25 February 2023
Alisdair Cusick explains how diesel fuel injectors can give trouble, and how they’re replaced
Need to know
Time: 2 hours
Cost: See below
Difficulty: 3 out of 5
Models: 2.4-litre engined Defender TDCi (the procedure for 2.2 engines is broadly similar).
Tools needed: Socket set, spanners, torque wrench, breaker bar, pry bar, tissue, injector seat cleaner/cutter kit, diagnostic software, drill.
Parts & costs: 4 x 2.4 injectors (LR006803G), £227.96; 2 x injector clamp bolts (LR019168), £5.56.
• Wear eye protection when working under a vehicle and/or with
• Always support a vehicle on suitably-rated stands, never rely on a jack.
• Use the right tool for the right job.
• If in doubt, get a professional.
Thanks to: Ian Baughan and IRB Developments. irbdevelopments.com
A contemporary diesel engine relies on high-pressure injector technology, and the Puma engine is no different. This Ford in-line four-pot diesel originated in the Duratorq TDCi for the Ford Transit, but it was used by several other manufacturers, including Land Rover in the Defender from 2007.
The 2.4 and 2.2-litre Defender TDCi (Puma) variants both use common rail fuelling technology which operates at incredible pressures: up to 1800 bar (that’s 26,460 psi) at the injector. That high pressure and the way the fuel is controlled helps reduce noise, emissions and fuel consumption, whilst increasing performance. However, those benefits rely on a fully- and efficiently-functioning injection system. If you’re noticing your Puma-engined Defender is idling roughly, cutting out, surging, or emitting faint white smoke from the exhaust, those are all potential signs of injector issues.
Symptoms and failure modes
There are several causes of injector deficiency. A common one concerns the bolts on the injector clamps stretching, allowing the injectors to loosen and ‘chatter’ under the clamp in use. This causes the cylinder to lose compression, through blow-by – the leakage of combustion chamber gas upward past the injector seal – massively increasing rocker cover pressure. This can be one argument for simply changing the injector clamp bolts around 60-80,000 miles on a Puma-engined Defender, though 2.2 engines don’t suffer so much because their clamp bolts are shorter.
Other problems include: water in the fuel which can cause the injector nozzles to balloon; carbon can build around the injector nozzles; and combustion gas can blow up past the injector body if the copper seal between the injector and cylinder head fails, exacerbated by the injector clamp bolts stretching.
It is possible to recondition the injectors, but results can vary, so consider the value of simply replacing old with new. New injectors need to be coded to the car using diagnostic software via the OBD port. There are two things to be aware of when changing injectors. Carbon deposits can form on injector tips, making their extraction from the head difficult. And the mating seat in the head must be free from dirt and deposits when refitting the new injector. Like all of us working on our Land Rovers, consider carefully if you can cope with either issue. If not, then it might be time to take the car to a specialist. There’s no shame in that: wise enthusiasts understand the limits of their abilities.
On this 120,000-mile 2.4 Defender belonging to Karl Jane, another garage had previously reconditioned and refitted the injectors. But after they were coded to the car, the adaption values were way out, which would ultimately mean the injectors weren’t calibrated accurately at the ECU. Rather than cope with compromised performance, Karl opted to have new units fitted, this time by IRB Developments, where Ian Baughan now shows us the procedure for injector renewal on this 2010 Defender 90.
Cleanliness within the fuel system is critical so, after removing pipes and components, ensure dirt cannot enter the resulting openings. The injector holes in the head also need to be cleaned to prevent dirt dropping into the engine, as explained in the captions.
Where are they? The 2.4 Puma engine bay: like all modern cars, the injectors are hidden under the plastic cover. Two bolts, off it comes, and we can see everything.
Spill pipes off: Pull off the spill return pipes. The green plastic locator clips normally securing these are missing after the previous injector work. Never be afraid to check workmanship.
Unplug the power: Next, unplug the injector loom feeds, then lever the plastic covers off from the loom mounts. These also cover the injector clamp fixing bolts.
Feed pipes: Remove the four injector feed pipes. Technically, these should be renewed, being part of the high-pressure system. Close inspection shows them to be perfect to reuse.
