Excuse my ignorance here . I have been chasing a fuel smell in the boot for a while. Renewed most hoses etc etc but it persists. I’ve just stumbled on a jaguar parts drawing showing the Rochester valve. The valve has three pipes coming off it with the smallest one going to a tee piece. From memory this smallest outlet on mine has no hose coming from it. I discounted the Rochester valve and this outlet early on because I couldn’t smell anything from it. This hose has not been removed by me but by a p.o. I recall from day one the boot smelling of fuel but put this down to the rotten tank and hoses. Could this be my problem and would it release fumes intermittently if that makes sense? Also if the pipe is a requirement what does it tee into? Many thanks once more. The hose going to no.9

 

It could. The RV allows fumes out, and also allows air back in. The small tube should be T'd off the ECU vac tube (at 10 in your diagram); its function is to open the valve to allow fumes out once the engine is running, as the vac opens the valve. The valve can easily get blocked, in at much as it will not either allow fumes out, or not allow them in, or both. If your vac tube is not attached, then the valve will not work as intended and may indeed result in fuel smells.
To test it, you should be able to suck inwards towards the tank with a small effort, and to blow outwards if you apply vac to the small tube. The entire thing can get blocked as the diaphragm inside can get stuck. You can prise the round bit open carefully and unstick it, or buy a new one.

 

That Rochester Valve is supposed to dump into the charcoal canister.

The small port is connected back to a vacuum pump.

Then one side of the larger ports goes back to the fuel tank while the last large port goes to the charcoal canister.

I suspect that leaving anything, other than the small port disconnected shouldn't hurt anything, but disconnecting the small port renders the valve useless, and stuck closed.

Disconnecting the hose that leads back to the tank should only help minimize the fuel smell in the boot. Disconnecting the hose to the charcoal canister should have no effect at all to your boot.

All this assumes that the valve and the vacuum work. If you want to find out, I'd simply disconnect the hose from the tank and see if that relieves the smell in the boot since any pressure buildup in the tank is free to exit at anytime.

 

Vee
Not all UK spec cars had the canister. My RV just vents to the outside. No idea if Brinny's does or does not.

 

Thankyou both. I don’t think I have a charcoal canister. I will need to have a good look at this again and see what’s going where. Will report back thanks

 

Brinny, the coupes with no canister have the same boot setup as those that do, but they both have the thin steel tube that runs along the back of the tank space and out under the car in front of the LHS rear wheelarch. On Uk cars this vents to air at that point, and on canister cars it joins a pipe leading to the canister in the front of the front LHS wheel arch. The pipe is shown in this photo

You can just see the RV at the RH top end of the vent tube attached to a flexible

 

Yes, I would start at the rotten tank, the rivet at the bottom of the tank, fuel sending unit gasket, fuel hoses and connections, fuel filler neck gaiter and gas cap.

 

All new and checked that’s why I’m looking at the Rochester valve

 

Hello Brinny

Do you still have the octopus thing in the top right hand corner?

This is what I did - I blocked off the 2 vents. top right of the fuel tank
Then I just put a 2 way valve (as high as I could) instead of the octopus thing

Car sits in the sum all day, and I only get to play occasionally, have not had any issues of a fuel smell in the car so far



Bottom hose leads from the 3rd vent of the fuel tank - top hose goes to the canister

 

Thanks for your input. I am going to investigate tomorrow, I’ve had the interior come back so I’ve been refitting that and finally got my steering rack back after a refurb so I’ve refitted that today. I had a quick look under the car but I can’t see the vent hose Greg mentions and in a way I’m hoping that is my problem. Will pull the boot apart tomorrow and see what’s what. Thanks for your help

 

Brinny
The vent outlet is just inside the line of the chassis rail that goes over the rear axle, just forward of the (unused on RHD cars) handbrake cable tube. If you look on the other side (UK driver's side) for where the HB cable enters the chassis, there is an equivalent tube unused the other side. Look around there and, on coupés at least, that is where the boot vent tube exits, it is only about 1/4 inch diameter. On USA cars, this tube is connected to a under-car tube that goes to the cannister in the LHS front wheel arch front cavity

 

I’ve checked back through my photos and it shows the thin vent pipe you describe in my pictures , prior to me pulling the tank for repair. I’m pretty sure I haven’t re fitted it for some reason when I put the tank back in. Probably didn’t realise what it was and ignored it. Will pull the boot out tomorrow and find out what I have or haven’t done. Thanks

 

So if your tank is venting into the boot, there is your problem.

 

Well as usual the best laid plans ......... Before I got stuck into the boot I nipped under the car just to marvel at my newly installed refurbished steering rack. Leaking. Couldn’t believe it. Phoned him up and they were very sheepish but I’ve had to remove it and drop it back off too them. I’m going to buy a number plate for this car that is 666. Had a quick look in the boot and my memory was incorrect and I had coupled everything up correctly at first sight. So the easy fix with the breather was a none starter. Not sure where to start looking next but somethings not right.

 

brinny
Star by carefully checking that the RV is actually working. They do jam shut. You should be able to blow outwards with a little effort no vac, and and to suck inwards, once vac is applied to the top spigot.
Disconnect the outlet side and blow some compressed air through that pipe, it might also be blocked.

 

will have another look tommorrow. Is it worth putting some compressed air through all the pipes to make sure they are working? Is the valve easy enough to strip and clean as I’ve no experience of these. Thanks

 

Only the breather outlet pipe to the outside is likely to be blocked as the steel pipe is very small diameter. The RV can be opened up, you have to carefully snap the top off the bottom. Buts first see if it is working as described. If it is all OK. If not, try fixing it, buy an after market valve
https://www.merlinmotorsport.co.uk/p...push-on-m-tpv8

or just get rid of it and connect the input and output tubes together and block the vac line.

 

Had another look this morning and did the following. Put compressed air down the pipes but couldn’t really tell if it made a difference. I then tried the Rochester valve but that was quite difficult to suck and blow. I opened it up but couldn’t really see anything out of place . Tried sucking and blowing again but didn’t seem any different. Think I will replace it just to rule that out. Initially I reconnected the pipes back the wrong way and pretty quickly noticed pressure at the tank filler which I haven’t had before. I realised that what I thought to be the breather pipe was actually the abs wire. Took the rear firewall plate off and located the breather. It came out exactly where you said Greg and you can see in the photo it’s been gunked up with underseal. I removed this bit of pipe and the breather looked clear. Do you think this could be the cause of my problem? I’ve shut the boot lid and put the cover over it and will see if it smells of fuel tomorrow.

 

Brinny
Did you blow out this tube from the RV end, having unblocked the outside end? If not, then you should do it. A blocked tube would certainly do it. It sounds to me from what you have written that the RV has not tested definitely good or bad yet. Either of these two problems could cause the smell, as could porous tubes from the tank to the RV and the cannister.

 

Have a look:
Alfredo