Not getting fuel in a couple of cylinders

[ruf-porsche]

Started the P car last weekend to move it out of the garage to work inside the garage. Started fine and parked it outside.

When I went to restart it to move it back into the garage, the engine started like before, but it seems to be missing. The engine also didn't rev as freely as before. Moved it back into the garage and the engine idle was definitely lumpy.

Pulled a couple of wires off the dizzy to determine which cylinders wasn't firing. Only three cylinders appears to be firing, idle rpm decrease when the wires were pulled.

The three dead cylinders are not all located on the same bank of cylinders. There was spark from the dizzy to the wire when I pulled the wire so I assume the wire are okay (new magnecor last fall).

I think it's a fuel delivery problem.

Can a fuel pump provide enough fuel pressure to operate only a few cylinders but not all of the cylinders?

Could something have plugged three of the injectors?

I have a spare fuel pump and will replace that this weekend along with a new fuel filter.

Any other thought as to why three cylinders are dead?

The engine still start on the first crank, but very lumpy idle.

[rpiper]

Periodically I have a similar problem with fuel delivery; I need to replace the injectors. In the meantime you might try what I do: get a big screwdriver, rest the tip on the back of the injector and tap the handle with a hammer. Don't gorilla it, just a few easy taps and the injector should clear. In a pinch I even used a rock to tap mine one time. Certainly got funny looks from other people in the parking lot when I opened the decklid, picked up a rock, whacked part of the engine, revved it, tapped it, revved it, then threw away the rock, closed the lid and drove off!

[ruf-porsche]

Well my engine must have pass the blockage because it is now running excellent again. Must be similar to passing a kidney stone for human.

Thanks rpiper for the tip on tapping the injectors with a screw driver and hammer. Apparently that dislodge whatever was blocking the injectors from injecting.

I am still going to swap out the fuel pump and fuel filter this weekend if it doesn't rain. How hard or easy is it to remove the injectors? My 82 911 engine has hard steel line instead of the plastic line like my old 74 911.

I did take it out for a nice drive and added a bottle of Techron.