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2011 Odyssey LX, 120k miles
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Discussion Starter #1
I found this while debugging a fuel gauge problem yesterday.

'99 EX, owned since new, 195+k miles now
fuel pump/sender has never been touched before (self-maintained except warranty stuff, so I'm sure)

Symptoms:
- maybe 60k miles ago, after filling up, the gauge would read full, then stay up there for over 100 miles, then very rapidly the gauge would drop down to 1/2 full, and we assumed it was accurate from there. It did this reliably for a long time. Not intermittent.
- starting maybe 30k miles ago, not long after filling up, randomly and infrequently, the gauge would suddenly (within a couple of seconds) drop from full to empty, with the light on, and then come back to full.
- starting a few hundred miles ago, the gauge registered on Empty, with the light on, all the time.
(my guess now is that these were distinct, progressive phases of the sending unit's float+bar falling off)

So I followed the debugging steps in the manual (after reading all I could here), and found one useful debugging step to determine if it's the sender or the gauge: put a 2 Ohm resistor (I used a light bulb) between pins 1 and 2 on the 5P connector you pull off the top of the fuel pump/sender, under the access port under the left middle seat. After several seconds (or switching the car off, then on), it should send the gauge up towards Full - if so, this confirms the problem is with the sender, not the gauge. That's what I got.

So I pulled out the pump/sender. All looked good, except the float+connecting bar was gone!

After draining the fuel out of the pump assembly, I reattached the 5P connector and by manually positioning the sending unit's wiper, I confirmed that the wiper and gauge were working just fine, even linearly (i.e., the delayed drop from Full to 1/2 tank I noticed above was probably not due to a wiper wear issue, which had been my guess at the time).

The place where the float+bar attach to the sending unit wiper looked OK - no broken plastic. But the float+bar was nowhere to be found. I used a mirror and flashlight, but could not see it anywhere. My plan now is to wait until the tank is near empty and take another look. It is obviously in there somewhere, and since nothing was broken on the wiper end, I expect I can just reattach it, probably with a zip tie to hold it on a little better.

I wonder if this failure could explain many of the weird intermittent problems others have been having with their fuel gauges.

I also replaced the fuel pickup strainer I had bought earlier (got from Advance Auto, maybe an AirTex brand, I think - perfect match), but the one in there looked OK. It did do its job though - there were many sharp little metal shavings stuck in the strainer that probably would have caused problems with the fuel pump.

If anyone happens to still have their float+bar after replacing the pump assembly, please let me know. I know mine is in there somewhere, but that tank is very large, flat, and irregular, so it may be tough to find mine. As far as I can tell, the only Honda option is to buy the complete fuel pump/sending unit assembly, so I can't just buy the float+bar.
 

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fuel gauge

I would be interested in what you find. I have had the intermittent issue for close to 2 years now. It mostly does not work, but every once in a while, it works just fine for 10 seconds to 30 minutes. Then sits at completely empty again. Not really a big issue for us as I judt track the mileage and then fill when necessary. This is on an '01 LX.

Still, would like to solve this and get it fixed as I hope to keep the van for 5 or 6 more years. 194K on it currently and hope to get to 275+. Pretty much runs like a top otherwise.

Chris
 

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2011 Odyssey LX, 120k miles
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Discussion Starter #3
I drained the tank and did my best to find the float+bar. Reached in past my elbow, using a long flexible magnet thing, and feeling around carefully. But did not find it. The tank is a lot more complicated than you might think. It's in there somewhere, but I could not find it.

Since I was already in that far, I rigged up my own float + bar using a coat hanger and small metal can with a screw top. Works surprisingly well. Needed some calibration (bending the wire). From looking at the plastic where the bar goes in, I can see how the bar fell off. Looks like a design flaw to me, unless there is some other part that is supposed to hold it there and fell off. The zip tie should hold it on there now, but the whole thing is a little loose.

I also found that just the Fuel Gauge Sending Unit 17630-s0x-a03, is listed in TSB 99-065, and available at hondapartsdeals.com for $35.21. Other than the listing in this TSB, it did not appear to be available separately from the $200+ fuel pump assembly. The sending unit includes the float, bar, and wiper/resistor circuit board. I may end up buying one of those before too long.

Chris, it's pretty simple to do some tests without cracking open the gas tank. Remove the left middle seat. Remove the screws + plastic covers over the chair docking points. Peel back the carpet to expose the gas tank access panel. Remove the 4 screws + panel. Then there is a 5P connector. One pin is empty; 2 (I'm guessing the middle of the 3 and the one to its left) are a variable resistance set by the sending unit; and the other two (side by side) are 12V power and ground for the fuel pump.

As I recall, the resistance (on my '99) goes from about 130 Ohms when empty to about 22 Ohms when full. You can measure the male pins going into the tank to see if the sender is putting out a resistance in this range - that may confirm that the sender is OK. You can then put a resistor (e.g., light bulb) across the female connectors and see if the fuel gauge responds accordingly. The service manual said to use a 2 Ohm resistor, but to not hold it on for long since it could damage the gauge. But I don't see why you'd want something that low, especially if it says it might damage the gauge. Just use a higher Resistor.

Anyway, all this is done without opening the tank, which is the potentially dangerous part.
 
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