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Discussion Starter #1
After a recent computer upgrade (recall repair), I found my fuel gage is completely out of calibration. After each complete fill up, it shows only about half full. And after it shows empty, I can still drive more than 200 miles. I knew it's a little bit out of cal before this upgrade due to my non-original tire size. The new tires make the odometer 2% short of the actual distance traveled. After I replaced the tires, I knew I have about 3-4 bars left after each fill up. Now it's much worse.

So before I take it back to the dealer for a recalibration, I just wonder if anybody here had the similar problem before and what do you think is the cause of this problem. Can the dealer input my new tire size into the computer to make everything accurate?

Thanks!
 

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I don't understand the tire size - fuel gauge correlation. I can see where the speedo and FCD would be off, but not the fuel gauge. If the fuel gauge is off wouldn't it be the sending unit that needs checked?
 

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Obviously the tires had nothing to do with the fuel gauge reading incorrectly.

This was most likely due to the computer recall upgrade. Or it could be the gauge was near failing before the computer upgrade.

Although many newer vehicles are experiencing similiar fuel gauge problems, due to the current fuels containing higher amounts of sulphur. You could try using a bottle of Techron or fill up with only Techron gas (all their grades have Techron) and see if that helps before returning to the dealership.
 

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Discussion Starter #5
Insightful Trekker, Resist, and Tranquility:

Here is why I think they are related:

For most of the cars like Insight, I don't think there is a separate speed/distance sensor. The speed/distance is from monitoring and recording the revolution of the wheel. Since I have bigger wheels now, for the same distance, I have less revolution. Therefore, the Insight computer calculates less distance (miles) with each gallon of gas I put in. So I have lowered MPG automatically (I noticed it already). If I am right (well, I may be wrong), because of this lowered MPG, the computer will calculate less gas still left in the tank. Therefore, it shows less gas on the gage.

Well, as I said, I may be completely wrong. The gage may not be this smart as Insightful Trekker suggested.
 

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You are wrong, again it has nothing to do with the Fuel Gauge reading the incorrect amount of fuel in the tank. Your reasoning is not how the vehicle calculates fuel remaining. It uses a simple float sensor, like in other cars.
 

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WhyHonda,

Therefore, the Insight computer calculates less distance (miles) with each
gallon of gas I put in.
There is a flaw in your theory and I think I can prove it with just two
questions related to the quote above. (Although the portion about why
your MPGs are presented lower is correct.)

How does the computer know how much gas the you put in the tank?
If you fill up and the car doesn't move, then why would it show full when
it was working before?

Meaning the computer does not calculate fuel tank capacity although it
does calculate fuel usage and presents the results on the fuel mileage
readout but not the fuel gauge. The fuel gauge reading is capacity only
(not mileage used or remaining - or should I say not directly)

There is a slim chance thast something in the instrument cluster just needs
to be reset. A quick and easy thing to try is to disconnect the negative
terminal from the12v battery for about 10 mins (just to be sure) This will
reset all electrical components at once. After that, like Trekker, Tranquility
and Resist already said, probably the sending unit based upon what I think
the way you described your problem at this point.

It may help to describe your problem again without introducing tire sizes
into the equation.

Here are some questions that may help you clarify the problem.

Before the upgrade:
If you filled the tank all the way, turn on ignition, did the fuel gauge show
full bars?
Have you every driven the car down to the point where the fuel reminder
light comes on? If so, how many bars are left when it does.

After the upgrade:
Did you notice the gauge problem immediately on the way home or after
your first complete fillup?
When the fuel gauge currently shows one bar remaining, does the fuel
reminder indicator light up and remain on until you refill?

JoeCVT - Just your average CVT owner
 

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Discussion Starter #9
I think we both agree the computer do get fuel information from the fuel gage circuitry. But our difference is if this is a one way communication or both way, meaning the computer may send back signal to the fuel gage circuitry to make it more "accurate".

OK, here is how this problem develops: Before I changed the tires (120K miles), the fuel gage worked perfectly. As soon as I changed the tires to new size, immediately I noticed the fuel gage can't show full tank anymore. After each fill up, it shows about 3 bars from full. But the indicator works fine, it lights up at 1 bar every time. And I know I have more gas left in it. After this computer upgrade and IMA replacement recently (180K miles), the next day when I fill up, I noticed the gage only showed half full. During the third fill up, I noticed the gage showed a little bit more than half full, but still less than the new tires caused. Now the indicator still lights up at 1 bar and stays on until next fill up, but I can drive 300 miles after it lights up.

So you see, this problem appears and gets worse every time I did something to the car, either tires or computer, of course I believe there is some connections there. I also understand why nobody else believes it.

I just added some fuel system cleaner into the tank today and will see if it will help at all. I will do the reset this weekend. I will drive it back to the dealer next week to see what they think. I will tell them it happened right after they replaced the computer, of course.

Thanks!

.....

JoeCVT - Just your average CVT owner
 

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WhyHonda said:
I think we both agree the computer do get fuel information from the fuel gage circuitry.
HUH :?: :?

I don't read any agreement on that point. Nor does the factory service manual or the factory ETM. There's no connection of your problem and any computer upgrade, period.
 

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WhyHonda,

If you read all of the replies again, you will see that no one has agreed
that the fuel gauge is calculated by the ECM. My reference to fuel gauge
circuitry in the instrument panel is only to display those pretty LED bars
instead of the typical needle gauge in many other cars. If you just stop
for a minute and think about what happens normally. Lets say you have
a quarter of a tank left and you drive your Insight to the gas station and
fill it up full. You get back in the car, turn the ignition on, and presto, all
LED bars are lit indicating the tank is full (normally - not in your case at
the moment). Now you have not driven your car yet but the fuel gauge
already shows full without anything to do with tire diameters, rotation,
miles traveled, fuel used so far etc...

