Car was running all day Tuesday.
Stopped at a friends; wouldnt then start.
Changed c/s sensor
Engine ECU
Neither fuel pump running when ignition on
Both pumps run when hot wired
No fuel coming out of pipe on top of tank with both pumps running
Is this the fuel outlet adjacent to the 4 pin electrical connector? (Ah just discovered this is the vent pipe)
Pipe at fuel rail in engine bay bone dry
Has pipe fallen off inside tank?
When rubber pipe connecteced to "fuel outlet"? no bubbles can be heard inside tank when blown through.
If the pipe has fallen off then why no electrical feed to pumps?
Relays checked and ok.

Any thoughts gratefully received...
Thanks
Charlie

 

"No electrical feed to pumps"

You are aware that the pumps only run a few seconds on key on, then shut off until the engine starts as evidenced by the pulses returning from the CKPS, right?

 

Thanks, I wasn't aware of that. I will do a test. But as there is no fuel in the injector rail, pipe bone dry?? Do the pumps not run until fuel rail pressure of 38psi is reached? One test I haven't done is to hot wire both pumps with the fuel inlet pipe to the injector rail disconnected and see if fuel os pumped through. My normally aspirated cars when disconnecting this pipe, on turning on the ignition fuel is pumped through.

 

Most of your evidence suggests inlet tube in tank has come off. Good idea to try blowing bubbles into tank, I hadn't heard of that. Pump prime will be only about two seconds after key on, regardless of fuel pressure. Do that flow test to confirm, be careful.

 

If you disconnect the pipe at the fuel rail and stick it in a bottle to catch the fuel flow, there should definitely be fuel in that bottle. There is no pressure limiting. Fuel should flow freely when the ignition key is moved to the on position. If you hear the pump kick on, but no fuel flow, then the likely culprit is indeed the fuel line in the tank has blown off. I know some here are against the procedure, but if you cut a hole above the tank as I've described in the thread below, it makes checking the fuel line, as well as changing the pump, a less than 10 minute process. I don't consider this an issue for a 16-19 year old vehicle, but some do. Just add it to your 'consideration' bank of knowledge.

https://www.jaguarforums.com/forum/x...asy-way-84363/

 

Not yet having replaced the fuel pump on this car yet, and reading that "the hose blowing off of X300 pumps is relatively common".... is there a fix, such as a [better] clamp, that the community has come up with to more securely fit the hose to the pump?

.

 

When I installed my new pump, I gave it a coating of fuel resistant rtv sealant on both the tube and pump - and used a normal screw hose clamp. I replaced the original hose with one that was about 1/2 inch longer so that it fit over as much of the nipple as possible, and also had the advantage of having a longer length to "wiggle/blow" off. No issues thus far.

 

Is there anything in the x300 which would cut off the spark if the fuel pressure got low? My 1996 XJ6 occasionally "cuts out" for a second or so and then comes back. It's just as if I turned the key off for a second, and then back on. It happens that fast. There's no sputtering like it was running out of fuel, it's just running along fine one second, and the next it's OFF. And the next second it'll be ON again. It happens so fast that I was convinced that it had to be a random electrical problem, until I realized that it was repeatable. I can make it happen by creating a high demand for fuel, and avoid it by keeping fuel demand to a minimum. But still, when it happens, it comes and goes so quickly, and so positively, that it still seems that something must be momentarily killing the spark. So, finally, the question: is there any way that a low fuel pressure condition would cut the spark off? It just seems that if this were a purely mechanical situation it couldn't come and go this quickly, or so positively.

 

Very similar problem has just occurred with my X300 XJR: have never had a problen in 3 years, but after leaving it parked at a friends for 10 days, it can now only be driven very slowly; between 40-50 mph it will run with the engine occasionally dying then coming back in within a couple of seconds. At this speed the engine dies then restarts very gently. If I take it above 50 then the fuel supply seems to give out more quickly and the engine cuts out with more of a lurch. Had to drive 100 miles home in the early hours of the morning, but the engine always cut back in again quickly so at 40-50 I got back. Any suggestions as to cause much appreciated.

