[vegacharger]

So I've made my 78 my daily driver! Been driving it back and forth to work as well as long weekend trips...been doing good!...But I gosta question...after driving the car..warmed up..like going to work...I shut it down and IF and ONLY if I try to start it within 10-45 min of shutting it off, it will start up and then die...the RPM drops after the starter disengages and it drops so low as to stall the beast. If I start it and quickly rev it up, it'll keep from stalling. What is supposed to prevent the RPM from bouncing down after the starter disengages? This is only after warmed up...starting cold is fine...or immediatley starting it after stopping..just when it sits for 10-45 min it gets wierd....thanks! I sold my 67 mustang so I could finish up this Z...paint is next!
chris

 

[john cross]

this is s common problem with zeds but in your case it souinds extreme. I just finished a total tune-up on mine and it still does it to a certain extent. I would look for something tune-up related. One question that may be helpful?? What is the idle like when it is running normally? If it is unstable that indicates a tune-up-type problem that needs fixing. Could be anything. The first thing you should look for ia a vacuum leak. Beyong that, could be the fuel system (regulator, pump) or more basic. However, even after you get it running really well, it will want to die immeadiately after you start it, until it gets it together. The only thing on mine I have not done in eons is the fuel pump. I am not goign to throw money around until it absolutely goes!! Good luck.

 

[szlash280z78]

I think I have read a lot of stuff about a vapor lock deal, the fuel rail gets so hot (or something) that it interupts the fuel flow for some reason which makes it hard to start after its been run for a while, they say that is why Datsun came up with the aux fan that blows on the injectors when the engine is first shut off. I dont know for sure. I dont think my 78 has ever done that except when its cold, I replaced my air regulator and now it stays on when i first start it.

 

[johnh240]

A couple of thoughts. Since you need to add air to it at the time you start it warm, it may be seeing a slightly rich signal which is not affecting the cold start. Try inspecting and cleaning the temp sensor connections and the bullet connectors. Could be as stated above and just a bit of vaporization or percolation, or regular idle setting. One other 'out on a limb' check to make. When it is warm (at the condition you expect it to start hard) disconnect the oil pressure sending unit before starting, this should kick the pump on in the 'on' key position. Let it prime for a short time and then try starting. If it stays running it could be EITHER the sending unit or just that there is some vapor in the lines that needs to purge. Reconnect the sending unit. Most likely is like szlash said.

 

[vegacharger]

Thanks guys...I will start to check all that out...it did start about the same time that I replaced my leaky oil pressure sender with a junkyard one...hmmm. I'll pull it and test it..it's good to know that if the pressure sender goes bad, all you have to do is pull the plug to it and the fuel pump will work.....that's VERY good to know. The car is tuned pretty good, I went through all that in September when I replaced the head gasket...vacuume is good too...when I replaced the oil pressure sender, I also replaced the air regulator..we'll be looking into all that as well. Once again, thanks for shedding some light!
chris