Parked 4 weeks ago, won't start

1990 XJS, ran great up until i moved to Florida. had it trucked here. drove it off the truck and parked in the garage. sat for 4 weeks. on trickle charger. now it won’t start. turns over, but no spark. suggestions, please?

have you tested the battery for CCA read out

yes sir. battery is fully charged and starter is cranking fine. it has been very hot and humid here. perhaps a condensation issue in the fuel? can I spray starter fluid somewhere to get it to start ?

how did you determine NO spark?..engine maybe cranking ok but not getting appropriate power, do you have or can get a spark plug inline tester/ it will light up when cranking if plug getting power…main points of power to start would be the start relay feeding EFI & EFI main relay…also is fuel actually getting through or just the sound of a fuel pump, can check that at the fuel press/ test point if fitted

Where in Florida?

The “could be” list is pretty long.

Are the injectors clicking when you crank the engine? If you suddenly have no spark AND no injector pulse, the crankshaft sensors are suspect

Do you hear the fuel pump run for 3 seconds when you turn the “on”? If not you’ll have to explore the pump circuit…or possibly replace the pump.

Dirty/loose/corroded connections and grounds are always a possibility

Pick a jumping-off point and see where it leads. Diagnosis is often more about eliminating possibilities than anything else.


which engine is it ?
I had a similar occurrence on our V12, and sorted it by disconnecting / blowing air / reconnecting the rear crank sensor plug

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Years ago, after reviving our XJS from a 20 year long storage, we had a random no start issue. Luckily our issue was very simple to fix as it ended up being the front crank sensor and once replaced the car has been trouble free since.
On top of the crank sensor I would confirm that the battery is fully charged and putting out 12+ volts and the battery cables are clean.

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Your first post stated “no spark”. If you don’t have spark then spraying starter fluid into the intake will do you no good. If you have good spark but a fuel delivery problem then spraying starter fluid might get the engine to briefly start if you had good spark.
Your 1990 XJ-S convertible is most likely equipped with the 5.3L V12 with the Marelli ignition system. I highly recommend that you search the Jag-Lovers archives for “crankshaft position sensor” and you will find lots of posts from people with similar cars that had no start problems due to a failed crankshaft position sensor (CPS). This sensor is located at the bottom front of the engine and sends a vital signal to the engine electronics about when to fire the spark plugs and fuel injectors. Without this signal your engine will not run. There are other possibilities that could cause your problem, but this is certainly a likely one. If the CPS in your car is original, then it is 33 years old and can have failed simply from age since it sits in a very hot environment. It can also have a failure at its connector located at the top left front of the engine. Some times disconnecting the connector, cleaning the contacts, and reconnecting the connector can resolve issues like your if the contacts have been corroded.


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Car not happy to be in Florida.

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Ponte Vedra, u ?

Used to be in Ormond Beach. Moved to Asheville NC two years ago.

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If you have a Marelli ignition system, this suggestion is likely not of any value to you… If you don’t have a Marelli ignition, then:

I’d check the ignition amplifier, a small box atop the engine on the left side, easily accessible.

It contains a GM ignition amplifier normally found in GM HEI distributors:
ignition amplifier innards

Here are instructions on how to test the GM amplifier after opening that box and removing the amplifier:

If it’s defective, fix it by replacing the GM ignition amplifier (I’d strongly suggest you buy a GM ampifier, not an aftermarket amplifier)