fuel leak down?

[ibnfe]

I'm feeling stupid today. Not that this is odd, but I think I'm missing the obvious. Just finished (650 miles ago) putting the healthy new 401 in, and after fixing the manifold leak, was running like a champ. Now I seem to have a gremlin with the fuel delivery. Sometimes, not always, when the engine rpm gets up a bit (about 4000-4200 rpm) she'll gag for a brief moment like she loses gas, then keep on trucking. This isn't with my foot in it either, just cruising a little fast or up a hill type thing. Also, my fuel seems to be draining out of my pump to carb line after sitting for awhile (two hours or more). No external leaks what so ever. Gas is staying in the carb cuz she'll fire right up, but dies within a few seconds til the pump reprimes the line and carb. Fuel line routing is basic, pump to filter, filter to carb. Filter has the vapor bypass to tank. I disconnected and plugged that tonight, but haven't taken her around the block yet. Any other ideas? Oh yeah, I haven't found the smell of gas in the oil either from a bad diaphram. The pump is only 650 miles old! ???? :confused:

[Iron Horse]

I thought that the return line on the fuel filter was for fuel not vapor? I am sure I have read here somewhere that it allows the fuel (hot?) to recirculate back to the tank, thus avoiding vapor lock. Am I misinformed?

[Veepster]

I do not think your problem is the pump but a leak in the carb bowl...it could be the power valve...........why you ask?? because you said that it will fire up but die after a few seconds...the fuel bowl will store enough fuel for at least 30 seconds of running time.....and the reason it fires up for a few seconds is because the accel pump stores enough for a few squirts........how to check..........after vehicle sits for a few hours pull the top off the carb, I would bet you a six pack that the fuel bowl is empty............good luck! let me know what you find!

[ibnfe]

There are no external leaks at the carb anywhere. For that matter, the edelbrock carb has no power valve. As far as the return line goes, you're probably right about returning warm gas to tank. I know mine used to leak a small amount of fuel from that line when it started splitting. Back to the carb, if it was leaking internally somewhere, where would the gas be going? If it was draining into the intake, I would think my engine would be flooded. Right? Also, I had no problems driving it today since I capped off that filter to tank return line, except for pinging (detonation), so I think maybe too much gas was bypassing, and capping off the return richened the mixture enough to cause the ping. I'm gonna "re-tune" my carb and tweak the timing to try and fix that and see how she does. I have my fingers crossed... :D

[SpruceMoose]

if the fuel hose from the pump to the carb is empty, then the pump's check valves are leaking, letting the fuel run back to the tank, trying to seek the same level as the tank. try this: hook up a piece of clear hose to the output of the pump. run it straight up a few feet. crank the engine to fill the hose (disconnect the coil so it wont start). watch the fuel level in the hose. it should not go back down.

i'd try the test myself to give you a baseline, but i have an electric pump and fuel injection, so that wont help much. maybe someone else could try this too.

sm.

[ibnfe]

Thanks all, it seems to be working much better with the return capped off. Now I have a timing question, in another post. Thanks again!