Shrinking fuel tank!!!

[Old.Tony]

If it were a dent in the bottom, it'd be the same as if there were junk in there - you'd still get the level sensor to reach the top of its travel and record a "full" reading.

The breather hose could be blocked, might be some stupid insect that got in and made a nest and then died after eating a quarter pounder. But I doubt that.

I'm actually thinking it's more likely something electrical. The signal from the fuel tank is usually a voltage - you pass 12V through a variable resistor set to "short" (zero ohms) and you get 12V. Pass that same 12V through the resistor set at some other value and you get LESS voltage returned. The computer reads the voltage returned and works out how much fuel you have. The float in the tank is connected to a resistor.

The resistor ("fuel tank sender unit", probably) may be faulty/corroded. The wiring might be loose and/or have some dirt in it. The ECU might have a fault and be calculating things incorrectly.

Please, let us know what you find!

 

[knighty]

Thanks for all those thoughts Tony. I will come back with the result as soon as I have found the prob. Not going to be driving anywhere for a week or so - and I have a full tank at present - so will be a week or more before I have an answer. I have spoken to the dealer with all the clues from this Forum - and interestingly they said there was a recall on the Pathfinders for a faulty fuel sender. According to them the sender set up differs on the Nav - but we'll see...

Cheers
Ian

 

[knighty]

Problem might be solved...

Tony et al,

Finally got some answers from Nissan.

First, I did run the thing dry, and yes, the 'missing' fuel was hiding below the red warning light. That is, I travelled 160km after the warning light and still hadn't run dry. (Usually would only get 80km after the light came on)

Anyway, took it to the dealer and their analysis suggested it was a communication error in something called the CAMBUS - which is some fandangled new computer communciation protocol.

Anyway - after telling me that gobbledegook, it seems replacing the sender unit might be the fix. Still waiting for the part - but hopefully that does it.

Thanks again for everyone's input.

Ian

 

[vsteve01]

CANbus

Controller area network - Wikipedia, the free encyclopedia

Though probably not the model, this looks like an example:
FuelCAN: fuel level sender to J1939 CANbus interface - FW Murphy Europe

 

[Old.Tony]

Good to hear that there's an end in sight, now to see if that truly does fix it!

'CAN' is short for Car Area Network. Could probably have been named better, because a few years ago none of us would want to be caught driving around in a can, and I know what we used to do when we went to the can and it wasn't making U turns.

Keep us posted!

 

[SOLID D22]

After all this worry it ends up being a small problem.
At least it all worked out alright.

 

[knighty]

Problem fixed under warranty

Hi all

Finally it's fixed. Nissan have put a new fuel sender in and voila, it works. Very happy Jan. Nissan were very helpful and didn't bat an eyelid regarding warranty. And thank goodness, because they said they needed the car for 4-5 hours to do the job! Frankly that seems pretty excessive - but if it's true, I'm glad I wasn't paying for the labour. Only just scraped in with one month left under the initial 3 year warranty.

Incidently, I've started another thread regarding a report of apparent timing chain problems - in the context of contemplating taking up an offer of 3 years extended manufacturers warranty ($1125 including extending the distance up to 150,000). Seems like a pretty sound deal to me.

Cheers
Ian

 

[SOLID D22]

Its always good to hear good news.