fuel system closed?

[manny1973]

On my 73 240z, I'm having problems keeping it running. Starts up fine but dies after it warms up. Acts like vapor lock. Anyway, I have new fuel filters front and back, new mechancial fuel pump and stock electric pump in the back. I thought the return line might be clogged so I blow air thru the return fuel line and after the pressure built up fuel started coming out of my fuel rail from the spot I removed the return fuel line. So as the air goes into the tank it forces fuel back thru the feed line. I did not think this is a closed system. Oh yeah I have z therpy 3 screw roundtop carbs.

Any ideas on what to check next. Can not drive the car now and spring is here.

[Bruce Palmer]

Try driving it around for the same period of time with the gas cap cracked to allow air in. The head Master at Zed Therapy confirms this. Or drive it til it dies and run around and quickly remove the gas cap and see if you hear a big inhale from the tank. Steve feels the vent is plugged but isn't up to speed on 73 Zs enough to know where they / it goes / go.

[Darrel]

Manny, Did you replace the filter inside the electric pump?

[5thhorsemann]

Try driving it around for the same period of time with the gas cap cracked to allow air in. The head Master at Zed Therapy confirms this. Or drive it til it dies and run around and quickly remove the gas cap and see if you hear a big inhale from the tank. Steve feels the vent is plugged but isn't up to speed on 73 Zs enough to know where they / it goes / go.

This is my feeling as well, although with half a tank it will take a long time to show itself. Fill up prior to doing the test. drive till she dies, try to restart, if no success crack the cap and try to restart.

[manny1973]

Darrel Yes replaced all fuel filters front and back. I will try running tonight, I can let it run without driving and after about 10 minutes it dies. Will open the gas cap to see if that changes things.

Where is the vent on the 73 that Bruce refers too?

I don't want to go for a drive because when it dies sometimes it takes 30 minutes before it will start again.

[5thhorsemann]

Could be a faulty flow guide valve pulling a vacume on the tank as well, if you only get 10 min of run time.

[Bruce Palmer]

When Steve and I were talking about this he told a story of a man with a 510 wagon who connected the tank vent to a manifold vaccum source. With an air tight cap he actually collapsed the tank. Looked okay from underneath but looking thru an access panel in the back of the wagon the top of the tank was about 8" below the floor.....

[manny1973]

I am getting totally frustrated with my Z. Seems like everything I touch breaks. Anyway went out tonight to try the suggestions on the fuel issue to discover my trickle charger very hot. Unhooked and tried to start the car and it is totally dead. No power anywhere. I'm pretty sure the battery is good. I'm hoping the fuseable link blew so that is where I will start. I will have to order one.

That puts my fuel problem on hold.

[manny1973]

Ok Need Help Please. I replaced the fuseable link and the cars starts again. Will only run till it warms up and then dies. I tried opening the fuel cap as was suggested but no change. It seems like it runs out of gas but I guess it could be electrical. I do have electronic distributer.

Any suggestions on where to start?