[Tiredofthis]

Hello All, I have had my Dodge for 5 years and it was not until this past January that I started to have problems. Currently my problem has something to do with the vacuum lines or the carburetor. I replaced my carb with a Holley remanufactured and something about the choke wasn't closing properly. So I got a new one and it has worked great until I made a long interstate drive and it started doing the same thing. Losing power. When I remove the cleaner and manually throttle it, a lot of air comes hissing out. I sprayed carb cleaner all on the vacuum lines and heard no signs of leak. I'm trying to decide if I need a new carb or if I am missing something.

Thanks for your help!

1985 Dodge D100 318 automatic.

 

[dodge man]

Unless the carb is cracked or badly warped,a rebuild should fix it. A carb will make a certain amount of hissing when it's running, so I can't say if what you hear is normal or not.

 

[Gen1dak]

They will whistle and howl when things aren't right (struggling to run at low rpm's, especially 1 and 2 barrel carbs). Keep in mind, these older carbs, unless specially noted, probably are not being built with ethanol in mind. I see AFB and Thermoquad rebuild kits that specifically mention alcohol-tolerant accel pumps, the rest of those carbs already fine with alcohol. Maybe the very latest remans might have improvements, but certainly not one made even a couple years ago. There could be something else going on, but just judging by how frequently I have to change the rubber part of my fuel line, I'd bet the carb is tired. Unless it has a metal fuel float, I'd suspect it as being currupted and causing the engine to run too rich from flooding.

 

[Tiredofthis]

So you think it is a carb problem and not a vacuum line?

 

[Warlock III]

They will whistle and howl when things aren't right (struggling to run at low rpm's, especially 1 and 2 barrel carbs). Keep in mind, these older carbs, unless specially noted, probably are not being built with ethanol in mind. I see AFB and Thermoquad rebuild kits that specifically mention alcohol-tolerant accel pumps, the rest of those carbs already fine with alcohol. Maybe the very latest remans might have improvements, but certainly not one made even a couple years ago. There could be something else going on, but just judging by how frequently I have to change the rubber part of my fuel line, I'd bet the carb is tired. Unless it has a metal fuel float, I'd suspect it as being currupted and causing the engine to run too rich from flooding.

So you think it is a carb problem and not a vacuum line?

I think G1D is right on the mark and there's an issue with the Acc pump. If you're able to exchange the carb again (if it's still under warranty) because it sounds like you bought an aftermarket Holly, I'd inquire as to the diaphram and if the acc pump is ethanol tolerant.

 

[Gen1dak]

So you think it is a carb problem and not a vacuum line?

Typically, a loose vacuum line, or leaky one will cause an increase in baseline idle speed, engine misses due to a run lean condition. I'll stick with carb issue due to corruption from ethanol based on what's been said.

 

[crazzywolfie]

do you have a vacuum gauge? it should be able to tell you if you have a vacuum leak.

 

[dodge man]

To be honest from what he describes, I don't think its the accelerator pump. The accelerator pump only does something when you step on the gas harder. It squirts a little fuel in to the carb which gives the carb a change to see an increase in fuel demanded and compensate. Thats whats nice about fuel injection, the response to more fuel is almost immediate, while a carb takes a second to catch up. The accelerator pump is there to compensate for this delay. Usually an accelerator pump problem would be when you go to pull out into traffic the vehicle hesitates badly.

There are so many things that could be wrong, it could be ignition, it could be a vacuum leak, it could be the fuel pump, it could be..........................

 

[Gen1dak]

To be honest from what he describes, I don't think its the accelerator pump. The accelerator pump only does something when you step on the gas harder. It squirts a little fuel in to the carb which gives the carb a change to see an increase in fuel demanded and compensate. Thats whats nice about fuel injection, the response to more fuel is almost immediate, while a carb takes a second to catch up. The accelerator pump is there to compensate for this delay. Usually an accelerator pump problem would be when you go to pull out into traffic the vehicle hesitates badly.

There are so many things that could be wrong, it could be ignition, it could be a vacuum leak, it could be the fuel pump, it could be..........................

I was using accel pump as an example of possible degradation. I'm leaning more towards degraded float and flooding/run rich causing immediate issue.

 

[dodge man]

I was using accel pump as an example of possible degradation. I'm leaning more towards degraded float and flooding/run rich causing immediate issue.

Yeah, there is a good chance if he doesn't have a brass float the foam float has soaked up fuel and is too heavy. The bad part of them is you can't tell by looking like you can with a brass float. I can't remember if rebuild kits come with floats or not, but I think they do. My experience was if you wanted a vehicle to run real sharp, you needed to rebuild the carb every couple of years.

 

[Nabby]

When I first got my slant six, I went through two carbs in the first two years because I was running ethanol gas... the floats just fell apart, fuel level in the carb was thrown off and passages got gummed up. Definitely learned my lesson and started only going to stations that carried non-ethanol gas... some of them around here have ethanol in every grade they offer. If you don't mind a carb rebuild, best to upgrade to brass or nitrophyl floats.

What's the issue you're having with the choke, though? It shouldn't fully close during engine operation (you have to let SOME air in), and it should really only matter when the engine is cold. Once the engine is warmed, it should be fully open and then you find out if you have any other problems with the carb. The really old ones use vacuum pull the choke slightly open at start up using a piston which can gum up or fail. The better ones use U shaped pull off link which you need to adjust when tuning your carb to get proper start-up choke - although the vacuum diaphragm that operates this U arm can fail - when mine went, I found just this part of the carb at NAPA and didn't have to replace the whole carb. The choke is connected to your fast idle cam, so on most carbs, it won't fully close unless you pump the linkage once - part of proper starting procedure on a carbureted vehicle. If your choke isn't going from mostly closed to all the way open at the proper rate as the engine warms up, or closing properly as it cools, suspect the heat sensitive coil spring is worn or bent or it's not getting heat from whatever source it's designed to - air from the exhaust, coolant hose, or electric heater - the spring is either in a choke housing on the carb or in the case of my 77, directly on the engine or exhaust manifold.