Will not start without starting fluid then runs fine

Yesterday I went to a doctors appointment. When I returned My 96 xj140 would not start. The engine would turn over but the car would not try to start. My wife brought me starting fluid and the engine started right up and idled fine. The car idles fine and runs smoothly with plenty of power but will not start without a small spray of starting fluid.

The 1996 XJ6 X300) did NOT have the AJ6 engine, but it has the AJ16 engine.

I think you are posting in the wrong forum!!!


My first thought was, the spark plugs are not hot enough. It is either the plugs themselves or it is not getting the correct message from the dizzy.

Coolant temp sensor acting up or bad connection

If your car was an XJ40 and had an AJ6 engine, I would say you have a classic case of fuel pressure regulator failure where the system is not holding fuel pressure in the fuel rail on engine shut-down and it takes a little while for the ‘priming’ pressure from the fuel pump to build up to the required start pressure.
Try the key cycling trick before engaging the starter - turn the key to position II - ON-OFF-ON-OFF-ON- five or six times and then crank the engine. If it fires then, the problem is as described above.

Perhaps the same applies to an X300 AJ16 also?

I finally had a chance to try your fix. I had no luck after several tries. Is there something else I can try before going to the dreaded JAG mechanic? Thanks for all of your help

Could you check the voltage to the plug?
Thank you,


papageek said earlier “The car idles fine and runs smoothly with plenty of power but will not start without a small spray of starting fluid.” so the fuel pump must be getting voltage at the plug and working.
I can only think that it is not generating enough pressure in the fuel rail to enble it to start without introducing a squirt of starter fluid. A fuel pressure test would prove/disprove that.
It could be of course that the EMS ECU is faulty and is not ordering the pump to give a priming burst whenever the ignition is turned on before engaging the starter - but I’ve not heard of that as a problem before.

Good point. I was just thinking that perhaps the plug spark will fire the starting fluid but not be hot enough to fire the gasoline.

I tried the key cycling trick with no results. Is there something else I can try before going to a mechanic?

Do you have a fuel pressure gauge to check the fuel pressure at the rail to do the test that Bryan suggested? The gauges are very cheap and you will be use it a lot more than you would expect.

You definitely need to take some of the previous poster’s advice and take a fuel pressure reading. Everything you describe makes it sound like the pressure is bleeding down when the car is shut off. With the fuel pressure gauge attached, you should be able to see this after you shut the engine off.

This is what the pressure test shows on a typical sequence.
Note how long pressure remains in the fuel rail after engine shut-down to facilitate the next engine start.