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I'm away from my car so I can't take a peek to fully describe what follows, but......
When you're looking at the hoses and valves, etc. you should be able to see that one of the small metal pipes clearly heads aft, apart from any others. This would be the vent pipe coming from the tanks. Just remove the hose so the end of the pipe is open to atmosphere. If the problem doesn't go away the pipe may be clogged ....or perhaps crushed?
I don't think ambient temperature has anything to do with it, it's a buildup of fuel gases under any temperature that need to be purged and are not purged because of these check valves.
I eliminated the problem in my car by removing the check valve and installing an open hose-to-hose connector, which is the same thing as pushing a drill bit through the check valve to break the membrane inside it.
I understand this purging system came about in the early 1980's through a recall, it was installed by dealers.
However, many things were changed by 1987 including the a/c system, and it looks like the purge system was too.
I drilled the other valve (#1 in my photo, which I reposted below) and drove the car twice today. It wasn’t as warm today. There was no more whoosh when I opened the fuel caps! So I’m pretty sure it’s now fixed.
Oddly though, when I back up slowly with the windows down, I get a slight smell of fuel. I’ve never noticed that before until I had the whoosh. There are no gas leaks. Also, my new fuel pump is noisy. Not as noisy as my last one but I can definitely hear it when I open the trunk. Does anyone else have a noisy fuel pump?
Oddly though, when I back up slowly with the windows down, I get a slight smell of fuel. I’ve never noticed that before until I had the whoosh. There are no gas leaks.
It doesn't have to be a visible, wet leak to make a big smell. A little ooooze will do it. Or, gasoline vapors escaping.
How are the seals on the gas caps?
While checking those, look at the little vent hoses going to the filler necks, just below the caps. Put your nose to the area.
Sometimes vapors and odors move in mysterious ways. One often overlooked leak (and odor) source is the very short fuel hoses at the front of the cylinder head.
Also, my new fuel pump is noisy. Not as noisy as my last one but I can definitely hear it when I open the trunk. Does anyone else have a noisy fuel pump?
Probably OK.
If you can hear it in the cabin, it's certainly too loud. I'm pretty sure any of them are loud enough to hear with the trunk open.
Thank you, Doug. I will check all those areas to see if I can smell fuel.
It’s good to hear my new new fuel pump is probably okay. I can’t hear it inside the cabin. At least I can’t while sitting in the front seat. If I put my ear near the closed trunk, I can hear it and I certainly can with the trunk open.
I did my homework on how to troubleshoot, jacked it up, removed wheel, found the sheet metal panel covering the fuel switch over valve (on the left side). Removed the two sheet metal screws. There is a bolt on the left side. (See photo) Loosened that but it feels like there is a nut on the other side. Now it just spins without coming out. Seems to be boxed behind it - can't feel a nut. Any ideas hot to get that cover off?
I'm sure you have discovered by now that the large 3/8 bolt through the cover plate does in fact go clear through the sub-frame box and there is a nut (9/16) on the other side. There is not a captured nut here. This bolt is one-of-two that holds one of the rear differential sub-frame rubber mounts to the car.
Dave
Thanks Dave. Yes, I finally figured that out. Good to know what it is there for. Seemed a little weird that they used two small sheet metal screws and a gigantic bolt to hold the cover on.
Turns out my fuel return valves were fine .... the electrical connections for the valves were corroded and that is why the valves were not working. The moral of the story is, if your Jaguar has something not working and it has an electrical connection, check that first before you start worrying about mechanical issues.
I am presuming they have these in order to control return flow EVENLY into each tank as they a basicly a small pump???
Cheers
Not sure about Series II, which I assume you are referring to.
On a fuel injected Series III the return valves are not pumps of any fashion. They're simply an open-or-closed valve to direct fuel back to the same tank it was drawn from.
Quick followup question on return valves while this topic surfaced. Running last week I noticed a slight moaning/groaning/low whine sound in my driver side rear wheel well. If I switched the tank from the dash button, the sound immediately stopped. Switch back and it returned. I assume there is something going on with my return valve in that wheel well, but I can't really think what would cause that type of noise. Maybe if the valve is not opening/closing fully, the pressure is causing that noise through a smaller opening. Kind of like when you almost close an air duct in your home and it whistles through that smaller opening??
I think you're on the right track, Randy. Movement of a fluid can cause noise under the right circumstances.
Over the years some have removed a lazy return valve and restored proper operation by simply cleaning it with a solvent or carb cleaner spray or the like.
Hello! I just bought a 1985 XJ6. Everything works fine when switched to the left tank, but as soon as I switch to the right tank (full), I can hear bubbling sounds and gas is leaking below right rear lower fender area.
Comfortablynumb, in the posts above you'll see about the fuel return valves in the rear wheel wells. The fuel is supposed to be pulled from one tank and the return is supposed to be returned to the same tank. Switch over and it pulls from the other tank and returns to that tank. So what you described with the switch in one position it's all good but in the other position it's pulling from one tank and returning to the other and thus over flowing. You need to make sure all three valves are working correctly (the changeover valve and both return valves). And that they are wired correctly. The changeover valve is messy to check, just make sure it is clicking when an assistant works the switch. The return valves can be taken out and checked without gas going all over. It is a hassle to check them all but fix it once and fix it right.
Alternatively, you can remove all three valves and plumb them together and make one virtual tank. There are threads here on the Forum on how to do that. Once you get everything sorted I'm sure you'll be very happy with your new car.
05-22-2019, 10:09 PM
