Why Does My R107 Smell Like Gas?

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A gas smell on an R107 always deserves attention. Sometimes it is a harmless whiff after a hot shutdown; sometimes it is a fuel line weeping onto a hot exhaust. Here is how I work through it.

When it is dangerous

Stop driving and fix it before using the car again if:

• You can see liquid fuel dripping or wetting a hose
• The smell is strong inside the cabin
• The smell appears with a hot engine bay after a drive

Fuel on these cars runs at high pressure. A leak sprays, not drips. Keep a fire extinguisher in the car and garage.

Most common sources, in order

1. The pump and accumulator cradle under the car: old rubber hoses and banjo washers crack and weep. See fuel pump and fuel filter.
2. Engine bay fuel lines and fittings: at the fuel distributor, the warm-up regulator, and the rubber sections near the firewall.
3. Injector lines and seals: a leaking injector seal lets vapor out of the intake area; see injectors.
4. Cold start valve: if it leaks, the car also floods after shutdown and is hard to start hot; see cold start valve.
5. Tank, filler neck and vent lines: a smell around the trunk or behind the seats points here, especially after a fill-up.
6. Running rich: an exhaust smell of raw fuel can come from a rich mixture; see running rich.

How to find it

1. With the engine cold, run the fuel pumps by bridging the relay so the system is under pressure without heat.
2. Look and feel (with a clean glove or a white paper towel) at every fitting in the engine bay and under the car.
3. Check the cradle under the car with a flashlight.
4. Smell the trunk and behind the seats after filling the tank.
5. After a short drive, check again for wet fittings, carefully, around hot parts.

Fixes

• Replace all old rubber fuel hoses with fuel-injection hose rated for high pressure and modern fuels.
• Use new sealing washers on every banjo fitting you disturb.
• Replace injector seals if you find vapor around the injectors.
• Check the filler neck seal and vent hoses for cracks.

Quick answers

• Is a slight smell after shutdown normal? A faint smell after a hot shutdown can happen, but a persistent smell is not normal.
• Does ethanol fuel cause leaks? Ethanol blends can harden or swell older rubber. See octane and ethanol.
• Can I use a rubber hose from the parts store? Use hose rated for fuel injection pressure, not low-pressure carburetor hose, and use proper clamps or crimped fittings as original.
• Why does it smell after I fill up? Check the filler neck, its rubber seal and the vent hoses near the tank; a cracked hose often shows only with a full tank.