 

I was looking at my fuel rail to see if there was a connector for a fuel pressure gauge, as some layer models have, but I didn't see one. I do see, however, some kind of vacuum-operated valve located near the front end of the rail. Does anyone know what function that serves? Looks like maybe it's to release the fuel pressure when the engine isn't running (no manifold vacuum). jagmanphil: Is that Northampton, Mass.? I'm in Westfield.

 

The issue that both you and tsfo2 describe is one of the symptoms of a faulty Throttle Position Sensor. But the first thing I would do is check the cheapest potential culprit, clogged fuel filter. If you're past 100,000 miles and you're uncertain if it's been changed, then it's time for a new filter anyway. that might just cure the issue. If not, then have a look at the throttle position sensor.

 

+1 for Suede's post:

tsfo2:
No fuel pressure port on an X-300 and they are a PITA to put one on. Some have butchered the hose, some have found enough fittings to tap, and (my favorite) is to tap a hole into the connector block and fit a Schrader valve.
The thing with the vacuum hose is the fuel pressure regulator- the hose is to set the fuel pressure relative to the manifold pressure- about 40 psi higher.

 

...and if the fuel pressure regulator (FPR) fails and is not holding ~40 psi of fuel pressure in the rail (a very common issue), then a sudden depression of the accelerator pedal can cause fuel starvation at the injectors. FPRs don't last forever and are reasonably inexpensive, especially compared to a new TPS and the cost of dealer calibration if necessary, so it might be worth replacing your FPR first to see if things improve. I would especially suspect the FPR if your engine takes a few more cranks to start than it used to.

In the U.S. you can find FPRs for as little as $55 or $60 (sometimes even less on eBay), but I paid $80 for an OE Bosch from a seller on Amazon. Replacement is fairly easy. Below are links to photos of the process on our '93, which uses the same FPR as the X300:

Welcome to Jag-lovers - Members Photo Viewing Page

Cheers,

Don

 

Thanks to all for the tips. Yes, the car is hard to start. I've learned to turn the key on and off several times to build fuel pressure before engaging the starter. For this, and other reasons, I'm inclined to think it's a fuel pressure problem rather than a TPS issue. So I guess my course of action will be to replace the FPR, and if that doesn't fix it I'll replace the fuel pump and filter (I spent some time today cleaning six years of accumulated junk out of my trunk so I can get the tank out if I have to). I'll let you know what happens.

 

My car is still dead but I have learnt that the second pump only powers up above 3000/3500 rpm. I have fuel at the manifold but the pressure is low and will not open the pressure regulating valve. I suspect pump(s) or the fuel pipe in the tank problem. Has anyone a diagram/drawing/schematic/photographs of what goes on inside the tank?
Thanks
Charlie

 

Well, my problem isn't gone yet, but here's a list so far of things it was NOT: fuel pump relay, fuel filter and FPR.

 

What are your fuel trims doing? Low pressure > High Trims

 

I took apart the connector where the high-pressure fuel line connects to the fuel rail. My intent was to place an additional section between the two existing ends onto which I could install a tap for a pressure gauge (or sending unit). From the slight curvature of the mating surfaces in this connector it would appear to be what the plumbing world calls a "union". Does anyone know the nominal size of this connector, or even whether or not it is metric? It's time to add some instrumentation to this problem, and end the speculation over fuel pressure. And, by the way, my above list of things it was NOT should also have included the ignition relay. That was the first thing I changed.

 

When I disconnect the two lines from the bottom of the tank is any/all remaining fuel in the tank gonna come pouring out in my face, or are there some kind of valves in the quick-disconnect fittings?

 

Don't worry. As bad as the engineering can be on these cars, you will only get a little that's in the lines.