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Shuggy110

Member Since: 25 Mar 2018
Location: Perthshire
Posts: 58

2001 Defender 110 Td5 USW Stornoway Grey

Chattering fuel pump relay

I have a 2001 10p Td5 Defender.

Two weeks ago the right hand relay in front of the gearstick (green - fuel pump) started to chatter/buzz. It didn’t affect the driving but it was noticeable. I laid it up for a couple of weeks and then today I did the following:

Changed the relay (no difference)
Took the relay block apart, cleaned up the female contacts
Checked continuity between the bulkhead bolts and battery -ve: all good
Cleaned the battery terminal and tightened it up
Contact cleaned both ECU plugs and sockets

It hasn’t made a difference. The chattering occurs intermittently with no obvious relationship with vibration or throttle position.

Fuel pump operates fine and engine runs smoothly. But something is clearly not right.

I’ve got two ideas in my head - frustrating chafed wire somewhere or mildly fried ECU.

Three weeks ago my horn started sounding at random times. I unplugged it behind the headlight. Could this be an immobiliser problem?

Many thanks for any ideas.

Last edited by Shuggy110 on 20th Jun 2021 9:20pm. Edited 1 time in total

19th Jun 2021 9:11pm

4RF RDS

Member Since: 19 Jul 2015
Location: Ottawa
Posts: 933

2000 Defender 110 Td5 XS CSW Epsom Green

As you suspect possibly a ground (earth) issue have look at the ground wires to the relay plugs and inside the under seat compartment. Also check voltage to the relay plug itself.

The alarm horn sounding, check your bonnet switch up by the bulkhead. Common failure point. Plastic plunger breaks or the bracket just needs a slight bend upwards.

Good luck. 2010 Range Rover MkIII Autobiography Super Charged (Idris)
2003 Range Rover Mk III (Desmond FitzWilliam)
2000 Defender 110 CSW TD5 (CTX)
1992 Range Rover Classic (Lizzy)
1972 Series III 300 Tdi (Stanwood)
1967 MGB GT

Every normal man must be tempted at times to spit on his hands, hoist the black flag, and begin to slit throats.
H. L. Mencken (1880 - 1956)

20th Jun 2021 6:54pm

Shuggy110

Member Since: 25 Mar 2018
Location: Perthshire
Posts: 58

Thanks - will do. I don't have a bonnet switch as I'm not sure I have an alarm - just the green immobiliser box behind the instrument binnacle.

I'll look under the seat and will check the fuel pump relay ground... I guess bonding it to the bulkhead bolts would be a sensible test.

Cheers.

20th Jun 2021 9:23pm

4RF RDS

Member Since: 19 Jul 2015
Location: Ottawa
Posts: 933

Pretty sure they all had a anti theft set up with a bonnet switch. 🤷‍♂️ Look for something that looks like this.

Click image to enlarge 2010 Range Rover MkIII Autobiography Super Charged (Idris)
2003 Range Rover Mk III (Desmond FitzWilliam)
2000 Defender 110 CSW TD5 (CTX)
1992 Range Rover Classic (Lizzy)
1972 Series III 300 Tdi (Stanwood)
1967 MGB GT

Every normal man must be tempted at times to spit on his hands, hoist the black flag, and begin to slit throats.
H. L. Mencken (1880 - 1956)

20th Jun 2021 9:42pm

dorsetsmith

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

green immobiliser box behind the instrument binnacle. and the alarm ecu all in one unit, bonnet switch may be fitted or not and how the alarm and immobiliser ecu is programmed will dictate witch add on parts all work but bonnet switch all work with out programming

21st Jun 2021 8:28am

Shuggy110

Member Since: 25 Mar 2018
Location: Perthshire
Posts: 58

A quick update. I definitely don't have a bonnet switch. It is a very early Td5 built by Special Vehicles for the National Trust. That aside, the chattering has stopped for now. I'd like to think that cleaning up the earth and the ECU plugs and sockets has helped but I'll come back and report again if it changes.

23rd Jun 2021 9:35pm

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