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I took the carb out of my F150 79 because it was only firing on 4 cylinders (verified spark on all cylinders). Cylinders not firing are 2,3,5,8. If you look at the attached picture one of the tubes on the ventury assembly is capped and the other is not. Every picture of this carb I have seen shows both tubes capped, is this normal? Thank you for the help.
I took the carb out of my F150 79 because it was only firing on 4 cylinders (verified spark on all cylinders). Cylinders not firing are 2,3,5,8. If you look at the attached picture one of the tubes on the ventury assembly is capped and the other is not. Every picture of this carb I have seen shows both tubes capped, is this normal? Thank you for the help.
Nope the expansion plug has fallen out, I have to say first time I have seen this happen.
If I recall correctly it is either a 3/8" or 11/16" aluminium expansion plug they are available from several sources.
Nope the expansion plug has fallen out, I have to say first time I have seen this happen.
If I recall correctly it is either a 3/8" or 11/16" aluminium expansion plug they are available from several sources.
Most small engine shops carry those little expansion plugs. Usually made from very mild steel or lead/steel composite. That should be a 13/32's if memory serves me.
I'd be very curious to know if that was missing when the carb was installed or if it went down the intake.
I just drive them with a brass rod, a small amount of swearing is necessary, maybe even a little heat if they get me really riled. My favorite is when I pull them out to do a "cleaning" and find nothing in there, that is what usually gets me really going.
Sorry for the rant, as far as for the symptoms, that carb wasn't running in that venturi at all, couldn't have been, so somewhere there had to be a lean condition, but with the layout of a dual plane intake that barrel fed the ones that weren't running, but they might not have been dead, since they could have possibly ran on the egr at times andalso would have sputtered a little from the accelerator pump.
You guys are good
Do they just pop in or do they have to be installed in particular way?
They are an aluminum expansion plug.
They are concave or convex depending on your point of view. Install the plug so it is concave out and give it a light tap with a rod as close to the same the diameter of the plug as you can get, till it is just about flat.
Most all expansion plug failers are due to improper installation , almost always due to using an improperly sized tool to install them. It has to be the same size or near the same size or the plug will not flatten properly and won''t have a tight seal. As you can see from the other one someone did not use the correct sized tool to install it and that is why it fell out.
In addition you can also use a bit of removable locktite around the edge to hold it in place and seal it.
In an application such as this it HAS to be used very very sparingly and you just want a very light smear around the edge.
Sorry for the rant, as far as for the symptoms, that carb wasn't running in that venturi at all, couldn't have been, so somewhere there had to be a lean condition, but with the layout of a dual plane intake that barrel fed the ones that weren't running, but they might not have been dead, since they could have possibly ran on the egr at times andalso would have sputtered a little from the accelerator pump.
That venturi missing the plug would still feed fuel on the main circuit of the carb. It would not feed properly the idle circuit as that plug seals the top of the emulsion tube.
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