Mahindra XUV700 has/had a problematic EVAP setup. I'm not sure if it's just my vehicle of it's to do with a particular batch of vehicles and I can't pin point which part of the EVAP system is at fault.
BHPian Mudhalaipatti recently shared this with other enthusiasts.
After almost 4 days at the SC (1 day was pure rest, owing to a Sunday), the Red Rage is back in action. It looks like this issue had reached some of the top execs at Mahindra and I was glad my email to Syed Abdul Hanif at Mahindra had spurred further action.
I was driving a loaner Marazzo for the last few days and getting back, behind the XUV was such a welcome relief. Boy I missed driving this beauty. Even after 4 months of driving, the pleasure of driving is compounded every day. Only now, I have this incident lingering at the back of my mind.
Now lets retrace the sequence of events, leading up to the engine power loss last week.
1-March-22 - At exactly 2.33 p.m, I fill 43.16 litres of petrol, after driving for about 4 km post the low fuel warning. ODO is 4654 km.
I always stand with the attender to make sure that the fuel top up is stopped at cutoff. Not a millilitre more or less. Drive around 22 km and call it a day.
2-March-22 - It's a hot day and my lazy bum doesn't move the car to a shade and the vehicle is baking till 2.30 p.m. I take it out and drive for exactly 17 km and keep the vehicle idling for around 18 minutes, before I noticed the fuel leak at around 3.18 p.m.
2-March-22 - I take the vehicle to the SC and the rest of the story is documented in this thread. Now there is a detail that I didn't think was unusual and I missed to report earlier, but here I am retracing the steps and think this could be key to the whole saga. As the flashing is completed, the Co Tech cranks the car, but it doesn't start. He tries at least 6 times, but the vehicle doesn't crank. And then on the 7th time, the vehicle starts. I didn't pay attention to this specific issue, but in hindsight, this is a pivotal moment.
Central to this drama is the EVAP system (Evaporative Emission Systems). What is this EVAP really ? Here is an excellent video of how it works in modern cars.
(There's a minor glitch at 5.50 where there's a bit of incorrect information. Read the comments for the right information, just for that tiny bit).
Had a longish call with the Area Customer Care Manager and he explains me in detail the diagnostic and the findings. I have given a gist of our conversion below.
The vehicle has a Canister, Purge Valve to handle the fuel vapour. (i.e in this BS stage VI regulation, no unburnt fuel can be let out and so all fuel vapour must be re injected in to the system, with out being let out in to the environment). In my case, somehow the canister, which is supposed to capture only vapour, had accumulated fuel, quite a bit. And then this accumulated liquid found it's way to intake manifold, which eventually let to the engine shutting down. Since there was lot of accumulated liquid in the canister, it started leaking out in the first place.
Now, if you had gone through the video and the explanation provided by Mahindra, you may find a number of questions arising, which is not very reassuring. But before I get in to my reservations, some replacements parts on the vehicle. Mahindra has replaced both the Canister and Purge Valve in my vehicle, due to "abundance of caution". They weighed my stock canister and a non problematic canister and apparently both weighed the same. If fuel had been absorbed by the charcoal, it would have weighed more. However since it was almost 3 days past the initial fuel leak, all the leaked/accumulated fuel would either have evaporated or been converted to fumes. Also some valuable logs had been lost during the flashing process (as part of the Android Auto Update )
Mahindra suspects that excess fuel was filled on 1-Mar, which might have seeped in to the canister that triggered the chain reaction. This is something that I can't accept. As I always fill fuel at cutoff and in this instance, the low fuel warning had come off just a few km earlier and so there's almost 0 chance of overfilled fuel causing this.
Even if that was the cause, how did liquid get accumulated in a canister, which is supposed to capture only vapour. Isn't there a sensor/valve to let in only vapour ?
How did the canister accumulate so much liquid and how did the canister leak fuel. Was it via the canister vent value ? If that's the case, is it designed to spill fuel all over the wheel well, with out a proper "Drain"/"Vent" mechanism ?
And the most serious of the issue - The purpose of the Purge Value is to let in only vapor in to the intake manifold and that too when the conditions are "right", as decided by the ECU. A vehicle with so many ECUs, determined that liquid could be let in to the intake manifold from the canister ? How !!! How !!! How !!!
Even if all other fail safe controls failed, the ECU controlling the engine parameters, should have thrown out a "check engine" light at worst and not shut down the engine, especially when the vehicle is cruising at highway speeds. Where is the redundancy in the system ?
And now, the critical missing link (my version) - While the canister had accumulated fuel and the EVAP purge valve is injecting liquid in the intake manifold, the injected fuel is getting burned up fast, as the engine has been running continuously. However once the engine is shutoff while flashing is in progress, the fuel in the EVAP system is in fact clogging the intake manifold. That should explain why the vehicle refused to crank for 6 times. But again, the diagnostic tool was connected to the vehicle when the cotech was cranking up the vehicle and it should have spewed warning after warning, which I'm thinking were ignored.
And it must be pure timing, where the engine didn't stop on a good 15 mins ride that we took with the vehicle, right after the flashing process, but started a good 2 hours after. By this time, the fuel in the canister has dried up and whatever left over liquid in the EVAP system found it's way to the engine again, which stopped the engine.
My Summary
Vehicle baking in direct sunlight for a good 6 hours -> Fuel vapours form -> Some faulty sensors/valves let liquid fuel in to the EVAP canister -> Canister leaks liquid fuel out of the vehicle -> Canister leaks liquid fuel in to intake manifold -> Engine power loss.
While Mahindra is of the view that this is a 1 in a million occurrence, and is an outlier, I can't buy this argument, especially considering what happened. The engine shutdown, for gods sake! And that too with so many ECUs in place to monitor so many vital parameters.
Verdict
And now my verdict on this issue - Mahindra XUV700 has/had a problematic EVAP setup. I'm not sure if it's just my vehicle of it's to do with a particular batch of vehicles and I can't pin point which part of the EVAP system is at fault (perhaps some solenoid, some sensor, some piece of software idk). This demands a more thorough diagnostic with a larger dataset. With many vehicles onroad, Mahindra should be able to get a much wider dataset to ascertain if there's a real issue with their EVAP setup or not. I wouldn't wait for a fatal incident to revisit this topic !!
Silver Lining
Mahindra has been cooperative and forthcoming in this whole saga, with keen attention to solving the problem. However in this case, the critical logs/data points to get to the bottom of this was lost in the SC goof up. I understand that a whole team of Mahindra Technicians were on this task trying out a lot of permutations and combinations. Their interactions with me very courteous and conveyed their earnestness in resolving this issue. I'm sure with more data points, this issue could be rectified ( if at all this is a wider issue)
I would be extremely glad if you guys could pick holes in my theory, my summary and verdict. I hate to draw this verdict on such a great piece of engineering and would love to be proved wrong.
In the meantime, I'll try to put this out of my way and enjoy driving as much as I can and should
PS : I almost forgot. There's no trace of a rat/squirrel or a cheetah infestation in the vehicle. And so something with sharp teeth having fun with tubes and pipes is ruled out.
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