408 stroker problem

[dukeboy_318]

my 78 powerwagon w200 4x4 that i got from my grandfather a few years ago has a 360/4spd stroked to 408 with a 600 cfm holley, when i first started driving it after it sat for 10 years, we replaced the fuel pump with a 110 holley mechanical pump, well last fall my brother tried running it and it would start, so he went out and put a new pump in(no clue what he put in) and ever since, it seems to have trouble pumping fuel from the pump to the carb? We ran it for about 10 minutes after he replaced it before it started having problems running, over the winter, i replaced the ballast resistor, ignition box and distributor as they all need to be up graded anyway but it seems like its starving for fuel too cause when i pour fuel directly into the carb, it runs like a charm but as soon as i stop, it shuts off. Ive got a clear filter and i can tell that it doesnt ever get full unless i hold it beneath the pump out let side. Think maybe he replaced the pump with a stock pump and maybe thats problem??  Course, he doesnt remeber anything nor does he have the box or recipt  . 

btw, i just rebuilt the carb thinking maybe that was the problem

[Musicman]

Have you disconnected the fuel line at the carb yet and check the flow from the pump?

[dukeboy_318]

yes, first thing i did but it seems to flow fine, not fast though, but yet not slow, i rebuiltthe carb and found a stuck float and i thought that was the problem, but didnt help it at all

[Musicman]

In that case, have you made the correct adjustments your idle circuit since the rebuild? I am assuming of course that the engine probably runs fine once it's off idle?

[dukeboy_318]

i tried but i cant even get the motor to stay running unless i dump gas directly into the carb or if i hold the filter donwn below the pump outlet, but that only works halfway.  i dont think the carb is the problem at all, i think its somewhere in the plumbing or with the pump itself, when i replaced the pump, i didnt change the plumbing or the way the lines were ran from the old one.  i had another guy email and tell me that its possible for my fuel sending unit to be clogged, think that would cause this type of issue??

[Musicman]

Well, you've already stated that you had a good flow of fuel to the carb itself... at least more than adequate enough to keep the engine idling anyway. This being the case, I have to look at the carburetor as a probable source of the problem. If the engine idled just fine, but started to crap out when you're driving, then I would suspect a possible fuel delivery problem... clogged filter, bad pump, etc....  but you say that's not the case here. One question however... you say that you can't get the engine to "stay running"... How long does it run before it starts to crap out? ... Have you changed the old fuel filter yet?

[dukeboy_318]

yep, new fuel filter, fully rebuilt carb. motor only runs if i dump fuel into the carb, i cant even get it to idle,  cant get fuel to flow up to it.  Ive got a mr gasket claer filter and it only trickles through it and its mounted 6 inches from the pump.   Im thinking i might have a collapse line or something clogging the pickup, or maybe just a junk pump, who knows, but its definetely somewhere in the delivery system somewhere, i dont think its the carb, guess i could always try it hooking an electric pump to it and seeing how she runs then.

[Musicman]

Now I'm a little confused... If the fuel is only trickling through the filter, then how can you have a good flow at the carb? Another thing... if there is fuel in the float bowl then it should at least run for a bit anyway before dying... Have you tried disconnecting the pump and running a gravity feed direct to the carb? Maybe try bypassing the filter?
It really does sound like low or no fuel pressure... could be a bad pump, a pinch in the supply line between the pump and the tank, or a clog at the end of the line in the tank.
You could check the pump by temporarily hooking up a piece of Tygon Tubing to the inlet of the pump. Then using a can of gas as your temporary supply, crank the engine and see if you get a good flow then. If it runs OK hooked to a can of gas, then the problem is somewhere in the supply to the pump.