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Jaguar Repair Questions and Answers

Answer:  Check for fuel pump pressure at the injectors.  If no pressure is present, check for 12-volts at the fuel pump.  If 12-volts are present and the pump does not run, it is obviously the pump.  Replacing it should fix your problem.

Question: 1985 Jaguar XJS V12 mileage: 96,000. Car will start and run sometimes dying right away or might drive 4 or 5 miles before it dies. I have changed the fuel pump and fuel filter (one in trunk), and checked all relays. You can turn the key off and it will start right back up. Sometimes it will run right away and sometimes it dies again. Is there another filter in the fuel system? What else should I check?

Answer: There is only one fuel filter, the one in the trunk. You should check for spark when you experience the no start condition. You may have a bad ignition module or pick-up coil.

Question: 1974 Jaguar XJ12L mileage: 195,000. My Jaguar failed the smog check again this year. The smog check station mechanic said that I need to have a Jaguar mechanic adjust the carburetors (4 carburetors) because the idle HC was 1405 the normal is 550. Does the Jag need carburetor repair/overhaul or just need adjustment of the 4 carburetors gas/air mixture? I can smell a strong odor of gas when I pop the trunk open.

Answer: Adjusting the carburetors may bring the hydrocarbons down to an acceptable level. Make sure the carburetors are evenly balanced so that each one draws the same amount of air. Also, check for vacuum leaks. The strong gas odor when you pop the trunk is definitely something to look at. You may have a rubber hose on the fuel line that is leaking.

Question: 1988 Jaguar XJ6 3.6L mileage: 119,000. While driving up a steep hill on the freeway, I kicked the gas pedal into passing gear and as I approached 70 mph, the engine just stumbled and began running with absolutely no power. I had just tuned the car a few thousand miles ago so I don't think that is the problem. The car starts fine and runs and shifts OK up to about 2000 rpm then the engine just makes a roaring sound like it is sucking air. I checked for vacuum leaks, none. Changed the fuel filter and checked the fuel injection system everything seems to check out. However, while test driving after I had done all this the exhaust transfer pipe blew out. I repaired the pipe and tried a test drive again but got the same results, the engine roars the transmission kicks down but no power. If I try to go up even minor grade hills it won't go over 30-35 mph. It seems to run fine all the way up to freeway speed if I don't accelerate hard but as soon as I floorboard it, it just bogs down. I have tried just about everything in my Haynes repair manual but to no avail. If you could give any insight into what my problem is, I would be eternally grateful,

Answer: Check to see if you have a plugged catalytic converter. This would account for your lack of power problem.

Question: 1986 Jaguar XJ-6  mileage: 200,000. My 1986 Jaguar XJ-6 is quite possibly the best car I have ever owned. I'm now approaching 200,000 miles and the engine shows no signs of giving up. Outside of a new thermostat and regular preventive maintenance, it takes little more than gas money from my wallet. The problem I have recently encountered is a slight shaking noise in the front passenger side when accelerating hard from a dead stop. The vehicle does weigh more than 5000 lbs, only makes this sound below 8-10 mph, and then goes away as speed increases.

Answer: Your car is equipped with a two-piece drive shaft. The center support for the middle of the drive shaft or possibly one of the U-joints on the drive shaft may have failed.

Question: I have a 1987 Jaguar XJ6 series lll and was hoping you could help me with a problem I'm having? When I turn the key to start the engine nothing happens, the engine won't turn over. I tried cleaning the battery connections, I changed the ignition switch, checked the neutral safety switch, and it still won't turn over, the starter solenoid doesn't even click. The lights, radio, clock and all the buzzers work and the battery has 12 volts with the headlights on. If you can give me any help with this problem, it would be much appreciated.

Answer: A starter relay puts power to the starter solenoid which apparently has failed. Locate the small wire on the starter solenoid and trace it back. It will lead you to the relay.

Question:  1971 Jaguar XKE 4.2l  mileage: 29,000.  My Dad has not driven the car in 8 years, it has been in storage.  He was wondering if he could use synthetic oil in the car, or if he should stick with conventional oil.  I think he is concerned there might be detergents in the synthetic oil that might cause oil leaks in the original engine gaskets.  The car is in mint condition, and I look forward to driving it once he's got it back on the road.  Would you advise for or against using the new synthetic oils in a car with this history.

Answer:  If it were my car, I would stick with the conventional oil.   The new synthetic oils were designed for newer cars.  When you get your chance to start driving this classic car, keep a close eye on the oil level.  Older Jags are notorious for going through oil and over heating.   Most of all have fun!

Question:  1997 Jaguar XK8  mileage: 110,500.  While driving my Jag, I periodically hear a noise coming from the front of my car that sounds like a far away horn.  It comes and goes but only after, I have driven it for several miles.  When I shut the engine off, I can hear what sounds like a fan running very fast for a few seconds coming from under the hood.  Is this something that I should be concerned about?  Thank You.

Answer:   Yes.  It sounds like your thermostat is stuck which causes the engine to run hotter than normal.  It would be a good idea to get it fixed ASAP.

Question:  1987 Jaguar XJS V-12 mileage: 70,000.  The engine will not idle down. At an idle it speeds, the rpm's go up and down from 1000 to about 1500.  I have tried adjusting the idle speed on the auxiliary air valve this has no effect on the rpms.  I have checked for vacuum leaks cannot hear any.  Sometimes the car idles OK.  I am new at working on Jaguars.  Need help.  Thanks a lot, Ed

Answer:    Check to see that the throttle linkage and butterflies are not “hanging up.”  In addition, check the overrun valves to be sure they are not sticking; they are located at the front end of each intake manifold.  Be sure the idle mixture is set correctly.

Follow-up:  Thanks a lot, I have checked the linkage, the butterflies and the overrun valves they are OK.  I do not know how to check the fuel mixture.  I am thinking about taking the auxiliary air valve off and checking it.  I can stop up the hole for it in the air cleaner and the engine will idle down, does this mean it is bad or is this normal?  You have to love these Jaguars to work on them, right?  Again many thanks

Answer:    We know what you mean about working on Jaguars – but we love um.  The auxiliary air valve may be your problem.  It is supposed to bleed more air when the engine is cold to maintain engine idle speed.  As the engine warms up, the valve closes down.  However, there is an idle circuit also in this valve that adjusts the idle speed when the engine is warm.  From what you have described, the valve is probably hanging up.  It is pretty common.  If you want to pull it off and test it, you can do it a pan of hot water on the stove.

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