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Thread: XJR lacking performance

  1. #61
    Senior Member jerry's Avatar
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    Fuel pressure shouldn't be as high as 70psi When I tested mine at Idle with a pressure guage attached it was about 55psi and that seems to be about the norm. Unless somebody knows different.
    Jaguar X350 XJR Freeflow SS Exhaust. / Jaguar X308 XJR

  2. #62
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    Quote Originally Posted by jerry View Post
    Fuel pressure shouldn't be as high as 70psi When I tested mine at Idle with a pressure guage attached it was about 55psi and that seems to be about the norm. Unless somebody knows different.
    The figure should be relatively easy to dig out of a manual somewhere.

    Obviously, above or below the figure is bad and at some point fault codes will be set, too

  3. #63
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    Mine is 380 kPa/55 psi at idle as well
    The jag tech guide notes that fuel rail pressure varies between 3.8 and 5.0 bar (55 to 73 psi)
    I'm sure I've read that WOT fuel pressure should be around 70 psi.
    Regards

    Chris
    1992 XJS 4.0 coupe red 80,000 miles
    2003 XJR black 83,000 miles

  4. #64
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    My pressure jumped like that when my #5 fuel injector failed. But it also registered a code. With yours bouncing around like that it makes me wonder if the injectors need a good cleaning. Have you run any type of cleaner in the fuel lately?

  5. #65
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    And just a heads-up, 55.7 psi is the highest I've recorded at the ODB port since I replaced injector 5. Regardless of how I'm driving it. It has less than a 1.5 psi variance.
    I'd run some Sea Foam cleaner with a ½ tank of fuel and then change the filter, again... Assuming you can get Sea Foam. Love that stuff, saved me from carb rebuilds on more than one Motorcycle and/or vehicle.

  6. #66
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    Here's a link to my ODB data:
    https://docs.google.com/spreadsheets/d/1SLCu7kgcGeHzmK-y0hl3MReyJaVjAPuS9IrjXxsIdgw/edit?usp=drivesdk

    The baseline isn't as accurate as I'd like. It took me some time to dial in the numbers for the advanced settings in Torque so things like the Effecíency Numbers would be as close as possible. The yellow is just a DIY CAI added. You can see when I changed that injector in the data.
    Mine is reading lean right now which is probably the filter. Going to try changing that later today. I'm doing the exhaust on the 3rd, Wednesday, my next day off.

    If time allows, we plan to first swap the rear mufflers for the Flowmasters and then get a WOT reading. Then move forward and take out the guts of both cats and get another reading at full throttle. Lastly and depending on the exhaust note, we're replacing the center resonator with an H-pipe an doing a final run.

    If you look at my numbers you can even tell if I'm running up or down hill based on the load, throttle, and speed. 77-79 mph the cruise is set.

    Hope to have new data by week's end.
    Last edited by Hillbillyhydroanvinyl; 30-06-19 at 11:25. Reason: Add link

  7. #67
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    I have really made any progress on this been distracted by my other car project.
    I have managed to test that wiring to the pumps at least is good and they have voltage.

  8. #68
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    Does anyone know how to test function of fuel pressure sensor I have the pin out test procedure, but over complicated and can't find the connection 73 which the sensor goes back to. Online there is generall test procedures to test 3 wire systems. However I would first need to identify what the 3 cables on the jag are.

  9. #69
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    Progress. I have just pulled both pumps from the tank and reinstalled my original pump motors. Result. Car starts and runs. Fuel pressure between 54 and 56 psi. I haven't test drove it yet as ran out of time. The new pump motors fitted by mechanic look identical but have different codes. So I assume the output was different. I will give an update as to what I have learnt about part numbers at some point.

    Removal of pumps is fairly easy. If
    Anyone knows the part numbers of the seals round the top of the pump housing. It would be helpful. Mine had gone a little baggy. Hope they have sealed ok

  10. #70
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    Quote Originally Posted by Martynxjr View Post
    Progress. I have just pulled both pumps from the tank and reinstalled my original pump motors. Result. Car starts and runs. Fuel pressure between 54 and 56 psi. I haven't test drove it yet as ran out of time. The new pump motors fitted by mechanic look identical but have different codes. So I assume the output was different. I will give an update as to what I have learnt about part numbers at some point.

    Removal of pumps is fairly easy. If
    Anyone knows the part numbers of the seals round the top of the pump housing. It would be helpful. Mine had gone a little baggy. Hope they have sealed ok
    That's great news
    So maybe the orignal problem was the fouling on the electrical plugs that you found
    The part number for the gasket is XR85049
    Regards

    Chris
    1992 XJS 4.0 coupe red 80,000 miles
    2003 XJR black 83,000 miles

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