Boiling fuel?

[2-4-T-Z-MAN]

Hey beandip,

Sounds like a reasonable consideration!!!!!

[dogma420]

You said your whole fuel system was replaced/refurbished....

Have you ever taken down your gas tank and cleaned it? It doesn't sound like this is the problem, but I would do it...replace all the hoses as well.

As a way to get you back on the road, I'd just take out the electric pump and use a mechanical for now....better than not driving her.

I have a good 6 cylinder and have always just used the mechanical...no probs. I'd at least try it.

[240ZMan]

If you're like me, when researching here you sometimes wish the final results got posted. Hopefully this is one of those times...

Last weekend I picked up a new clue as it was warm enough that sometimes the problem would continue (engine stumbling periodically at idle) even with the hood up. Turns out that if I took off the air cleaner top with the filter, the problem immediately went away, at least mostly. I tried removing the filter but as soon as I put the top back on the problem returned. I tried routing cold air to the intake on the filter but this made no differnce.

This bugged me for the last few days and today I figured it out. I have one of the early 70's air cleaners and there are fittings for the vents from the carbs to be connected via rubber tubing. As soon as I disconnected the tubes from the carb vents the problem went away completely.

Of course, now I need to figure out why the vents are discharging enough fuel vapor to cause the engine to stumble. I know fuel evaporates at elevated temps, but why am I having this issue when others in warmer climates, such as Arizona don't have it?

Anyway, I thought I would try to bring a little closure, and if anyone can offer any insight it will be much appreciated.

[Bambikiller240]

Float bowl valves bad? (not shutting off when bowl is full?)

[Dreco]

I have a similar problem. I've narrowed it down to heat. It's either my fuel getting hot (carbs and float bowls right above a header) or my coil is getting to hot. driving to the drag strip, it runs perfect. get in line and wait my turn with the engine at idle (meanwhile getting hotter), light goes green and I misfire all the way down the track. the higher the RPM the worse it is. I drive around a bit, and it goes away. Could the coil be getting to hot?? its on the same side as the header. well, I think my header is just heating fuel in the bowls. and when driving it around awhile, the fuel isn't sitting in there long enough to heat up, plus more air moving through the engine compartment. I think I'm going to install a remote thermometer, and watch it when I idle, and when I drive around, to see the difference, and when the problem goes away.

[240ZMan]

In my case, one of the first things I did was suspect the fuel float levels. I played around with setting them higher or lower than spec ( there's only a little you can really do before the float hits the side) and it made no difference. I even put new float valves and seats in and swapped floats from anther pair of carbs I have. Still, Carl, I have to think there is something going on with them

Dave, I too have a header but I fabbed a large heat shield that completely shields the carbs. Plus, I had this problem before I put the header on. And I know plenty of others run with headers and I don't hear them having this issue. BTW, I had misfires at high revs on really hot days with a lot of heat soak in the engine. Try routing the vents away from the carb intakes and see if it helps. It's a quick and easy experiment and cheaper than a new coil.