I have a healthy drip/leak out of the big hose on top of the evap canister. This is my new to me 20,800-mile 1985 XJ6 VDP. I have done some research and have read where the charcoal can solidified from raw fuel contaminating the charcoal, but with only 20k miles I am not sure if this could still be my issue. The car was off the road for a number of years before I bought it and am starting to encounter and fix all the things that can happen when a car sits dormant for a number of years.

Thoughts on cause and fix?

 

Is the fuel switching system working? If not, and one tank overflows, raw fuel can drawn into the canister.

Cheers
DD

 

The fuel gauge reads differently when each tank is selected, and the car doesn't stall as if running out of fuel as if one tank was not working. The seller prior to listing the car for sale replaced the fuel tanks with new ones, new sending units, new switchover valve and had the injector rebuilt and replaced.

So, now what?

 

MSG, with this don't troubleshoot using assumption. Tanks may be new when the PO installed them but you have to know without a doubt they are completely clean. I suspect the new valves were changed before the tanks, of course it only takes about five seconds to contaminate them with fuel from the bad tanks, then as a last resort tanks get changed, but with fuel lines and new valves full of crud. And pre filters won't get it all and neither will the main filter. But a stuck valve is causing the fuel to back up into the evap system (as Doug previously said), You'll probably have raw fuel smell in the cabin too from the separators in the c-pillars. I despise this problem with XJ's, I worried with it for a long time with my 86. But be careful, I consider this problem extremely dangerous, I've had raw fuel pouring out of the canister under the front fender more times than I care to remember, lots of fuel vapor, lots of raw fuel. btw, the changeover valve can be partially closing (from crud) causing one tank to fill from the return, so you'll see fuel pass through the valve but not realize that it won't close completely in one direction. Clean tanks first, blow out fuel line to the front (not that hard), then new valves and filters and hope it's done. Just make sure the tanks and lines are clean first.
There is not supposed to be any raw fuel in the evap system or the charcoal canister, only vapor.

 

Tanks were new and not just used replacements installed about 2 months ago. I have the receipts. The car had been sitting and off the road, last registered in 2019. It sounds like the original tanks were rusted as the tanks, change over valve, fuel pump, filter and injectors were all changed at the same time.

At this time I don't have fuel odors in the cabin.

So yes, probably crud elsewhere. What is the "ultimate" fix? disconnect all the fuel lines and blow compressed air through them to make sure they are clean? Replace the one way valves? Are they even available?

I see what look like 2 one way valves near the charcoal canister. I also read somewhere that the charcoal cannister is the same as used on some GM cars? Any part number or model?

 

back around 1992 I was told this canister was a maintenance part so I replaced it even though there were no issues with it. I saved the original canister. My Xj-6 is a 1984 model / year built in 1983, so the canister is a 1983 part.

I can't figure why you would have liquid fuel spurting out of the canister because those lines are for fuel vapors, not liquid.

there is a check valve attached to one of the vapor lines that connect to the canister. Those check valves are GM but as I understand it, they were fitted due to a recall in the early 1980's. The check valves are supposed to allow fuel vapors into the canister, and from the canister to the engine where they would be burned in the combustion.

But the check valve calibration is wrong for the evap system and the check valve does not open under the pressure, causing a buildup of vapor pressure at the tanks which expand and contract the tanks until they end up leaking at the seams.

the solution is to remove the check valve and connect the two remaining hoses with a non-restrictive connector. Or just push and pull a 1/8" drill bit through the valve ports to break the membrane of the valve and this will let the vapors pass through the check valve to the canister.

this will not fix the liquid fuel problem, only the fuel vapor pressure problem.

 

Thanks Jose.

I did find several thread on either eliminating the valve or puncturing the diaphragm. I've also read where the canister can be cut open and refilled with aquarium charcoal then resealed, but I need to find out why fuel is being dumped into the canister in the first place. Seems something is being over pressurized if this is only supposed to see fuel vapors.

 

some reasons for the canister to fill with liquid gasoline:
1) overfilling tanks
2) purge valve stuck open *
2) charcoal canister is over-saturated and needs replaced. I think part number is CAC2664 but Not sure.


