89 XJS WONT STAY RUNNING....ANY SUGGESTIONS WOULD BE HELPFUL

Hi Harold,

Doug mentions that your Cat might have more than one issue clouding the diagnosis; one particular problem is the coolant temperature sensor (driver side - LH drive) towards the front between the AC compressor and the valve cover. Faulty sensors can fool the ECU into running rich - replacing the temp sensor is simple with an extension socket - and a cork plug to prevent coolant from escaping - foi course the engine must be cooled down with not pressure in the coolant system).
Be careful removing the thin spring retention wire (whatever it is really named I do not know) and then the electrical connect will pull right off. Look for the wire lead with the tag "water" I thnk?

Good Luck!
Dwight

my suggestion was the ecu has no vacum from the manifold

By any chance have you resolved this issue. My 89 XJS is suffering the same symptoms, Very rich, black smoke, wont idle..Replaced fuel pump,filters/ B bank (drivers side) pressure regulator. checked vacuum line to ecu..ect..ect. All of this steming from my father running it low on gas. ???? Thanks Scott Dumas

Harold hate you are having such problems but to help us help you I think as do others you have to check the fuel rail pressures. The car does not have to "run" you simply need to turn the key on. If the pressure of the fuel is within spec we can eliminate that but right now that is my prime suspect.

never surrender...... just ask for helpppppppppppppppppp

you could also remove.... just make sure the pipe is clear ,you could also disconnect at the manifold and attach a vacum gauge....... a simple fuel pump / pressure gauge tool will do............... you could also attach a vacum pump at the ecu end to the ecu, pump up to about 10 pounds vacum and the car should run / idle no problem............if it runs like this run a new vacum line. note part of the line under the body is steel or some such metal tubing........
good luck once more.......

THANKS ART ILL GIVE IT A TRY BUT HELP ME UNDERSTAND SOMETHING....WITH THE BAD PUMP THE CAR RAN FINE BUT WOULDNT STAY RUNNING...NOW WITH GOOD PUMP ITS RUNNING SUPER RICH AND STILL DIES BUT TRIES TO STAY RUNNING..SO YOURE SAYING WITHOUT A VACCUM SIGNAL TO THE ECU THE CAR WONT STAY RUNNING PERIOD..CORRECT?...I CANT KEEP CAR RUNNING LONG ENOUGH TO CHECK VACCUM SO ILL JUST HAVE TO PULL IT AND BLOW

hey H, pull the hose off the ecu when it is running and ensure there is VACUM there ( just put your finger on the end..)... if no vacum remove hose from intake manifold and try blowing down the hose with your lips. if you cannot blow down there it is blocked........so get compressed air and blow down with the ecu end disconnected..... it is imperative the ecu gets a vacum signal...........do not blow into the ecu.........

THANKS DICK..I JUMPED THE CONNECTOR AND NOTHING CHANGED...THE HOSE ON ECU WAS CONNECTED....ITS RUNNING SO RICH ITS BURNING MY EYES FOR THE LIMITD TIME IT DOES RUN.....IT STILL AT BEST ONLY RUNS FOR A MINUTE BEFORE IT SHUTS DOWN BUT NOW WITH THE GOOD PUMP IT TRIES TO STAY RUNNING ITS JUST LOADING UP!...SO NOW I HAVE TO PUT A FRESH SET OF PLUGS IN IT..ANY RECOMMENDATIONS?...ANY OTHER IDEAS FOR AN OVERRICH CONDITION THAT WONT STAY RUNNING FOR MORE THAN A MINUTE,,,I WISH MY UNCLE GAVE ME THE CAR WHEN MY AUNT PASSED INSTEAD OF WAITING YEARS.......

On your car, the fuel injection temp sensor has a habit of going bad. When it does, the system goes full rich and if it cranks, it will only run for a few seconds. Easy way to verify this is to disconnect the sensor and using a gem clip, cross the two wires in the connector and try cranking. The sensor is located in the water boss on the left front of the engine.

THANKS DOUG AND ART...IM GONNA REPLACE BOTH REGULATORS CHEAP FOR THE PRICE...AS FOR THE VACUUM LINE ILL CHECK IT,BUT WITH BAD PUMP IT WASNT RUNNING THIS RICH.........THE CAR BARELY RUNS A COUPLE MINUTES STILL SO UNLESS THE COOLANT TEMP SENSOR CAN CAUSE AN OVERRICH CONDITION WITHOUT GETTING HOT AS TEMP GAUGES STILL REGISTERS COOL..BUT LIKE WE ALL KNOW IT MAY BE A COMBO OF PROBLEMS...THANKS FOR EVERYONES HELP!...

The most reliable way to test the regulators is by perforing a fuel pressure test....which isn't easy on a V12 XJS because you have to cut into one of the fuel lines to attach the pressure guage. But, still, it's the only way to know for sure if they are doing their job. If you want to do it you'll need to cut the fuel line at the left side of the fuel rail and "tee" your pressure gauge.

