99 XJ8 has not been driven a lot over last two years. Very difficult to start, but runs fine once started. Has relatively new fuel pump and even newer fuel filter. I've changed the plugs recently using Jaguar recommended plugs. I've cleaned mass air-flow sensor using CRC cleaner. I've changed the oil and filter. I've checked full load breather and replaced tubing on part load breather which was broken in several places using rubber fuel line. Battery is two years old, fully charged and checked OK at Interstate Battery.

Before all these checks and updates, car was difficult to start and did not always respond to starting fluid.

Now car will start pretty easily when I put starting fluid into air duct leading to throttle body. But it rarely will start without starting fluid.

What could be the problem?

 

I would start by checking the fuel pressure at the Schrader valve on the fuel rail. For some reason the fuel pumps do not like sitting around. There seems to be a rash of pump failures each spring as stored cars come out. Sounds like your has sat up for some time also.

Starter fluid response says no fuel.

 

What should the fuel pressure be while starting and while idling?

 

Fuel pressure gauge shows 43 psi while starting. Is that adequate?

 

Yes, 43 is just right.

Now, on to compression. Is the hard starting after not running for awhile or does it occur even after just being shut off?

 

Hard starting occurs when engine is both cold and after engine has been running. Occasionally it will restart after I turn it off.

But under typical driving conditions (including acceleration) it seems to have normal power.

 

I checked compression on a couple of the cylynders on engine when it was cold and reading was between 150 and 160 psi.

Car runs very smoothly after starting.

Could it be crankshaft position sensor or faulty mass air flow sensor?

There are no error codes.