Fuel gauge fault

Fuel gauge fault

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Discussion

nigelj77

Original Poster:

200 posts

136 months

Sunday 11th June 2023
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I hope someone can give me some advice on an issue with my fuel gauge that started today.

Car currently has around quarter tank in it, went for a drive today and noticed the needle constantly moving between empty and quarter, after a few minutes it went up to full where it stayed for around 10 minutes then showed quarter. Drive home similar, mixture of moving between quarter and empty and also sometimes showing full.

My suspension is the sender unit has had it but expect I'd need to pull it out to check.

Car is a 2000 X 500 if that makes a difference.

Any suggestions?

Thanks in advance.

Nigel

Jordie Barretts sock

6,018 posts

26 months

Sunday 11th June 2023
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When I bought my Chim, I was delighted to discover the previous owner had left ¾ of a tank of fuel.

It was only approaching Swindon from London that it started dropping cylinders and then ground to a halt, still with ¾ of a tank.

Suggest you rule out the gauge first. Remove the sender unit from the tank and earth the green wire. Gauge should show full. It might be the copper arm isn't connecting properly with the coil of wire as well. A bit of judicious tweeking and you should be able to get the gauge to mirror what you're doing with the float as you move it up and down.

But like you, my money is on the sender. Motaclan or Racetech will provide a replacement.

nigelj77

Original Poster:

200 posts

136 months

Sunday 11th June 2023
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Thanks for the quick reply, I suspect its the sender as you say, I'd rather it was tbh as I don't fancy pulling the gauge out of the dash, it looks like a nightmare.

I'm expecting there are 2 wires connected to the outside of the sender, I expect touching them together would show full on the gauge?

I'm expecting I'll need to fit a new seal too?

I'd rather not disturb the sender until I've got the replacement at hand, the car lives beneath our bedroom and I'll not be popular if it stinks of fuel...

Jordie Barretts sock

6,018 posts

26 months

Sunday 11th June 2023
quotequote all
Yes, gauge comes with new seal.

Yes, on my Chim (and your Griff I bet) there are two wires off the sender. Conveniently they are on a plug at the top of the sender that you can remove without removing the sender.

Green goes to the gauge (this may have broken on the way to the gauge, but it would more likely be earthing where it has rubbed through on whatever has cut into it, which would cause a full reading) and black goes to earth. As you say, jump these two together and you gauge should show full.

Careful removal of the sender shouldn't disturb the seal so much that everything stinks of fuel while you are waiting on a replacement.

Keep us posted!

If you do have to get to the gauge, it's a dash top off job, but relatively easy after that. Three wires, green from the sender, ignition live and earth. Plus the bulb for the dash lights. Whilst you're in there, you might want to swap all the dash bulbs for LED. This is what I did on the Chim.




nigelj77

Original Poster:

200 posts

136 months

Sunday 11th June 2023
quotequote all
Thanks again, I was fearing a damaged wire tbh, I've just done oil, filter & air filter but surely jacking the front of the car up shouldn't bring this on as I'd expect all that wiring to be inside the car.

I'll check the wiring which is accessible first, I wonder if I could check continuity of the green wire to earth too.

I'll just have to hope this doesn't grow arms and legs or I'll be relying on counting the mileage instead...

Jordie Barretts sock

6,018 posts

26 months

Sunday 11th June 2023
quotequote all
Green wire can be earthed, but that will show a full all the time tank. It runs (on my Chim, can't imagine your Griff is different) from the sender on top right of the tank as you look in the boot, across to the left, through the bulkhead behind the passenger seat, through the sill and up the A pillar to the dash instruments. It won't be broken.

If you disconnect the electrical block on the sender, you.can earth the green on the tank, or the black wire in the connector. This will show immediate full tank on the gauge. You can now discount the sender wire and be 90% certain it isn't the gauge either. Only by removing the sender unit and manually moving the float up and down will you be 100% certain it isn't the gauge.

I had weeks of fun until I'd discounted everything but the sender unit. This is one of those jobs on a TVR where it is most likely to be the obvious thing.

nigelj77

Original Poster:

200 posts

136 months

Monday 12th June 2023
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Update, I've pulled out the necessary interior to get to the sender, there's a multi plug plugged into the sender with a black wire and a green and black wire attached. There's also shrouded female spade connectors with a red wire and a green and blue wire in them but not connected to any male plugs.
I've not connected anything to anything else for fear something goes bang.....

Jordie Barretts sock

6,018 posts

26 months

Monday 12th June 2023
quotequote all
Earth the green and black. Gauge should show full.

