How to refit injector seals

Td5 running problems are often due to poor injector sealing in the cylinder head. Alistair Cusick explains the cure.

The Td5 engine first appeared in Defender and Discovery II models in January 1999. Originating from a plan to have four, five and six cylinder diesel engines, the five-pot version was the only one that was to see the light of day. To the concern of Land Rover fans, it relied on complex electronic management software, and a drive-by-wire throttle. For many, it marked a shift from the mechanically simple, and easy to fix vehicles that went before, but new engines were needed to meet increasingly stringent emissions regulations. 

Crucial to the Td5 are the injectors, known as Electronic Unit Injectors (EUI). They not only inject the fuel into the cylinder, but they also receive the fuel from the 4 bar supply and pressurise it to over 1000 bar needed for injection purposes. They were a common fitment to larger commercial vehicles, but were specially adapted for the Td5 - indeed, the Defender and Discovery  were the first passenger vehicles to use the technology. Compared to a Common Rail system, which needs very high pressure to be maintained in a relatively large length of the fuel injection system, EUI injection only uses high pressure at the very point of injection, thereby avoiding many of the issues associated with more conventional systems used elsewhere.

One notorious problem that does occur on the Td5 system is failure of the seals on the EUI injectors. There are two: one rubber O ring that seals the injector to the cylinder head, and a lower copper washer which seals the injector tip to the head. If either fail, then expect the vehicle to show signs of poor starting or poor running, or a noisy fuel pump working much harder to expel any air in the system. In extreme cases of failure, it’s possible for fuel to leak down past the injector, into the engine oil. Sniffing the dipstick in this case usually reveals the tell-tale diesel smell, combined with a raised oil level on the dipstick. 

If you suspect a failed seal, then it’s best practice to change them on all five injectors. The 158,000 miles 2002 Td5 Defender shown here was gradually becoming harder to start of a morning, so the immediate diagnosis was likely failure of one or more injector seals. Diesel wizard Ian Baughan of IRB Developments has done many injector seal changes, and he guides us through how to do the task in a couple of hours. Whilst there is an official tool to remove the injector, it is possible to make one.

Obviously, if you decide to make your own, you will need to take extra care not to damage the head as you lever out the injector. If you are careful, and don’t have badly carbonised injector tips, you should be fine. Of course, if you do have severe carbon build up, then you’ll likely disturb lumps of it into the cylinder, meaning head removal is then needed to ensure no damage is done when you start the engine again. Throughout this job, cleanliness is essential top avoid any dirt getting into the fuel system. If you have noticed an increase in the sump oil level on the dipstick caused by fuel leaking down past the injector seals, then an engine oil and filter change is needed too.

Time: Two hours Cost: £34

Health and safety

• Wear eye protection when disconnecting fuel components until it is confirmed that all residual pressure has been lost from the system.• Wear gloves or barrier cream to avoid suffering any adverse effects of oil on the skin.

Click on the gallery below for our handy step-by-step guide…

Recommended

Twisted launches electric Land Rover Defender conversion kit
Land Rover Defender

Twisted launches electric Land Rover Defender conversion kit

Twisted’s pure-electric conversion package gives the old Defender up to 320bhp and a maximum claimed range of 200 miles
22 Jul 2020
New Land Rover Defender 110 roof tent launched
Land Rover Defender

New Land Rover Defender 110 roof tent launched

The hard-shelled two-berth Land Rover Defender 110 roof tent is priced from around £2,800 and includes a full-size mattress
22 Jun 2020
New 500bhp+ Land Rover Defender V8 spied again
Land Rover Defender

New 500bhp+ Land Rover Defender V8 spied again

Plate check reveals new Land Rover Defender prototype with a 5.0-litre engine is roaming the grounds of Gaydon
29 May 2020
New Land Rover Defender P400 2020 review
Land Rover Defender

New Land Rover Defender P400 2020 review

The new Land Rover Defender P400 is the fastest Defender on sale and it’s a lot of fun, but the cheaper diesel models make more sense
14 May 2020

Most Popular

New 2022 BMW M3 Touring officially confirmed
BMW 3 Series Touring

New 2022 BMW M3 Touring officially confirmed

New hot BMW M3 Touring estate on the way and it’ll feature the same 503bhp straight-six engine as the saloon. Our exclusive image previews how it coul…
12 Aug 2020
Next-generation Nissan Qashqai spied ahead of 2020 launch
Nissan Qashqai

Next-generation Nissan Qashqai spied ahead of 2020 launch

Our spy photographers have spotted the new Nissan Qashqai during its development programme – although it’s still wearing heavy camo
13 Aug 2020
New 2021 Kia Stinger facelift revealed with new look and tech
Kia Stinger

New 2021 Kia Stinger facelift revealed with new look and tech

The Kia Stinger gets a subtle new look as part of a facelift for 2021
12 Aug 2020