G’day to you all. My 2.1ltr (petrol) is only achieving 10mpg. I recently replaced the fuel pump with an original Jaguar part, replaced the seals of both inlet manifolds, replaced 3 injectors, cleaned remaining and replaced 3 new coil overs. So the rear 3 cylinders are perfect. The car is running perfectly now but As mentioned fuel consumption is excessive. I have measured the fuel pressure at the injector rail and have 70psi not 55 as Jaguar stated to me. I have searched for the fuel pressure sensor but can’t find it. Apparently the control module is located on the passenger side rear around by the back seat but again can’t find it after stripping the back seat out and surrounding trim. Also there is no indication of black smoke at the exhaust.
Any suggestions? As stated the car is running great but expensive.
Jim

 

OOPS.

Mine sits at around 8L/100km mostly. 35MPG Imp

A/C knocks this little engine about badly, and in Summer down here, around 12L/100km, 23MPG Imp. Townsville will have the A/C on 24/7.

Also, when mine is getting close to the oil change kms, the economy does drop off slightly, maybe 1 or 2 MPG.

I run 5W30 Full Syn in it, and its good as.

I run our 95RON fuel, and NO ethanol, which is not popular way down here.

No help on the FP Sensor, never gone looking, but I will later.

O2 sensors are a service item, and 160000kms is the recommended kms for changing them, but I dont agree 100%, and NOT about to debate that with anyone on a public Forum.

 

I have a PDF that might help.

It is USA spec, so 2.5 & 3.0 as they never got the 2.1 V6, mores the pity, but for what you are seeking it will do.

Its 5.4 MB, so toooooo big to attach. PM me your private email address, and I will send it to you.

Scroll down, page 17, the section after Engine Cooling is Fuel Charge and Controls, and the Fuel pressure sensor is Item # 11. It is at the end of the rail, nearest the front of the engine. Not sure of access, maybe without taking the manifold off??

 

Jam, I would first start with actually looking at the e-brake. When I had my x-type, I noticed that when my mileage started to drop, it would be because one of the rear calipers was binding up. You can simply go for a 5 mile (10 KM) drive and then as soon as you stop at the end, put your hand near all 4 wheels. You should feel a little bit of heat, but nothing serious. If it is really hot, then that is your bound up caliper. You should also notice that when you apply the e-brake, the handle will go up fairly high, if not max'ed out.

After that, I would be looking in the plug wells for oil. These motors are known for developing leaks between the valve covers and the plug wells. You get a little oil down in there and it can cause the plug to not get its full spark and lead to a weak spark. Then the trick is figuring out which plug wells have oil in them.

Finally I would tell you to switch brands of gas for a tank or two and also use a fuel injector cleaner too. I say this because if you use the same brand for a long time, the detergents in the fuel will allow some deposits to build up. By switching brands, they use a different detergent package and it will normally get rid of this build up. Adding in the fuel injector cleaner (a third detergent), it will make sure that you are changing things up yet even more. Granted, you mentioned you replaced the fuel pump. When was the last time you replaced the fuel filter. It could be that you dislodged a bunch of gunk and you have plugged up the fuel filter. So, you can get good pressure at idle, but you start driving the car, the flow gets too much and you end up with too much of a pressure drop.

With the mention of the fuel pressure, you do have an issue there though. The fuel rail pressure should be 50 psig above the intake manifold pressure. So, if you turn the key to the RUN position (engine not turning), the fuel rail should go to 50-55 psig. If you start the engine, it should drop to 40-45 psig (you now have a vacuum in the intake). If you don't see a drop, then you may have a vacuum leak at your intake manifold sensor or your sensor is kaput. The only other issue that I can think of is you have a wiring problem back at the fuel pump and it is running all the time. The way that Jaguar controls the fuel rail pressure is by pulsing the fuel pump on and off really fast. So, it monitors the fuel rail pressure and then tries to keep it the 50 psig above the manifold pressure. The pressure gets too high, it leaves the pump off more and on less. It is turning the pump on and off hundreds of times a second. Something you can try is to get your hands on a code reader with real time data views. You can then bounce between fuel rail pressure (as the computer sees it) and manifold pressure (should be around 20 inches most of the time except immediately after moving the gas pedal). If you find that you are seeing the fuel rail pressure at some really low pressure or the manifold pressure near 0 inches of vacuum, then I would be starting with that sensor. If both of those are good, then you are looking at a wiring problem with the new fuel pump you put in.

