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diesel_jim

Member Since: 13 Oct 2008
Location: hiding
Posts: 6168

Td5 fuel guage...

I have a problem with my fuel guage...

If the tank is brimmed, the guage shows full. AOK.

Once it starts to drop a bit, the guage will sometimes drop to half, quarter, sometimes reads accurately. all over the place really.

Once the tank is half empty it'll usually drop to "empty" and the orange light will come on.

I thought it was my old speedo (As that controlls the damping of the guage needle), but swapped it with another used speedo and it does the same; now it could be the same fault on both speedos (I've read about the transistor that can cause this fault)

But I wonder if maybe the connection on the top of the pump/sender could be dirty, or maybe the sender itself?

Anyone got any ideas before I strip the tank out?

I suppose bypassing the speedo would eliminate that bit (albiet give me a bit of an erratic guage for a while)

5th Feb 2020 11:37pm

dorsetsmith

Member Since: 30 Oct 2011
Location: South West
Posts: 4554

Click image to enlarge

Click image to enlarge
with fuel gauge out of cct use meter check

tank sender resistor

E = 326 ohms

1/4 = 245 ohms

1/2 = 121 ohms

3/4 = 63 ohms

F = 8 ohms

you may have bad ground return from the sender

Click image to enlarge

ground path from sender

C0287

C0550-9

Click image to enlarge

The gauge grounds go thought C0278 and to C0550

Click image to enlarge

Last edited by dorsetsmith on 6th Feb 2020 12:53pm. Edited 7 times in total

6th Feb 2020 10:45am

diesel_jim

Member Since: 13 Oct 2008
Location: hiding
Posts: 6168

Cheers DS.... I'll get metering.

I wondered if there was a dodgy earth somewhere; will get underneath with a torch as well and see if anything is amiss.. maybe run a temporary one to the instrument panel and see if there's any change.

6th Feb 2020 11:06am

Martin
Site Admin

Member Since: 02 Apr 2007
Location: Hook Norton
Posts: 6662

2015 Defender 90 Puma 2.2 XS CSW Montalcino Red

The sender is already earthed back at the instrument pack loom and not locally at the sender, see the A47 splice on the right of the bottom diagram in DS's post.

To take the speedo out of the circuit, disconnect the pink plug with the green/black and light green/wires and bridge those wires.

You can still drive with that pink plug disconnected from the speedo as it's only the fuel gauge control wires on a Td5, on a ROW Tdi it also has the coolant gauge control on that plug.

The power and speedo signal go via the other pink plug.

1988 90 Td5 NAS soft top

2015 D90 XS SW

6th Feb 2020 1:24pm

diesel_jim

Member Since: 13 Oct 2008
Location: hiding
Posts: 6168

Thanks Martin, I'll have a play later on

6th Feb 2020 9:56pm

diesel_jim

Member Since: 13 Oct 2008
Location: hiding
Posts: 6168

Finally had chance today to whip the dash off and short the two green/black wires.

Perfect, guage read instantly as it should. Although now bounces around like it's a series 2 fuel guage! haha

Soooo.... aside from sending my speedo off to someone to get the transistor changed (or pulling it apart myself but I don't really want the bezel damaged), does anyone have any links for a small dampening circuit that I can put inline with (i assume) the green/blacks to stop the needle from bouncing around all over the place?

26th Feb 2020 6:22pm

donmacn

Member Since: 07 Nov 2017
Location: Nth Scotland
Posts: 1885

Watching this, as think I would also like sometthing like this.

Put the Td5 gauge in yesterday (into a 300tdi loom/Td5 tank) and it does just as you've described. Sits fine if the car is stationary or on a good flat road surface, but any movement or bends, and it's jumping about the place. Donald

1994 Defender 300Tdi 110 SW - owned since 2002 - 230k miles and going strong
(The 'rolling restoration' or tinkering thread: http://www.defender2.net/forum/topic58538.html )
2000 Range Rover P38 4.0L V8

in the past..
RR classic - fitted with 200Tdi
1984 RR classic - V8 with ZF auto box
1993 Discovery 300Tdi

not to mention the minis and the Type 2 VW camper...

8th Mar 2020 8:23pm

diesel_jim

Member Since: 13 Oct 2008
Location: hiding
Posts: 6168

After driving it for a week or 2 like this, ^^^^. It's not actually that bad.... certainly better (And more accurate) than the way it was before.

Unless I can come up withg a damper circuit, or another speedo, I'll just leave it as is.

8th Mar 2020 9:21pm

Martin
Site Admin

Member Since: 02 Apr 2007
Location: Hook Norton
Posts: 6662

If the speedo isn't faulty (like diesel jim's) then the gauge should be wired via the speedo for the damping.

1988 90 Td5 NAS soft top

2015 D90 XS SW

8th Mar 2020 9:40pm

donmacn

Member Since: 07 Nov 2017
Location: Nth Scotland
Posts: 1885

Thanks Martin.

I'm guessing that might not apply to the 300Tdi speedo?? Great if it did.

Mine is a 300Tdi 1994, and while I've changed other stuff, including the tank, I have kept the original speedo exactly as per the 1994 wiring.

(I did post another thread about trying to get the TD5 sender to work with the Tdi gauge, but the gist of that was that I would need the TD5 one. I got that, fitted it yesterday, and while it works and lights up, the needle isn't damped.)

It hadn't occurred to me, coming from the Tdi electics, that there would be anything as complicated as a damper built into the speedo!

This was my first test drive. I think I'll need to brim the tank, then see what happens over the coming days. If there's a solution I can work on fine, but I might end just accepting it like DieselJim. Donald

1994 Defender 300Tdi 110 SW - owned since 2002 - 230k miles and going strong
(The 'rolling restoration' or tinkering thread: http://www.defender2.net/forum/topic58538.html )
2000 Range Rover P38 4.0L V8

in the past..
RR classic - fitted with 200Tdi
1984 RR classic - V8 with ZF auto box
1993 Discovery 300Tdi

not to mention the minis and the Type 2 VW camper...

8th Mar 2020 10:50pm

Martin
Site Admin

Member Since: 02 Apr 2007
Location: Hook Norton
Posts: 6662

Tdi gauge will work fine. I’ve run a Td5 sender with a pre-Td5 fuel gauge no problem.

1988 90 Td5 NAS soft top

2015 D90 XS SW

8th Mar 2020 11:29pm

donmacn

Member Since: 07 Nov 2017
Location: Nth Scotland
Posts: 1885

Thanks Martin.

This is the other post ( https://www.defender2.net/forum/topic68833.html )

The new Tdi gauge just didn't seem to read correctly. Not showing a properly full tank; dropping off full faster than it used to; generally behaving differently and making me question its accuracy.

I thought the Td5 one was the answer (and maybe it is) but on the road today it was jumping about the place, so I thought I'd see if I could find a further fix hence the posting here.

I have to confess I haven't done the resistance test as recommended on the other thread. Figuring out positive to negative current flow, crimping on a few terminals, and working out a relay circuit is as techy as I get. Measuring resistance is juju I haven't tried yet - but every day's a school day and I guess I need to try that. Donald

1994 Defender 300Tdi 110 SW - owned since 2002 - 230k miles and going strong
(The 'rolling restoration' or tinkering thread: http://www.defender2.net/forum/topic58538.html )
2000 Range Rover P38 4.0L V8

in the past..
RR classic - fitted with 200Tdi
1984 RR classic - V8 with ZF auto box
1993 Discovery 300Tdi

not to mention the minis and the Type 2 VW camper...

9th Mar 2020 12:17am

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