N54 Injector Replacement

The N54 runs piezo injectors straight into the cylinders, and they wear out. Six of them, three to a bank, and BMW has strict rules on which ones can sit next to each other. Get the index right, code every one you touch, and this is a Saturday job.

Is it an injector?

• Rough on a cold start for a few seconds, with misfire codes stored. That's the pattern BMW wrote its bulletin around.
• Wet spark plugs on the misfiring cylinders. Pull the plugs on that bank: a plug that's wet with fuel points at a leaking injector.
• Shop tip: suspect the whole bank. The N54 has one oxygen sensor per three cylinders, so a leaking injector can make a healthy neighbor be the one that misfires. Check every plug on the bank, not just the cylinder in the code.
• Long crank or lost power on its own sends BMW to the high pressure pump side first. A bad injector is one of eight causes on that list.

Read the index before you buy

Every N54 injector has an index number printed on its plastic body, facing the ignition coil, right after the part number. Read all six with a mirror or a borescope. Don't pull an injector just to look: once it's out of its bore it needs a new seal ring.

BMW says its current number, 13 53 8 616 079, is index 11 or higher. Parts sites call it "index 12". BMW's own paperwork only ever says "11 or greater", so that's the number to look for.

The parts

Same parts on every N54 and N54T: 135i, 1M, 335i and 335xi up to early 2010, 335is, 535i and 535xi, X6 xDrive35i, Z4 sDrive35i and 35is, 740i and 740Li.

Check BMW before you pay

BMW stretched the injector warranty on many N54 and N54T cars to 10 years or 120,000 miles (SI B01 02 15 and SI B01 17 15). That has run out by age on every one of them now. Two others are worth a check: emissions recall 10E-A02 for N54 cars built April 2, 2007 through November 30, 2008, and a 2019 service action for N54T 335is coupes and convertibles built June 30, 2012 to October 1, 2013. Only a BMW dealer can tell you from the VIN whether one is still open on your car. Call before you buy injectors.

Torque

Injector hold-down bolt, M713 Nm

High pressure line nuts, both ends23 Nm, threads oiled

Ignition coil cover4 Nm

BMW coats a reused line's nut threads with a little transmission oil. New lines come pretreated. The lines can be undone and tightened up to 10 times, then they're done.

Fuel and coolant first. Work on the fuel system only with the coolant below 40 °C (104 °F). Disconnect the negative battery cable. The fuel pump runs on its own when a door opens. Face shield and gloves: fuel can spray out of a line or injector at high pressure.

Out

1. Coil cover and coils off. On E8x and E9x cars the microfilter housing comes out first. Pull each coil slowly straight up.
2. Stuff a clean rag in each plug well. Fuel on a coil boot kills the coil.
3. Vacuum the injector wells. Dirt in a direct injection system is the enemy.
4. Line off: rail end first, then the injector end. Hold the injector's hex with a wrench while you turn the nut. Mark each line with its cylinder and cap every open end.
5. Bleed it off. Rag over the injector and tap it gently with a wrench.
6. Connector off, clamp bolt out, injector out. Tag each one with its cylinder.
7. Stuck? BMW uses its punch 13 0 180 and puller 13 5 250. No aftermarket slide hammers, pry bars or power tools: BMW says they can damage the head.

In

1. Check the bore. Only clean it if it's dirty. Clean the decoupling element seat, then a new decoupling element.
2. New injector: take the cap off the tip no more than 10 minutes before it goes in. The PTFE ring swells.
3. Clamp curve faces up. Injector in, clamp on, bolt hand tight only so the injector can still turn.
4. Connector on. Old copper seals on the lines are not used anymore: throw them out.
5. Both line nuts on by hand, no force. If one fights you, turn the injector a little until it threads.
6. Clamp bolt to 13 Nm. Then the injector end nut to 23 Nm while you hold the hex, then the rail end.
7. Code the injectors (below), blow the plug wells clean, coils on, check for leaks.

Reusing an injector

A ring that has seen one heat cycle is done. BMW fits a new PTFE ring with its tool set 13 0 190: pliers to take the old one off, a cone to slide the new one on by hand, then three sizing sleeves in order to shrink it back down. No fingernails, no oil, and it goes in within 10 minutes. Wipe carbon off the round part of the tip with a lint-free cloth only, and never clean the very tip. No tool set? Read the founder's note.

Founder's note: the pen trick

New Teflon seals come very tight and not stretchy at all. BMW's tool for this runs about $200, which is a lot for what should be a once in a lifetime job on an N54. Here's how I do it without one.

Break apart a ballpoint pen and pull the insides out. Push the narrow end of the empty shell, where the ink comes out, into the seal so it starts to stretch over the taper. Wrap electrical tape around it, around and around, to keep the tension on. Leave it 15 minutes, then see if it slides over the injector. If not, push it a little further down the pen, tape it again and wait again.

Go slow. Stretch it too far and it's a loose seal. Not far enough and a 5 or 6 hour job turns into a day or two of pushing with your fingers. Buy 2 or 3 extra seals in case you ruin one: a few bucks against a $200 tool. Seal $5.99 →

On tools: the injector seal kits I've seen on Amazon come incomplete. The injector puller I bought on Amazon, a slide hammer style one listed for the N54, is practically the same as BMW's own puller, and I was surprised how gentle and easy it was the first time. The installer bracket is almost never needed on a direct injection BMW if you take your time.

Fun fact from the dealer world: most BMW techs, especially the veterans, almost never use the shop's special tools, because walking to get them eats into repair order time. A lot of them buy their own online, test them, and post reviews on Bimmerpost or Facebook so other techs know which ones are up to par with the real BMW tool.

Owner's shop experience, not BMW's procedure. BMW's own bulletin rules out aftermarket slide hammers: see step 7 under Out.

Code every injector you touch

Each injector carries its own calibration code: two blocks of three digits on the label. The engine computer needs it for the cylinder that injector sits in. BMW says skip it and the engine can run rough or not start.

Write down each code and its cylinder before the injector goes in. Two blocks on the label:

575 210 → 575210

That's BMW's own example: both blocks, in order, one six-digit entry per cylinder. Moving an old injector to a different cylinder means coding it again.

• ISTA (BMW's software): Service functions, Engine electronics, Adjust injectors. BMW calls it injection quantity compensation.
• INPA, Autel MX808 and the Schwaben scan tool all have owner-written procedures. Owners report INPA takes a wrong number without warning, so check every digit twice.
• "Was a new DME installed?" Only answer yes if you actually replaced the engine computer.

Where people mess it up

• Mixing index on a bank. One new injector next to two old ones is exactly what BMW says not to do.
• Skipping the coding. Six digits per cylinder, every time.
• Old decoupling elements. They're cheap. New ones every time.
• Fuel on the coils. Rag in the plug well before the line comes off.
• Turning a line nut without holding the injector. You twist the injector in its bore.

Steps, torque values and part rules come from BMW's repair instructions for the injectors and high pressure lines (main group 13) and BMW's US service bulletins on N54 injectors. Part numbers come from BMW's parts catalog. Check yours by VIN.