Update…bummer. I ran the car a few times in the driveway to try and better understand the problem. I noticed it idled about 800-900 rpm. I’d rev it to 2k or 3k then when I’d let off the gas, the tach would drop down to almost nothing then pop back up. So, I fiddled with the air flow sensors and butterfly valves, no improvement. So, I was convinced it was fuel related. Tonight I hooked up a fuel gauge at the fuel rail and turned the key…nothing. No fuel pump prim whine, nothing. Didn’t attempt to start, just nothing. I put a voltage meter to the leads on the fuel pump and noted no voltage jump when I turned the key. Should there be? Does this sound like a fuel pump that went out? I bought a new sump screen I was planning to put on, after I tested the pressure, but I’m wondering if now I need a pump too, or if I’m totally off.
You didn’t knock your fuel pump relay loose by accident?
No power at the pump leads is not a pump going out. As mentioned check back at relay, fuses but you should first check the inertia switch, you may have tripped that which will cut power to pump.
What air flow sensors did you fiddle with? just a load throttle position system. Vacuum hose runs from engine back to EFI unit in boot/trunk which might be worth a look/check.
Locate both ends of vacuum line and check for leaks.
The butterflies should be set at .002"
My car is also fitted with an idle switch on throttle linkage which needs to be right. Not sure if it is fitted to all cars though depending on market.
I fiddled with the sensor on the back of the passenger side air filter housing. Then removed then carbon from around the butterflies, as one was carboned up pretty good. Then it started. Nothing changed, so I drove it in the garage. Now nothing. I’ll try the inertia switch and giggle with the relays. I might even try jumping the relay to get power to the pump. If anyone has a picture, that would be great. Something else I noted, with the key “on” I tried to turn on the radio, it wouldn’t come on and gave me the beep, as if the key wasn’t in. I’m not sure if whatever was I totally the problem finally went out.
I went out this evening and took the cover off the relay box. Turned the key, and the fuel pump pressurized the line. I didn’t do anything other than remove the cover. I’ll run the fuel pressure test later. My question now is, is there really supposed to be this splice connector coming off the fuel pump relay? These things are terrible. Once it stops raining I’ll see if it starts then jiggle everything back there. image|375x500, 50%
I was going to point out that the fuel pump control circuit in the 6CU is notorious for failing, but I see your car is a 1990 and hence well past the 6CU era. I agree, those splice thingies are unreliable – but it probably wasn’t added to jumper a failed fuel pump control circuit. Perhaps someone added an accessory of some sort and that’s where they chose to get ign power.
Problem solved! After changing both crank position sensors, the filter in the sump tank (wow, was that thing clogged), cleaning the air intakes, and fiddling with every hose and sensor, I found this topic…https://www.jaguarforums.com/forum/xjs-x27-32/fuel-regulator-problem-91248/
It was the inlet fuel pressure regulator!!! While I’ve read plenty of threads that the inlet regulator doesn’t matter…it does on a 1990 XJS Convertible. It fixed the problem as well as quieting any of the previous pinging. Prior to installing the new inlet regulator, a fuel pressure gauge installed at the rail read a constant 38psi, no matter the rev or idle. So I assume the inlet helps attenuate. Anyway…I’m back on the road!! Thanks!!
That means your outlet fuel pressure regulator is NFG. Or the vacuum line connected to it is plugged or disconnected.
So based on your comment I need to look at replacing the outlet regulator. It’s actually brand new, purchased from rock auto for about $50.
Sorry…I didn’t finish. It’s probably a cheap POS. Where would you purchase one? Thanks!
Then it’s time to check the vacuum line. If your car has the hot start sensor on the fuel rail, you should try bypassing it.
Update to the update. Well, it seems I’ve been chasing red herrings! Had everything running great, went to the store, came out to leave, and nothing! Absolutely nothing when I turned the key. Had it towed home and started trouble shooting. Turns out there was a dirt dobber nest in the dash, under the steering wheel panel. I cleaned everything out, including all the connectors, and everything’s been running great since. The connector for the ignition switch is round and looks like a barrel. It was full of dirt. If you look back through my symptoms, ignition wires cutting in and out explains everything. I had initially explained it as just a sudden cut out, maybe it came back on, maybe not. Then one day, nothing (thought it was the battery) but got it working again. I’d like to replace the whole electrical portion of the switch, but it seems the round barrel connector is common only to the 90, maybe 91 and I can’t find it. Anyway, while I did need to replace the leaking fuel regulator, I ended up replacing the inlet regulator, both position sensors, and the fuel sump screen. All needing to be done on a 30 year old car. As of now, she’s purring again!