Jaguar Repair: My 1984 XJ6, fuel vapors, intake horn

Question
Howard,

I haven't had a question in a while as my XJ6 has been running so well, so well that I'm doing nit-picky kinds of things such as painting my air intake horn, filter housing and elbow, cleaning hoses and clamps, etc. Then, I found something I hope you can shed some light on. I opened the throttle body butterfly by hand, and peered in with a flashlight, and spotted a puddle of fluid. A paper towel wrapped around a long screwdriver revealed this fluid is brown, and smells of gasoline. Should that be there? Why, or why not? I have no issues of running or drivability, fuel economy (according to the trip computer) approaching 17 MPG. Is this normal?

Thanks!

Answer
Hi Michael,

It may not mean anything to find puddled fuel in the intake manifold as the intake manifold on a series III XJ-6 is not well designed and will condense fuel vapors and have wet fuel from the cold start injector. If you check it just after a recent start up and the engine is cold.

If you run the engine on a long drive and shut down quickly and remove the throttle body assembly you will probably not see much if any fuel. If you do you may have one or more leaking injectors as there is some fuel pressure left in the rail when you shut down and if one or more injector is leaking it will puddle in the manifold and this includes the cold start valve.

It depends on your driving habits but 17 MPG is low for highway driving. You should see about 20 MPG highway and 14 to 17 city.

The trip computer is not a reliable method of checking fuel mileage. Fill it up on the left tank at a specific pump and drive straight down the highway for a known distance (mile markers) about 10 miles and return to the exact same pump and fill up again to see how much you used and then you will know a more accurate mileage and you can compare the mile markers with your trip computer. A different tire then original will give you false readings too plus the error of the trip computer.

Howard