WRONG!!!!



The fuel tanks design and the location of the fuel pump "UNIT" generally in most Gasoline F/I application has foreign material sink to the bottom of the tank and most foreign debris caught in the fuel pump "UNIT" filter.
If owners of gasoline F/I engines when getting fuel use the reverse from the common habit when close to empty fill to 1/2 tank (or full) instead 1/2 tank to full you are less likely to ever have a fuel system delivery problems caused by debris in the fuel tank.
This is a practiced recommendation from service shops for last couple or more decades to preventing most fuel system delivery issues. This includes fuel injector issues as well.
In any random service shop including dealerships the number one cause of fuel delivery issues is from people that tend to use poor fuel filling habits.
Simply contacting any independent service shop anywhere in USA and Canada and ask them is likely to find what I posted VERY accurate.

ASE

 

Dude .....as you pointed out the OP no longer has the Mazda.
And as such we will likely NEVER be able to ask further questions and EVER get the results of what the conclusive cause and solution was at this point?
There really is a LACK of information to doing any service diagnosis otherwise the issues would have been found and presumably corrected.
How ever the preventive suggestions are accurate!

As for your example of fueling habits even all your combined vehicles do not suggest or have any conclusive data to support really anything. There are just too few in the BIG PICTURE of sheer numbers out there. The fuel system contamination problems causes, and solution have NEVER been statistically cataloged for data conclusions EVER!!!

My contribution about issues with fuel delivery systems customers based is generally from miles of service in years and miles and not contamination of debris in a fuel tank. I am not saying that we have never had them, but they are far and few as you would know if you worked a few years in an independent service shop.

 

I strongly recommend as an *Automotive Master Automotive Technician with years of servicing vehicles of all makes and models not to do emulate what this member posted or suggested

People claiming to have not had "any issues" really regarding any noted problems only means that what they should have included in their wording is "YET". Reminds me of smokers that claim they smoked for years with no problems until they are diagnosis with lung cancer.

Decades ago, most would word when close to empty as "reserve" fuel. In Aviation the reserve fuel capacities was used for extreme cases that you could not reach a landing site or airbase to refuel. That really does not apply generally speaking living in the USA and Canada and a few other countries anymore. Now does it?

*
ASE

 

I posted on this thread a couple years ago, and still have no resolution on my wife's 2017 CX-5 which has had this same issue since 40k miles.

I'm pretty sure I know what's causing this though!

I’m guessing you have an AWD CX-5?

I’ve read about a few folks also having the issue, but it doesn’t seem widespread. This actually happened to me again today (with the most fuel so far, 67 miles to empty).

What I believe is happening is: Because of the rear driveshaft, the CX-5 AWD has a “saddle” shaped fuel tank. There are two sumps, with two fuel level senders. The fuel pump is in the driver side sump. There is a “syphon” Venturi in the main fuel pump that sucks the fuel from the passenger side sump.

I think that the syphon system doesn’t work properly sometimes.

The driver sump empties, but there is still a good amount of fuel in the passenger sump. The driver fuel sensor knows it’s empty, but the passenger side sensor still shows a lot of fuel, and the gauge in the dash is the average of the two (aka, ~1/8th tank).

I’ve disassembled the fuel system and haven’t seen any obvious problem. I haven’t started replacing parts yet, but it’s time to dig into it.




@redpoint5 can you confirm yours is AWD?

Thanks
-Rob

 

That only further indicates that not going below a 1/4 tank of fuel, would indeed, be a simple solution to alleviate the issue of running out of fuel.
Though I would be interested to learn if your siphon theory reaches the stage of a scientific hypothesis.
Please keep us informed, should you find the actual reason why this happens to a relatively small percentage and not the majority.

 

What a refreshing thing! Someone who actually studies the issue and attempts to come up with a solution!!!

 

The average driving mileage of a 2.5L CX-5 is roughly 458 or 114 miles per 1/4 tank.
The physics of how a siphon works would explain his theory but it is still a theory.
The solution would be in the physics, specifically correcting the atmospheric pressure differential which is causing the loss of the siphon effect.
Simple physics shows that can be achieved by altering the hose size, tank volume or combination of both.
Or by the easiest pressure differential solution, which would be adding more fuel. Which translates to not letting the full tank go below 1/4 in the first place.
I too applaud people wanting to know the reason for something.
But if keeping your tank 1/4 full or more which resolves the issue as everyone with the issue has stated, why wouldn't you just stop and get gas?
It's much easier than replacing a fuel tank or parts and/or keeping an extra gas can in your car, which requires a trip to a gas station to fill anyway.

 

I always used to try to do that, but I now receive significant discounts on fuel if I fill up twice monthly with each fill being at least ten gallons. With MX5, there is no way I can do that and keep a quarter tank of gas since it only has a 12.5 gallon tank. The CX5 is a little easier, but it can't always be done. The Jeep is no problem with its 25 gallon tank, but I don't drive it very often except in the winter or on long trips. If the Jeep didn't have the siphoning prevention stuff in it, I would fill it and then siphon gas to the CX5 (the MX5 uses 91 octane and I run 87 in the other two)

 

um, hate to break it to you, that or this system of fuel tanks has been around since the early 20’s maybe older. It was used by BMW on many models and predominantly on the 2002-2012 BMW/MINI. That member posted fuel tank is almost an exact duplicate system used on the BMW. Although what he mentioned is good DIY thoughts there is is NO actual way it could happen unless the tank itself was deformed or damaged during either manufacturing or installation and the it would not be a problem that ocationally happens but all the time and likely the fuel monitor would be effected worse.

 

Have you experienced an issue of running out of fuel in any of your vehicles whose fuel gauge read 1/4 tank or more?

Keeping the tank at 1/4 or more can easily be done, you have just chosen not to do it because of your perceived cost benefits of not doing so.
The average price of gas in the US is currently $3.45 a gallon.
The best discount most fuel cards offer is .10 cents per gallon (perhaps you have a better deal).
At .10 cents per gallon your maximum savings would be between $1.25 - $2.50 per fill-up which really isn't a huge savings.
Unless of course your driving requirements mean filling up a couple times a week.
As for discount cards I personally use a cash back credit that covers ALL purchases, even fuel.
Though I've found in my experience (personal and otherwise) if someone has three road ready non-business vehicles, discounted fuel costs are not really a priority.
I can honestly say the few years I had 4 motorcycles (sport tourer, off road, two track bikes), boat, pick-up, wife's SUV, a corvette and a BMW Z3, the fuel costs for them were the least of my concerns