Im at work we have a truck that we use to run over hydrants been working on it all day thought i had it running good enough to do what we need but after lunch we went back out and it will only run if you have the choke fully closed i mean tight. So no air can get through. Its a 4 barrel holley unsure of what model. But if you hold the choke closed with your finger and then open up the secondaries (the rear to barrels) it runs fine but the instant the choke opens up even a crack it starts to die. I figured its a fuel problem and with the choke shut its sucking raw fuel in and the instant its opens at all it gets starved of fuel. Guessing a weak fuel pump..... Any thoughts or ideas? Its a piece of crap truck so i was just going to visegrip the choke closed and run it like that and hook the throttle up to the secondaries but we reved it a few times that way and all of a sudden she took off, the secondaries opened up wide and it was just pouring in the fuel and it wouldnt come back down so we have to kill power. So thats where i am now.

Thanks in advance

Eric

p.s. removed the fuel filter and ran it without one and no change.

Sounds like you have a major vac leak and the carb is drawing air in from somewhere else. When you open the choke it's just too much air.

That makes more sense cause it gets plunty of fuel when it needs it enough to make it redline uncontrolably. The main vacuum line on the back of the carb is just plugged.... where should i look for leaks? How many places are there on a carb for vacuum leaks. I know a tad about carbs thats about it.

Im heading home for the day but please post ideas i need to get this thing running in the morning. Thank you so much its really appreciated.

Idle passages may be plugged up. You could blast the air bleeds with carb cleaner and give it the old compressed air reverse flush to see if that helps.

just some more info it idles at about 1000 rpms. If you do anything but push the gas as slow as possible it just dies like you turned the key off. If you open the choke and slam it back shut you can save it from dying. If you push the gas as slow as possible it will get up to about 1500-1700 rpms before it starts to miss/die (all of this is with the choke closed if you open the choke at all it just dies no matter what rpm its at) if you feather it once you get it up to 1500 rpms and get it past the point of wanting to die you can get it to rap out without a problem but its nearly impossible to get it past the 1500-1700 rpm range. And since its a 20,000 pound truck with air brakes and a 16 speed its a bit hard to deal with. I will pull out the idle screws and blast the holes with carb cleaner. Will any vacuum leaks cause this??? or just ones dealing with the carb? I unplug the main vacuum on the rear left side of carb it the idle increased a tad but no change it how it ran still same symptoms maybe a tad more unwilling to get about 1500 rpms.

Any more ideas?

Thanks guys

Pulled the carb apart and cleaned everything and put it back together seems to run pretty good runs okay without the choke still dies if you floor it but if you ease the throttle it will rap out. Would a leaky intake to cylinder head gasket cause this? That seems to be the only thing i can think of. How can you tell where the idle mixture screw needs to be with out a vacuum gage?

If you don't have a vac gauge, you can use a tach and adjust the idle/air for the highest rpm reading. That should get you pretty close.
If you have some carb cleaner or starting fluid, spray it around the intake and bottom of the carb. It the rpm's go up, you have a leak.

What would not having the vacuum advance hooked up do? Also should the engine drop 500 rpms when you open the choke?

Well a choke on a warm engine will flood it out due to the lack of air mixing with the fuel so yeah your rpm will drop... dennis is steering you in the right direction spray carb cleaner (i dun recommend starting fluid) or wd40 (either one will clean ur intake manifold and carb real nice as an added benefit) if your RPM increases when u spray you have a vaccuum issue with that area of the carb .. it could be anywhere .. base gasket... linkage... jus spray everywhere around the outside of the carb.. if this shows nothing than i guess we will have to cross another bridge to get to your answer.

Well a choke on a warm engine will flood it out due to the lack of air mixing with the fuel so yeah your rpm will drop... dennis is steering you in the right direction spray carb cleaner (i dun recommend starting fluid) or wd40 (either one will clean ur intake manifold and carb real nice as an added benefit) if your RPM increases when u spray you have a vaccuum issue with that area of the carb .. it could be anywhere .. base gasket... linkage... jus spray everywhere around the outside of the carb.. if this shows nothing than i guess we will have to cross another bridge to get to your answer.

With the choke closed the rpms are around 1500 with the choke open its 1000 rpms (out of gear) It idles fine anything below below 1500 and above 2000 it seems to do okay. It still misses but it also had horrible exhaust manifold leaks. Im just trying to get this thing to beable to reach 25mph in about 500 feet.