First, I've spent a few hours looking through as many threads as I can, the Haynes manual, and general internet searches. I got a lot of answers, but I still have several questions.

1991 XJ6 Sovereign. 119,800 miles. Just bought about 2 months ago (i got a great deal on it, not terribly disappointed something went wrong).

Since I've had it (about 800 miles), when starting the car it would take several seconds (7-8 seconds) to start up. I'd turn the key almost all the way, then attempt to start, then turn the key back and then start again, and then a third time if necessary. The car would start about 20% of the time the first turn, about 75% of the time on the second turn, and about 5% of the time it took a third, but never more. I assumed this was a fuel pump related issue and was taking time to pressurize the system... and that it might turn into a bigger problem eventually. 3 days ago (about 103 degrees, if it's relevant) the car wouldn't start at all (it's getting battery power, just appears to not be getting fuel). I let it sit till the next morning, thinking maybe it was heat related and it still won't start, nor in 5+ attempts since.

When I attempt to start the car, I don't *think* I hear the fuel pump working, but i'm not sure what i'm supposed to be listening for. If it would be DEFINITELY obvious that i'd hear it, than i guess i'm not hearing it.

I'm guessing the problem is the fuel pump, but a lot of these questions are to make sure i've checked all the easy stuff in advance of doing a fuel pressure test and/or actually pulling the tank to replace the pump.

Question #1: Is this a valid way to validate the relay is good? I simply took the Horn relay and plugged it into the spot for the Fuel Pump relay and it still wouldn't work. As best as I can tell they are the same relay... and the horn works otherwise. (I am getting 12V at the relay connection)

Question #2: When checking the voltage to fuel pump at the rear connector hanging outside the tank, I disconnected it and put my meter leads on the two connections (on the to-battery side, not the to-tank side). I then turn the key to start and the meter jumps up to ~8V and then goes right back down.... what does that mean? (i'm not sure what it is supposed to do)

Question #3: Can I check the fuel pump is working or not by disconnecting the filter, and attempting to start the car? If the fuel pump is fine, would it then start spitting out a little fuel?

Question #4: Do I have to buy a fuel pump gauge? Meaning, if all of the above points to the fuel pump, should I just replace the fuel pump without bothering with a pressure test? Or will I need the fuel pump gauge to properly configure the system anyway once the fuel pump is replaced?

Question #5: Assuming I go through all of this and decide it's definitely the fuel pump, how the heck do I unhook the fuel lines from the bottom of the tank? The Haynes manual, almost as an irrelevant aside, says to "Remove the driveline to gain access to the fuel line connectors next to the tank". Does that mean I have to remove the rear differential?

Thanks in advance!

Other info if it is relevant, the previous owner gave me a ton of somewhat random receipts for stuff he did to the car.
Feb 2013 - New Fuel Filter (and the one installed does look relatively clean, so I assume that is the new one)
April 2006 - New Airtex Fuel Pump

 

The fuel pump relay is attached to a bracket near the brake booster. Put a jumper wire in slots 30 and 87 and check the harness at the EVAP loss flange.

bob gauff

 

Bob (motorcarman), thank you for helping out! I don't quite understand your instruction. I know where the fuel pump relay is on my 1991 model, and I can jumper slots 30 & 87 if needed but I don't understand the "check the harness at the EVAP loss flange" part. I was effectively checking those same wires that go to the Evap loss flange, but earlier in the circuit at that the connector about 2 feet away. I didn't see an easy test point at that connector or at the Evap flange, so that's why I disconnected that connector. Is it important that I connect it back up and test at the actual evap flange?

If I do that, what am I looking for the result to tell me?

 

If you place a 'jumper wire' in place of the fuel pump relay do you get 12V instead of ~8V??????????? BAD RELAY CONTACTS????

Maybe the harness has a poor connection somewhere?????

bob gauff