1999 XJ8 91K aka Satans Kitty or as my wife says, our garden gnome.
After a long list of repairs, including replacing the fuel pump, throttle body and much, much more, everything was fine for a few hours and the fuel pump stopped working.
Checked fuel pump and it ran when powered from battery but no fuel to injector tubes. Switched relays, no workie.
Checked fuel pump relay activation slot and no power. Rechecked it and had power then tried to fire up.. nothing.
Then checked and again no power to the relay.
Checked JTIS wiring diagram which shows a 2001 XJ8 wiring.
Determined the ECM port was EM83-04 for fuel pump.
JTIS showed WR wire but mine is a PB at that port, but also have PB wire going into luggage compartment fuse #7 which is fuel pump.
Pulled connector at ECM and used electronic cleaner.
Checked PB wire before fuse box and then coming out of EM-83-04, both no power at startup.
Three questions
First, is ECM port EM83-04 the fuel pump activation on a 1999?
Second, is there anything upstream that might cause the ECM not to send activation to the relay? Since the fuel pump when powered up did not get fuel to the injectors, perhaps something at the throttle body??
Third, how long does it take to bleed out after you cut your wrists?
Just kidding!
Thanks for all your help in the past.
Ken

 

Ken:
Attached is a pdf of the page you need for the MY 99. The schematics show a KN wire to pin EM13-1 for MY98, changing to a KN wire on pin EM83-04 for MY 99, chnaging to a WR wire on pin 83-04 for MY 2000.

The Fuel pumps run for a few seconds when you turn the ignition on, then shut off until crankshaft pulses are seen. I would jumper the relay contacts on the fuel pump and see if you hear the pump run and if you have fuel pressure.

 

The relay will not always be activated at the exact moment of startup since the fuel rail is supposed to be pressurised at key on. There is no fuel pressure sensor, so it is all assumed by the ECM. There is some sensing in that it senses RPM.

Some thoughts ...

1) fuel filter?

2) pump was replaced, did the hose pop off? (it might gurgle when jumpered)

3) jumper the fuel pump on, and try to start as a test of pump function

What brand of fuel pump did you use? There is one brand where the hose retaining nipple comes off the pump when the shipping seal is removed. Some people don't catch this.

 

I was mistaken on the wire colors and you are correct. At the car I wrote down PB to remind me it was pink/brown but forgot to look at the electric diagram for the right letters.
When I jump the fuel pump I can hear the pump but get very low pressure at the injectors and car will not start. I hear no gurgling.
I may jump again tomorrow after I loosen the fuel line at the filter and see if I have high pressure there.
There is zero juice coming out of EM83-04 pin at start up attempts or if I leave the ignition on. I have a multimeter with alligator clips and can watch it through the windshield or back window.
Car starts when primed and runs till fuel in intake is used up.
Fuel filter is quite new.
Now the radio does not work.
Is there anything along the fuel route to the injectors to keep from getting high pressure when fuel pump jumped?
What triggers the ECM to activate the fuel pump?
Any and all ideas are welcome and thanks so much for your insight.

 

Turning on the key tells the ECM it needs fuel. It moderates this based on other conditions such as rpm, knock sensor. Simple as that.

How is the battery?

Like I said, jump the pump and start it. It will tell you if it is upstream or downstream of the pump.

 

And to answer your question, there is nothing along the way that would normally reduce the pressure. The pressure is regulated by a regulator at the right rear rail that controls the flow to a return line to the tank..
I'm guessing something bad happened inside the tank.

 

Hello, my 98 xj8 did the same thing. She stopped on the highway would start but cut off when pushing the accelerator. I had to have her towed home, thought it may be the fuel pump even though I just had it changed 6 months ago! Today it started right up, let it run for a while, shut it off and it started right up! Rode around the block a few times and it ran fine. My question is what could have caused this???

 

I really appreciate all the advice and upon further checking, the battery is a week old, when jumped the fuel pump whirls with no gurgling and no output at the receiving side of the fuel filter. So need a new fuel pump.
Also, there is zero output from the ECM pin for the fuel pump relay, checked the ECM fuses and all good, so need a ECM as well.
Question, does a replacement ECM require programming at the dealer??
Wife finally said that after 6 years it is time for the garden gnome to go. She is much smarter than me!
Called a young man who is a mechanic that I knew since he was knee high and offered him to take the Jag, repair it and I would pay for parts and we would split any profit when we got it running and sold it.
Can't wait for the tow truck to show up as it was becoming a real downer to see our beautiful Jag up on blocks all the time.
Must say, it was the most wonderful auto I ever owned.. on the few occasions when it ran..
Cheers

 

The ECM can be repaired. I sent mine to ASI and no problems. Replacing it may require a reflash at a dealer.

 

Hi Guys, I want to thanks everyone for their assistance. The pump is bad and the ECM is also bad. Not surprising with this car.
My wife said it was time to get rid of the garden gnome, as she calls it.
Contacted a young mechanic we have known since he was 5 years old and going to give him the car to repair with me paying for parts and then selling it and splitting the profits.
It was just getting to be a burden at my age.
Again, Thanks