Not your typical hot start issue. Suggestions needed.

[240260280z]

I also cut and reworked my "bugle" shaped rail into a straight line. I am not sure if it will help but it holds less fuel and has less surface area than the original thus it may clear faster and absorb less heat.

Edited July 16, 2011 by Blue

[cozye]

Blue, did this work for you? What are you going to use for an FPR ?

I have more information. I stayed up late last night digging through old threads etc.. It appears to me that a few years ago, the increased ethanol used in fuel along with reformulated gas lowered the boiling point enough that 280z owners started having heat soak issues. Lots of old owners who had cars running for years with no issue, suddenly started having hot start issues. I looked up the boiling points on gasoline, and my quick searches did not yield definitive hard facts but I did find that ethanol definitely lowers the boiling point. I also found that winter gas has a much lower boiling point than summer gas. My car still had winter gas in it, since I had a full tank early this spring and it's been getting painted since.

I filled up this morning and drove it running errands, is not as hot today but I did not have any hot start issues today.

I can't fathom that these cars were boiling fuel on the rail when new. The only thing that has changed since the mid 70's is the gas formula.

I wonder what fuel additives could be used to raise the boiling point ? Zman of washington in a thread suggested putting a quart of oil in the gas. I'm not a fan of that idea, although he is very knowledgable.

This theory works for me. I don't think there is anything mechanically wrong with my car, and I know for a fact that the fuel rail gets extremely hot and fuel is boiling.

I think I may try several approaches. I will find a way to either replace the fuel rail, or preferably insulate the one I have. I will install a 170 degree thermostat. I will look into fuel additives and see if there is anything that will raise the boiling point. Another idea is to scrounge up a ZX injector fan and install it.

Edited July 16, 2011 by cozye

[cozye]

link to old thread that has useful information

http://www.classiczcars.com/forums/showthread.php?38752-Are-more-280-owners-noticing-difficult-restart-when-engine-is-hot&highlight=hot+start+issue

Link to thread where ZMOW and another well known z car member (that I'm not a fan of personally) discuss theories. I like Zman's post #8. It makes a lot of sense. He works on a LOT of customer, street driven Z cars, so he has the experience. I've talked to him previously about other Z stuff and he's a hell of a nice guy and very helpful.

http://www.zcar.com/70-83_tech_discussion_forum/vapor_lock%20_heat_soak%20_voodoo%20_whatever_you_wanna_call_it_%20%20%20_883144.0.html

[Allen Rondeau]

Had the same problem with my stock 76 280z.The problem was traced to a faulty fuel pump check valve. ( no longer available ) I had to step up and purchase a new NOS Nissan fuel pump that came with the valve. Problem solved, she starts hot now. Thank you Doug at FairLady Z.

[mjr45]

Allen, if the fuel pump was good with just a bad check valve, you could have just done the check valve. There is a thread on how to do it.

[FastWoman]

To elaborate further, there are non-Nissan check valves that can be adapted. Someone started a great thread on it -- perhaps Captain Obvious? If you still have the pump, throw it in a box, and save it to sell/give to someone else with a failed pump, for the good of the Z universe and general good karma!