1971 510 – strong fuel smell

[goose_F24]

Long time listener, first time caller. '71 510 1400 owner in London, UK.

 

Haven't had the car all that long, and the other day after filling up with fuel, I noticed an insanely strong fuel smell in the cab. So strong that I thought "christ, my eyes are burning".

 

Visual inspection of fuel line – no leaks. No pool under car (after being stationary all night). Fuel consumption not noticeably excessive.

 

Not overfilled with fuel to my knowledge (I always wait for the "click" on the fuel station nozzle, and then stop filling).

 

Fuel cap not vented, and clicks shut.

 

Took off the board covering the fuel tank area in the trunk, and found that the breather tube has a T-piece – with only two of three ends connected. I can only assume this is obviously causing the smell... 

 

This is the work of someone before me, but I'm just trying to understand what's happened here? One end goes to the fuel filler hose as expected, and one end onto the breathing nozzle on top of the tank. Where should the "missing" hose from the unconnected end of the t–piece be going to? I can't find a vapour reservoir. Does this mean that the vapour from the fuel tank is literally venting into my trunk?

 

Perhaps someone might be able to shed some light, as there seems to be a lot of variation around pre / post 1970 models and their fuel / vent hose structure.

 

Many thanks

 

[datzenmike]

 

 

 

#8 is your plastic Tee. The missing line #14 goes toward the engine. Do you have the missing hose??? May have dropped down behind tank. 

 

There is a fuel vapor line #14 to the engine. This is weird but the fumes are stored inside the engine block when the engine is off. When started, the fumes are sucked into the intake manifold and burnt. If this fitting was broken before you would have noticed the smell earlier, maybe this just happened?

 

Filling the empty tank would have displaced a couple of cubic feet of vapors from the tank. 

[goose_F24]

Hi datzenmike,

 

thank you for the response, and diagram - most useful.

 

Re the missing vapour hose - i’ll have to take the rear seats out and have a look I suspect, to see if it’s dropped down. The “sheered off” T piece (pictured) makes me suspect that this was done on purpose, and the vent hose deleted. In any case, would this vapour hose follow the fuel line towards the front of the vehicle?

 

To be honest, I rarely fill the car up fully - which is maybe why I haven’t noticed it before. There’s away been a faint whiff, but I suspected that was typical for my 55 year old beauty.

 

When you say the vapour fumes are stored inside the engine, is this by hose #14 on the diagram, meeting up with the evaporation control valve?

 

many thanks again 

[datzenmike]

Yes #14 passes through the floor with the fuel and return lines but become steel hard lines while the vent pipe is made of aluminum I believe. The vapor line quickly moves over to the left side of the body and forward to the base of the left strut tower where it connects to the flow guide valve. As fuel evaporates in the tank with the engine off a slight pressure opens the the flow guide valve which directs fumes into the engine vent tube sticking horizontally out of the engine block. When running, as the fuel level lowers from use, a slight vacuum opens the guide valve allowing filtered air back into the tank.

 

  

 

Engine vent tube. The flow guide valve connects to the little tube on the larger block vent tube.  The block vent is connected to the intake vacuum through the PCV valve on the intake which opens when engine running drawing stored fumes out to be burned.

 

 

These were replaced with charcoal canisters on later Datsuns.