Why won't my VW Karmann Ghia start, and what is that knock?

Short answer: An old Ghia that won't start usually needs the basics: fresh fuel, then check that fuel reaches the carburetor and that you have a strong spark. A knock from one side of the engine can be a bent pushrod. Popping out the tailpipe means a rich mixture or an exhaust leak, not a real backfire.

Symptom: The car cranks but won't start (sometimes only now and then), there's a tapping or knocking from one side, or it pops out the tailpipe when you let off the gas.

What to check first

1. Drain old fuel and fill with fresh gas.
2. Look for fuel at the carburetor.
3. Pull a plug wire and check for a strong spark while cranking.
4. Adjust the valves and look for a bent pushrod if you hear knocking from one side.
5. Check the exhaust gaskets and heat exchangers for leaks.

Likely causes

1. Old or stale fuel. Gas that sat for months loses the parts that make it light easily, so the engine won't fire.
2. Weak or missing spark. Points, condenser, coil and plug wires all need to be in shape on these simple ignitions.
3. Bent pushrod or valve train problem. A pushrod links the camshaft to a valve. A bent one makes a tapping or knocking sound from one side and a misfire.
4. Rich mixture or exhaust leak. Popping out the tailpipe usually means too much fuel or air getting into the hot exhaust through a leak.

What it usually costs

Owners in these threads didn't post prices.

Is it safe to keep driving?

Popping or knocking means something is wrong. Short trips are OK while you check basics, but don't run it hard with a knock. Exhaust leaks into the heater can bring carbon monoxide into the car.

DIY or shop?

Fuel, spark, valve adjustment and gaskets are DIY on these engines. Pushrod and internal engine work may need a VW shop.

Recalls, bulletins and complaints in plain words

• Recalls: NHTSA's recall lookup returned no data for the Volkswagen Karmann Ghia for 38 model-year queries on 2026-10-29, so we couldn't confirm recalls here. Check your VIN at nhtsa.gov/recalls. If your car is part of a recall, the dealer fixes it for free.
• Plain words: The complaint count below shows how often owners reported problems that mention these words to NHTSA. A count is not proof of a defect.
• NHTSA complaints: 0 keyword-matched complaints for Volkswagen Karmann Ghia 1956–1974 (of 0 unique complaints queried, NHTSA complaints API by model year, queried 2026-10-29; keywords: start, backfire, knock, engine, fuel) (NHTSA returned no data for 38 model-year queries). This counts complaints that mention these words. It is not a defect finding.

What owners report

• In 72 Karmann ghia starting on Car Talk, a '72 Karmann Ghia had an intermittent no-start. Members said to suspect old fuel and to check for fuel at the carburetor and spark at a plug.
• In Karmann Ghia engine knock on Car Talk, an owner chased a knock from one side of a Karmann Ghia's engine. A bent intake pushrod was found, and a bent spark plug was also mentioned.
• In #1208, Karmann Ghia Backfire Is Not Backfire on Car Talk, a Car Talk column on a Karmann Ghia explained that the "backfire" out the tailpipe isn't a true backfire. It's unburned fuel igniting in the exhaust from a rich mixture or an exhaust air leak.

Quick tip

These engines like regular valve adjustments. Doing them yourself keeps it running and lets you catch a bent pushrod early.

Vehicle focus: Volkswagen Karmann Ghia, 1956-1974, air-cooled four.

Safety / mechanic note

Exhaust leaks can let carbon monoxide into the cabin. Verify with a mechanic.