Posted on 08/03/2017 1:19:24 PM PDT by rickmichaels
It’s a habit many of us as drivers have and exercise every day – when refueling, we keep clicking at the nozzle handle to round out our purchase or to squeeze every last kilometer possible out of tank-full. But did you know that feeding your vehicle enough fuel, especially until it levels out well into the filler neck, can cause problems with emissions systems?
Every vehicle on the road that meets current emission controls’ regulations has some type of vapour control system. It’s there to capture raw fuel vapors from escaping into the atmosphere. With most gasoline powered vehicles, this system usually involves a canister with a charcoal medium, sensors, valves, and lines.
When fuel is removed from a station’s underground storage tank and pumped into the tank of a vehicle, the change in the temperatures it’s exposed to can cause the fuel to create non-liquid vapours. The same thing can happen when the fuel in the vehicle is exposed to the normal sloshing from driving.
With some systems, any errant fuel vapours are simply controlled and piped forward to the engine’s intake to be burned in a normal combustion cycle. With others, these emissions are directed back into the tank. An air-tight canister does the job of temporary storage of these vapours.
So what happens when the tank is chock full of fuel? This can create enough positive pressure in the tank to cause the vapour control system to have problems due to the lack of expansion space in the tank. It can lead to failed valves and seals and, in rare cases, it may actually bulge the tank, rendering it in need of replacement. As a vehicle ages, the likelihood of these failures increase as our sometimes dry and salt-laden road environment takes its own toll on small-diameter hoses and plastic components.
If your vehicle does develop a problem with this system, its onboard computer will illuminate the check engine light. The trouble code that will be stored will often be called a ‘small evaporative leak,’ which means a cumbersome diagnostic process to determine the exact location of the leak. Techs will often have to hook up a specialized piece of shop equipment to such a vehicle, which introduces a non-toxic yet visible ‘smoke’ vapour into the system that will help pinpoint the leak’s source.
As you might suspect, this can lead to an hour or more of diagnostic time and its related fees, not to mention the cost of any replacement components and installation charges. Think invoices well over $200 or more. This one trouble code is consistently one of the 10 biggest causes of a check engine light.
Avoiding this trouble and its related expenses is as easy as shutting off the fuel station nozzle action at the first click when the tank is full. As most of us pay at the pumps with some sort of plastic, trying to round out the purchase is rather meaningless. And any money saved by trying to jam as much fuel as possible in when a particular station is offering a low price is often less than a few pennies and more than offset by any repair bills that might come up down the road.
As opposed to liquid vapours?..............
Two words:
Subaru Forester
What a LEMON! That and the engine gasket problem.
I’ve had an interesting problem crop up with my FR-S. It has a 13+ gallon tank and up until the 110,000 mile mark I was able to always get at least 75 miles past the “low gas light” coming on, and still only put 2.5 gallons at the most.
But with two consecutive tanks I ran out of gas at the 40 mile mark and was only able to put 11 gallons in. I now only trust it to 35 past the light coming on.
BTW, I have a 150 mile round trip commute. I fill up every two days.
2.5 = 12.5
Concur.
I’m assuming they are right.
Love that stuff!................
I have heard from people that it isn’t good to go “as low as you can go” towards an empty tank as it has a possibility of sucking in sediment or debris from the bottom of the fuel tank and introducing it in your fuel injectors which will cause them to clog. Not sure if there is truth to this but I try to refill my tank once it gets near 1/4 tank.
“small evaporative leak . . . a cumbersome diagnostic process to determine the exact location of the leak”
Pump clicks off after a gallon or so.
Yep, had me some of them.
Smoked it a few times, vac tested, replaced carbon canister, had lines, soft lines, tank vent etc . . .
Come on now. My near 20 year old Cherokee only has 284,000 miles on it. It’s just getting started.
What year?
Perfecto
Change you spark plugs.
Don’t just clean and re-gap them.
Change your oil, filter and air filter.
Make sure your tires are properly inflated.
If it has a fuel filter in-line, change it too................
I typically run my F-250 down to dangerously low. Did so for 130,000 miles. I heard the same thing as you, so I changed out the fuel filter, which turned out to be a waste of time. The old one was as clean as could be.
My previous vehicle was a 2006 Chrysler Town and Country and I had to stop at the first cutoff as pumping more gas into the tank would cause it to overflow. My current vehicle is a 2016 Mazda CX-5 and I found I could pump gas in spurts past the first cutoff the few times I paid cash for gas and wanted to round it to the next dollar, but I mostly pay for gas with the credit card now, so I don’t bother and stop pumping it after the first cutoff.
I drive a 1986 Volvo 740, and for over twenty years I have done what the author states is a bad thing. My only question is when would I notice this problem?
My car is a daily driver with over 360,000 miles on it, gets 32 miles to the gallon and the crank case has never been opened.
A full tank has less risk of exploding in a wreck. An empty fuel tank is a sort of crude fuel/air bomb.
Use cash when fuelling your vehicle. My little putt putt car takes about $23 to fill up from empty so I throw in a $20 when it gets low. No credit card or debit card, since that seems to be the place where a lot of people get their info skimmed, and no topping off.
I was told to fill the gas tank with non ethanol fuel every once in a while to clear up the gunk in the bottom of the tank, or at least keep it at a minimal level.
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