Fuel Guage issues

Here’s my most recent of the many problem points with an 01 td5. Hopefully someone has the expertise I’ve yet to gain. It’s a fuel guage/sender/pump/electrical conundrum I present to you. So..

Fuel gauge when ignition off, the needle sits at the E/empty mark.
When ignition switched on fuel gauge moves slightly upwards to rest just below bottom of red quarter tank mark as the pump hums to its end point.
After fuel pump has run its course, then the guage reading/needle flies up to beyond the full mark and rests.
Once the engine is switched on then the needle it slowly falls back to the bottom of the red quarter mark.
Of course, I’m desperate to avoid the whole struggle of removing the fuel pump as I’ve had particular problems with that several years ago. But, I can’t figure out what the cause might be and I know, unless I’m pointed elsewhere then fuel pump will have to come out for at least a solid inspection. Until then, I’ll be content to hazard a guess at where the actual fuel level would be. Appreciate your time with this one.

Sounds like an earthing issue...

+1 for earthing issue

marksman said:

+1 for earthing issue

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Ok, thanks. But can I press you on the specifics. I’m not up on electrics and the earthing problem suggests, to me, I find where there is a grounded earth point on the vehicle associated with the fuel sender and clean it til it’s better connected. Is that close to an understanding of the matter? Should I expect other issues with respect to that particular earthing point from other items using it? Thanks in advance as I know you e probably regretted already taking the time to answer I; the first place.

I believe there is a specific earth point on the fuel tank or the fuel tank mountings (you could run a supplementary earth to the chassis or a known good earth)

The fuel sender is earthed through the tank and it´s connection to the chassis but if there is a fault in the wire from sender to gauge then it will give odd readings as it will pick up an earth supply before gauge...take off sender wire from gauge not the low level light indicator and ground it to tank or chassis it should go straight to full on the gauge...the gauge is also earthed behind the dash...

Thanks for that advice, and info re earths. I will check it tomorrow and get back to you. Have a good one regardless.

marksman said:

I believe there is a specific earth point on the fuel tank or the fuel tank mountings (you could run a supplementary earth to the chassis or a known good earth)

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Thanks for getting back on this. I will check it out tomorrow and let you know result of doings.

Cashpat said:

Thanks for that advice, and info re earths. I will check it tomorrow and get back to you. Have a good one regardless.

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No probs enjoying a glass of good Portuguese red wine down here...lol

Shippers said:

The fuel sender is earthed through the tank and it´s connection to the chassis but if there is a fault in the wire from sender to gauge then it will give odd readings as it will pick up an earth supply before gauge...take off sender wire from gauge not the low level light indicator and ground it to tank or chassis it should go straight to full on the gauge...the gauge is also earthed behind the dash...

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The TD5 has a plastic tank, so it can’t Earth through that.

I think there is a specific earth wire for the sender, but I don’t know it’s location. I think the question was asked a few months ago, can’t remember who by, or the answer.

I would start looking around the fuel tank for the loom that feeds the pump and sender. See if you can locate the earth wire. I would guess it goes to the chassis, possibly near the rear lights.

mick 1986 said:

The TD5 has a plastic tank, so it can’t Earth through that.

I think there is a specific earth wire for the sender, but I don’t know it’s location. I think the question was asked a few months ago, can’t remember who by, or the answer.

I would start looking around the fuel tank for the loom that feeds the pump and sender. See if you can locate the earth wire. I would guess it goes to the chassis, possibly near the rear lights.

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Cheers for the heads up re Earth point. Advice taken.

Cashpat said:

Cheers for the heads up re Earth point. Advice taken.

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I don’t know the layout of the TD5 wiring loom, but I would guess it’s around the rear lights as that’s a common earth point. I tired to find the other thread, but had no luck.

Get underneath with a torch, start looking along the chassis rails at tank, both sides, and see if you can see the loom. If you can, follow it. You will find one of two things, either a branch off to earth, or not. If it branches off to earth, strip it and clean it, if it doesn’t, then it’s a bit more complex in that you should open the loom and try a second earth wire onto the original.

mick 1986 said:

I don’t know the layout of the TD5 wiring loom, but I would guess it’s around the rear lights as that’s a common earth point. I tired to find the other thread, but had no luck.

Get underneath with a torch, start looking along the chassis rails at tank, both sides, and see if you can see the loom. If you can, follow it. You will find one of two things, either a branch off to earth, or not. If it branches off to earth, strip it and clean it, if it doesn’t, then it’s a bit more complex in that you should open the loom and try a second earth wire onto the original.

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Have been out and looked under drivers side rear where a loom is lurking. Course,note I’m a complete wiring-novice, and what I don’t see is any particular wiring heading off towards a chassis point. Could be I’ll need to check again as I imagine the earth wire is there or thereabouts. I also had a look behind the dash panel but again, not exactly sure I’m aware enough of what to “see”. Nonetheless, I’m working on the basis that any earth point that I find in this searching I will check, secure and clean up. Frustrating as I know so little. As a possible side matter, could someone explain why when the fuel pump is humming at ignition on, why when it stops is this when the fuel gauge needle flies up to the full mark?

Cashpat said:

Have been out and looked under drivers side rear where a loom is lurking. Course,note I’m a complete wiring-novice, and what I don’t see is any particular wiring heading off towards a chassis point. Could be I’ll need to check again as I imagine the earth wire is there or thereabouts. I also had a look behind the dash panel but again, not exactly sure I’m aware enough of what to “see”. Nonetheless, I’m working on the basis that any earth point that I find in this searching I will check, secure and clean up. Frustrating as I know so little. As a possible side matter, could someone explain why when the fuel pump is humming at ignition on, why when it stops is this when the fuel gauge needle flies up to the full mark?

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On a TD5, the sender and fuel pump are one unit. I’m guessing something could be wrong with the actually sender if it’s linked to when the pump stops.

If you can’t find an earth coming off that loom, then it’s possible it doesn’t have a separate earth, and actually uses the loom earth/return.