My Ninety four gets to much fuel and then you have to press the relief valve on the intake manifold to start it. I’ve replaced the EGR, Fuel filter, put in new coil and it still gets to much fuel. I replaced the temperature plug and when I removed the throttle assembly the Intake was full of carbon residue almost like the exhaust is cycling thru the intake. Any suggestions?
Check the fuel pressure regulator vacuum line for the presence of fuel/fuel vapors. Should be none on the vac side. If there is it means the diaphragm has a hole in it allowing unmetered fuel in the intake. These are also notorious for dirty mass airflow meters.
It’s also possible that your injector is leaking, not closing completely, or that your fuel pressure regulator is bad, allowing too much pressure.
However I should add that the EGR valve & solenoid and the coil are unrealated to rich operation, and the fuel filter can cause lean operation of it’s plugged, but cannot cause rich operation. Are you certain that rich operation is the cause of your symptoms? I hope you’re not just taking a “shotgun” approach to fixing it. Does it have difficulty starting regardless of the engine’s temp?
If excess fuel is being used up by the engine, it will definitely affect the exhaust smoke. The exhaust will be more smokey with rich mixture. And if that’s not the case, you should probably inspect the engine itself.