2020 Mahindra Thar: Petrol smell in the cabin & how I resolved it

They also checked the fuel vapor canister and that was also all fine.

BHPian Dr.AD recently shared this with other enthusiasts.

I also started getting petrol smell, on occasion, sometime back in March. Initially, it went back on its own, so I did not care much.

However, recently, it started getting more frequent. I noticed that the smell was strong when I had about half or less than half tank full - that meant a lot more sloshing around of petrol in the tank, and lot of evaporation and fumes.

So I went to check with my Service Advisor. I was worried about some fuel leak in the engine bay like @abirnale discovered in his XUV7OO. The service center inspected the cabin bay thoroughly, with me standing next to it, and there was absolutely no leak anywhere there. The engine bay was clean and dry. There was no petrol stain or smell anywhere there. It all looked fine.

They also checked the fuel vapor canister and that was also all fine.

Then they checked the next suspect - the fuel filler lid - and voila, the O-ring in that had gone bad and the seal was poor. Clearly the smell was coming from the fuel cap. It was leaking the vapors. That is why the smell was stronger when fuel tank was half full or less. Lot of sloshing and vapors there in half tank, and those were leaking out from the fuel cap.

I also Googled it and found that a leaking fuel cap is one of the most common sources of fuel smell in the cabin.

The solution was quite simple. They ordered a new fuel lid cap for me (it was not in stock). And once the part arrived, they changed the lid cap. And now the petrol smell is completely gone!

So just wanted to share this simple check and solution with everyone, in case anyone else has petrol smell in cabin, in a Thar.

Here's what GTO had to say on the matter:

Am pleasantly surprised that it was a one-off bud (like so many others in the Thar) and hasn't happened again. But thank you for the solution. Who would've thought that the fuel cap will be the culprit?

Here's what BHPian NomadSK had to say on the matter:

You didn't get a check engine light ? That's the first tell tale sign for vapor leakages and among one of the most frequent ones. Was OBD plugged-in to generate the fault codes ? Your vehicle’s fuel system is a sealed system designed to trap fuel vapors before they can escape into the atmosphere. When the fuel evaporates inside your fuel tank, the harmful vapors get moved to a charcoal canister. The EVAP system draws in fresh air, gathers up unburned vaporized fuel and delivers them back to the intake system to be re-burned in the engine. Almost same thing is done by PCV valve, waste gases are fed back for combustion in the engine.

Any EVAP leakage from the fuel system (from fuel tank to EVAP canister) will give the "check engine light" first, that's when ECU detects any issue with the EVAP system and generates a trouble fault codes. The fuel caps (a part of the EVAP system) are specifically designed with pressure and vacuum relief valves to prevent the evaporation of fuel. It can be both vented or non vented as per the car design. Even a blocked vent can trigger the "check engine light"

Long time back I had fuel smell in the cabin, which was diagnosed to faulty fuel pump and this was sitting right under the rear seat, in the cabin . I was surprised to see the fuel leaking under the seat when mechanic removed the back seat and the foam was drenched wet with fuel, quite scary situation. Fuel pump had gone kaput and it was such a strange design to put the fuel pump, inside the cabin.

Another thing, how a fuel cap vapor leakage was smelling inside the cabin ? I can understand, google pointing out this, but I cannot comprehend how, since the fueling system is all external to the car.

Here's what BHPian asingh1977 had to say on the matter:

I got this vapor issue on my brand new Thar too. Maybe the jeeps 4th or 5th fuelling. After a tank full, I kept noticing a distinct petrol smell in the car, while driving back home. Initially I thought it was the petrol bunks residue smells. Opened the windows, ran the AC in circulation mode. Still persisted.

I inspected the lid. It had been closed/locked with the cap connector cord (thick black wire) lodged between the lid and car body. Tucked it in, and locked the lid. Petrol smell did not come back.

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