I have a 95 Del Sol with the D16Z6 and on a road trip last week i started having a weird issue. After about an hour running at around 75 mph & 3500 rpm it will start to feel like it hits a fuel cutoff if i give it more gas or try to accelerate. After pulling over and stopping for 5-10 minutes it seems to get better, and it will take another 45 to an hour to start acting up again. In addition, it seems that the lower the fuel level, the more quickly this happens. My current diagnosis is that the check valve in the fuel pump is broken and because of this the pump has to run all the time, and has worn out enough that it starts to overheat after an hour and needs to cool down for a little while, hence the problem going away after stopping. Additionally, it has to turn over a bunch if I Immediately turn it to start, but if i let it prime for a second it starts instantly. Before I buy a new pump I was wondering if the check valve is in the pump itself, or if its separate in the in-tank assembly so I can replace that too. Also, let me know if you think it could be anything else, as I don't want to replace the pump if its not actually causing the problem

 

two things.. I had an intermittent issue with the igniter (brains of the distributor) doing something similar to that until one day POOF! Nothing.. Car died on the highway and I coasted to the side of the road! I had to replace the igniter and I did use a thermal paste on the backside of the new igniter, the type of thermal paste you use on a computer cpu. That helps the circuitry inside the igniter to dissipate heat away. The other issue I had was that power around 3-4k rpms would "lean out" and hardly any acceleration would occur. I finally replaced the fuel pump and no more issue with power. I don't know of the check valve you're talking about, I know that with the fuel pump assembly there's not much to it.. There's a fuel pump with a sock attached at the bottom for intake of the fuel, on the top there's an electrical connector and a hose going from the pump to the top of the hangar assembly. If you're talking the pressure check valve to equalize the vapor pressure when filling, that's on the side of the fuel tank.

Either way I responded because it sounded like what I've had in the past.. hope that helps..