I have a 2000 Jaguar s type 4.0L with a misfire in cyl 4 i have tested everything and nothing stands out except that the fuel pressure is at 25-30 PSI and should be at 43.5 PSI idle and 55.1 PSI wide open throttle, i heard there was not 2 but 3 fuel pumps on this car!! there are 2 in the tank (1 for each side) and 1 for the injectors??? i would like to know if the fuel pump is in fact the problem and if there really are 3 fuel pumps in this car, i have tried everything known to man to get the cyl to stop misfiring is it as simple as the fuel pump?

 

Just 2 pumps. JTIS free download with full details.

Blocked fuel filter? Cheap to change.

 

i already changed the fuel filter....... is it possible that the inertia shut off valve could lowwer the fuel pressure thus causing a misfire

 

No. It's a power switch. If off, no power and no fuel at all.

 

Have you checked the compression in the offending cylinder?

 

Ouch - but good catch.

 

Swap the coil on that cylinder to another one.

Have the plugs been changed or even looked at? Oil in the plug wells can be a problem.

Have the timing chain tensioners ever been changed? Do you know if the timing is off because of a jumped timing chain?
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done

i have looked at the plugs and they are fine there is no oil

the timing chain did not slip, im sure you know there is something like 4 chains for this thing and they couldnt slip with out making a noise

 

Er... wrong. The 4.0 is known for tensioner failure and chain slip.

Plenty of horror stories on here, sadly.

 

wouldn't the cam postion sensor send an error code? my big problem is fuel pressure it needs 43.5PSI idle it has 25 PSI give or take 5 PSI and it needs 55.1PSI at wide open throttle.

 

One - The transfer pump may be on it's way out giving you the lower fuel pressure reading.

Two, sounds like an intermittent misfiring coil - swap out the #4 coil for another and see if you still get a P0304 or does it go to the other cylinder.

If so, time for a new coil... (More than likely the lower fuel pressure and misfiring coil are not related) also, check the fuel injector connector's - all cylinders - make sure they are nice and tight. Start with the connector on injector for Cyl #4

 

i have swapped the coil, i have checked the injector connections and even put in a new injectorcould it be that pump, would that cause lower fuel pressure?

 

Another thing to do is pinpoint tests - see JTIS.

 

Well it could be the pump? Have you tried a different fuel pressure tester?

What is the fuel pressure at WOT? The thing is the fuel pump will affect all the cylinders and you only have codes for one. So this really does NOT point to a fuel pump problem.

It won't be the transfer pump because all that does is keep the two sides of the fuel tank even. It does NOT feed the engine on your model of S Type.

You might pull a cam cover to just take a look? The timing chain problem can cause one or both cylinder banks to jump a tooth.

You can turn the engine over to verify that the cams are in time pretty easy. The factory has machined a flat on each cam. They MUST be aligned for everything to work right. Here are two cams just slightly out of time. Most likely by one tooth only. You have not posted the mileage but don't discount this as the problem. The 4.0L engines will all suffer from this eventually. They will fail completely too so run them at your own risk!


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that got me thinking but wouldn't it have made a noise if the chain had slipped and would if affect only 1 cyl?

 

Only way to be sure is to look and bear in mind if not yet changed then the tensioners are overdue and you're living on hope. Do read the existing threads as your entire engine is at real risk.

 

will do, how hard is it to get to the cams?

 

Well it's an OHC engine so real easy! Just look at my pictures to see you only need to remove the cam covers (they were called valve covers too).

Plus they use nice reusable factory gaskets now so you should be able to inspect things without tearing up the gaskets.

The secondary tensioners are visible with the cam covers removed. As someone posted they usually are the first to fail. Don't be surprised if you find them broken or missing pieces.

I have put a red arrow showing the secondary tensioners in the picture below. The updated ones will be steel and silver in color not stained white plastic like these.



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can i just ask how many miles you guys have on your cars, i have like 96K on it and it's a 2000

 

2000 S Type - 4.0 - 210,950 miles - newest all metal tensioners and guide rails - installed.