Are they loose? Remove injector clamp bolts and clamps. These are stretch bolts, so single use. They can stretch further over time, allowing the injector to ‘chatter’ under the clamp.
Moment of truth: The injectors should now come out with a good wiggle and some persistence, but they can be very tight if they suffer from carbon build-up or swollen tips.
See a problem? With injectors removed, check for signs of carbon blow-by or swollen tips. Our four (recently reconditioned) look fine – we’re replacing them for fuelling issues, remember.
Clean is good: The injector aperture is wiped clean before tackling the seat inside the head. This seat cutter is often used to remove carbon, though Ian prefers a special brush set.
Special tools: Less abrasive cleaning kit incudes (from top) temporary plug on insertion rod to block injector tip hole, helical brush, flat-ended brush for injector seat, abrasive pad.
Follow the process: Plug is located in the tip hole to prevent dirt ingress. Then helical brush (inset), spinning in drill, cleans the sides of the injector bores in the head.
Clean up: Now, a flat-ended wire brush (inset), followed by the abrasive pad, is used to clean the injector seat face. Alternatively, the seat cutter works well using gentle pressure.
Spick and span: Using a torch, inspect the injector seats. They now should be clean, flat, and free from any carbon or crud. If not, repeat the process until they are.
New injectors: Each injector has a unique code on the top. Write each one down, noting which injector is in which cylinder. You’ll need that code for the software, later.
Fit them: Fit each injector (with a new copper washer) into the engine. Locate the clamp over each pair of injectors. This orientates the injectors for spray pattern.
Torque matters: The clamp bolts are stretch bolts, so correct and accurate tightening is critical. When set, they stretch a set amount, but remain elastic. Torque first to 8Nm.
Second step: After torque tightening, the bolts need a further rotation of 180 degrees. This angle precisely sets the bolt torque, based on thread pitch and calculated stretch.
Refit, refit, refit: Check the spill pipe O-rings (replace if necessary) then refit them to the new injectors. Refit and connect the fuel rail-to-injector pipes and wiring loom.
Replaced clips: These are the spill pipe locating clips we found missing on our vehicle. They are brittle, and not easy to buy, so do take care with them.
Wear eye protection: Bleed the fuel pipes by cracking the nuts loose at the injector end, placing tissue underneath. Crank the starter until fuel spills onto the tissue, then retighten.
Under-bonnet done: Have a last check to make sure you haven’t missed anything, refit the plastic engine cover. That is the injectors fitted: we now need to tell the car about them.
Code work: Using general diagnostic software, code the injectors to the car. You need to input the four unique codes for the injectors. You did write those down, didn’t you?
Last job: With a hot engine, the software automatically sets and adjusts the injector adaption values over five set points according to engine parameters.
Maintenance is everything
ED EVANS SAYS: Injectors tend to be forgotten about until there’s an engine running problem and, of course, not all problems are down to injectors. A multitude of other engine defects can affect the state and lifespan of the injectors, so it’s vital to keep the engine correctly maintained and properly used to avoid replacement of these relatively expensive items. Before thinking about replacing injectors, the engine needs to be inspected by a good specialist to confirm the cause of the symptoms, and the full effects.
Engine abuse: The state of this injector, from a different TDCi Defender, shows why it’s important to maintain the engine in good health. The injector nozzle is coated with carbon and oil, making an efficient fuel spray pattern impossible. This injector hasn’t failed on its own, it’s been destroyed by neglecting other aspects of the engine.
Well shot: The copper sealing washer from the same injector is deformed and eroded on the near side, allowing combustion gas to blow upward over the injector body, and engine oil to leak down into the cylinder.
Section through cylinder head: The injectors (black) are seated deep down into the cylinder head with the nozzle protruding through, between the four valves of each cylinder. The copper sealing washer is shown in yellow.
Seat repair: When the injector seat in the head is contaminated or damaged, it can be cleaned or refaced by inserting a special cleaning or cutting tool down through the injector opening to re-create a flat, sealable face for the new sealing washers.
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