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.
I had a Fiat once that the low-level red light stayed on so much...I finally burned it out.
2007
Water, sediment and separated ethanol are all heavier than gasoline (and diesel) and hence will be nearest the fuel pick-up (which is close to the bottom of the tank) regardless of the fuel level.
It is still a good idea to keep the tank full as practical to exclude moisture-laden air. But you don’t need to make a fetish of it.
Another problem with letting the gas in the tank run too low, most cars have the electric fuel pump immersed in the gas tank, which has a cooling effect. If the tank is almost empty the pump could overheat and they are an expensive PITA to replace.
Thanks
I know a couple of folks who have 2012 and newer models.
They have been very happy
A friend of mine had a Fiat X-1/9. Fun little car, until you came to a hill. I had my foot to the floor and I could’ve swore I heard a noise from the engine that sounded something like “I think I can I think I can”. The car soon developed some electrical issues and he learned the hard way what Fiat stands for, Fix It Again, Tony.
Fuel cools the pump—too little fuel reduces heat transfer away from the pump. Running dry of fuel can result in pump failure due to overheating of components.
The injectors and the computer determine the amount of fuel dispensed at each tick of the pulse. As injectors are simply solenoids, the mechanical components and the passage orifices wear over time. As the pulse width may stay the same, if the injector orifice enlarges from erosive wear, the amount of fuel flow each pulse increases. Outside of changes in the feedback from the O2 sensor, the computer has no way of knowing how much fuel is dispensed per pulse.
I would suggest having a service done on the injectors and also replace the O2 sensor. To properly service and check the injectors, they must be pulled and tested externally.
Likely above the explosive range inside the tank. Agitated gasoline tends to vaporize and displace air entry while the vehicle is in motion.
I’ve watched a lot of youtube videos and read a lot of articles about this and there seems to be no small amount of voodoo going on about running your tank close to empty. Some of it has been refuted and some has not. The one thing that is irrefutable is that once you run out, you don’t want to try to start the car until you’ve gotten some gas in there to lubricate the pump. Regarding the sediment, it is always there and that is what the fuel filter is for.
Some argue that running too low affects lubrication, but I’ve not seen that position effectively supported with evidence or a reasonable explanation for why.
I drive a Scion FR-S 150 miles a day to work. I bought it new four years ago. It currently has 126k miles on it and has the original spark plugs.
I bought new plugs a few months ago for $100, but the dealership wants hundreds to install them because this is an extremely difficult job. So far performance and mileage have not been affected. I monitor my mileage tightly and it’s pretty easy since I go through almost a tank of gas every two days.
I also started a brake job a month ago but there was so much pad left I threw it back together and will check again at 135k.
Meanwhile, I’m on my 7th set of tires (Bridgestone RE11 or Michelin PSS). I drive it kinda hard on the Kentucky twisties. It’s a slot car.
From a Prepper standpoint, or just to be always prepared like a boy scout, try to keep your vehicles full or near full.
In an emergency, gas can become unavailable in a big hurry!
When the Southeast gas pipeline broke in Alabama last year, gas become unavailable or extremely expensive in about one day—or about 24 hours after the news went out.
I also keep a couple of battery powered inverters in the trunk/toolbox just in case. These things can get AC power from the cigarette lighter/battery of a vehicle. It can mean the difference between a working cell phone/laptop/light/fan, even hook up the fridge (a big inverter needed, to be sure) until power can be restored.
Looks like you nailed it. Thanks!
I’ll do that if my mileage or performance drops. So far I’m still getting 32 mpg with a six speed manual. And performance is great.
If your car or truck has a electric gas pump in the tank you never want to go below 1/8th of a tank because running the pump dry will cause extra wear an tear to the pump and it also uses the gas in the tank to lubricate and cool the pump parts.
But I may be missing some nuance to the whole thing.
My Father was a Mechanic and always told me to fill up the Tank at 1/4 Tank.
He ran out of Gas once and I never let him forget it. LOL
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