XJ XJ12 ( X305 ) 1995 - 1997

Important - Check Under Your Engine Cover!!

Old 12-11-2018, 02:30 AM
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Default Important - Check Under Your Engine Cover!!

Last week I was making a minor adjustment to the throttle cable. It seemed like there was some slack that I could remove, to get the greatest throttle opening at full pedal travel. But the more I opened and closed the throttle (it's right on top), the more it seemed to bind. Then I decided to take a look under the engine cover, to make sure the cruise control actuator was working smoothly. Well, it was shot. The rubber bulb was shredded and the rod was askew and beginning to bind on surrounding components.

I removed the cruise control rod and found that the throttle worked very smoothly without it. I last used the CC in October and it worked fine, so I did not suspect the bulb was torn open now. The take-away is that it is possible for a broken CC bulb to cause binding on the throttle linkage. Binding is bad, whether it prevents the throttle from opening, or from closing!!

Remnants of the bulb and spring inside it, with vacuum line attached. The rod is already removed. It would extend rearward (to the left) to the throttle pedestal.

But notice the other problem in this photo: the crossover fuel hose between the rails. Normally this hose is not visible with the engine cover in place. The fuel hose is all cracked up. So now, I am led directly into a very important repair, which I took on immediately after researching it in the XJ-S forum! I learned a lot about the issue and also got a good schooling about hose clamps: to clamp... or not to clamp.

The crossover fuel hose is simply pushed onto two barbed metal connectors on the fuel rail. That is true here and for the XJ-S V12 too. In general, the consensus is that a barbed connector should not need to be clamped. This is how the cars came from the factory. I depressurized the fuel system and cut into the old hose. It was dry and brittle and basically fell apart as I worked it off. The nylon braiding was still strong, and it was tough to get the last of the remnants off from the ends under the caps.

The 3/8" bare hose barbs facing each other, all cleaned up.

The new fuel hose MUST be rated for Fuel Injection systems. It is usually rated at least 125 PSI, and also it is a barrier hose to prevent vapors from leaking out over time. This hose costs $5.49 per foot at Napa. This type of barrier hose is REQUIRED for US states that have CARB requirements, as invented in California. For this X305 XJ12, you will need 3/8" hose. The older versions of the V12 in the XJ-S use a 5/16" hose here. I'm unsure which size the XJ81 XJ12 uses.

New rubber in place, a nice tight fit.

But wait, there's more.... take a look to the right of the throttle pedestal in the picture below (right side). There's another crossover fuel hose! This hose is visible with the engine cover in place. Ironically, it appears to be in much better condition than the one hidden under the cover. I assumed they were both ok, Nope! The rear hose looks ok, but must get replaced too. After all, it is the same age as the front hose. It is a little harder to access being so near the throttle linkage.

A topless V12! Right side of picture, another fuel crossover hose resides behind the throttle linkage.

The importance of durable fuel hosing above the engine is obvious. Especially with dual fuel pumps working at high engine loads, the fuel pressure behind even a pinhole leak could be catastrophic. Our X305s are now of the age where neglect in this area could have dire consequences.


I already had a blow-out of the aged oil cooler hose. That was scary enough! It is documented here. Those hoses are difficult to replace, so I had a Jaguar shop do it. These fuel hoses are relatively easy to replace - so no excuses. I'm thankful that a simple adjustment led me to an important repair that needed doing NOW.

The earlier XJ-S also has rubber fuel hoses above each fuel injector. They all needed changing out. May we always remember fondly, the too-many XJ-S that were lost due to unfortunate failures in the old fuel hoses. And of course, condolences for the injuries and losses probably suffered by some owners and passengers.

Many thanks to our predecessors; namely those contributors in the XJ-S section!

Please excuse all the dirt in the valley (the Valley of the Sun, and the Valley of the V12). I have a new set of spark plugs and when I get to that project, I'll return with much cleaner photos!

May we all stay safe and sound in our X305 XJ12s. Let's keep the Last Gens alive and well.

Last edited by SleekJag12; 12-11-2018 at 02:48 AM. Reason: Added info
The following 4 users liked this post by SleekJag12:
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Old 12-13-2018, 12:43 AM
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To follow up, I found that the XJ81 XJ12, and the last gen XJS V12 use the same fuel crossover hoses as the X305 XJ12, 3/8" or 9.5mm. Apparently all the 6.0L cars have the 3/8" fittings on the rails. Part # EBC8269. The originals might be available somewhere, but you wouldn't want to use 20+ year old hose anyway.

I did some research on the SAE ratings of fuel hoses, which is a whole can of worms. Looong story short: the latest standard I found for the correct fuel hose is SAE 30R14T2. CARB approved (USA). Other fuel hoses with ratings such as SAE J30R7 are NOT up to the standards for pressure, resistance and permeation, and don't meet the CARB requirements. The CARB standards generally apply for fuel injection system hoses on all vehicles these days, since many states have adopted the standards and more are expected to follow. Look for the SAE rating stamped on the hose.
The following 2 users liked this post by SleekJag12:
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