car run with choke on but dies when off

Guys,
I really need some help.... I have a 62 Fairlane Sports Coupe that has a 221 V8... but I am at a loss. I had bad gas in it so I got a new manifold and Holley 4bbl carb (390 cfm) and had the tank cleaned. Now I have replaced the fuel pump and the car won't stay running when the choke opens about 1/2 way I checked for air leaks but couldn't find any... does anyone have an idea why this is happening? I'm stumped!!! Thanks for any input you may have.

Kris

 

Have you started with the basics, tune up, timing, points, carb adjsutment?

 

Vacuum leak

 

Vacuum leak .......or carb rebuild...if it won't run..without richening the fuel..
that says there's too much air....

 

Yes, I did the tune up and replaced points, cap and roter. As I said it is a new carb... its just one of those things I can't figure out.

 

OK how do I find a vacuum leak... I tried spraying starter fluid around all the normal areas and nothing happened.

 

probably a vacuum leak some where. All those mating surfaces need to be checked to make sure they are not sucking air. And are there any openings on the maifold like a port for power brakes or vacuum accessories that is not connected or open? Are thee any ports onthe carb, like pvc connections that are not hooked up.

Running with false enrichining like the choke does, indicates an lean condition. So you either need more fuel or less air. Try using an unlighted propane torch, and pass it over the carb then open the choke, if the propane keeps the engine running that will confirm the need to plug holes down stream of the carb. Inside the carb are both primary main jets open or is there some debris blocking the jet. Are both idle air mixture screws set properly?

 

Fuel filter

 

Float level way too low because of a careless rebuild, or a mistake during assembly?

You might want to check if the fuel level in the bowl is high enough to be pulled thru the jets easily. Pulling the choke often helps a low fuel level flow a bit better through the jets.

I had an air cooled VW once that acted that way if a tiny bit of dirt got past the filter. It always clogged the low speed passages if I let the gas tank level get low and the pump picked up a little dirt from the bottom of the tank. For some reason, a fuel filter always let something through, just enough to clog a low speed circuit.

 

I wouldn't spray starter fluid around to look for an air leak! Did you mean carb cleaner?

It's either too much air or not enough fuel. I doubt it is a clogged fuel filter. I had one once when a batch of bad gas came up to Minnesota in the '80's. The symptoms there were that it would start and idle just fine but would starve out at anything over 40 MPH. Even if the fuel pump were giving out, it would probably idle but you wouldn't be able to drive it.

Air leak is easiest to test for. Spray the carb cleaner around and try pinching off the hoses.

Second, you can test the fuel pump and filter because even though I am really sure that isn't it, it's the next easiest thing to test for. Just disconnect the coil and and just crank it over a couple of times, aiming it into a bucket. You'll know if it's working. Yeah, and do that outside.

If that doesn't work then it's gotta be the carb...

 

Too much air means vacuum leak . I used a spray bottle with water so the engine would run worst if the water got in .
I would say if you changed your intake then I would start looking there for a air leak .

RetroJim

 

Water in the gas will make them do some crazy stuff.

 

As someone else said, with the motor running remove gas plugs on each bowl and adjust the fuel level so gas is even with plug holes. then put plugs back in and adjust air fuel mix.

 

Do the metal fuel lines have ferrals on them? Is there too much line past the ferrel that is hitting sonething and plocking fuel flow? Found this on a Model A Ford last week ,drove us nuts.

 

I'm with a few others, it's either a very bad vacuum leak, or your floats are not adjusted right and are too low.

 

I would think the new carb (should) already be set, I would never start adjusting on a new carb unless I really knew what I was doing.
That sounds like a sure way of asking for more trouble than you already have.
If I thought the carb was the problem I would just take it back.

 

I would have to agree - vacuum leak sounds likely with the changes made. Check the intake. The propane torch works good.
I understand the carb is new, but that doesent mean anything. Is it just at idle or have you been able to drive it?

 

I'm with Retro Jim in that you may have created a leak when you swapped intakes or with the carb gasket.

