92 300E Fuel Injectors Troubleshooting
 

Own a 1992 300E(125,000 miles) w/M103 SOHC engine. Recently replaced all six fuel injectors along with new injector seals. Engine starts up rough after a day or so without starting and smooths out after a few seconds. Runs smooth during normal driving and after restarts throughout the day. Suspect that one or more of the new injectors is not quite closing off at shutdown and a slow leakdown is taking place overnight or over a few days when car is not started/driven. Is there a simple/easy way to check the injectors individually to see which injector/injectors are leaking down without taking the injectors out and having them tested? THANKS!!!!!
Gilles Kay
GKay737@aol.com:)

Normally the first test ( if injector leak-down is suspected ), is to install a pressure gauge at the fuelrail, note the pressure upon shut-down & then look at it before starting the engine the next morning.
Once leak-down has been established for sure, then is the time to isolate the offending injector. ;)

Some injectors have been sitting on the shelf for many years and have hardened anti-rust wax in/on them...may take a few more miles to wash this out of the tips. Try running a bottle of Techron in the tank.

Failing that, you'll need to have them bench tested.


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An experienced view of the firing line on a scope pattern will ID the missing cylinder. Maybe an infrared gun on the exhaust manifold would reveal it if it happens long enough. Start the car, shut it down when the misfire goes away, measure.