Or....you can just replace the regulators. Or, replace the left regulator and bypass the right regulator. The car will run fine with the right (inlet) regulator bypassed.

Many on-line web sites don't list parts correctly for these cars. Seek out a parts outfit specializing in Jaguars: Conventry West, Motorcars Ltd, Welsh Jaguar, etc. The dealer is obvously wrong in this case as well. I'll wager a lot of dealer personell these days have never even seen an older XJS V12.

Besides the vacuum line that Art mentioned there are other possible causes of over fueling....with the coolant temp sensor being a prime suspect.

Cheers

DD

make sure you have NOT disconnected the vacum line to the ecu in the trunk RHS. or it will just run quadruple rich... Art

ROUND 2...IVE REPLACED THE FUEL PUMP AND YES IT WAS BAD!...OBVIOUSLY THE PRIOR PUMP HAD A LIL PRESSURE LEFT IN IT TO JUST GET IT TO START...NOW WITH THE NEW PUMP INSTALLED THE CAR FIRES UP BUT NOW LOADS UP AND DIES!...SO IS THIS NEW PUMP OVERIDING THE INJECTORS DUE TO FAULTY PRESSURE REGULATORS?..THERE IS NO EVIDENCE OF FUEL COMING OUT OF THE REGULATORS WHICH WOULD RESULT IN NO PRESSURE I WOULD ASSUME..IS THE OUTLET REGULATOR PLUGGED AND NOT ALLOWING ENOUGH FUEL TO RETURN CAUSING A HIGHER PRESSURE?..THE PUMP I INSTALLED IS OE......ALSO IN REGARDS TO PRESSURE REGULATORS MOST PART HOUSES ONLY LIST ONE REGULATOR..AND ON THE BOSCH WEBSITE THEY ARE ONLY CALLING FOR ONE PART NUMBER..I EVEN CALLED MY LOCAL JAG DEALER AND HE ALSO ONLY LISTS ONE......ARE THE NEWER PRESSURE REGULATORS BUILT TO DO THE SAME FUNCTION DELETING THE NEED FOR AN INLET AND OUTLET?..........WHAT SHOULD I DO NEXT?..HOPE EVERYONE IS HAVING A GREAT MEMORIAL DAY WEEKEND!

If the fuel filter has rust in it then the fuel pump will have rust in it as well....and that could cause peculiar pump operation...causing the car to run, die, then restart.

I agree that a fuel pressure test is in order....not convenient on a V12 as you have to cut into the hose to attach your gauge....but the hose probably needs replacing anyway :-)

One thing you can do is to pull the vacuum hose off each regulator and see if any fuel drips out. This clearly indicates a faulty regulator. If fuel doesn't drip out it doesn't prove that the regulator is good, though. Only a pressure test will do that.

I just recently finished working on an '89 XJS where *both* regulators had leaky diaphrams and raw fuel was being sucked directly into the inlet manifolds.

You may have a stack-up of faults....not unusual on old cars. Certainly the rust issue will have to be dealt with even IF it doesn't have a direct bearing on the immediate problem at hand.

What's the history of this car? Did the problem crop up over night or ?

Cheers
DD

Harold regulators are different-one for in one for out. EAC6314 (in) and EAC4864 (out). Yes there is a pre filter in the sump (CAC3762) and no they usually do not leak--they fail internally. As far as the backfire and other issues until you have a reasonable belief that you have proper fuel pressure we are in the dark. Might I suggest you visit the JCNA Shoppe on this site and invest in a parts and service manual for your car. They will more than pay for themselves and our prices for members are excellent.

ok george ..i havent been able to find my pressure gauge..so heres what ive found...if the regulators were bad wouldnt they leak fuel and wouldnt there be no pressure when i disconnect the fuel lines?...i replaced the fuel filter and the old one flowed well but i noticed rust in it!....is there a pre-filter in the sump tank?....if the fuel pump was bad and lacked pressure why would the motor fire back up after it quits?...exactly what function does the fuel inertia switch play?..ok my last question is the inlet and outlet regulators identical as far as part numbers or two completly different units?..thanks for all your help..im getting closer!

Harold possible--but you would have some very rough running and super black exhaust--while I have not seen that (regulators failing more usual) it is worth a look if the pressure is good--remember to check both sides (in and out). Good luck and let us know. One last thought --when you turn the key to run but do not start do you hear the pump cycle then stop--if so then I doubt the injectors.

Thanks george..im in aggreeance with you about fuel pressure,because when it starts to die i can pump the throttle to no avail and it feels like its just running out of gas......so ill check fuel pressure this weekend......do you know if i have a couple stuck open injectors will that also result in a loss of fuel pressure?

Harold I would start by checking the condition of your air filters then fuel pump pressure--make sure your requlators for the fuel rail pressure are operating correctly. Let us know.