The Idle mixture screws could be backed out way too far too. Have you tried adjusting them? Screw each one in and gently seat it and back it out a turn and a half for starters and see how it does. If there is no change when you do that I would be looking for a gasket that had slid or one that was installed wrong. Or the wrong gasket for the application that doesn't seal right.
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you made a bunch of changes, any chance your ride flooded during any attempts to start with old carb or new? do a quick compression check a couple cylinders washed down will make you pull your hair out, easy fix

 

BAD GAS!

I forgot about that one.
That's exactly how it acts.
YEP, check that first before you go around changing things.

Run some very fresh gas from a different station through it first to see if the problem goes away.

 

have you tried adjusting the idle mixture screws? how many turns are they out?

 

How long have you had the car? The bad gas I assume was due to a long time not running. Did the car ever run right for you? The symptom you describe is most likely a vacuum leak. Fuel supply shouldn't change just by the choke butterfly opening. If the car ran o.k. before the manifold swap I would be looking for a leak there. If you have any type of opening in a valve cover, pinch off the p.c.v. line if present. Then feel the v/c opening for vacuum, it should not be present. You can also check at the dip stick tube. Vacuum inside the crank case shows a leak at the manifold gasket or warped or cracked manifold, even new ones can be bad. (quality cotrol at beer thirty on friday) Let us know what you find.

 

Check the idle circuit on the carb,sounds like it got a lean condition at idle.

 

vacuum leak or dirty jets.....its hurting for fuel

 

Did you check your fuel line from the tank to the pump? Could be partially plugged up.

 

wow, really?... lol, carbs are not set out of the box unless you order them for a specific application, they may run, but are not set. That's why so many carbs get bad reps.

 

I'm with Koob and Big Chuck saying the fuel filter or fuel line may be clogged.

 

It has to be a vacuum leak. When you close down on the choke you shut off the normal air supply. If it still runs then it is getting air from someplace that it is not supposed to be getting air. Your problem is to find out where the air is getting into the induction system. The most common problem will be a gasket leak between the carb and the valves...base gasket, intake gasket etc.

Check for any open ports on the carb.

Needle nose pliers are great for pinching off any vacuum hoses. It could be as simple as a vac wiper hose or heater damper control vac hose falling off up under the dash. You won't find that spraying around the intake manifold. If it's a modern vehicle look for vacuum manifolds (some are on the firewall) that may have had rubber caps on non used ports. A backfire can blow one off and it won't idle for shit until it is closed off again. Brake boosters and the hoses that lead to them are often culprits.

If you pinch off a hose and it runs better then trace out where that hose goes to find the vacuum leak.

 

There is a problem in the idle circuit. It runs with choke parially closed and that creates enough low pressure so that fuel flows from the main wells and supplies the engine, when choke opens fully the depression in the venturii lessens and fuel won't flow. That whole family of holleys are not my favorite, junk in my opinion - but they do work kinda - the trash will be in the idle circuit well. If it is a brand new, newly manufactored carb the idle restrictor will be at the top of the idle well, stick a needle in it to see if small trash has wormed its' way thru filters and is plugging the hole. If not then the trash is inside the main well leading to the idle restrictor (the fuel crosses over down low (an oblong shaped hole with a supply hole from the main jet and another hole suppling the idle circuit well, earlier carbs have the idle restrictor in this location). When it is a new carb and there are idle problems it is usually from machining bits and pieces have not been cleaned out of the idle circuit well and are kept in there by the brass plug at the top of the metering block. I'd take the carb back or find a good carb guy and he can pull the brass plugs clean the things out or i can send you some plugs and you can clean it out. Whew, that was wordy enough i think. Good luck, oj

 

My neighbor had a '77 Ford pickup that was exactly the same way. He spent a couple weeks dicking around with this and that (new manifold gasket, etc.) and then he finally replaced the carburetor and it instantly cured the problem. (And he replaced the carb with one that he pulled off of a truck in a junkyard!)
Either you have a major vacuum leak or something in that carb is not right.