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LANDROVER

Member Since: 13 Feb 2016
Location: EAST OF ENGLAND
Posts: 208

Fuel & Temp gauge not reading correctly...earth fault?

I have had this problem before and thought it was the corroded relays under drivers seat.
Replaced all relays.

Cranks for a while before starting, though main battery flat had to start using AUX battery.

Once starts runs fine - Idle fine etc.

The fuel gauge reads low sometimes brings fuel light on.....plenty of fuel though!

The Engine Temp gauges goes down relative to throttle movement? If you press throttle gauge goes down...release throttle gauge returns up.

I have replaced all relays under seat.
Replaced plugs and spades.
Earth points look clean
ECU plugs have been sprayed with brake cleaner
New Injector Harness

Where should I look next? Have I missed something?
The gauges have been fine for ages, I'm sure it's related to the Yellow relays but these are now both new!

The reason I changed them is it had a misfire once in a while and cut out. Playing with the yellow relays and it would return to normal.

Should relays get warm in normal usage?

The 110 still pulls like a train....even with the warped exhaust manifold

Thanks again everyone.

14th May 2020 3:48pm

Martin
Site Admin

Member Since: 02 Apr 2007
Location: Hook Norton
Posts: 6605

2015 Defender 90 Puma 2.2 XS CSW Montalcino Red

Relays should get slightly warm in use, they use power in the coil to keep the contacts closed.

As the coolant gauge signal comes from and the pedal goes to the ECU, I would be looking at the ECU earth. There is a single ring terminal but it then splits 4 ways to 4 pins on the black ECU connector (pins 1, 2, 24, 25).

So check the ring terminals near the seat box, I would be removing them, cleaning the stud and the ring and refitting

1988 90 Td5 NAS soft top

2015 D90 XS SW

14th May 2020 4:15pm

Martin
Site Admin

Member Since: 02 Apr 2007
Location: Hook Norton
Posts: 6605

Perhaps also look to add a new dedicated ground wire between the battery negative and the ECU ground stud, as at the moment it relies on earthing through the seat box. You can do this temporarily to see if it makes a difference

1988 90 Td5 NAS soft top

2015 D90 XS SW

14th May 2020 4:20pm

LANDROVER

Member Since: 13 Feb 2016
Location: EAST OF ENGLAND
Posts: 208

Martin wrote:
Relays should get slightly warm in use, they use power in the coil to keep the contacts closed.

As the coolant gauge signal comes from and the pedal goes to the ECU, I would be looking at the ECU earth. There is a single ring terminal but it then splits 4 ways to 4 pins on the black ECU connector (pins 1, 2, 24, 25).

So check the ring terminals near the seat box, I would be removing them, cleaning the stud and the ring and refitting

I will double check them. It might be worth me crimping a new ring terminal on? The others have been corroded inside the wire etc or poorly crimped.

Is there a wire in the loom which has no insulation on? I noted one coming out of the grommet then it has insulation on at the plug.

I have a ECU extension harness going to the ECU Mounted inside the headlining on the roof.

Hopefully I can get this reliable and my confidence will return. Hoping to put the roof tent on and use it for what it's designed for.

Thank you again for your help Martin.

14th May 2020 5:18pm

Martin
Site Admin

Member Since: 02 Apr 2007
Location: Hook Norton
Posts: 6605

Uninsulated wire may be the crank sensor shield drain, which pin does it go to?

1988 90 Td5 NAS soft top

2015 D90 XS SW

14th May 2020 5:56pm

LANDROVER

Member Since: 13 Feb 2016
Location: EAST OF ENGLAND
Posts: 208

Good Morning Martin,

I believe it's pin 16. Bare wire with a small section of Back insulation where cable meets plug.

Just double checking the earths.
Both look good and crimped securely attached to separate posts not together.

15th May 2020 10:12am

Martin
Site Admin

Member Since: 02 Apr 2007
Location: Hook Norton
Posts: 6605

Yes it's the crank sensor screen, that's normal.

I would run a new temporary earth lead direct from the battery negative post to the earth stud(s) - perhaps one stud at a time - and see if that makes a difference.

There might be a poor earth path between the stud and the battery.

1988 90 Td5 NAS soft top

2015 D90 XS SW

15th May 2020 10:15am

LANDROVER

Member Since: 13 Feb 2016
Location: EAST OF ENGLAND
Posts: 208

I will try making a earth extension up and see what happens.

Thank you

15th May 2020 10:38am

LANDROVER

Member Since: 13 Feb 2016
Location: EAST OF ENGLAND
Posts: 208

Martin wrote:
Yes it's the crank sensor screen, that's normal.

I would run a new temporary earth lead direct from the battery negative post to the earth stud(s) - perhaps one stud at a time - and see if that makes a difference.

There might be a poor earth path between the stud and the battery.

Good afternoon Martin,

What thickness of wire would you suggest. I only have 1.5mm here so think I will get some thicker posted in.
One wire looks alot thicker? Not sure what you suggest?

Thank you.

26th May 2020 2:28pm

Martin
Site Admin

Member Since: 02 Apr 2007
Location: Hook Norton
Posts: 6605

1.5mm2 will be fine, if you are worried run 2 of them in parallel

1988 90 Td5 NAS soft top

2015 D90 XS SW

26th May 2020 2:31pm

RLD

Member Since: 29 Jun 2007
Location: Lancs
Posts: 858

RLD fabricator of Hidden Winch Mount for D3/4 roof racks jerry can holders CB aerial mounts and much more and agent for Helsport Tents and gear

1st Jul 2020 1:12pm

LANDROVER

Member Since: 13 Feb 2016
Location: EAST OF ENGLAND
Posts: 208

Just to update as Ray has also experienced this.

I put two earths from the negative pole of my battery to each earth post and a bonding strap linking the earth posts under the seat.

This cured the problem.

It now starts instantly and gauges read correct....well fuel does it's own thing but gives a good clue

Thanks to Martin's advice!

I was convinced earth was good as terminals clean etc. I also replaced all relays etc. I'm glad I did all relays as they are definitely a weak point once corrosion and age set it.

I pushed the earth through the existing grommets so it looks neat.

1st Jul 2020 8:35pm

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