JustEnoughTruck

Finally, on a hunch, I installed a line direct from the pump to the carb, and filled it with fuel before connecting. Floods of fuel into the carb. This is still an old pump that's rebuildable. Should I do that, or can you shed any other light on this?

Thanks Guys- I did check the end of the hard line that connects (via some rubber line) to what I assume is the return line to the tank, and that's where I found the restriction, as expected. A deeper question is, how can I tell the difference between return line and the supply line? They both just disappear under the chassis. I believe I have traced every inch of both of them under the vehicle, and am pretty darn sure I have them hooked up correctly, but how can I tell for sure? As I said, I have disconnected the output of the pump, and have seen a bunch of gas shoot out when the engine is cranked. I have been suspicious that the float valve needle was sticking to its seat, because of the shit gas we have now, which was why I replaced it with one from another carb. Based on blowing through it while pressing and not-pressing the valve needle, it seems to be fine. Unless you have anything more to add, my next attempt is going to be bypass everything with a piece of rubber line connected directly from the pump to the carb and see how that goes. I am inferring from what you've said, that the pump has a pressure-bypass valve built in that will prevent the pump from just blowing the float valve off its seat and flooding the carb.

I went back and added the images I had promised the first time, mostly to see what worked, since the "Insert image from URL" button button doesn't seem to do anything. For the record, I right-clicked images I had uploaded to Flickr, picked "Copy Image Location" then clicked into the text of my message, right-clicked and picked Paste. Seemed to work fine. Thanks very much for your concise, to-the-point response! It's exactly why forums are often so much better than references.

Is this small flow of fuel intended to keep it cool and prevent vapor lock?

This seems like such a simple problem, but it's been plaguing me on and off for months. The Hitachi carb on this has a fully-glass float bowl cover (from an earlier model), so it's easy to see what's going on. If I prime the carb by pouring fuel down the bowl vents it appears in the bowl, and the float (brass) actually does float. The engine will then start and run perfectly until the bowl is empty, then die. It's easy to see that there is no fuel spraying out of the float valve at any time. The float follows the fuel level, and rests on the bottom of the chamber when the fuel runs out. This fuel system, unusually for a carb setup, has both a fuel feed line from the tank and a return line. Here's what I've done: 1) removed the tank and took out the sender to verify that there is no corrosion. Replaced the rubber lines at the tank. 2) verified that both the feed and return hard lines are fully open. 3) verified that the stock fuel pump delivers large mounts of fuel. 4) changed the fuel filter and replaced the rubber line to the carb. There is a device I initially assumed was a junction block between the fuel feed, fuel return, and line to the carb, which I'm now thinking is some kind of sealed pressure regulator. I'm about to eliminate this "regulator" and the return line and run hose from the pump directly to the carb, but I'd like to learn how this system works before I eliminate it. My Haynes Book of Lies hasn't been of much help, and I haven't found anything better online. I've attached photos of the "regulator" and the hard lines around the carb. TIA for any help. Richard

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Runs smooth, idles like glass at 700 or so, then blaahhh... Like flipping a switch it suddenly drops and tries to idle at 200. Fuel and spark are fine--it doesn't stall like it was shut off, the idle speed just drops like a rock. Give it a little pedal and it idles fine. It seems like some emissions equipment is mis-adjusted. BCDD? Something else I never heard of? It initially always idled too fast, like a vacuum leak, even with the idle screw backed all the way out. Is some valve open to outside air most of the time, then closes?? Also, erratic instrument panel operation. Gauges/turn signals sometimes work, sometimes not. Anybody know where the panel ground wire is? J.E.T.