2012 BMW X5 E70 N55 Engine Crank No Start Issue Troubleshooting

You’ve got a crank/no start with even but low compression (100 psi) across all six, spark, injector pulse, and both fuel pumps working. That points hard at a mechanical timing issue or a Valvetronic (variable valve lift) fault. Battery voltage can affect cranking speed, but it won’t drop all six cylinders to 100 psi unless it’s dead flat. Normal N55 compression is much higher.

If the timing chain has jumped or the Valvetronic system is stuck in a low-lift position, you’ll get exactly this: low, even compression and no start. If the DME sees cam/crank correlation off, it’ll often set a code, but not always trigger a CEL on crank/no start.

If you prove timing and Valvetronic are good, next up would be a DME (engine computer) or immobilizer issue, but that’s less likely with your symptoms.

Most likely culprits

• Timing chain jumped/stretched — Even, low compression and crank/no start fits a slipped chain.
• Valvetronic stuck or failed — If stuck at minimum lift, you’ll get low compression and no start.
• DME/immobilizer fault — Less likely, but possible if timing and Valvetronic check out.

How to narrow it down

1. Scan all modules for codes (not just engine)
   Look for cam/crank correlation, Valvetronic, or immobilizer faults. Any timing or Valvetronic codes = focus there.

2. Check battery voltage during crank
   Needs to stay above 10.5V. If it drops lower, repeat compression test with a jump pack. If still 100 psi, battery isn’t the cause.

3. Check camshaft position while cranking
   Use a scan tool to see if cam and crank signals are plausible. If not, likely timing chain issue.

4. Remove valve cover, inspect timing marks
   If marks don’t line up at TDC, chain has jumped. That’s your root cause.

5. Check Valvetronic operation
   With ignition on, see if Valvetronic motor moves through its range. If not, motor or eccentric shaft may be stuck.

6. Check for fuel in the oil
   If chain jumped, sometimes you’ll get fuel washdown. Smell the dipstick.

Possible parts (if needed)

• Timing chain kit (if timing marks are off)
• Valvetronic motor (if stuck or not operating)

A few questions

• Did this happen suddenly, or was there noise/rough running before the no-start?
• Any recent work done on the engine (valve cover, timing, oil leaks)?
• When you scan the DME, do you get any cam/crank or Valvetronic codes, or is it clean?

Let me know what you find on those checks. If timing or Valvetronic is off, that’s your fix. If not, we’ll dig deeper.

Good info. A tight chain means it’s not obviously slack or broken, but it doesn’t rule out a jumped tooth—the chain can jump and still feel tight. The fact that the RPM rises a bit while cranking is normal; it just means the crank sensor is reading.

Here’s what matters now:

1. Timing Chain “Tight” ≠ “In Time”
You need to physically check the timing marks at TDC, not just chain tension. A jumped chain can feel tight but the cams will be out of sync.

• Pull the valve cover and set cylinder 1 to TDC.
• Check if the camshaft alignment tools fit, or if the cam lobes point as they should.
• If marks don’t line up, the chain has jumped.

2. Compression Still Low
Even with a good battery, 100 psi is way too low for the N55. That’s not a battery issue.

• If the Valvetronic is stuck at minimum lift, you’ll also get low compression.
• If the chain has jumped, you’ll get low compression across all cylinders.

3. Codes?
You didn’t mention if you scanned for codes. Even with no CEL, you need to check for pending or stored codes in the DME and Valvetronic modules.

• Any cam/crank correlation or Valvetronic codes?
• Any immobilizer or EWS codes?

Next steps (in order):

1. Scan all modules for codes—especially DME, Valvetronic, and CAS/EWS.
2. Physically check cam timing—don’t trust chain tension alone.
3. Check Valvetronic operation—does the motor move when you cycle ignition? Any codes for it?
4. Compression test with a fully charged battery or jump pack—just to rule out cranking speed.

If timing marks are off:

• You need a timing chain job. Don’t keep cranking, you’ll risk valve damage.

If timing is good and Valvetronic is stuck:

• Diagnose the Valvetronic motor and eccentric shaft.

If both are good and no codes:

• Then you’re into rare territory—DME, immobilizer, or something weird.

Bottom line:
You’re not going to solve this without checking cam timing marks. That’s the next move. If you don’t have the tools or experience, this is where you get a BMW tech involved—timing mistakes on these engines are expensive.

Let me know what you find with the timing marks and codes. That’ll tell us where to go next.

That’s a solid clue. If you cranked a lot and cylinders 1–4 are dry (no fuel mist, no raw gas smell, nothing blowing out with air), but you have injector pulse and voltage, that points to no actual fuel delivery into the cylinders. Here’s what that means:

Most likely causes now:

1. Injectors not opening

   • Could be clogged, stuck, or not getting the right control signal (even if you see voltage).
   • If all 4 are dry, it’s probably not a single bad injector—could be a wiring or DME issue.

2. No fuel pressure at the rail

   • You said low and high pressure pumps are “good,” but did you measure actual rail pressure with a gauge or scan tool during crank?
   • If the HPFP isn’t building pressure, injectors won’t spray.

3. Valvetronic stuck closed

   • If the intake valves aren’t opening enough, you won’t get air/fuel in, and you’ll see low compression and dry cylinders.

What would change my mind:

• If you find fuel in cylinders 5 or 6, that points to a partial injector or wiring issue.
• If you measure good rail pressure during crank, then the problem is likely not fuel supply.

Quick checks you can do:

1. Scan for codes

   • Look for HPFP, injector, or Valvetronic faults.

2. Check rail pressure during crank

   • Use a scan tool to read actual fuel rail pressure. Should see 50–200 bar (700–3000 psi) on crank.
   • If it’s zero or very low, HPFP isn’t working right.

3. Try starting fluid

   • Spray a small shot of brake clean or starting fluid into the intake and crank.
   • If it fires briefly, you have a fuel delivery problem.
   • If it doesn’t, you have a mechanical or spark/timing issue.

4. Listen for injector click

   • Use a mechanic’s stethoscope or long screwdriver to see if injectors are actually clicking during crank.

Safety callout:

• Don’t keep cranking with low compression and unknown timing—if the chain jumped, you risk bending valves.

Summary:

• If you have no fuel in multiple cylinders, focus on fuel rail pressure and injector operation.
• If you have low compression and dry cylinders, Valvetronic stuck closed or timing jumped are still top suspects.
• If you have spark, injector pulse, and fuel pressure, but still no start, it’s almost always mechanical (timing/Valvetronic).

Let me know what you get for rail pressure during crank and if it fires on starting fluid. That’ll narrow it down fast.