Answer
Nov 27, 2025 - 05:35 PM
If it fired up after sitting forever and now suddenly won’t start again, that old fuel system is usually the troublemaker on these early-80s SLs. The 380SL uses the Bosch K-Jetronic mechanical injection, and it hates stale fuel.
Here’s what I’d check first:
- Fuel pump not building pressure — Sitting kills the pump and the rubber inside the check valve.
Crank it and listen under the rear — no hum = no fuel. - Fuel filter or lines gunked up — Old fuel turns to varnish. Car might start once then the junk clogs everything up again.
- Cold start valve / thermo-time switch acting up — Gives one good fire when you first try, then floods or starves it after.
- Fuel accumulator leaking down pressure — Very common engine won’t restart once pressure bleeds off.
- Spark still good? — Old plug wires, green corrosion in the cap, or the ignition module playing games — one minute it runs, next minute it doesn’t.
To do a quick test, spray a little brake cleaner/carb spray into the intake and crank.
- If it coughs → fuel issue
- If it’s dead silent → ignition issue
If you need diagrams, pressure specs, or the step-by-step fuel tests, this manual has it all and walks you through them.
