I agree with the posters who suggest replacing all of the fuel return lines, including the one from the spin on filter to the first injector. The hose is inexpensive, and if you have never replaced it, the old hose is almost always a little leaky. However, I would also suggest that you check your spin-on fuel filter carefully. Once, I though I had a leak at the first couple of injectors, and then learned that the filter had been replaced without an o-ring, so a fine spray of fuel was leaking from the top of the fuel filter and spraying onto the front of the engine. It only looked like it was leaking from the injectors.

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Gene

1983 300d (133k)
1983 300sd (118k)