* there is an electronic purge valve located sort of hidden under the air filter canister, engine compartment. This is a GM or Ford purge valve with two wires. One "IN" hose comes from the charcoal canister through the inner panel, the other "OUT" hose connects to the engine and vacuum line. How it is controlled I do not know, may the ECU does it.

remove this purge valve and test it connecting it to the battery, it should click open and close.
I don't think anyone ever replaces this electronc purge valve, I know I haven't replaced it in my XJ-6. My Ford minivan has an identical purge valve hanging near its charcoal canister just like it hangs in the XJ-6. I think it is a "universal" purge valve used in many cars since the 1980's. A round cylinder with two ports and wires.

 

I have seen the purge valve that you speak of and now I know what it is. Another piece to add to the puzzle. When I got home this evening just for the heck of it, I opened up the fuel doors on the passenger's side and fuel spewed all over me and the car. This tells me that the right fuel tank is being overfilled. Cause?

I know the tanks were replaced, but at this point I am guessing anything could have been screwed up.

I am considering towing the car to a great independent Jag shop here in Massachusetts or possibly merging the two tanks together with a check valve and just not park on a side slope.

 

I will try to test the changeover valves. After being dormant for a decade or more the connections could be corroded and or the valves just need to be brought back to life with some carb cleaner? Is that possible or am I just better off buying two new changeover valves?

 

new changeover solenoids. The tank is overfilling.

 

I think the series 3 has one changeover valve in the boot, 1 each return valves in the rear wheel wells behind a small shield. Your system sounds like it may be pretty clean, just lingering trash from before the tanks were changed. I would put prefilters in the rear before the changeover valve, if it's large specks of trash this will get it. And depending on how competent your mechanic is about not letting trash back into a new valve, I would be inclined to buy all three valves new. Save the old ones in case these become NLA. The charcoal can is a judgement call, on my 71 vette I wasn't successful changing out the charcoal, it had a removable bottom but once removed I couldn't get it to stay put. Ended up leaving it off and venting the tank to the atmosphere, will do the same for my xjc. I have a long thread on this subject on JL but I can't seem to find it, it would be helpful though. I hope you get it sorted soon.

 

New valves from SNG Barratt will arrive tomorrow.

Knowing the charcoal is now saturated in fuel and ineffective, I just may vent to atmosphere like others have.

 

bad idea in my opinion, evap system should be kept as originally designed for safety.
Maybe the new eolenoids will eliminate the liquid fuel problem, if they do, replace the charcoal canister.

 

Worth a try! Others have been successful doing just that

Cheers
DD

 

Controlled by the "Air Switching Module" (which also controls the air injection diverter valve). The ASM is on the RH side of the engine bay near where the diagonal fender brace attaches.

Cheers
DD

 

Can a bad tank selector switch cause issues. Am I correct that this little hole is where fuel is returned to the tanks? Fuel is returning to the right/passenger's side (USA) tank no matter if the left or right tank is selected. The gauge goes read different tank levels when switch from one to another. The right valve is new and I can only imagine the left/driver's side is as well, just haven't gotten to that side yet. What is stopping fuel from returning to the left tank when that tank is selected? bad valve? Bad switch? The valve wired or installed so the fuel is not allowed to enter the left tank?

 

I removed the Evap cannister and was able to separate the bottom from the cannister. The bottom appears to be glued on and I was able to scrape around where the two meet and remove the old glue with a very small flat blade screwdriver. Eventually I was able to wedge a large flat blade screwdriver between the two and slowing pry around the circumference until the two pieces were separated.

As you can see it is nothing more than charcoal medium with a perforated plate on each end. It should be easy enough to refill with new charcoal and reseal the cannister. I will reinstall it once I have my fuel issues all sorted.

 

looks good. But the replacement charcoal must be of a specific type, not just any aquarium charcoal. It is called ACTIVATED CHARCOAL.

everything looks good and clean with the solenoid, hoses too. Have you tested to see if there is 12v power tobthe solenoid with only ignition switch set to ACCESSORY?

 

I have not tested. I assume the valve with the silver end goes on the right side and the one with the black end on the left side? Both with this end pointing towards the front of the car. How do you know how to wire them when both wires are black?