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Jaguar XJ-S Throttle Linkage Safety Shield

Jaguar XJ-S

Throttle Linkage Safety Shield

There have been a couple of reports from XJ-S V12 owners that the B bank throttle linkage pullrod can get fouled by the low pressure freon hose from the firewall to the fuel cooler.  In the worst case scenario, the driver floors the throttle and the resulting torque twists the engine on its mounts, shoving the linkage up into the hose and jamming it wide open.  Ungood.  This problem may be exacerbated by a failed motor mount.

The obvious solution advocated by some is to tie the hose to the diagonal brace, which should hold the hose up and out of the linkage.  There are a couple of problems with this solution, however.  First, if the problem is the engine rising up rather than the hose dropping down, tying off the hose won't help.  Second, the engine will be moving around on its mounts but the diagonal brace won't, so tying the hose down may stress it.

The book now contains a diagram for fabbing a simple sheet metal shield that should keep the hose and the throttle linkage from ever meeting.  Here is a picture of such a shield installed on Kirby Palm's '83:

Low pressure freon line arching over throttle linkage

That's the device in question to the left of the far end of the throttle pullrod.  It is bolted down under the heads of the upper two bolts that hold the fitting assembly to the rear of the LH intake manifold.

The term "shield" may be misleading in that this device doesn't actually sit over the throttle linkage.  It sits about an inch aft of the linkage.  However, it effectively keeps the hose from fouling the linkage because the hose won't bend sharply enough to go over this plate and down into the linkage.

Note that this may not be a typical arrangement.  Palm had new hoses made up, and in the case of this particular hose he changed the configuration a bit.  The fitting that connects to the fuel cooler -- to the right in this picture -- was originally a 45° fitting, but he went with a straight fitting.  The fitting at the other end (not visible) was originally a long 45° fitting and he went with a standard (short) 45° fitting.  Finally, the overall length of the hose was reduced by about 1-1/4".  The end result is that this hose fits a lot better than the original did -- but your hose may not be sitting in the same place as his.  If yours crosses the throttle pullrod more than a couple inches closer to the centerline of the car than Palm's, the design of the throttle linkage shield may need to be revised a bit.

There are a few unrelated things of note in that photo.  That black box in the foreground is the famous Lucas AB14 CEI ignition amplifier, which has a common GM ignition amplifier module hidden inside.  This is the ignition system of choice to have on the Jaguar V12 -- no excessive proclivity to get cooked, excellent performance, cheap to repair.

That brake fluid reservoir is from a Mitsubishi.  It is connected to the master cylinder by a conglomeration of red hoses with reducers, necessary because the fittings on the Mitsubishi reservoir are larger than the connections on the Jaguar master cylinder.

The fuel hose in the foreground has been replaced, and replacing involved cutting off a cup surrounding the push-on hose fitting and reassembling it with only the dished washer end of the original cup.

Partially obstructed from view is a blank-off cover where the cold start injectors were originally intended to go.  The cold start injectors were deleted from the H.E. somewhere along the line, and sometime later they ceased drilling the holes at all so these blank-off covers could be omitted.

The OEM cam covers are painted black.  Palm's cam covers have had the paint removed so they appear as bare aluminum.


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