 

Thanks for all your prompt replies. Just to answer a few of your ?'s.
The fuel filter was changed at the same time as the pump so has done about a 1000k's. There is only 98000k's on the clock. Low for a 2003.
Although the 2.1ltr motor is supposed to be a derivative of the 2.5 is fuel rail is different. The fuel injector rail is a dead end. I rang a couple of Jaguar parts companies in Melbourne and all said it at the end of the injector rail and had to go and check when I said it isn't. They were surprised.
I had the inlet manifolds leaking upper and lower due to dodgy work done with previous owner. Instead of replacing the seals they used silicone and as it still leaked they over tightened the upper manifold bolts and stripped the inserts.
As stated I have rectified that problem with new seals and as the back 3 cylinders are difficult to work on I replace their injectors and coil overs with the assumption that if there is a problem it will be on the front 3 cylinders therefore easy to access. The remaining 3 injectors were cleaned and tested OK by me. Had fun with my 9v battery, ultrasonic cleaner and a can of cleaner. Did my mates series 3 whilst I was at it too.
I think your right it saying that the 70psi is problem and think I will have to invest $168 with our trusty jag dealer and get them to diagnose the problem for me. I have had the car up on the hoist and checked underneath but cant see any sensor in the fuel rail under there.
It is understood that the pump pressure is regulated but it has to sense the pressure somewhere surely.
Have a good W/E
Jim

 

Sorry I forgot to mention that it doesn't have an e brake it is a cable hand brake and the I did the caliper check whilst on the road and hoist.

 

Lol, e brake is = emergency brake, not electrical brake. All Jags are cables.

 

Funny thing, I just came here to check for "excessive fuel consumption" posts myself. I replaced the bad downstream o2 sensor yesterday but I'm still getting about 10 miles/per (car runs great though). And I just had the radiator hose assembly replaced. Good times. I'll start running down Thermo's list.

 

What did you typically get for MPG before you started averaging 10MPG? You say the car is running "perfectly" now. I am not very familiar with the 2.1liter engine, but I would have to guess in normal driving you would get probaly in the mid-20s at least. WouId be correct in assuming you do not have any lights showing on the dash or any messages showing in the message center? I just find it hard to believe that it couold average that low of an MPG without any symptoms or running real rough and maybe running real rich.

Have you changed your driving habits recently and now go on just a lot of very short trips? Any other clues on just when the MPG dropped? Any other issues with the car you have not mentioned? The 10MPG, over what kind of distance did you achieve that?

 

A point of clarification = the 10 m.p.g. is being measured by actual gallons used divided into actual miles driven (not relying on dash info, etc.)?

 

Just for comparison: My 2.1 is running in NSW (Aust.) and I give it a pretty good workout on the highways, but only average around 44 KPH around town. In my town I average around 11.5 to 12.5 litres per 100 kilometres in fuel consumption. However, out on the highways on a long run (such as down to Melbourne and back) I use down to 8 litres per 100 kilometres, with an average of around 8.4. And here I was thinking I was using a bit too much fuel.

I also think that if your consumption is that high, there should be other obvious signs. You don't have a fuel leak, do you?

 

Yeh I thought. Of that about 30 mins after I posted the thread! My x350 is electric though.

 

Not sure what the car was doing before I got it as it was a non-runner due to fuel pump defective.
No lights are up and no error codes recorded.

 

I have just filled the car up and from the trip meter it managed 300klm just from a fall tank. This is all town driving by my daughter.
So it seems to have be improving. My calculation about 17mpg. Being age-ed and steam driven ltrs/100klm means nothing to me.

 

No no fuel leaks. I expect to get around your figures but it is difficult to track the problem when no codes are up. About the only thing I haven’ Changes is the mass air sensor but it’s an expensive change for a maybe.

 

17 m.p.g. Is what I get on my 3.0 on town driving. If the car is showing km, and you prefer miles, just change it.

8/100 is around 29, 12.5/100 is around 18 m.p.g.

 

Just clean your MAF first and bear in mind the little bulb you can "see" is the IAT not the MAF. The MAF is down inside the little "tube". Only use MAF cleaner, spray liberally, let evaporate and reinstall. Also check your air filter. A dirty one will SIGNIFICANTLY reduce your m.p.g.

 

Turns out my problem was due to a downstream o2 sensor. Since I replaced it my fuel consumption numbers are back to normal.