I am having touble with my 86 Isuzu pickup. It is a 2.3 four with 5 speed manual, it has over three hundred thousand on it, but only a litle over one hunred thousand on the present engine. It has been developing a strange intermitent problem for some time now, it would run fine for months, and then satrt to miss and loose power. After you get where you are going and shut it down, it would start up and run like a champ for a few more months. The last time I drove it I barely made it home, stalling several times. I drove home in second gear at 4,000 rpm as it would die below 1,000rpm… The next day it satrted up and ran fine, I drove it about 10 feet up the drive, and now it won’t run. I have done all the usual checks, fuel filter, plugs, leads, distributor cap, rotor. cam timing, disributor timing, induction air leaks on any hoses. I finally blanked of the EGR valve and blocked most of the vacuum lines, the float level in the carb is correct, it has a good spark on the plugs, and the compression is almost at 200 on all the cylinders. Yesterday I tried to start it again, and it started and idled just fine for a while, this was without touching the throtle, and using a remote start switch outside the truck, and then it stopped, since then it will not start again. I have also checked the electric anti run on valve, which seams to be OK… I am almost at the point of replacing the carb with a Weber, but not sure the carb it the problem. It’s a great truck, and I really need to get it going again, nobody makes a small truck anymore, why it that?
Any ideas?

Is it getting vapor locked? How do the plugs look? carbon fouled, white and powery? If you have good compression, spark and correct timing the last item is the fuel. Did you check for water in the gas?

No vapor lock, the carb has a window on the float chamber, you can see the fuel level quite clearly. Have drained the carb several times, no sign of water there or in the filters. Have cleaned the plugs, although they looked good, no sign of fouling. All the plugs fire when you lay them on top of the valve cover, there is also excellent spark from the coil lead to ground. I have even cranked it while spraying ether in the intake, have also pumped the throttle to flood it, and then taken a plug out, the plug is always bone dry.I think a rat must have crawled into the intake and died, something is stopping the fuel from getting into the cylinders.
Thanks for your response, have a good one. Riley.