How can i tell if my sending unit is bad? - Mazda3 Forums : The #1 Mazda 3 Forum
 
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post #1 of 6 (permalink) Old 05-13-2010, 10:47 PM Thread Starter
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How can i tell if my sending unit is bad?

My gas gauge reads less than 3/4 full whenever I fill it up. i know the tank is full because I've overflowed the tank a couple times and it still only read 3/4 full. How can I tell if the sending unit is bad? Or does anyone know what else could be wrong? Thanks.
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post #2 of 6 (permalink) Old 05-14-2010, 08:46 PM
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Re: How can i tell if my sending unit is bad?

no idea. take it to a dealer?
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post #3 of 6 (permalink) Old 05-15-2010, 09:31 PM
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Re: How can i tell if my sending unit is bad?

well there are really only a few things that could be wrong with it.
1. your gauge
2. the sending unit
3 the wiring

I would start by checking your gauge. your gauges do a self test every time you start your car, they go through a sweep. Which means it goes from one side of the gauge all the way to the other and then settles where it is suppose to be. So the next time you start your car watch you gauge if it goes from empty all the way over to full then it is not your gauge.

If the gauge is some what reading like does it ever fall below 3/4 of a tank? if it does or you are getting any type of reading then i would say that it is not you wiring.

I have seen the sending units come off of the fuel pump assembly and just be floating around in the tank, So it might not be a bad unit either but may have just come off of the pump assembly
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post #4 of 6 (permalink) Old 05-19-2010, 04:05 PM Thread Starter
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Re: How can i tell if my sending unit is bad?

[quote author=jfann link=topic=172723.msg3660166#msg3660166 date=1273973502]
well there are really only a few things that could be wrong with it.
1. your gauge
2. the sending unit
3 the wiring

I would start by checking your gauge. your gauges do a self test every time you start your car, they go through a sweep. Which means it goes from one side of the gauge all the way to the other and then settles where it is suppose to be. So the next time you start your car watch you gauge if it goes from empty all the way over to full then it is not your gauge.

If the gauge is some what reading like does it ever fall below 3/4 of a tank? if it does or you are getting any type of reading then i would say that it is not you wiring.

I have seen the sending units come off of the fuel pump assembly and just be floating around in the tank, So it might not be a bad unit either but may have just come off of the pump assembly
[/quote]

My gauges dont do the "self check." It just goes straight into what its reading and doesnt sweep from one side to the other. Maybe the newer models do that...? Mine is an 05.

To answer your, question, yes the gauge funtions properly from the initial reading (3/4 full) on. It seems to be proportional to my driving mileage. But because the starting point is 3/4, my Fuel Light comes on after about 220 miles. I fill up around 240 miles and it fills it with 9-10 gallons. I believe its a 15 gallon tank so theres still about 5 gallons left in the tank when the fuel warning light comes on. Its more annoying than anything and I hate when stuff doesnt work properly.
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post #5 of 6 (permalink) Old 10-21-2013, 11:50 AM
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Originally Posted by Ronnieb8406 View Post
[quote author=jfann link=topic=172723.msg3660166#msg3660166 date=1273973502]
well there are really only a few things that could be wrong with it.
1. your gauge
2. the sending unit
3 the wiring

I would start by checking your gauge. your gauges do a self test every time you start your car, they go through a sweep. Which means it goes from one side of the gauge all the way to the other and then settles where it is suppose to be. So the next time you start your car watch you gauge if it goes from empty all the way over to full then it is not your gauge.

If the gauge is some what reading like does it ever fall below 3/4 of a tank? if it does or you are getting any type of reading then i would say that it is not you wiring.

I have seen the sending units come off of the fuel pump assembly and just be floating around in the tank, So it might not be a bad unit either but may have just come off of the pump assembly
My gauges dont do the "self check." It just goes straight into what its reading and doesnt sweep from one side to the other. Maybe the newer models do that...? Mine is an 05.

To answer your, question, yes the gauge funtions properly from the initial reading (3/4 full) on. It seems to be proportional to my driving mileage. But because the starting point is 3/4, my Fuel Light comes on after about 220 miles. I fill up around 240 miles and it fills it with 9-10 gallons. I believe its a 15 gallon tank so theres still about 5 gallons left in the tank when the fuel warning light comes on. Its more annoying than anything and I hate when stuff doesnt work properly.[/QUOTE]

did you ever get this fixed? If so, what ended up being the problem - I am having the same thing with an 07.
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post #6 of 6 (permalink) Old 10-21-2013, 12:00 PM
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Quote:
Originally Posted by tvmaster View Post
My gauges dont do the "self check." It just goes straight into what its reading and doesnt sweep from one side to the other. Maybe the newer models do that...? Mine is an 05.

To answer your, question, yes the gauge funtions properly from the initial reading (3/4 full) on. It seems to be proportional to my driving mileage. But because the starting point is 3/4, my Fuel Light comes on after about 220 miles. I fill up around 240 miles and it fills it with 9-10 gallons. I believe its a 15 gallon tank so theres still about 5 gallons left in the tank when the fuel warning light comes on. Its more annoying than anything and I hate when stuff doesnt work properly.
did you ever get this fixed? If so, what ended up being the problem - I am having the same thing with an 07.[/QUOTE]

Had this issue on an older car. I just pulled the needle off the gauge, topped the tank, and reset it on the F mark. I would say I did this after making darned sure I had fuel left when the needle hit E so I wouldn't run empty, but it sounds like something that simple would fix your issue.

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