73E MFI - Injector seal replacement

I own a 73 911E with MFI, On cold start up
One injector nozzle sprays copious amounts of
fuel onto the engine. I am assuming it is the injector rubber seal which has failed. I have heard it a semi-common occurrence on 914s and on some 911s. Planning on replacing the seal/ring and would imagine it is a fairly straight foward project. There is a Tech Article on Injector replacement, however it is for a CIS system. Is there anything I should know before I start removing my #5 injector to replace seal/ring?

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There are NO rubber seals in the MFI fuel injection system!!! The injectors are threaded and sealed to the cylinder head with a copper sealing ring, but that is not likely to be the source of the leak! The lines from injection pump to injector are steel, and the lines are DIN double flared. A pair of flare nut wrenches are required to remove the lines from the pump and the injectors. DO NOT try removing the flare nuts without the PROPER wrenches ... irrepairable damage will probably result!!! Your leak is most likely because of rust, and the operating pressure in those lines is 260 psi, so a proper repair is probably replacement of that #5 line with an exact replacement from the dealer of your choice ... 'Excellence' has several regular advertisers that are dealers.

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Warren Hall
1973 911S Targa

[This message has been edited by Early_S_Man (edited 02-25-2000).]

Warren, Thanks for the prompt and detailed reply. I'm sort of new to this, but seeing that the fuel pumps at high PSI's it's understandable there could occur a leak. My concern is that the leak lasts 30 seconds then ceases once the engine is remotely warm. I will take your advice and take this to my favorite new Porsche mechanic.

Regards,
Bruno

There is one other remote possibility, but I didn't consider it, because you said it was from an injector. If the leak only occurs when the engine is cold and quits after starting, it is NOT likely to be a rusted steel feed line to the injector, it is most likely the low pressure rubber fuel line to the cold-start enrichment nozzles that are fed from the cold-start solenoid on top of the fuel filter over behind the CDI-unit on the left-hand side of the engine compartment. It would be VERY easy to test ... just disconnect the single wire going to the solenoid, insulate it with tape or a ziplock bag around the end of the wire and connector, and start the engine! If the leak is gone, all of the 5 mm rubber tubing going from the solenoid to the nozzles should be replaced! The lines are crimped with metal bands, but small worm gear clamps should be fine if you are careful ... the nozzles are plastic, as the operating pressure is only 15 psi!!!

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Warren Hall
1973 911S Targa

[This message has been edited by Early_S_Man (edited 02-25-2000).]