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EFI Hose Connections

Jaguar V12 EFI

Fuel Hose Connections

In general, if you have fuel leaks at the fuel injector hoses, it's time for new fuel injector hoses.  In fact, if your hoses are more than ten years old, it's time for new hoses -- before they start leaking!  This page describes some of the steps in the hose replacement.  Note that many owners will opt to pull the injectors themselves out of the car at this time and replace the pintle caps and the rubber seals as well.  This is also not a bad time to consider replacing your injector harness.  And you might even throw in a spark plug replacement.

The fuel injector hoses on the Jaguar V12 sometimes have clamps, but sometimes they don't.  If they don't have clamps, don't add clamps!  The barb underneath the hose is either designed for use with clamps or designed for use without clamps; if you put a clamp on the type designed for use without clamps, you may just make things worse.  And, believe it or not, the clampless style is less likely to leak than the clamped style.

Reportedly, the very earliest Jaguar XJ-S's in the mid-70's may have had clamps on both ends of each injector hose; it's hard to tell for sure today, since so few of those cars remain in original condition and getting reliable data on historical items that may actually have been grounds for lawsuits is really difficult.  In any case, apparently Bosch, who makes the injectors themselves, figured out around that time that the clampless connections were better.  As a result, for several years in the late 70's the injector end of each hose was a clampless connection while the upper end of each hose required a clamp.  Beginning sometime in the early 80's, the fuel rail also had clampless connections, so there are no clamps on either end.  All of the early H.E. engines were recalled at some point and the rails updated to a type made of square tubing, and all of these have clampless fittings; there should not be any hose clamps on such rails.  Also note that there are usually other clampless connections on this fuel system, such as on the hoses connecting the rail to the pressure regulators.

Pascal Doxarve owns a 1980 pre-H.E. that has clampless connections at the injectors and a fuel rail that requires clamps.  He provided the following picture:

This is a photo of  the "fir tree" style barb on the injector that should not be clamped; the hose is simply pressed on.  There is a dished washer that is put into place first and sits neatly around that bottom step on the barb, but the dished washer doesn't appear to have any useful purpose other than to hide the cut-off end of the fuel hose; it doesn't clamp down on the hose in any way, and in fact can usually be spun around with your fingers.

To replace the hoses, first you must depressurize the rail, which can be done by disconnecting the fuel pump relay in the trunk and starting the car; it'll run for about five seconds and die, at which point the rail has been depressurized.  Remove the PCV piping that goes over the rail.  Disconnect the throttle cable and move it out of the way.  Disconnect any spark plug wires that go over the rail or otherwise get in the way; you can disconnect them at the distributor end where they're easy to get to.  Disconnect the fuel supply and return lines from the pressure regulators.  Then, being careful to catch any spilled fuel with rags, cut all 12 injector hoses between the rail and injector and lift off the rail.  You then can take your time in removing the short pieces of hose from all 24 barbs.  Do the ones on the rail first, since you can sit somewhere comfortable and get practiced on those before tackling the ones you need to lean over the car for.  Also, the ones on the rail are steel and therefore harder to damage; the ones on the injectors are aluminum, so it helps to have the procedure down before you get there to avoid boogering up the barbs.

Suggested removal method:  Cut the hose off right at the tip of the barb.  Then, using a sharp razor knife, "skin" the remaining piece of hose on the barb down one side (making it D-shaped), cutting deep enough to cut through the cords in the hose but not so deep as to contact the ridges on the barb.  When you get down into the dished washer, you'll need to use the point of the razor knife to cut the cords all the way to the bottom.  An X-Acto or hobby knife with a brand new blade is helpful here, and if you can find them, X-Acto makes some claw-shaped blades that work even better.  Make sure the sharp edge of the blade is always pointed away from the ridges on the barb; it doesn't matter if you scratch up the inside of the dished washer, but you want to minimize damage to the barb.

Once the cords are all cut, grab the hose on one side of this cut with a pair of pliers and squeeze in such a way as to pinch the hose but not crush the barb.  When you pinch one side of the hose this way, it will break loose from the barb and tear at the point where you have cut through the cords.  If you've done it right, with a little twist and pull the entire remaining piece of hose will come right off.  If it doesn't, you may need to revisit that spot right down in the dished washer with the razor knife again.  With a little practice, you can get the old hoses off only spending a minute or two on each barb.

Pascal apparently got a little hasty with his, as you can see some damage to the barb itself.  This kind of damage doesn't seem to hurt anything, especially if you clean it up a bit before installing the new hose.  Believe it or not, Palm "cleaned up" a couple of these barbs on his car by merely grabbing them in the deep teeth of a pair of pliers and turning the injector around so the teeth would chew off a little bit of the tip of each barb all the way around.  It may make the barb a bit shorter and not as sharp, but it ensures that it is circular with no notches.

