Boxster 1999 : fuel gauge spinning

[privateselling]

Hello,

As from today my 2.5L Boxster's fuel gauge started spinning.

The fuel gauge needle jumps from one side of the gauge to the other side.

This morning when the fuel tank was half filled the needle indicated O liter (fuel tank empty), when turning the ignition off the needle went to 1/4L. Again ignition on and the needle stayed at 1/4L.

After filling up the tank it became worse. The needle just climbed up until it touched the temperature gauge needle...!

When turning the ignition off and on again I took some pictures (see attachment, these 5 pictures were taken in about 30 seconds).

I did not check anything yet. I only disconnected the battery to 'reset' the instrument but this did not help.

The needle never returns to '0' when turning the ignition off.

Has anyone experienced such phenomenon and can you give me a hint to find the root cause.

Is it possible that a poor mass connection causes this problem? (I doubt it because all other functions of the instrument work fine, also the measured distance to go and also the average fuel consumption seem to work as the temperature gauge does).

Thank you for reactions,

Alfred / Belgium

jumping_fuel_gauge_needle.PDF

Edited March 28, 2007 by Loren
Removed 30 MB download

[Loren]

Either the fuel level sensor (connections) have gone bonkers or the cluster is bad.

If you hook up a PST or PIWIS it should tell what the fuel level sensor is doing.

[privateselling]

Loren,

thanks for the quick response.

I'll check the fuel sensor tomorrow. I found some 'Ohm-values' on a German Porsche website.

But I still wonder why the needle stays activated with ignition 'off'.

There is a company in Germany which is specialised in repairs of ECU's and Instrument clusters. In the worst case I have to send the unit to them.

Nevertheless if you or somebody else has a hint, then I would appreciate to hear it.

Regards,

Alfred

[privateselling]

Loren,

I read in the shop manual that a calibration of the fuel level sensor might be necessary wit the PST2 or PIWIS when the battery, cluster or fuel level sensor have been disconnected.

Unfortunately this feature is not covered with the Durametric Tool...

Is it possible to arrange a so-called 'manual self calibration' i.e. by filling and driving the fuel tank empty repeatedly or disconnecting the battery at a certain fuel tank content ?

Regards,

Alfred

[Loren]

You could try filling the tank - then disconnect the battery for 5 minutes and then re-connect it.

If that doesn't do it then you may need a PST2. It still could be a bad sensor or cluster.

[privateselling]

Hello Loren, Toolpants,

My fuel gauge seems to be defect.

I have a spare cluster with speed indication in miles instead of kilometers.

Do you think it is feasible to replace the NOK-fuel temperature gauge and the fuel gauge by an OK-one separately, since I think they are similar on both versions.

I saw a picture of a dismantled cluster somewhere else on the site.

Is the dismantling self-evident and can I find somewhere a description with fotos or pictures ?

Thanks,

Alfred

[privateselling]

Hello Loren and other forum members,

My fuel gauge problem is not solved yet.

I attached a picture to explain what happens :

- the fuel gauge needle stays beyond the 'FULL' mark. When turning the ignition on then the needle starts to jump up & downwards some mm's and then remains above the 'FULL' mark.

- the board computer seems to work fine since the 'RANGE' follows the content of the fuel tank.

- when the fuel tank is nearly empty, the 'RESERVE' indicator telltale lights up.

This makes me believe that the fuel gauge is working correctly (I already measured the resistance with the tank full and nearly empty and this seems OK to me).

Replacing the instrument did not help either.

Do you think that a calibration with the PST2 would cure the problem taking into account that the OBC and the 'RESERVE'telltale work correctly?

Additional information :

1. All other functions of the instrument panel work fine.

2. with the Durametric Diagnostic Tool I have no access to the instrument panel although I can communicate with all other computers (ABS, engine, HAVC, alarm,).

Therefore I rather suspect a ground or cable problem.

Any useful hint would be welcome !

Thanks

Alfred

[Tool Pants]

Never seen that. Don't see how it could be a calibration issue since the needle is all over the place.

When you say you replaced the instrument, does that mean you tried another instrument cluster and it is doing the same thing?

[privateselling]

Loren,

Indeed, the sympton is the same with an other instrument panel, so I exclude an internal defect in the instrument panel itself.

After changing the instrument panel, I installed my genuine one back in the car and then I had the similar phenomenon with the RPM-counter and with the speedometer (they both jumped to the max. values and stayed there ...!).

Then I dismantled everything again and noticed that one of the lugs of the instrument panel assy was not fully engaged. After correcting this the RPM-counter and the speedometer functioned normally again.

Only the problem with the fuel gauge remains...unsolved.

Would appreciate any further suggestion...

Alfred

[Loren]

Actually Tool Pants responded to your about the cluster - but that is the same question I would have had.

I guess you could try and re-calibrate it with your PST2 but if that does not work I think you just have a flaky sensor.

[privateselling]

Hello,

My problem is solved at the end !!

I wrote that I tried a second instrument panel which showed the same failure (although the needle gauge was in the '0' position before I installed the instrument in my car).

Fortunately I got today the opportunity to try-out a third instrument panel and everything functions perfectly now.

Conclusion : MURPHY must have been hidden in the 2nd instrument panel. Those things happen and as we know : never say 'impossible'...

Thanks to all of you who gave me hints to locate the problem cause.

Alfred