I learned something new today I thought I'd pass on. My 96 XJS 6 cyl would not start which is unusual because it always starts and runs great (drive it once a month or so). Checked fuel pump fuse, relay, reset the inertia switch, etc... no luck.

Came to find out these cars flood easily if you say, start it - move it out of the garage then turn it off and then in about 5 minutes start and return to garage.

A Jag mechanic told me today to get in it, pull the floor mat out of the way and mash the accelerator all the way down on the floor and leave it there, insert key and then crank the engine. Apparently this tells the car (ECM) it is flooded and goes into that mode.
I did that (cranked for about 15 seconds), turned off the ignition, removed my foot from accelerator and then cranked again and it fired right up. Who knew?

 

Interesting. On slightly different subject, I've always wondered how much is the carpet in the way to true max acceleration on this car (mine's a '94, same thing down there).

Cheers,

 

Due to the weight of these old 6 cylinder cars, I wouldn't even term the motion generated leaving stops as acceleration. I don't drive mine because it is fast but because it looks fast and is very beautiful.
Cheers, RagJag

 

El Gato,

As you've found out, the AJ16 is really prone to getting its temp sensor confused if you turn off the engine after only running it briefly. Never do that!

You mechanic's method will work but is a bit risky. It works because complete, and I mean complete, throttle when cranking will disable the fuelling. However, it's not really be to recommended because if you get it even slightly wrong and give it 99% rather than 100% throttle, you'll massively overfuel it and make the situation worse! I would suggest that a better approach is to pull the fuel pump fuse or relay, and then crank the engine with throttle open to discharge the unburnt fuel, then replace the fuse or relay and then try and start it.

Hope that helps

Paul

 

My 96 XJS was flooded, tried your advice but it did not work two times. Then I tried full throttle cranking longer and slowly the engine started firing up after some thirty seconds. Is this a know variation of your suggestion?

 

On the AJ6 I was told to disconnect the fuel pump power supply (fuse or impact trip), crank it for 10 turns, leave it for 1/2 an hour, then reconnect the fuel pump and start it; worked straight away.

 

Seems there is no clear recipe.
Is the AJ6 behaviour similar to the AJ16'?

 

This symptom is all caused by emissions reduction efforts on petrol engines. All the manufacturers try to keep the engine on enrichment for the absolute bare minimum time. So if you start a cold engine with this sort of fuelling regime, drive it out of the garage and stop it, the following happens:
The engine is not warmed enough to ignite the normal mixture
The engine IS warm enough to stop any mixture enrichment
The engine will not restart until cold enough to activate the cold start regime again because the mixture it is being fed is too weak

Cranking it just fills the cylinders with unignited mixture. Foot on the floor MIGHT make the mixture rich enough to start the engine. It also may, and often will, provoke a huge backfire and blow a hole in the inlet manifold etc etc.
Most modern cars handbooks warn their owners to properly see the car is up to normal operating temperature on the gauge before stopping the engine after a cold start.
Greg