I just started noticing this condition in my 79 ZX. It only happens when you try to start the car after is has already run and been sitting for about fifteen minutes or so. Sputtering, missing, backfiring. Seems like a "hot soak" issue. I found this link on Zcar.com. Note two other long time 280 Z owners have had the issue recently, for the first time. I just celebrated 20 years with this car, and it's never happened before. Wonder if it's related to ethanol in gas these days? There is a great discussion of it at this link:

http://www.zcar.com/forums/883144/vapor-lock-heat-soak-voodoo-whatever-you-wanna-call-it

Note the discussion includes references to the check valve on the fuel pump, and fuel pressure issues, but I still wonder about the alcohol fuel, given that it seems to be cropping up more in cars that have never had problems. I'm not even sure where to get non alcohol gas, since all pumps in Washington state say the gas "may contain up to 10 percent ethanol".

No hard starting for me. My 280z has triiple webbers

Hey Bill, try starting the triples when it's below Zero out...

We've had state mandated E10 (10% ethanol/alcohol) in our gasoline in Minnesota for years ... and my Z has never given me the issue you describe.

Have you tried other gas stations? Some places have a proprietary E35 mix too.

Sometimes when it's hot my car will take an extra half second of cranking (presumably due to a leaner fuel mixture), but otherwise no issue.

10% mixtures of Ethanol were being used in places worldwide in the 1970's ... I have a hard time believing that all of a sudden introduction of a bit of ethanol into the gas would cause such severe problems. (If that's even what's going on)

... you'll also notice how these guys (on the original, linked thread) are talking about how running on 'summer gas' (i.e. less oxdized) gives them no issue.

All things considered the fuel injection systems on our cars aren't all that complex, and Ethanol (in its purest form) is much cleaner and acidic than gasoline, and in many ways can act as a good decarbonizer.

I've been tempted a few times to run E85 in my Z, without modification, just to see what happens... (Don't forget that E85 has an octane rating around 105 ... cheap racing fuel for those of you running high compression).

my 78 z has also picked up this habit of starting rough after sitting for 15-20 minutes...i can fast idle for a minute or so and it goes away, but if not it's pretty rough...

the cold start injector and the thermotine switch are the only FI components i'v never changed, I've been tempted to swap them out to see if it goes away...(they test ok according to the FSM.) everything else is new under the hood...why stop now...

Hey Bill, try starting the triples when it's below Zero out...

Move to Arkansas and you won't have that problem

Open your hood right after you shut it off. Try to start in 15 Put you hand on the fuel rail after the car is off....hot as sin.....btu rating goes way down on hot fuel.....This happens every time i shut my MS powered efi off. Its hot under there. It is indeed a Heat Soak like issue. Nissan took notice put a fan in there. Took notice again on the z31 and put in a fuel temp sensor and fuel temp map.

Edited June 4, 201014 yr by yetterben

KD Matt,

Here in the Spokane area we did have mandated 10 percent ethanol for many years in the winter months, but I never drove this Z in the winter.

You may recall Congress passing the ethanol bill about two years that mandated increasing the use of ethanol in gas sold in the US.In the last year, the gas pumps in Washington have read "this gas MAY contain a blend of up to ten percent ethanol."

Apparently my car is now reacting to it. It could be something else, but I'm basing this in part on reports that other FI owners are having similar issues. I know it's definitely a heat related issue, given the little experiment I did yesterday starting the car with hood open and closed. I do plan to buy gas at some different places to see what happens. I also have the option of going over to Idaho to fill up, to see if it's any different.

A new thread here regarding another report of vapor lock:

http://www.classiczcars.com/forums/showthread.php?threadid=38754

and the new Oxygenated fuels break loose particles and such like water does. Fuel slows rust by not allowing oxygen to reach the bare metal but Oxygenated fuel gives the rust air to help it rust. Kind of a catch 22, better oxygen in the fuel but it can loosen deposits and clog the filter and such.

What do ya do?

Dave

Hey Bill, try starting the triples when it's below Zero out...

You actually drive your Z when it is below zero?:paranoid:

You actually drive your Z when it is below zero?:paranoid:

I do. But we don't salt the roads here...

I'll try and find the thread on NWN, but this same topic came up. One member posted a link to a site that had a decent list of gas stations that don't use any ethanol.

I'll edit this post once I find it.