Leave the loose wires alone. They're nothing to do with the fuel sender.

nigelj77

Original Poster:

200 posts

136 months

Monday 12th June 2023
quotequote all
You're on the ball, thanks for that.

Ok, tomorrow's job, I'm fairly confident it's the sender, about £70 posted, doesn't say the seal is included so worth a few quid extra I reckon.

Thanks again

Jordie Barretts sock

6,018 posts

26 months

Tuesday 13th June 2023
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No problem! I'm 99% certain it has a seal with it, but a spare never hurts.

Glad you got it sorted. You may also be able to save the old one as a spare unit too. I'll bet the slider isn't covering all the resistance wires.

Jordie Barretts sock

6,018 posts

26 months

Tuesday 13th June 2023
quotequote all
One last thing, when you tighten the screws for the new one, do them up loose all round then nip them up like you would wheel nuts - opposite each other. That way the sender is pulled flat against the seal.

nigelj77

Original Poster:

200 posts

136 months

Tuesday 13th June 2023
quotequote all
Started my first diagnostics today, unplugged the plug from the sender, turned ignition on, still reading full, I guess I'm now looking at gauge or more likely wiring fault?
I think griff dash is 1 piece so not like on a chimaera where you lift the top off......

Jordie Barretts sock

6,018 posts

26 months

Wednesday 14th June 2023
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What happens when you earth the black/green?

nigelj77

Original Poster:

200 posts

136 months

Wednesday 14th June 2023
quotequote all
I was scared to try to be honest, I'm worried that with the plug disconnected and the gauge showing full its being earthed elsewhere and wherever it is finding an earth may be affected if I earthed the green to the black.

Jordie Barretts sock

6,018 posts

26 months

Wednesday 14th June 2023
quotequote all
Well, to check the gauge, it's going to have to come out of the dash. And that's beyond me in a Griff.

But when you do get it out, it'll have a black (earth) green and black (sender) and an ign fed live. Bridge between earth and green and black will show full. If you remove green and black and it still shows full, then the gauge is no good because it's earthing internally somewhere. Removing the green and black should drop to empty.

Earthing the green and black at the sender won't affect anything, if it's earthing as you suspect, it'll make no difference. There won't be a massive bang!

nigelj77

Original Poster:

200 posts

136 months

Wednesday 14th June 2023
quotequote all
Jordie, thanks again for the advice.

Looking into getting the gauge out of the dash I'd say it looks awful, remove the radio and lower air vents, undo this and that and hope you can ease the veneer dash panel out without damaging the dash or veneer, I might entrust it to the local tvr specialist.

No massive bang, what about a sizzling noise from deep inside the car, just kidding.

I can try linking the black & green and black wires via the plug, these as you mention would be the same in the back of the gauge behind the dash panel, problem I currently have is with ignition on the gauge is showing full with the ignition whether the sender is connected or not, I suppose that could be an issue with the insulation in the gauge itself allowing a connection to earth.

There are currently gauges on ebay for £40 2nd hand so if it's that the part isn't expensive but I expect the labour would be.

Jordie Barretts sock

6,018 posts

26 months

Wednesday 14th June 2023
quotequote all
The gauge is held in by two knurled nuts that screw a locking bar in place.

This is one from a Jag, but you get the idea...



You're going to need to see what you're doing from the rear or be very careful you don't drop anything. Once that locking bar is off, the gauge will come out forwards. It shouldn't be necessary to remove the wood veneer. In fact I don't think you can without removing all the gauges.

nigelj77

Original Poster:

200 posts

136 months

Wednesday 14th June 2023
quotequote all
Hi jordie, I've seen that type of gauge in the past, I'm not 100% they're like that on the Griffith from a photo I've seen.
On the Griffith the veneered aluminium dash panel can be pushed out of the dash to access the back of the gauges.
Whether or not some sort of contortionist can reach the back of the fuel gauge in situ I don't know, I don't think my ample hands will manage it.

Jordie Barretts sock

6,018 posts

26 months

Wednesday 14th June 2023
quotequote all
Never having had a hairy enough chest for a Griff, I bow to your better knowledge.

One way or another you're going to need to get that gauge out. But once it's out, you can jury rig power and earth and eliminate it or not.

indigochim

1,656 posts

137 months

Friday 16th June 2023
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[quote=nigelj77There are currently gauges on ebay for £40 2nd hand so if it's that the part isn't expensive but I expect the labour would be.
[/quote]


Just email caigauge who make the gauges mine for the Chimaera was £58.80 inc post and VAt not worth looking at the ones on ebay which when I looked had dents and nicks in the bezels. It's worth trying to get it out as you can mock the circuit up easily. and test both the sender and the gauge.