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Richard
Richard, Jaguar Technician
Category: Jaguar
Satisfied Customers: 13791
Experience:  12 years at a Jaguar dealer as technician and shop foreman.
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2002 Jaguar XK8: the gas cap..light goes..service engine soon

Resolved Question:

I have a 2002 Jaguar XK8 and the check gas cap light keeps coming on and after you get out of the car open the gas cap and put it back on (is is never loose to begin with) the light goes off and then after about 100 miles back on again. After the third time this happens, it trips the service engine soon light and it has been to the shop for this problem 2 times now, it has the new pressure gas cap (recall) and many other new components. I called Jaguar and they said to replace the fuel neck? Can we just disconnect this crap because it is just something to spend money on, totally unecesary....I have my car serviced by a independent facility that works on all foreign and high dollar vehicles and Jaguar seems to claim their dealers are the only ones that are qualified to work on their crap cars and I refuse because I had a very bad experienced with the dealer in my area and they don't know what they are doing....please help
Submitted: 3 years ago.
Category: Jaguar
Expert:  Richard replied 3 years ago.
Chat Conversation Started
Richard :

Hello and welcome to justanswer.com

Richard :

When the engine light came on did the dealer run a scan for fault codes? If so what code was logged? Can I have the last six digits of your VIN?

Customer:

A27420, I don't know what fault codes were found, but they replaced the gas cap, with the new and improved version and some emissions components, I didn't take it to the dealer because they don't know what they are doing. I take it to a independent facility that has been working on foreign cars for 30 years, jag, mercedes, ferarris...

Richard :

OK when that warning comes on the ECM has detected a large leak in the evaporative emissions system and assumes that the fuel cap was left loose. When the engine light comes on the ECM has seen the fault a second time in it's drive cycle. This tells me that there is either a leak in the system or the canister or purge valve is faulty. The first step would be to read the fault codes next time those wanrings come on. The codes may be P0442 and/or P0455. If that is the case the system needs to be checked for a leak. We use a smoke machine to pinpoint leaks. On your vehicle I see issues with the canister cracking at the seam where the brackets attach to the body and issues with both evap valves.

Customer:

Code I believe was 442

Richard :

Ok that is a small evap leak.

Richard :

THe first step would be to check the system for leaks.

Richard :

\The way I do this is I use a scan tool to close off the canister valve. Then I use a smoke machine which checks the system with pressure as well as the smoke.

Customer:

they performed a smoke test and repaired whatever needed to be but it is happening again

Customer:

They replaced the evap cannister.

Customer:

Just spoke to the mechanic and all that has been replaced....

Richard :

So both canisters, canister valve, purge valve and fuel cap have been replaced?

Customer:

Yes, I am very disappointed with this vehicle, it has always been my dream car and has turned into a nightmare.

Richard :

Ok I also see issues with the hoses going to the purge valve. Heres what I do on problem EVAP cars. I smoke test the line from the tank side to the purge. There should be no leak and the float in the smoke tester should go to the bottom. Then I go from that line and smoke the tank side and do that same test. Lastly I smoke the canister side. Usually splitting the system helps in finding the leak. Also while smoking the system have them sprya soapy water as this will also aid in finding a pin hole leak.

Richard :

Evap problems can be a pain. The shop is most likely going to say that they have done all this but there has to be a leak somewhere. Also they can check the voltage on the fuel tank pressure sensor then open the purge valve electrically then close it off and close off the canister vent to put the tank into a vacuum and see if it will hold. This is the same test the ECM does to see if a leak is present.

Customer:

All this has been done, they dropped the gas tank and didn't see any leaks there or in the fuel pump...

Richard :

Have them electrically do the test which has most likely not been done.

Customer:

What is the electrical test?

Customer:

Are there any other issues with this car that I need to be aware of and maybe get rid of it before it becomes a total nightmare? What is your expert opinion...I have a large car note and can't continue to make repairs on this thing...

Richard :

First the voltage on the fuel tank pressure sensor needs to be read with the engine off and the fuel cap off. I believe it shoudlbe about 3.3 volts but I will double chekc that for you. Then install the cap then start the engine. Next jump the purge valve open then close it. Next jump the canister valve close and watch the voltage on the fuel tank pressure sensor to see if the voltage is stable. If it is not then there is a leak. This is the test the ECM does when it flags that P0442 code.

Richard :

Overall the 2002 Xk is a solid vehicle.

Richard :

I do however see issues with the timing chian tensioners but on the 2002 they are rare.

Customer:

And if that doesn't fix it, what else can it be?

Richard :

That will just be a test to see if there is a leak. If the test proves there is no leak then either the purge or canister valve may be the problem even though both were replaced. The last thing would be the ECM itself but I can tell you that I have never had a bad ECM cause this.

Customer:

I have written all this information down and am going to fax it to my mechanic....anything else and is the 3.3 volts on the fuel tank pressure correct, you were going to check and make sure.

Richard :

Sorry for the delay as there was a problem with the chat function on my end.

Richard :

The voltage is actually about 3.2 but it may be 3.1-3.3 as long as it is in range. If it is way off then that can be your problem. Here is the test. Your mechanic should understand what we are doing.

Richard :

First he will need two leads for power and ground on the purge valve and canister valve. Start the engine and bring it up to temperature. With a voltmeter monitor the Fuel Tank Pressure sensor signal voltage as it should be 3.2 volts. Apply 12 volts and ground to the vent solenoid on the canister to close it and the FTP voltage may rise. Then energize the purge solenoid and monitor the sensor voltage and see how long it takes to go from 3.2 volts to about 0.20 volts. If the engine stalls then restart the test but have an assistant keep the engine rpm up a little. When the voltage comes down to 0.20 volts de energize the purge valve and the voltage may rise some then deactivate the vent and see how long the voltage takes to rise back to 3.2 volts. You may not have a leak but a restriction in the system.

Customer:

I have written all this down and faxed it over to my mechanic and we will take it from there...this was a whole lot better than taking it to Jaguar and spending $200.00 for diagnostics. Hopefully this will resolve the problem, if not is there any other solution or area that may be causing this to keep happening?

Richard :

Between this test and the smoke/pressure test we should find either the leak or restriction/blockage.

Richard, Jaguar Technician
Category: Jaguar
Satisfied Customers: 13791
Experience: 12 years at a Jaguar dealer as technician and shop foreman.
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Expert:  Richard replied 3 years ago.
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