Diesel Trouble Codes

Hard Start or Long Crank — 6.7 Powerstroke

Diagnostic reference for hard start or long crank on 2011–present 6.7L Power Stroke. Covers fuel supply and high-pressure rail pressure loss, air ingress…

Updated October 15, 2026

What’s going on

On the 6.7L Power Stroke a long crank is most often low fuel rail pressure — low supply from the frame-mounted fuel conditioning module, air in the fuel, a leaking high-pressure component, or a failing CP4.2 pump — or, when cold, weak glow plugs. A crank/cam correlation fault can also prevent or delay starting.1

Most likely causes

  1. Low fuel rail pressure from supply side or high-pressure pump — Frame-mounted fuel conditioning module delivering insufficient volume/pressure, clogged filters, supply-line restriction, or a failing CP4.2 high-pressure pump. Often sets P0087, P008A, P0093. A CP4.2 failure can send metal through the fuel system; if metal is found in the filters, stop and have the whole fuel system inspected.12
  2. Air ingress in low-pressure fuel supply — Leaking seals, fittings, or the fuel conditioning module allowing air into the supply. Air causes rail pressure to drop and long crank, commonly with P0087 or P008A.1
  3. High-pressure fuel leak — Leaking injector, high-pressure line/fitting, or pump internal leak causing rail pressure loss on crank. Typically sets P0087 or P0093. High-pressure fuel can penetrate skin.1
  4. Weak or failed glow plugs / glow plug control module — Cold-start hard start with rough idle and white smoke that clears as engine warms. Often sets P0670.13
  5. Crank/cam position correlation or sensor fault — Erroneous or missing crank/cam signals prevent or delay start. Typically sets P0016.14

How to narrow it down

  1. Read stored trouble codes and freeze-frame data first; prioritize codes from P0087, P008A, P0093, P0016, P0670.
  2. Check low-side fuel supply pressure/volume at the frame-mounted fuel conditioning module and inspect filters for restriction or metal debris. If metal is present, stop and have the whole fuel system inspected.
  3. Inspect low-pressure fuel lines, fittings, and seals for air ingress; perform a leak-down/prime test to confirm supply integrity.
  4. Monitor commanded vs actual high-pressure rail pressure during cranking with a scan tool; look for slow pressure build or inability to reach start threshold.
  5. Inspect glow plug system: check glow plug control module output and individual glow plug resistance; correlate with cold-start symptom and P0670.
  6. Check crank and cam sensor signals and correlation with a scan tool; inspect reluctor wheels and wiring for damage if P0016 is present.
  7. If a large high-pressure leak is suspected, do not disassemble high-pressure components under pressure; use scan data and professional inspection.

Specs and test values

CheckNormal readingWhen to measureSource
Battery and charging voltage12.6–12.7 V at rest when fully charged; about 13.5 V runningEngine off, then running with loads onDieselHub
Glow plug resistanceLow — usually no more than about 6 Ω — and similar on every plug; an open reading means a failed plugEngine off, meter lead to engine groundDENSO

Common mistake to avoid

Replacing only the high-pressure pump after a CP4 failure. A failed CP4 can send metal through the injectors, lines and tank; check the fuel and filters for debris first, because a contaminated system needs more than a pump. Source: DieselHub — common 6.7 Power Stroke problems.

Parts and tools you may need

Tools you’ll need

Rough cost and difficulty

Likely repairPartsShop laborWho usually does it
Fuel filter service$30–$1500.3–1 hrsEasy DIY
Glow plugs (full set)$80–$2502–6 hrsDIY with tools and a manual
Lift pump / fuel transfer pump$100–$4001–3 hrsDIY with tools and a manual
CP4.2 high-pressure fuel pump$1,000–$2,0004–8 hrsShop

Typical US independent-shop figures; labor runs about $120–$180 per hour (dealers charge more). Confirm the diagnosis before buying parts.

When to see a pro

If metal debris is found in filters, if high-pressure fuel leak is suspected, or if timing/correlation faults persist after sensor checks, have the fuel system and timing components inspected by a qualified diesel technician. High-pressure fuel can penetrate skin and cause injury.

Check for recalls

Recalls are tied to your truck’s VIN, so check yours directly: enter the VIN at NHTSA’s recall lookup. Open safety recalls are repaired free at a dealer.

Sources

  1. Curated symptom seed — 6.7 Powerstroke (curated) ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎

  2. Curated symptom seed — 6.7 Powerstroke (curated) ↩︎

  3. Curated symptom seed — 6.7 Powerstroke (curated) ↩︎

  4. Curated DTC seed — 6.7 Powerstroke (curated) ↩︎