2002 GT TDI: Misleading Fuel Level Information Reported on Dash!

[rjsdavis]

Hello to all

I am trying to fix the last few issues on my mother's GT TDI. This is 1 of 2!

It has a fuel level reporting fault, and I wanted to run this past the group to make sure I don't fit / buy the wrong parts! Ok, from full, and right down to about 1/4 full, the gauge on the dash appears to report correct information. I've run it from full to empty (with a spare tank in the boot) to see what it does.

When you watch is closely from about 1/4 downwards through use, it continues to drop as you'd expect, right down to the upper white line of the reserve tank area. I watched, and noticed that during use, it reached the upper reserve line, and then "jumped" (which is where the mis-reporting seems to start) back upto nearly the 1/4 line. From there, it started dropping back down (through usage) towards the upper reserve tank line again and whilst driving the car and the car was still showing the upper reserve tank line, the engine died and it came to a halt. At no point did it drop into the reserve tank zone, or did the yellow warning light come on.

From the point that it jumped back upto the 1/4 full line, until it actually stopped from running out of fuel, I reckon it did about 50-60 miles. So... is it the fuel sender that sits in the tank that's likely to be at fault here? If not, is there anything else it could be?

Many thanks for any suggestions or ideas!

[herby0001]

I'd start with checking out the sender unit on the lift pump. Easy to access - it's under the rear o/s passenger seat. I replaced my lift pump a few years back and the sender and float came with it. Hopefully it's an inexpensive part to replace.

[rjsdavis]

Thanks Herby

How does one check the sender, without buying a new one? They are over £100 for gen parts, just for the sender unit on their own - not including the lift pump! Therefore, I'm trying to avoid splurging on a new one, without being fairly certain that this is the part that's causing the problem!

[herby0001]

Ouch, didn't think it would have been that much.Lift pump and sender was £218 in 2009 when I replaced mine. How to check it? Guess you'd need someone handy with a multi-meter, but that person isn't me. GSF are selling the sender on ebay for £25 - VW Golf Mk4 Mk5 1997-2008 OEM Fuel Tank Sender | eBay (http://www.ebay.co.uk/itm/VW-Golf-Mk4-Mk5-1997-2008-OEM-Fuel-Tank-Sender-/302171149879?_trksid=p2385738.m2548.l4275)
Whip out the old one, check the part number and buy. At that price, I'd just change it.

[rjsdavis]

It's probably what I'll need to end up doing - I just try avoid pattern / aftermarket parts where I can, as they are often a totally false economy in the longevity/performance stakes.

[Alan G H]

It's probably what I'll need to end up doing - I just try avoid pattern / aftermarket parts where I can, as they are often a totally false economy in the longevity/performance stakes.

On a 15 year old car, I wouldn't worry whether a part was genuine or not, how many more years do you expect to keep it going? Also, there's a good chance that part is made in the same factory as the ones originally fitted by VW.

[niall campbell]

I would go for the fuel sender first at £25 myself


You could price an OEM part, if they still stock them, then take it from there

[rjsdavis]

On a 15 year old car, I wouldn't worry whether a part was genuine or not, how many more years do you expect to keep it going? Also, there's a good chance that part is made in the same factory as the ones originally fitted by VW.

Well, it's utterly immaculate, less than 100k miles, and likely to go on for another 10-15 years and at least another 100k miles! Almost no expense has been spared keeping it sound. It's rare to find one in this condition and this well looked after.

If I knew it was made by the same manufacturer as OEM, I wouldn't hesitate.

[herby0001]

If you spend £25 on a pattern part and it fixes the fault, happy days. if you really can't sleep at night, spend the extra £100 on one from VW and replace the sender again. That way you've only wasted £25 rather than £100 (if you went for a VW part from the start and the problem wasn't fixed). Like Alan said, it's 15 years old and will become more of a drain on money as it ages, so a balance has to be struck. I'm surprised the good ol' GT TDI ARL chocolate cam hasn't had you weeping/cursing yet.

[rjsdavis]

If you spend £25 on a pattern part and it fixes the fault, happy days. if you really can't sleep at night, spend the extra £100 on one from VW and replace the sender again. That way you've only wasted £25 rather than £100 (if you went for a VW part from the start and the problem wasn't fixed). Like Alan said, it's 15 years old and will become more of a drain on money as it ages, so a balance has to be struck. I'm surprised the good ol' GT TDI ARL chocolate cam hasn't had you weeping/cursing yet.

Guys

We're getting a bit caught up on pattern -v- gen. The point of the OP was to work out whether this was going to be the offending part to begin with! Is there anything else it could be, given the pattern of behaviour on the dash guage?

[herby0001]

Part of the discussion. You yourself brought it up.

[Alan G H]

Guys

We're getting a bit caught up on pattern -v- gen. The point of the OP was to work out whether this was going to be the offending part to begin with! Is there anything else it could be, given the pattern of behaviour on the dash guage?

The likelihood is that it's the sender unit in the tank.
BUT, it could also be the wiring, or gauge unit, or anything else.
I would go for the sender unit first.

[rjsdavis]

The likelihood is that it's the sender unit in the tank.
BUT, it could also be the wiring, or gauge unit, or anything else.
I would go for the sender unit first.

Thanks Alan

[rjsdavis]

RESOLVED:

In the end, no parts were required at all.

I watched a video on how to remove and refit the unit on YouTube. (How to install a VW MK4 TDI Lift Pump and fuel level sender - YouTube (https://www.youtube.com/watch?v=2T7D2YcOZWA))

At about 3m 30secs, he talks about aligning the arrow on the top of the lifter directly towards the small hole in the car chassis, and states that if this is not aligned, the fuel level will read on the dash incorrectly. Sure enough, after the replacement fuel pump had arrived and I went to swap them out, I found that the present fuel lifter was incorrectly aligned in the car.

Un-tightened it, aligned it correctly, tightened it back up and gave it back to my mum & sister to drive around and see if they could cause the yellow reserve fuel light to come on and for the car to correctly report that it was into the reserve tank. They were nervous about doing it, as they didn't trust the car (they did had a 5 litre spare tank in the boot), but eventually they gave it a go. Sure enough, the fuel gauge now appears to display the fuel level correctly!

How annoying is that?

My mother had her car attacked some years ago, some scalli's punctured the plastic fuel tank with screwdrivers to steal/drain the diesel. It would appear that after the replacement fuel tank had been fitted, the fuel lifter was re-fitted, but incorrectly aligned and had been reading incorrectly ever since... :banghead: