fuel smell only with windows down

[bartsscooterservice]

I used the search but couldn't find a real answer to it.

When I drive with the windows closed there's no fuel smell in the interior, but when I drive with the windows down there's a smell of fuel...

I have to say it is less now with the new rebuild carburetors, but I can still smell it.

Does it come from the engine bay ?

[Virto]

Exhaust being sucked into the cabin thru the hatch, possibly? I know rolling the windows down will often make the effect worse.

It's possible that you have a fuel smell under the hood - rolling the windows down would allow it inside the cabin. I'd think you'd be able to notice it under the hood if you're leaning over while outside the car, though.

[Powderkeg]

Bart,

I found some notes and hope it helps.

Check the Following Areas:

The Firewall

Put in new seals and grommets especially around the throttle rod. Apply silicon around the old rotted grommets. Make it as airtight as possible.

The Exhaust:

Fix any exhaust leaks.

Rear Quarters:

Remove the inside drivers side panel where the antenna goes. This can be a major source of leaks from under the car.

They are through the inside quarter panel just outboard of the muffler. To view these shine a light under the car and check for light coming through when looking inside the rear quarter panel section.

The smaller of the two at the bottom is the power antenna drain plug. Replace or plug with silicon

The other, larger higher up, appears to be some sort of drain plug. You have to get under the car to see it. It’s about 1.5 inches in diameter. Replace or use silicon to plug.

Passenger side rear quarter panel: Check for rotted gas tank vent lines. Check for rotted grommets and replace or patch with silicon.

Rear Deck & Tail Panel:

Check gas tank vent hoses, Remove the taillights and check the condition of the gaskets. Replace as needed.

Check rubber coverings around the bulbs.

Be aware that the taillight assembly has a drain hole in the bottom. Do not plug this.

The Rear Hatch:

Check the condition of the 4 plugs in the inside lower edge below the narrow vinyl covered panel. Replace as needed.

The inside panel inside of the hatch is about 2 ft x 6 inches. Remove this and attach clear polyethylene sheeting (like the vapor barrier sheeting in the door). Seal with silicon and attach the run a bead of silicon around the panel.

[AZ-240z]

I'm probably not going to explain this well, but here is my reasoning. With the window open, or down, there is a venturi effect at the window,. ie.,

an area of low pressure resulting from outside air passing over the car which will tend to draw the cabin air past the drivers seat and out the window.

This area of low pressure created inside the car will draw air into the car's cabin from any orifice that is not properly sealed,. ie., worn or missing

grommets, worn or ill fitting weatherstripping around doors and rear hatch, tail lights, body seams at edges of rear deck flooring not sealed, leaking fuel filler tubes, hoses, and hose clamps in the right quarter panel void, and the list goes on. Any number of the correct grommets and floor plugs are readily available, either NOS or aftermarket and well worth the cost.

I removed all of the interior plastic finisher panels, carpeting, and anything else I suspected might hide a leak. All grommets, weatherstripping, and plugs are either NOS or, when NOS was not available, reproductions, and along with the use of 3M body seam sealer, I have no intrusion of gas or exhaust smells in my restoration. I believe there are any number of threads that give very good explanations of this problem discussed in the past.

The down side of all of this, is, I cannot shut any door or hatch without cracking a window.

Dan

Edited October 2, 2013 by AZ-240z

[bartsscooterservice]

I do now I am missing the rubber strip in the engine bay where the hood closes on... ( getting that this week I hope ) could it be that carburetor/engine fumes are leaking past that, and going into my cabin when I open the windows when driving ? ( the natural flow pushing the gasses in ? )

I am thinking that because there's also alot of air from both the fan and the wind is pushing into the engine bay when driving...

[djwarner]

The other replies seem very comprehensive. Since you rebuilt the carbs, I suggest you double check that the vents from the float bowls are piped back to the air cleaner assembly with rubber hose. If your car does not have a vapor canister, there is a vapor control valve on the driver's side that has two lines. One is ported to the air cleaner assembly, the other is ported to the PCV pipe coming out of the block.

These things significantly reduce the fuel smell in my Series I car.

[jfa.series1]

Check the plastic fresh air ducts near the radiator frame. If they are broken down, that could also be a source of engine bay gases getting into the cabin.

[240260280z]

A/F ratio of the mixture has a lot to do with the intensity.

I rebuilt a Series-I 240z and completely sealed/bagged it. All the window rubbers were replaced, all body openings closed, all vent and fuel hoses replaced and grommets sealed. The only openings left were the refurbished stock rear hatch vents, the front air vents and the heater system.

It still smelled just above faintly when a window was opened and the A/F was too rich. It is less noticeable at stoichiometric.

I would guess the later side vent Z's would do better for lowering gas reversion into the cabin.

Keeping the two front vents open helps a lot as well to help pressurize the cabin and reduce outside fume inversion.

Edited October 2, 2013 by Blue

[madkaw]

Have you checked for leaks ? Just one drop of raw fuel somewhere will stink up a whole garage - let alone a small cabin like the Z. After driving have you stuck your finder in the carb inlets to see if any fuel is pooling there?

Then there is the tank vent box, but I would think you would smell that more with the windows are up

[grannyknot]

I have to say it is less now with the new rebuild carburetors, but I can still smell it.

Bart, that statement says it an existing situation, get her up on blocks and check every inch of the fuel line right back to the tank, pay close attention to all of the fuel and fuel/air hoses that are inside the cab behind the rear passenger side interior covering. You might have the original plastic surge tank, might be time to renew those 32 year old hoses.

Chris

[bartsscooterservice]

I'm going to do this once the weather get's better in a few months..

[Stanley]

I've got some of those rubber fittings missing or shot at some of the firewall openings like choke cable, accelerator linkage, etc. Noticed a smell when decelerating at freeway speed. I've got K&N's on the SU's and had a little filter on the cam cover vent. When I pulled the filter off and put a hose from the vent, that ends right between the K&N's, it stopped the smell. Not 100%, but way better.