Gas Smell (1 Viewer)

[rstoddard]

I’m smelling gas from my ‘78 FJ40. I can’t see any gas leaks, but there could be a micro leak somewhere. Obviously you can’t see for certain unless you pull the tank which in my case is a huge problem since I have a roll cage that replaces my stock seat frame mount. In order to remove the tank, I have to unbolt and lift the entire cage high enough to get the clearance to get the tank out.

Does anyone have any thoughts on how to diagnose the source of the smell, before pulling the tank? Is it possible it’s a hose leak or a faulty canister? I don’t mind going through the (major) effort of getting the tank out, but if there are some things I can check first I appreciate the ideas.

 

[1911]

I’m smelling gas from my ‘78 FJ40. I can’t see any gas leaks, but there could be a micro leak somewhere. Obviously you can’t see for certain unless you pull the tank which in my case is a huge problem since I have a roll cage that replaces my stock seat frame mount. In order to remove the tank, I have to unbolt and lift the entire cage high enough to get the clearance to get the tank out.

Does anyone have any thoughts on how to diagnose the source of the smell, before pulling the tank? Is it possible it’s a hose leak or a faulty canister? I don’t mind going through the (major) effort of getting the tank out, but if there are some things I can check first I appreciate the ideas.

The first thing I would check is the rubber fuel lines that connect the hard fuel lines right above the frame. They get old and cracked after 45 years.

 

[peesalot]

have a look at the drain hole under tank, wipe finger around hole & smell, check fill/vent hose for cracks, verify lines from evap to charcoal can are clear, if all those are good and you have wetness around drain hole it is probably pin holes

 

[rstoddard]

have a look at the drain hole under tank, wipe finger around hole & smell, check fill/vent hose for cracks, verify lines from evap to charcoal can are clear, if all those are good and you have wetness around drain hole it is probably pin holes

I drained and replaced the plug awhile back (before this all started). I put a new gas gasket on. I’ll check that closely.

What exactly is the “evap”? There is a plastic manifold behind the filler tube. Is that you mean by the evap? I don’t really understand how all that works. Lots of little tubing from the tank and charcoal canister.

 

[Chungas Revenge]

Just behind the cover, passenger side just left of the door opening (silver in pic #1).

You should see something that looks like pic #2. Sometimes these connections can loosen or the lines go bad.

 

[GA Architect]

I drained and replaced the plug awhile back (before this all started). I put a new gas gasket on. I’ll check that closely.

What exactly is the “evap”? There is a plastic manifold behind the filler tube. Is that you mean by the evap? I don’t really understand how all that works. Lots of little tubing from the tank and charcoal canister.

FYI - be careful with the plastic separator/manifold, it can be brittle after many years of service. The below pic was the culprit of my gas fume smell inside my rig.

...

 

[peesalot]

That evap lets pressure from tank vent & separate funes go to charcoal canister & fluid goes back to tank. The inspection of drain hole is NOT for a leak at drain plug, usually the edges of the hole will be wet just a bit and it can be fuel from pin holes in bottom of tank.

 

[phroger]

I’m smelling gas from my ‘78 FJ40. I can’t see any gas leaks, but there could be a micro leak somewhere. Obviously you can’t see for certain unless you pull the tank which in my case is a huge problem since I have a roll cage that replaces my stock seat frame mount. In order to remove the tank, I have to unbolt and lift the entire cage high enough to get the clearance to get the tank out.

Does anyone have any thoughts on how to diagnose the source of the smell, before pulling the tank? Is it possible it’s a hose leak or a faulty canister? I don’t mind going through the (major) effort of getting the tank out, but if there are some things I can check first I appreciate the ideas.

I had a similar scenario on my 77. Cleaned the lines, checked evap canister, everything looked fine. Finally fixed the issue by replacing my gas cap - it wasn't properly venting and caused a backup of fumes in the cab.

 

[cbmontgo]

Just behind the cover, passenger side just left of the door opening (silver in pic #1).

You should see something that looks like pic #2. Sometimes these connections can loosen or the lines go bad.

View attachment 3564153

View attachment 3564154

The vent tube labeled "4" in the pic above was loose on my '77 and caused a gas smell a few years back.

 

[charliemeyer007]

Back in the mid 80's I had a seam in the gas tank start to weep every so slightly. I did the alcohol resistant tank liner treatment from JC Whitney. Has been fine ever sense.

 

[cruiserkev]

I also had fuel smell issues the last couple of years. Before ripping out your fuel tank try replacing these 4 hoses that go to the evap unit from the tank with new fuel line. (Apologies for stealing this picture) My lines were original and didn't have any obvious cracks but I replaced them anyway as they were over 45 years old last summer. Completely eliminated the fuel odor in my 76 plus it was an easy and inexpensive fix.

 

[wolfbak]

If you replace the fuel or vapor hoses, be sure to use materials rated for gasoline. Even brand new lines not rated for fuel can pass vapors through the rubber. I know first hand !

 

[rstoddard]

That evap lets pressure from tank vent & separate funes go to charcoal canister & fluid goes back to tank. The inspection of drain hole is NOT for a leak at drain plug, usually the edges of the hole will be wet just a bit and it can be fuel from pin holes in bottom of tank.

If you replace the fuel or vapor hoses, be sure to use materials rated for gasoline. Even brand new lines not rated for fuel can pass vapors through the rubber. I know first hand !

I’ve been looking for material. Toyota sells it for $46+ but I can’t understand the length and if it’s enough to do all three or four connections at that price. Guess I can hit the auto stores buts its never a sure thing anymore.

 

[rstoddard]

I may have found the source of the smell (hopefully). After taking into account all the great feedback and comments, I checked the Evap Separator and tubing and discovered that one of the nipples had been broken off a LONG time ago and the whole thing was Jerry rigged by the PO with a piece of steel tubing pushed into the Separator and the tubing half-assed taped on. It wasn’t working at all. Do, assuming that is the problem, I’m on the hunt for a replacement Separator.

One other question: I see references to a check valve on that return line that goes under along the frame, but the Toyota Microfiche I have from Coolerman doesn’t show a check valve for a 1978 FJ40. I believe that was only for like ‘75-‘77. Does that sound right?

 

[charliemeyer007]

I think you fix that janky connection. New part, gas tank epoxy, threaded barbed nipple or something like that. I have bought several 25 ft rolls of nice gas hose off ebay for very good prices.

 

[wolfbak]

I may have found the source of the smell (hopefully). After taking into account all the great feedback and comments, I checked the Evap Separator and tubing and discovered that one of the nipples had been broken off a LONG time ago and the whole thing was Jerry rigged by the PO with a piece of steel tubing pushed into the Separator and the tubing half-assed taped on. It wasn’t working at all. Do, assuming that is the problem, I’m on the hunt for a replacement Separator.

One other question: I see references to a check valve on that return line that goes under along the frame, but the Toyota Microfiche I have from Coolerman doesn’t show a check valve for a 1978 FJ40. I believe that was only for like ‘75-‘77. Does that sound right?

If you can find a replacement separator, you can probably use some JB weld around the metal tube. It's not the first choice, but when one of my nipples broke off, I superglued it just to hold it in place and then built up JB Weld around it with several layers. It's working fine so far. If you get a replacement which will be used I assume, be really careful with it. Most of them have become brittle over the years. Make sure your hoses are long enough that when you install it, it doesn't pull and break another nipple off.

 

[pb4ugo]

I think GA Architect fabbed up a unit with brass and pipe fittings. You might search his thread.