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Long crank on the first start: pressure that leaked away overnight
Three seconds of cranking on the first start and instant restarts all day. That pattern points at fuel pressure, and there is a two-minute test for it.
The pattern is specific: the first start of the day takes several seconds of cranking, and every start afterwards is immediate. The car then behaves perfectly until the next morning.
That is a system losing something overnight and rebuilding it during that long crank.
Related: engine cranks but won’t fire.
The two-minute test
Before anything else, and it identifies the most common cause directly.
- Leave the car overnight.
- Turn the ignition on for three seconds, then off. Repeat three or four times, without cranking.
- Now crank.
| Result | Meaning |
|---|---|
| Starts immediately | Fuel pressure was not being held overnight |
| Still cranks a long time | Something else — see below |
Each ignition cycle runs the pump briefly. If several primes fix it, you have proved the system loses pressure and that priming restores it.
Why pressure leaks away
A leaking injector
An injector that does not seal drips into the cylinder or bleeds pressure back. Often accompanied by a faint fuel smell, and sometimes by a rough first few seconds of running.
P0201 to P0206 injector circuit diagnostics.
A failed check valve in the fuel pump
The pump contains a one-way valve to hold pressure in the line after it stops. When it fails, the whole line drains back to the tank overnight.
Usually replaced with the pump assembly.
A leaking pressure regulator
Bleeds pressure back to tank when it should hold.
An external leak
Rare, and it would smell. Check for damp areas under the vehicle and around the engine.
Diesel: glow plugs
On a diesel, a long cold crank has an additional and very likely cause.
Glow plugs preheat the combustion chamber so a cold engine can achieve ignition. A failed plug or a failed relay means the engine has to compress its way to ignition temperature, which takes longer.
Signatures:
- Worse in cold weather, better in summer.
- White smoke on start-up.
- Rough running for the first thirty seconds.
- A misfire that clears once warm.
Diesel glow plug diagnostics P0670 to P0674 and glow plug light flashing.
Note that a flashing glow plug lamp is usually a general engine warning, not a glow plug fault. Read the code.
The other causes
Battery and cranking speed
A slow crank makes everything harder. Cold reduces battery capacity and thickens oil at the same time.
Check cranking voltage — below about 9.6 V is a supply problem rather than a fuelling one: winter starting tips and car not starting in cold.
Coolant temperature sensor
The ECU uses it to decide cold-start enrichment. A sensor reading warm on a cold engine means insufficient enrichment, and a long crank.
The overnight check: coolant and intake air temperature should agree within a few degrees after standing: P0116 to P0119 coolant sensor performance.
Camshaft position sensor
Without the cam signal, the ECU must work out cylinder phase by trial, which costs an extra revolution or two. On vehicles that can start without it, the symptom is a long crank rather than a no-start.
P0341 and P0344 camshaft sensor.
Oil viscosity
Oil too thick for the temperature makes the engine harder to turn. Worth checking the grade against the specification if the car has had an oil change recently.
Engine oil viscosity and approvals.
What to log
Leave logging running overnight and capture the first start:
| Parameter | What to look for |
|---|---|
| Fuel rail pressure | How long it takes to build |
| RPM during cranking | Speed, and whether the signal is present |
| Battery voltage | Sag below 9.6 V |
| Coolant temperature | Plausible against ambient |
| Fuel trims once running | Rich or lean during warm-up |
Why not to ignore it
A long crank is hard on the starter, the battery and the engine — oil pressure takes longer to reach the bearings while it cranks.
It also tends to get worse. A leak that costs three seconds today costs ten next winter, and eventually becomes a no-start.
Sequence
- The multiple-prime test — the fastest split.
- On a diesel, check glow plug operation.
- Log the first start of the day.
- Check cranking voltage.
- Compare coolant and intake temperature after an overnight soak.
- Check oil grade against specification.
Pair an ELM327 adapter, open the free tier of the app and record the first start of the morning. How long fuel pressure takes to build is the number that answers this question.
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