So I have been restoring an 85 RX7 GSL 12A Engine with 71,500 original miles. As part of my initial restoration two falls ago, in cleaning the engine compartment I removed the oil filler pipe cleaned it up and painted it.
Anyway, I am down to getting the car to idle and some cosmetic stuff to get it on the road. It will start only with the choke fully pulled out and sometimes needs a couple of pumps on the gas pedal. It has always started this way.
So tonight after a start and almost immediate die, I could hear air in the engine compartment (vacuum leak?). So I think I narrowed it down to the oil filler pipe or possibly the hose that goes into the engine in that area (I haven't looked up what hose this is).
So the long winded question is, if the oil filler pipe was not seated tightly, could that be any source of an air leak. Is there suppose to be a rubber ring where it seats into the engine? There are no cracks in the return hose and when I plugged the return hose and covered the filler cap hole with a clean rag, it seamed to start better but still wouldn't idle. I know I still have a lot of other things to check, but I put seafoam, along with 10 gallons of 91 octane in it on Sunday and I am getting close to it being able to be on the road again, I'm getting anxious. Thanks for any thoughts.

 

the oil filler tube has nothing to do with how the engine runs. if covering it makes any difference, u may have a vacuum hose connected to it that shouldn't be.

 

The engine crankcase is under a small amount of vacuum when the car is running (PCV system, essentially) but when set up properly, the vacuum is limited by a small port in the vent valve.

If your emissions system has been altered, you might (as rxtasy3 mentions above) have manifold vacuum run directly to the crankcase. That might allow for enough of a vacuum leak to affect operation if the crankcase isn't sealed up properly. Couple big "if's" though.

There's no seal or ring at the base of the filler pipe, it's just supposed to be press-fit tightly into the hole.

If you suspect it is leaking vacuum, you could put a small amount of oil around the bottom of it and see if it gets sucked in when the engine's running.

 

Just to clarify, in looking through the shop manuals tonight, the air I was hearing around the oil filler pipe when the engine died was / is coming from the purge valve that has a line running to it. I can guarantee the car is 100% stock and no modifications have been made to the engine compartment.

On a side note, I have confirmed one of the primary nozzles is not delivering fuel to the carburetor, which is why it won't keep running. Well, at least one of the reasons why it won't keep running.