I have been chasing the PO193 code for 4 years and at least $10,000.00

My direct precise question is related to the photo attached.

If you bring the 2007 XKR up to about 100 mph, let off accelerator pedal and let it coast down to say 50 mph it will pop the PO193 code everytime.
On the coast down from 100mph the fuel pressure continues to rise(see photo) until it reaches the absolute high of 78.3 and will hold there until auto down shift or if you feather the throttle. The problem is when it holds at that 78.3 psi it pops the Check Engine light code po193.

Does anyone else's car ever do this this?( or what does everyone else's car hold at on coast down ) I thought it should reach max 70 and open the purge valve to release pressure.

Everything pertaining to fuel pressure has been replaced with genuine Jaguar parts.( when I say everything, I mean everything ( the List is very long )

Any Ideas what would cause this fuel pressure to hold so high until po193 triggers

 

Either you replaced a faulty component with another faulty component, or your ECU is being a pain.

 

mine does not behave this way.

 

vacuum on decel is heavier than idle, you can get some big delta pressure

take the manifold ref hose off the sensor see if you can get yourself out of dtc tripping range

 

Does anyone have a way to share their fuel pressure on deceleration coast down, like my photo above or can anyone share what there deceleration pressure is ?

 

if this gets me away form DTC tripping what does this trial prove or take me to as a permanent solution ?

Does it point to a certain item or part failing or what would be my next move.

 

Hi Argon18,

I don't know if this could apply to your car, but I have dealt with a couple of X350 4.2L cars with P0193. On one, which had been purchased at auction, I discovered that the fuel pump had been replaced with a salvaged higher-flow pump that I think i recall was from a supercharged S-Type R. Apparently, the ECM in this normally-aspirated car could not properly manage the fuel pump duty cycle. The client's regular mechanic subsequently found a correct salvaged pump and resolved the issue.

On the other car, in following the pinpoint tests in the Workshop Manual, I found that the wiring harness behind the engine had been damaged by a rodent that was nesting in the cabin air filter housing. I repaired the wiring and resolved the issue.

I have also had to replace faulty Fuel Rail Pressure Sensors in a couple of 4.2L cars.

Have you followed the pinpoint tests? The most likely causes of P0193 are related to the electrical circuit for the Fuel Rail Pressure Sensor A or failure of the sensor. Here's a quick summary, but the Workshop Manual has more detailed instructions for testing the circuits:





Cheers,

Don

 

Yes have followed this and changed to a new Fuel Rail Pressure Sensor A

Still builds up pressure on deceleration

 

Have you connected a mechanical fuel pressure gauge and watched the indicated pressure while the FRPS is reporting excessive pressure? I keep a 10-foot-long piece of hose with my fuel gauge set so I can connect to fuel system and place the gauge on the dash so I can watch it while I drive. If I recall correctly, on the 4.2L engine the Schrader valve is on the left fuel rail and it is the smaller size valve as used on BMWs and Fords.


The purge valve is part of the Evaporative Emissions system, which, to minimize fuel vapors released into the atmosphere, collects vapors from the fuel tank and stores them in a canister filled with activated charcoal/carbon. Under certain engine operating conditions, the purge valve pulses open like a fuel injector to release fuel vapors into the engine intake. The purge valve is not part of the liquid fuel system.

The fuel system is "returnless," meaning there is no return path from the fuel rail to the fuel tank, so fuel pressure is regulated by several components working together.

Can your scan tool monitor the fuel pump duty cycle, fuel injector activity, fuel pressure and manifold absolute pressure while driving the vehicle?

I may be misremembering, but I think the ECM duty cycle commands to the FPCM range from 5% to 50% and the FPCM doubles these commands, so the pump receives signals to run between 10% and 100%. To shut off the fuel pump, the ECM sends a 75% duty cycle command. You'll have to double check this in the manual - I may be wrong.

I will be curious to know if you have confirmed that the actual fuel pressure matches that indicated by the FRPS.

Cheers,

Don

 

What do you mean you replaced "Fuel Rail Pressure Sensor A"? Can you post a picture as I don't know what or where that is?
Can you list all the parts that have been changed?

You need to replace the FPR (Fuel Pressure Regulator). It has a vacuum hose and electrical connector on it. As Xalty posted remove the vacuum hose. This will force the system to a fixed fuel pressure. Part Number AJ87977.
Here is my thread on my old STR that uses the same engine.
FPR Replacement
.
.
.

 

Hi clubairth1,

What you are describing is the fuel rail pressure sensor. On these cars, the fuel pressure regulator is built in to the fuel pump assembly in the fuel tank (according to the Workshop Manual). Argon18 has reported that he has already replaced his FRPS.

However, I noticed in your thread that the first FRPS you received had the metal baseplate installed incorrectly. Perhaps Argon18 also received a defective FRPS?

Cheers,

Don

 

The list is way longer than this but here are the major items
Fuel pump ( Twice ) Yes entire rearend dropped 2 times
Fuel Filler Cap
FRPS
Main Ground Wire
Fuel Filter
New Battery
I'll look at the last few receipts tonight and add to the list

 

What is your MAP sensor reading during the deceleration conditions when P0193 is triggered? The MAPS, FRPS and MAFS/IAT signals are all critical to the correct operation of the The Fuel Pump Driver Module:

 

We believe we have finally solved the problem. this is the 3rd FRPS ( Fuel Rail Pressure Sensor ) we have installed on the car after taking the great suggestions from Don here to compare "Electronic Fuel Pressure" to a high end mechanical pressure gauge pressure.

We found that the 2 New parts (FRPS) one from Jag one from Ford, were manufactured faulty, see photos. The hole in the Pressure Sensor was not machined completely through, which was making the sensor read 10 psi high. The car now is maxing out at 70 psi which I believe to be 100% accurate.

The car was hitting 78.3 and holding which would trip the check engine light.

Fingers crossed. I believe this was the manufacturing error that I have been chasing for 4 years.

I think this is a good item to document for future owners to be on the lookout as 2 different brands had the same exact manufacturing error.

Thanks for everyone's advice on this thread. we may not have ever found this without the forums help.

 

Fantastic news, Argon18!!!

That is definitely something we all need to file away for future reference. So where did you source the part that works and what brand is it?

Cheers,

Don

 

The Brand that ended up working was NTK.

Both Ford and Bosch were not drilled through all the way causing 15% higher reading. Car decelerates at 70 psi now and is 8.3 psi away from Check Engine trigger at 78.3.

Thanks everyone especially Don for helping me find the solution to a long fought battle.

 

https://diag.net/msg/m58pmqwdo0158ff07zihodgasb

whatever you did with the aftermarket sensor is a band-aid. you maxed 3 original sensors out at 5V\5 bar (78psi) for 8+ seconds to trip a P0193 on decel fuel cut..some weird **** is going on in the tank or the driver is still overdriving the pump. i can datalog my own car

 

Odd response. The 2 ford and bosch were manufacturer defects. The "so called after market" was built correctly with the correct hole in the tip. Explain how this is a band-aid ?

 

the vacuum port is supposed to be like that. your vehicle has a tank pressure relief problem on decel fuel cut, injectors stop pulsing but pressure doesn't relieve. if you hook up a mech gauge it's going to be over the max output of that sensor

 

But the problem is fixed after 4 years...... Why are the last 2 post saying its a band-aid or its not fixed. Please help me understand what I need to look for now, if its not fixed.