Information Running out of fuel. Half tank on gauge (Solved)

O

oneflewover

Member
Been let down by the A2.
Many moons ago, car ran out of diesel with 1/4 tank showing. Fitted 2nd hand fuel sender unit. Few days later ran out of fuel 1/4 tank showing. Fitted new OEM sender from main dealer, being a wise boy, never let it go below 1/4 of a tank.
Last thursday, Filled up tank did four commutes 210miles, 1/2 tank.
Today 218 miles on ODO, 180mile range on DIS, ran out of diesel, lane 3 65mph, busy M1 chucking it down with rain. Made it to the hard shoulder, phew. Wait 1hr, recovery arrive, take me to Tescos, fill up again and engine restarts.

When I last did the sender, the tank was clean and the bowl was clean. The fuel filter was changed last service at WOM. Was looking at other A2s over the weekend, have I upset it?
 
So you're getting 50% of your predicted range with needle still indicating around half tank? I'm assuming the late 42 litre tank rather than 34. We've got the opposite problem with my diesel A2s - <20 miles to go when refill proves >7L in tank without 'over' filling. Gradually adjusting dashboard needle calibration to reflect accurate values, but this sounds rather simplistic given your issues.

How are your thermostat and temp sensor? My 1.4Tdi (BHC) averages around 57mpg commuting, never getting properly warm and long distance motorway journeys are done at speed rather than for economy getting similar mpg figures - managed nearly 68mpg when limiting myself to 50mph on a summertime A90 trip north from Dundee. This is, however, with new temp sensor and thermostat ; the first few months before I fixed these were 3-4mpg worse. My AMF project car is currently averaging 57.8mpg commuting with a low fuelling remap I developed last month to eliminate wheelslip in winter, will see how things go after the recent cold-snap once I sort the alternator problem out.
 
depending on exactly which year of car you have, some A2s have a needle that moves positively, the rest are the opposite. I got the tutorial for this from a youtube clip using a TT, but in my 02 car the calibration settings were graduated in the opposite direction to those in the TT so I had to move the setting upwards to get the needle to read higher rather than lower.

I use a VAG401, but VCDS would be the more normal route for this.

Go to the instrument cluster menu, then adaptation, then channel 30. The default setting is normally 128 (apparently) ; however, change this higher and it moves (in an 02 car) the needle positively, and below this, negatively - you will need to test this with your car to see if it is a positive or negative setup. The standard range is 120-136 or something like this, but in my car if you change it to 80, with an actual full tank it then reads just over 50%. I moved mine up to ~132 and it goes a wee bit further before the fuel light comes on but still has a reserve volume.
 
oneflewover said:
Thanks @Robin_Cox @steve_c
Took 18ltrs to fill up the 34ltr tank. Like all diesels takes a while to warm up, when it does, it's bang on 90°.
@AndyP That's what i'm inkling towards, shall see when I take sender out again.
Click to expand...
Sorry if I’m stating the obvious here, but you haven’t run out if it only took 18ltrs to fill the tank back up, and it’s correct that the gauge isn’t showing empty as your not, the problem is with fuel pickup.
 
First chance to get it in bits today.
Just under the rear off side seat, with the big black cover removed.
DSC00096.JPG

Colour coded pipes and electrical plug. The big plastic ring just unscrews.

DSC00098x.jpg


On the table, black covering of diesel filled dust all over

The bowl assembly is removed with 3x tags and a disconnect the 2x sender wires (blue)

DSC00100.JPG


At the bottom there is a mesh filter type bowl this is held by 3x push clips. A small lever allowed that to pop off.

DSC00105.JPG


Under that shows the first build up of debris. The big black float operates like a toilet float switch.

DSC00106.JPG


The main bowl is actually 2x bowls, one inside the other. Taking out the inner shows the seal that the float switch operates on. This was also filled with crud.

DSC00108.JPG


The amount of crud, which on inspection was all organic, bits of leaves and sycamore wings, was quite impressive. That's a 200x300mm sheet of paper towel. Blew out the pipes and a clean in fresh diesel and back together. Not much more than a 40min job.
I looked at the fuel filler area, and it is clean so not sure how it got in there.

Replacement is a reversal of removal, though fitting the seal to the tank first is advised.

My car is 170k miles, I would advise that this should be a maintenance job. It is all made to come apart.

I have now driven over the miles it failed at and will continue to do until fuel warning light comes on. Then i'll remove and inspect, clean tank and bowl assembly again.
 

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Must say that I'm impressed by your determination to get this fully resolved. Pleased of course that it's proving comparatively straightforward thus far.
 
oneflewover said:
Driving around today in uncharted territory, it has never been so low since I got it.

Have 5ltrs in the boot just in case.
Click to expand...

This is a good thread - it has a begining, middle and hopefully good end.

Good investigative troubleshooting work and supporting pictures, and thanks for following up the thread on how the results are ending up.
I'm sure you've cracked the problem.

When my low fuel buzzer sounds on my 2002 AMF engined TDI can drive around 50 miles before the "range to empty" shows zero.
From that point I have driven a further 11 miles without running out of fuel.
The car is driven with just me and is moderately heavy with an OSS, heavy 17" rims.

Great post
Thank you
Jeff
 
oneflewover said:
First chance to get it in bits today.
Just under the rear off side seat, with the big black cover removed.
View attachment 58482
Colour coded pipes and electrical plug. The big plastic ring just unscrews.

View attachment 58483

On the table, black covering of diesel filled dust all over

The bowl assembly is removed with 3x tags and a disconnect the 2x sender wires (blue)

View attachment 58484

At the bottom there is a mesh filter type bowl this is held by 3x push clips. A small lever allowed that to pop off.

View attachment 58486

Under that shows the first build up of debris. The big black float operates like a toilet float switch.

View attachment 58487

The main bowl is actually 2x bowls, one inside the other. Taking out the inner shows the seal that the float switch operates on. This was also filled with crud.

View attachment 58488

The amount of crud, which on inspection was all organic, bits of leaves and sycamore wings, was quite impressive. That's a 200x300mm sheet of paper towel. Blew out the pipes and a clean in fresh diesel and back together. Not much more than a 40min job.
I looked at the fuel filler area, and it is clean so not sure how it got in there.

Replacement is a reversal of removal, though fitting the seal to the tank first is advised.

My car is 170k miles, I would advise that this should be a maintenance job. It is all made to come apart.

I have now driven over the miles it failed at and will continue to do until fuel warning light comes on. Then i'll remove and inspect, clean tank and bowl assembly again.
Click to expand...
Quite an old thread, but I wanted to thank you for posting it anyway, it gave me some added confidence to do mine today!
 
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