Ken Gray describes another hose removal method:  "I used the soldering iron method cited by somebody on the list.  You poke the hot tip of the iron into the fuel line just above the top barb and push it down the length of the fuel hose and into the seemingly useless cupped washer at the base where you just work the tip around a bit to completely severe the hose.  The whole process takes a few seconds due to the very hot tip of the weller.  You can grab hold of the barbs immediately after hose removal and they are barely warm.  I would not use any other method now as the soldering iron works perfectly without any damage to the barb or internal plastics of the injector.  You do however need to use the correct soldering iron; I ended up using a Weller electric iron which seems to have a temperature control in the tip."

When the old hoses have been removed from the injectors, use a flashlight and magnifier to look down into the fuel inlet on the injector.  There is a screen in there.  If you are not planning to replace these screens, at least make sure they appear clean and that no chunks of the old hose fell in there.  If you're not planning to install the new hoses immediately, use some tape or something to cap off these openings while you work in the area.

The new hose you'll be installing must be suitable for this application.  Don't use regular fuel hose, it's not safe.  "EFI hose" is available at most auto parts shops, and it will work, but better yet you should visit an industrial hose supplier and ask for "push-on hose".  This stuff is designed for hydraulic applications while simply pushed on over barbs like this, and is typically rated at 250 psi or more; the fuel rail on the Jag V12 never sees more than 40 psi.  Push-on hose is typically available in either a smooth-surfaced hose or with a cloth-wrapped surface.  Both have similar specs; apparently the only advantage to the cloth-wrapped stuff is in abrasion resistance.

There are all sorts of weird claims about what size hoses fit this fuel rail -- including from Jaguar itself.  Craig Sawyers says Jaguar lists hose CAC8901/22 for the injectors and describes it as 7.0 mm or 9/16".  I'm sorry, but the only plausible explanation for such listings is that the British use some oddball method to define hose size.  Here in the US, a hose size is defined by the size fitting it is intended to fit -- and the barbs on the rail and on the injectors themselves are 8mm, as can easily be confirmed by simple measurement while the hoses are off.  Here in the US, 5/16" hose (which is sometimes sublabeled either 7.9mm or 8mm) will also work perfectly.  The original hose may look smaller than that, but this is probably because it is old tired hose that has shrunk over the years.

5/16" push-on hose may be a bit difficult to find, since some hose manufacturers only make 1/4" and 3/8".  Weatherhead, however, makes the two types of hose described above in 5/16".  It's not very expensive, only a couple of dollars per foot.

The barbs on the later square-tubing fuel rail on H.E. cars look exactly the same as the one in the injector picture above.  The only problem is that they are upside down, so the dished washers fall off while you're trying to assemble them.  So, you need to assemble in the correct order: with the rail upside down on the bench, set 10 washers in place and push on a 1.75" piece of hose.  Then, with the injectors still on the engine but their hoses removed and the barbs cleaned up, place all 12 washers in place, offer the rail up to them, and push the five rear injector hoses on one bank all at the same time.  Then push the five rear on the other bank all at the same time.  The front injector hose on each bank can be cut to length and installed last.

This photo shows the barb on Doxarve's early style round-tube fuel rail, which has a single enlarged area at the end and a smooth diameter to tighten a clamp down on.  Assembly of new hoses onto this car works similarly to that described above, except that while the rail is on the bench you need to be installing a clamp on each one of these barbs.

You can use an "EFI clamp", which are now available at many auto parts stores, or you can use a crimped collar if you have the tools to install them properly.  You can use the type of spring clamps that are made of flat spring steel rolled into a ring (I wouldn't try the type made of thick wire, though).  If you're careful, you can even use stainless steel locking wire wrapped around the hose two or three times tightly with the ends twisted together.  You should not use a worm-screw clamp; with this size hose, worm-screw clamps provide unreliable sealing and should be avoided for safety reasons.

On the clampless fittings at other places besides the injectors, there is usually a deep cup around the end of the hose instead of this simple dished washer, but the cup is clearly not crimped and can still be spun with fingers.  The only thing the cup does is make it harder to get the old hose off -- probably in an effort to force the owner to pay $$$ for the entire fuel line assembly from Jaguar.  Palm's recommended method: using a hacksaw, carefully cut the deep cup circumferentially, separating it into a dished washer and a cylindrical ring.  Cut the hose off at the end of the barb, remove the cylindrical ring and throw it away, then use the same methods as described above for the injector hoses to remove this piece of hose.  Reassemble with the dished washer portion of the original cup only, making it easier to replace next time.  This is what the hose on the left rear side of the rail ends up looking like:

The barbs on most of the other fuel hoses in the engine compartment are exactly the same size as the ones on the rail, 8mm or 5/16".

The metal fuel lines from the back of the car into the engine compartment are 10mm.  On the supply side (right side) on the H.E. with the square-tubing rail, there is a length of 10mm hose, then an adapter with push-on barbs and deep cups on both ends, then an 8mm hose the rest of the way to the right side pressure regulator.  On the return side (left side), the connection into the fuel cooler is 8mm but the outlet is 10mm, so a larger hose is used from there to the return line.  Both of these larger hoses can be replaced with 3/8" (9.5mm) hose, and since one of the four connections is a push-on barb, push-on hose is recommended once again.

Again, Craig Sawyers says Jaguar lists an oddball size:  CAC8900/11, described as 8.5mm or 11/32".
 
 

 

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