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Doug, ASE Certified Technician
Category: Car
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Experience:  16 years automotive and OTR repair including specialized training from Toyota and Mitsubishi
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Jaguar XJS V12: I am hoping to restart an old XJS V12 1986

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I am hoping to restart an old XJS V12 1986 that has been put away in a garage for 9 years!What precautions are needed to start the motor?

This is very cool to see a car sit for this long and come back to life, but you need to take many precautions before you start.

First, pull all of your spark plugs out. Take some good penetrating oil and spray into all cylinders a healthy amount. The purpose for this is to make sure that the rings are not try on first start up.... with 9 years of sitting, the oil film on the rings and cylinders is certainly gone, and first start up will likely damage the rings or even the cylinder bore.

Let the penetrating oil soak in the cylinders over night. The next day, add a few more sprays, then use a socket and breaker bar to see if you can rotate the engine. If it is free, awesome! If it is stuck, you may need a pipe extension and go back and forth a bit trying to break it loose (do not rotate it anti-clockwise, just put pressure back and forth to help loosen it).

If you are unable to rotate the engine free by hand, you will likely be doing internal work to the engine.
If the engine is able to be rotated, you will then want to drain the engine oil entirely so that you get not just the old acidic oil out, but also the penetrating oil you sprayed in that ran past the rings. Put in fresh engine oil (5w30 for first start, then you can change to manufacturers recommendation for your climate afterward... we just don't want a lot of resistance at first start up).

Drain the coolant out of the radiator. At this point I would recommend taking a radiator hose off as well and using a garden hose to try to flush out the system some. The old coolant will crystallize and form build up that will cause cooling problems. We want to get any issues out of there. If there is heavy gunk, you can try removing the thermostat for better flow in flushing it. If it is extremely bad, you may find yourself replacing the radiator, heater core and even the water pump.... at 9 years, it is a tough bet on how bad it will be... I would wager the majority of the water has evaporated out of the coolant, however you won't know until you go in there.
Put fresh coolant in the engine/radiator.

This is where things get ugly. If there is gas in the tank... it is probably gelled like old shellac which can be an issue. Hopefully the tank is empty or near empty. If it is 1/8 tank or so you can try just putting fresh gas in there to dilute it, but if there is over 1/4 tank you will need to pull the tank to drain and clean it properly.

Install a new set of plugs if the old one are even a little questionable looking. Install a new battery.

At this point you will be able to attempt to start the vehicle. All things being equal, it should start if nothing has failed over time... but you probably have more work ahead of you. While freeing the engine, putting fresh fluids and gas in there and a new battery will get you ready to start the engine like you asked, there is a good chance more work will be needed after that point.
Specifically, you run the risk of the fuel pump being seized and the fuel pressure regulators rotted out. Those are your big what-ifs. Beyond that, you should be able to get it to run from there; how well it runs will depend on if anything else electronic failed over time, but it should run at that point.
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Customer: replied 3 years ago.

Thanks!I gathered that much about gas line ,coolant and cylinders ; this engine is packed with unconventional parts and will procure hours of research and a dirty garage overall.It was pratically given to me to play with and possibly take it out for a spin(9 miles to the gallon) next summer.

You're welcome.

The V12 is rather shunned by all but the purists, but is a neat and smooth ride when functioning correctly. Starting out at a nearly $0 cost of admission, you definitely have a comfortably 'buffer' to get her running tip top again.

Good luck!

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