to be placed on either end of the fuel rail as that is the regulated fuel pressure .Clean up the inside seat where the injectors install as this is the most critical and hidden area . In doing a leak check place some smooth writing paper under the injectors to see any drips . A paper towel is harder to see evidence of a leak .
If you used your drilled fuel rail you might end up with a smoking hole in the ground....
Last edited by Lady Penelope; 02-27-2018 at 07:51 AM.
Jensen Healy I think your mod is potentially dangerous. I believe the method I used is much safer.
I fitted a tee between the feed hose and the fuel rail, with a hose leading to the pressure sender mounted off the engine where it was safe from vibration (actually used an existing bolt on the throttle cable servo). Unfortunately no photos of it fitted.
Using an electric gauge meant I could safely fit it where I could see it inside the car while the fuel under pressure was kept safely in the engine compartment.
The downside to this method is that the plastic fuel rail and injector cover did not fit over the tee without modification.
I admit it was difficult to find a tee with the correct threads and seal form.
Do you have any idea what size/type "tee" you used? Are there any markings on it to identify what it is so others could buy one? I see some numbers on the tee in your photo, but they are too indistinct when enlarged to make them out.
02-24-2018, 11:42 AM
Drilled and tapped hole in fuel rail
What type and size tee was used?
