Fuel Vapour Control Valve

simontaylor · September 2, 2005

I am planning for a 120,000 mile service which I will do myself and the service booklet mentions to "check fuel vapour control valve".

Where is it and what am I supposed to check for, just cleanliness?

Johnny5 · September 2, 2005

You are doing the service yourself, and you don't know what this component does??

Trust me. Servicing from a Haynes manual or whatever does NOT make good sense.

I have run a garage for twenty five years, and still take my LS to a dealer, as I believe a guy who is familiar with the machine will do a better job despite my own quest for perfection, as you will probably have yourself.

IMHO of course :D

The valve forces the fuel vapour to be retained under pressure rather than let it contaminate the environment.

This is why fuel tanks frequently hiss when the cap is removed.

I believe around 2-3 p.s.i. is correct....

simontaylor · September 3, 2005

Thanks Johnny5, good point, very good point actually. I have had company cars too long and like to do it myself, like a hobby. I only paid £3k for it and am just looking to run it into the ground over the next 10 years.

I guess you are not sure where this valve is or how to check it? as you get yours done at the dealer.

Any one else know?

dipstick · September 3, 2005

"The valve forces the fuel vapour to be retained under pressure rather than let it contaminate the environment.

This is why fuel tanks frequently hiss when the cap is removed."

Eh? Does that mean the hiss is the release of the vapours - into the environment...?

Leadfoot · September 3, 2005

Where is it and what am I supposed to check for, just cleanliness?

My 92 LS service manual states that the vapour control valve is located on the right (facing engine bay) side of the plenum chamber. There are three round components in that area, the one with the smallest diameter of the three is the VCV. It has three pipes connected to it, 1 above the center rib, 2 below.

It is a vacuum operated valve. Vacuum from the intake chamber is applied to the VCV when the coolant temp rises above 56C and another valve upstream opens (the BVSV). This then allows the intake vacuum to purge any hydrocarbons stored up in the charcoal canister.

Note upper means as installed in the car, please note its original orientation carefully.

TO CHECK VCV OPERATION

(1) Remove VCV.

(2) Apply vacuum above 9.3 kPa (70 mmHg, 2.76 in.Hg) to

the single upper pipe.

(3) Check that air flows from the middle pipe out the lower pipe.

(4) Stop the applied vacuum.

(5) Blow air into the middle pipe and check that the air does not

come out of the lower pipe.

If a problem is found, replace VCV.

(6) Reinstall the VCV and reconnect the vacuum hoses.

I will check mine now! I am doing long term research into Lexus reliability, mine has 150K so far.

I have not had mine serviced by Lexus yet, don't know if I ever will as I can do the work myself. The service manuals are very simple to use. Do a bit of research first or ask here before taking something in for work, you will save yourself a lot of expense I am sure.

Cheers,

Leadfoot

simontaylor · September 3, 2005

Leadfoot, we are on the same wave length together.

At £90 ph my car is destined never to see a dealer. even if it takes me 3 times as long to do something, I'm better off. and if I do it in my own time it costs me nothing.

What manuals do you have?

I have a mitchels CD, but it is just descriptive, no pictures or part numbers.

I was looking at the TIS, but they are just for the US cars.

I was thinking about the real lexus ones, but £200 is a lot.

I need to do the EGR pipe as mime is leaking badly, I'm told it is quite a job, but I do have the luxury of a double garage and a 2nd car, in case I'm not finished in a weekend.

Simon,

'95 Mk III.

Leadfoot · September 3, 2005

At £90 ph my car is destined never to see a dealer. even if it takes me 3 times as long to do something, I'm better off. and if I do it in my own time it costs me nothing.

I am a big fan of knowing how my car works. I bought a lexus because they are just such a brilliant piece of machinery (for instance a six bolt main end cap and forged steel crank as standard!!). The dealers may have all the special tools but for a majority of the work I believe a knowledgable owner with time to get the job done will do a better job. I have been horified to see how rough some mechanics are.

What manuals do you have?
I have a mitchels CD, but it is just descriptive, no pictures or part numbers.

I was looking at the TIS, but they are just for the US cars.

I was thinking about the real lexus ones, but £200 is a lot.

I downloaded the entire set for the 92 model from the TIS. It lists the US and Canadian models, mostly the car is the same, I have not found any major variations yet. Difficult to navigate but very useful. The real ones are worth it if you are planning to do all the work yourself. I am happy to print out the sections as I need them (thanks boss!)

Good luck,

Regards,

Leadfoot