After all the work I've done to my '83, I'm done. After adjusting the upper timing chain tensioner, and replacing the plugs, I found oil leaking out of the valve cover. I used Permatex to create a new gasket, and upon cranking it, it flooded out.
I removed the spark plugs to air out the cylinders, unplugged the fuel pump and cranked it over a couple times. Thereafter I refitted the spark plugs, and proceeded to crank it over...it fired up...without the fuel pump connected.

It proceeded to idle as normal, blowing a little blue smoke out the exhaust, but it was running. I revved it up to 3,000 rpms for about 10 seconds, expecting it to die, but it never did. I just barely touched the wire to the fuel pump and it immediately died. Getting too much fuel??? but HOW???

This boggled my mind, as well as my father's who had been a mechanic for 25 years. How can the engine run without the fuel pump running? So, I'm done. I'm finished with Jaguars because it has been nothing more than a pain. I'm going to sell the P.O.S. for $300...hopefully. Anyone want to tow home a Jaguar?

 

Wanna bet you've got a gallon of gas in the crankcase and the PCV is sucking in fumes?
Or, does it have 2 fuel pumps and you only killed one?
If pressure exists, and the fuel pressure regulator has holed, vacuum pull raw gas directly into the intake plenum.

I don't know if yours has a high and low pump, some cars do.

I would be unplugging the vacuum line to the regulator, turning the ignition on to energize the pumps, and seeing if it pees gas out the port.

I would also pull the dipstick, walk AWAY from the car, and hold my zippo under the wet stuff (and, 40 years of doing this, it's what we did to quickly determine the presence of fuel in the oil).

 

Some time ago I heard about one running without the fuel pump.....never did hear the final outcome as to why.

Where did you disconnect it? It powers up via two different sources.

Give it a rest for a couple days and then come back for a fresh start. Jags can be a little weird but they're worth it in the end.

Cheers and good luck
DD

 

Theoretically, a blown regulator diaphram COULD do that, even with fuel pumps disabled.
Depending on the type of pump, if it has check valves and does not have a rotary vane, the vacuum from the intake could function just like a good old fashioned mechanical fuel pump.
I cannot imagine it working smoothly, however.

Generally, fuel dump is a poor choice for idle control.

Still, check the diaphram, check the oil for mass quantities of fuel, see if you are pumping fuel from a secondary pump.
The reason I mention two pumps is A) experience with several marques that have just that, and B) the SNG Barrett Catalog showing "immersed" and "remote" pumps.

 

Just so you'll know, the Ser III fuel injected cars (4.2 and 5.3 engines) had one fuel pump. The Ser III carburetted cars (3.4 engine) has two fuel pumps

Cheers
DD