W124 - High on Fuel Fumes... (monitoring)
So after taking Rhino for a short drive and about 90 mins later, there seem to be fuel fumes in the cabin and trunk. I cannot seem to isolate where the smell is coming from. I have in the past replaced the fuel tank (used), the vent valve, fuel sender (VDO), fuel filter, fuel pump, fuel hoses between the fuel filter and fuel pump, the MOT valve and even replace some of the rotten metal hoses that leave the charcoal canister and into the MOT valve with no success.
On the MOT valve, to know if it's working is to simply hold it when the engine is running. If there is a continuous pulse to it, it is most likely fine. On mine, there wasn't a pulse of any sort and I suspected that it would have been dead with the valve closed. This means fumes from the charcoal can will not be ingested by the engine.
When I found the donor MOT valve and fitted it, which is as simple as removing the clip for cables and just wiggling it out from the mount, the valve started pulsing which signifies that it works. There is also vacuum suction from the engine to the valve which sucks fumes into the engine.
At this point, the fumes were still strong in the cabin, but the engine seems to be more responsive, marginally. To limit the possibilities of items to be fixed, a used valve was sourced by my mechanic and it was installed. To install it, have the car on a jack and remove the front left wheel. The charcoal can is located at the back of the left fender liner, held by 3 hoses.
Upon undoing all the hoses, the charcoal can was released. One of the hose plugs was found to be blocked with rush sediment. Unsure how all this will affect it, but it is safe to say that fumes will either not be able to come into the filter or the return to the fuel tank will not be there.
After installation, the engine was started and air-cond was turned on, initially, the petrol fume smell is mildly present, this could also be due to the fumes clinging on the fabric.
On my 45 mins drive home from the mechanic, I realized that I am still getting some fume but this could be smoke from the outside as the air circulation system may not be working and is left open, allowing smoke and pollution to be sucked into the cabin. This will be dealt with when the air-cond is fully serviced.
At the moment, it seems like this issue has been resolved but this will only be confirmed once we are sure that there is no more petrol smell in the cabin after letting the car sit overnight.
Update #1:
The replacement charcoal canister solved the issue. We found some rust on the rear of the front left fender that needs to be fixed before the fuel smell goes off completely.
Update #2:
The mechanic also noticed that the fuel hose that connects the fuel tank to the fuel pump was leaking fuel. However, when the undercoat was done, the fuel hose was also sprayed on. When fuel leaks over the exterior of the undercoated hose surface, it results in a brown color axle oil-like residue on the floor that looks like the differential oil. The differential gaskets were fine and there were no leaks there. I took the advantage to have the differential oil replaced to Castrol EP 140 since the mechanic was at it.
While the hose was being replaced, the fuel tank strainer was replaced as well to avoid rework in this area. The fuel tank strainer was in decent condition with some minor residue at the mount but the strainer was rather clean.
I am not able to monitor the fuel smell in the cabin much as the car is in the wiring garage for the wiring work. Will update my observation once it is done.
Update #3:
So the car is back from the wiring garage and on my drive back, there was no fuel smell in the cabin.
Reopening of this issue:
This issue has not been completely resolved and I am unsure why. This issue will be revisited and there are a few changes that are being planned to resolve the issue. The key item includes the installation of a brand new charcoal filter.
Update #1:
After the AC job (read here) and replacing the fuel float sender with the proper flange o-rings (full story here), the petrol smell does not seem to be coming into the cabin anymore. I am unsure if this is the complete fix of the job, but will monitor for a while if this issue is completely resolved.
Update #2:
The petrol fume in the car issue is not yet resolved as it was present earlier, I have ordered a new replacement charcoal can that I will replace and while doing that, I will also have the lines completely checked to remove any potential failure. The fuel gauge is no more flickering, but I am monitoring it to ensure that the gauge is accurate.
More updates are to be shared when they are available.
Hot tip:
When a fuel tank is replaced, to receive the best benefit from it, the following is what I have learned and will recommend being followed:
- Replace fuel tank (if there are corrosion)
- Check the fuel level sender, if it does not work well, have it replaced
- Check the fuel tank strainer, this will allow almost all access (stale) fuel to be drained
- Flush the tank with 4 to 5 liters of petrol and discard the fuel (safely of course)
- Check fuel cap, if there is no backpressure, best to replace
- Check fuel tank to fuel pump hose, if not in good condition, replace
- Check air vent valve
- Check charcoal canister located at the front left fender, if the charcoal is bad, it has been reported to cause the tank to suck in under pressure and denting the tank inwards
- When all the above is done, put in a can of Mercedes Fuel System Cleaner which helps in inhibiting corrosion in the tank and also clean the fuel system from the tank all the way up to the injectors. It cleans the injectors too.
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