Hi all, sorry for all the posts lately, we're so close to getting this thing running.

Truck is a '75 w200 5.9l with a holley 2 barrel carb. I've recently rebuilt and cleaned the carb. I have experience tuning and rebuilding single barrel motorcycle carbs, but I've never worked an anything this big, and I've never seen an automatic choke setup before so I have no idea how it's supposed to work.

We're getting good spark, fuel pressure, and compression.

Symptoms: Starts after 2 or 3 cranks with full choke, revs very high for a second and then just dies. There is occasional backfiring through the intake. Seems like it's starving for fuel, but I don't know.

I have no cables or anything hooked up to the carb at the moment, we've been choking and opening the throttle by hand.

So what do ya'll think? I don't really know where to go from here. Are there any websites you can point me to that will help with carb diagnostics? Thanks in advance.

 

have you tried disconnecting the return line and pluging it? that will get you a bit more fuel at the carb. i did it do my 318.

 

We got it going. I'm kinda embarrased to admit this but the problem was that the throttle was stuck halfway open the whole time. It's kinda hard working on this stuff in the dark.

We can get it to run great with full choke, but as soon as we open the choke up it dies. Does this sound like a clogged jet?

What exactly is the return line? Is that the large tube coming out of the back of the carb? I don't have anything connected to that right now, should I?

 

you should plug any holes currently not being use. if there is a vacume leak it could cause the engine bog down. i would run it with the choke on for 5-10 minutes. you have to remember how long this thing has been sitting. you have to let some problems work themselfs out sometimes.

 

Large tubes from carb are two things: PCV valve or brake booster or both. Plug it for now and sort it out later.

 

Thanks for the replies, I'm thinkin it's creating a giant vacuum leak and that's why it won't run without full choke (vacuum leak is letting air in so closing the choke creates the right fuel/air mixture, opening the choke lets even more air in causing an extremely lean mixture, makes sense?)

 

Update: The truck runs great but has a very high idle and won't rev very much. Still can't figure out what's supposed to be connected to the tube coming out of the carb. . The tube is sticking out of the back of the carb on the passenger side down low right above the manifold. The truck is getting 95% of it's air through this hole, so the choke can only be opened up a couple millimeters before it runs rough and dies. If we try plugging it the truck dies instantly, no matter how much throttle we give it or how much the choke is open. Anyone know whats going on here?

 

you might have to adjust your carb idle mixture. On cars with two-barrel carburetor, there are two idle mixture screws. they might help. heres some more info on adjusting the idle mixture screw and tunning the carb. i can't think of anything else. it looks like that was not too common of a carb. http://www.allpar.com/fix/carb-tuning.html

 

Where can i go to find out which carb i have. 87 d150 318 numbers on the front 40214....4324629......2406