The largest online repair guide library for every car

About us
Contact support
FAQ
Sign up
Sign in

2017 Q7 Cranks But Won't Start Intermittently

0

Paul Z. · rep 0 · May 22, 4:23 AM · 1 replies · solved · Question

Vehicle: 2017 Audi Q7 3.0T Premium Plus

My 2017 Audi Q7 3.0T Premium Plus has an intermittent no-start issue. It cranks strongly, but the engine just won't catch and fire up. Sometimes it starts fine, other times it takes several tries, or just won't start at all for a while.

There's no Check Engine Light on, and I've tried cycling the key a few times. It has about 75,000 miles. This is really frustrating, especially when I'm in a hurry.

Could it be a fuel pump, crank sensor, or something else? What's the best way to narrow this down without just guessing?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:23 AM

0

ClearTheCode admin answer:

An intermittent 'crank but no start' condition on your 2017 Audi Q7 3.0T can be challenging, especially without a Check Engine Light. This typically indicates a problem with one of the three essentials for combustion: fuel, spark, or air. Here's how to approach the diagnosis:

  1. Confirm the Basics:
    • Battery: Even if it cranks strongly, ensure the battery is fully charged and healthy. A weak battery can sometimes provide enough power to crank but not enough to properly power the ignition and fuel systems simultaneously.
    • Fuel Level: A simple check, but ensure there's adequate fuel in the tank.
  2. Check for Fuel Delivery Issues:
    • Listen for Fuel Pump: When you turn the key to the 'on' position (before cranking), listen for a faint hum from the rear of the vehicle. This is the fuel pump priming. If you don't hear it consistently, the pump might be failing.
    • Fuel Pressure: The most definitive test is to measure fuel pressure at the fuel rail. Low or inconsistent fuel pressure will prevent the engine from starting. This requires a fuel pressure gauge.
    • Fuel Filter: A clogged fuel filter can restrict fuel flow, especially under demand. While less likely to cause an intermittent no-start, it's a possibility.
  3. Inspect Ignition System Components:
    • Crankshaft Position Sensor (CPS): A failing CPS is a very common cause of intermittent no-start conditions. If the ECU doesn't receive a signal from the CPS, it won't know when to fire the spark plugs or inject fuel. This often doesn't trigger a CEL immediately.
    • Spark: If you have a spark tester, you can check for spark at one of the coil packs during a no-start event. No spark points to an ignition system issue (CPS, coil packs, ignition module).
  4. Air Intake: While less common for an intermittent no-start, ensure the air filter isn't completely clogged and there are no major obstructions in the intake.

When to See a Shop:

Given the intermittent nature and the complexity of modern Audi fuel and ignition systems, it's highly recommended to have your Q7 diagnosed by an Audi specialist. They have the necessary diagnostic tools to read live data from sensors like the crankshaft position sensor, test fuel pressure accurately, and identify specific component failures that might not trigger a generic CEL. This will prevent unnecessary part replacements and ensure a correct, lasting repair.

Menu

Help & account