I've posted an earlier problem related to this but we'll try it again as I have been unable to solve the starvation problem. 86, E350 w/ 460. Carb starvs. Bypassed the fuel vapor separator with staight fuel line and blocked off the return line...it runs fine. After trying a new separator with the smallest return size (.0040) it still dies. I discovered the the soleniod on the secondary vent bowl line leading to the charcaol canister (holley 4180) does not close all the way when the ignition is in the run position. The primary soleniod closes all the way. Could this cause the evaporation of fuel in that bowl while driving under load and be the cause of my starvation problem. Also, I am not required to smog so is there anything else I need to disconnect if I bypass this other than blocking off the vent tubes on the bowls?

 

First of all do not block the vents on the carb in any way if anything the carb will always work fine with the vents wide open. If any fuel evaporates while driving or what ever it will always be replaced with new fuel when the float drops just as using it for acceleration. I suggest undoing the (stuff) on the bowl vent and try it out. Just a hunch. All that vent solenoid stuff is for emmisions anyway.

 

When you check your fuel flow, check it with the vapor separator connected to the return line.
If you get good flow to the carburetor, the problem is in the needle/seat assembly inside the primary (front) bowl.
It could be restricted by teflon tape from a previous repair or the float set too low from a previous rebuild!

 

I,ve checked the float levels, and the float valves. However, I do believe I'll throw some new float valves in there just to be certain their not sticking. The problem seems to be fairly intermittent. I'm still questioning those soleniods,(SB-CBV). Primary solenoid is closing all the way and the secondary is not. (run position)
As a result the secondary bowl is venting to the cannister while running.
As for the vents, This is a 4180. It's got two sets of vents. The vents on the bowls themselves, which go the the canister via the lines the soleniods are connected to and the overflow vents behind the bowls. Love2 fixit, (fyi) if you disconnect the forward bowl vent lines and don't block them, and the vehicle sits for sveral days all the fuel evaporates from the bowls and results in far too much cranking in my opinion to start up. (On my other 4180 I just ran a hose from front vent to rear vent and it works great.) However it's has no emission cr@$ on it. No vapor separator either.

 

I was just thinking about a normal holley carb has vent tubes that run vertically upwards into the air cleaner area. All aftermarket Holleys are this way along with my stock Holley on my f250 460 engine. I takes several weeks for the fuel to evaporate from the bowls. If it empties any sooner than this there is a leak. (power valve, acceletor pump, gaskets ect.) I have worked on holleys for a very long time, not that i am an expert rebuilder or anything but I know my Holleys. Like on every hot rod with a holley the fuel in the bowl with wide open vents does not evaporate in a few days. Takes a few weeks. I have had bad experiances with vent control devices like what you are dealing with. Usually while driveing and and vent doesn't open. Fuel pressure will build up inside the bowl from the heat and vibration fooling the float to stay closed. All the fuel is used float doesnt open and starved engine. Sometimes it will flood out too. Had both happen. Thats why I suggested elimitating the valves all together and trying it. Then putting back the pieces to see when the problem starts again. The other question I have is the fuel line before the carb. Does it have a pressure regulator bofore it goes into the carb(would have a return line on it). If so this ragulator has a screen in it. Make sure the screen is clean.

 

Yes, u are correct. I dont' know which holley u have but I have a 4160 in my 250 and the motorhome has a 4180. Both not only have the vents going up to the air cleaner but also have on both bowls a 1/2" tube comming out of the top front of each bowl which go to the canister via the solenoids. Trust me, it evaporates thru those 1/2" tubes quickly when they are left uncapped or not connected to the lines to the canister, especially in the summer months. I took off both solenoids today and blocked both vents (as I did with my 250) and the coressponding hoses to the canister. Put in new float valves as well. Same problem only it died much quicker with the vapor separator with the .0090 return. So I said screw it and took off the separator. I figured some engineer had what he thought was a great idea, all the guys downstairs told him it wouldn't work and upstairs did it anyway. U know how that goes. Dress em up, buy em books, send em to school and what do u get?

Seriously, it's a fuel to the carb issue. Perhaps my fuel pump is getting weak, but according to my guage it was at 4.5 to 5 psi before the separator and volume was 1 pint in 16 secs. I have to rig a sepcial fuel line setup to test it after it due to lack of room....van u know. I'm not sure what the pump pick up tube is made of but the thing sat alot so corrosion could be a factor. All I know right now is that the thing runs great w/o the separator. Soooo I popped a beer and....in the trash it went (the separator not the beer). Is this a life story or what. As the smog stuff breaks... off it will come. (That makes me feel especially good living in Kalifornia.) No state can ruin a good motor like Kalifornia. Thanks for all of your input. Everone. If I find out it is another issue I'll let u all know.! Thanks again.

 

I really hope you find the problem. These things can be ******* agrivatting(however you spell that.) I had a starvation problem too and it was that little screen in the fuel regulator. Had what looked like rust in it. My truck got drove 200,000 plus miles then sat for years. Took me forever to find where the blockage was being a daily driver for me. Well like I said, hope you find the problem. Good luck. By the way, sorry you live in Cally. hehe