Doesn't that prove that the ECM is not doing any calculations for the
fuel gauge display?

My suggestion: Try the reset that I mentioned earlier. It's quick and easy.
It takes us longer to type this stuff than doing the reset so it is worth
a shot (in my opinion) Although, chances are that it is the sending unit

JoeCVT - Just your average CVT owner
 

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WhyHonda said:
Before I changed the tires (120K miles), the fuel gage worked perfectly. As soon as I changed the tires to new size, immediately I noticed the fuel gage can't show full tank anymore.
Nothing more than a coincidence.
 

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Discussion Starter #13
Yes, if it didn't happen for the second time when I have the computer upgraded. When something happens again and again, most people will think there is something more than coincidence here. :roll: Agree?

Resist said:
WhyHonda said:
Before I changed the tires (120K miles), the fuel gage worked perfectly. As soon as I changed the tires to new size, immediately I noticed the fuel gage can't show full tank anymore.
Nothing more than a coincidence.
 

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I understand but what you don't get.....and again.....is that the fuel tank sensor is only a float valve and is not used to determine mpg.

If you don't believe what other more experience Insighters have been telling you, then buy a set of service manuals and read it for yourself.
 

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WhyHonda,

Before I changed the tires (120K miles), the fuel gage worked
perfectly. As soon as I changed the tires to new size, immediately I
noticed the fuel gage can't show full tank anymore.
That is my point...If the gauge did not work immediately after you
changed the tires then your theory can not be correct because your
theory involves distance travel and MPG calculations over time.

Couldn't you consider that when you jacked up the car to change the
tires you put the float (in the tank) at some strange angle and because
of its age (120K) got partially damaged?...

I give up on trying to convince you that the fuel gauge level is not
calculated by the ECM and tire sizes. It would probably help to search
some earlier posts about fuel gauges being off. This one is a great
example of the problem you are having:

http://www.insightcentral.net/forum/viewtopic.php?t=3457&postdays=0&postorder=asc&start=15

Full tank only shows 4 bars before replacing the sending unit. Now it is
fine after replacing it. If this does not convince you then I guess nothing
else I post will either. If you are not convinced, take it to the Honda
dealer and ask them to calibrate your ECM according to your current
tire size (as you suggested earlier) and watch the expression on their
faces carefully :D

JoeCVT - Just your average CVT owner
 

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joecvt said:
Couldn't you consider that when you jacked up the car to change the tires you put the float (in the tank) at some strange angle and becauseof its age (120K) got partially damaged?...
Maybe WhyHonda's got us Joe :!:

I can imagine a floor jack being put under the fuel tank and the resulting damage to the tank and sender unit...
 

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Discussion Starter #17
Thanks guys for all the information. I tried to reset the computer and found it didn't work. So your guys must be right. It's the fuel sender unit.

The reason I thought the computer has anything to do with it is because I confused this car with my Expedition. Both my '98 and '05 models have a "trip computer" which can tell you how many miles you can still drive with the gas left. So they use both the fuel meter and MPG data. I thought my Insight is the smarter one.

My Insight is at the dealer today and they just called and tell me I need a new fuel pump assembly and the whole thing will cost more than $900. I didn't let them do anything, of course.

I just checked and found the fuel sender unit costs only about $18. Is this the only thing I need or I need something else? Since the car drives fine, I don't think I need a new fuel pump.

Thanks again.
 

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WhyHonda said:
I just checked and found the fuel sender unit costs only about $18. Is this the only thing I need or I need something else? Since the car drives fine, I don't think I need a new fuel pump.
Can't imagine why you'd need the whole pump either, but let them explain why.

IIRC the sender is a bit more than $18 ($30 something) :?: )the last time I checked, but the price could have come down.

HTH! :)
 

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Discussion Starter #19
I didn't bother to ask them why because I know they won't tell me the truth. But considering they replaced my IMA for free (I am over 180K), I don't blame them too much.

As for the fuel sender unit, it costs $18.28 at both Majestic and Mesa (http://www.onlinehondaparts.com), but since Mesa charges only $7.5 for S&H and Majestic wants $13.62(!), I just ordered one from Mesa.

Thanks again for all the information and I will let you know the result when I get the part. Of course, if you don't hear me for a couple of weeks, that means I probably blow up the fuel tank...
 

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Discussion Starter #20
I finally replaced the sender unit and it works as good as new now. It only took me about an hour to do it and here is how I did it:

1. Disconnect 12V power in case I make a spark in the fuel tank;
2. Remove the carpet in the trunk and on top of the cross beam (the one on top of the wall behind your seat);
3. Remove the cross beam;
4. Remove the fuel fill cap to release residual pressure in the fuel tank;
5. Down the left part under the beam, you see the fuel pump assembly cap (a big black plastic ring screwed down press the fuel pump in place). Disconnect the two fuel lines and the electrical connector. Remove the plastic cap ring by knocking it CCW with a rubber hammer or something;
6. Carefully lift the fuel pump assembly. Replace the sender unit on it;
7. Reverse the steps to put everything back together.

I can't believe such a simple job would cost me more than $900 from the dealer.

Also since I was there, I opened up the IMA cover to check everything inside. I cleaned up all the power leads (6 of them) and re-torqued them. I also unplugged all the connectors and replugged them. I just want to make sure all the connections are good.

After all these, I did find I have faster charging and the battery holds longer too. So I guess good connections did make a difference.
 
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