Hello, I have a Jaguar S-Type 3.0 model 2000, the vehicle for a while now here is presenting a problem with the strength of the engine, it happens that the vehicle lights up well but when accelerating it starts to fail at that moment. We have changed the fuel pump, filters and cleaned the injectors with new seals and even the problem persists.

The car does not turn on any type of check light or warnings like Safe-Mode, everything seems to be in order and I would like to know if this case has happened to someone around here.

Thank you.

Fernando Nuņez
wifranco53@gmail.com

 

Hello Fernando,

Have you checked the fuel pressure? There's a test fitting on the fuel rail.

Working from memory, but I think your car will have a fuel pressure regulator that senses inlet manifold pressure. When the throttle is opened, manifold pressure increases (less vacuum) and the fuel pressure should increase at the same time. Can anybody else confirm this? I can check in my manuals tomorrow.

 

Also, have a look at the fuel trims as it may have an air leak

 

Here's a partial answer. Scroll down to pages 41/42 in this document (courtesty of Gus) for some vague details of the Fuel Injection Pressure (IP) sensor:

http://www.jagrepair.com/images/Trai...es/870B_SG.pdf


The schematic on page 41 shows how the IP sensor is connected to the intake manifold. Per page 42, an almost useless description states:

"A pipe connects the sensor to the intake manifold for sensing manifold depression (manifold vacuum). The voltage signal from the transducer is "conditioned" within the sensor."


So if I understand this correctly, the IP sensor reads the rail fuel pressure, but this signal is then modified (conditioned?) by intake manifold vacuum. In other words, it sounds like the signal deliberately fibs, depending on intake manifold vacuum.

Reading between the lines, the PCM controls the variable speed fuel pump (via the Rear Electronic Control Module) to maintain the desired pressure at the injectors. However, the target pressure may not actually match the physical pressure because the IP sensor intentionally fudges its output signal.

If I'm extrapolating this information correctly, it seems a little complicated. Maybe not, as it looks like one sensor sort of does the job of two, at least as far as fuel pressure is concerned.

I will have to do some more digging to confirm this, but don't have JTIS access on this computer.