AMC Eagle Update: In Which My Saturday Goes On A High-Carb Diet

"AncientOfDays" (ancientofdays)
05/05/2014 at 17:00 • Filed to: 1985 AMC Eagle

Longtime readers may remember way back to when I first got the Eagle, and how I gave the transmission every chance to not need a total rebuild. In the end it was for naught. The die was cast, and the rebuilt transmission has worked great.

Well, it came time to have that same sort of epiphany about the carburetor. This one took a little while, since it had technically been rebuilt not long ago, and so I ruled that out as being necessary at first.

In the end, a low-tech but foolproof test for vacuum leaks pushed me off the fence. When I sprayed carburetor cleaner around the base of the carb while the engine was running, the telltale change in engine speed was very obvious. The thing was leaking vacuum like a sieve. And leaking gasoline fumes when it was parked.

All of that was soon explained when I finally broke down, got another rebuild kit, and pulled the thing out on Saturday. This is the complicated contraption that uses some witchcraft known as the Venturi effect to mix gas and air for combustion:

It turns out that a carburetor is highly complicated for something that is usually thought of as a single part. This is the instruction sheet.

From this close-up you can see how many tiny little things go into the process.

This carb has basically 3 main layers which you can see on the table here. I used the same "bag-and-tag" parts tracking method from the transmission rebuild, and it was successful once again.

So it had been rebuilt recently, like I said. Thing is, whoever did it either had very little experience or cared very little about what they were doing. I found two huge red flags, either one of which could have explained the stalling problem on its own.

First , the "layer" on the left side, the throttle body, wasn't tightened down to the rest of the carb. It just sort of hung loosely, and the attaching screws were at least 2 or 3 full turns away from being tight.

Also , an essential part on the back, called the stepper motor (#50 on the parts diagram, middle right), was attached tightly, but incorrectly. The prong that's number 54 in the diagram was bent away to the side of where it should have been.

With those problems fixed, and all the new gaskets and parts put on, I put the carb back together. Putting it back on the car was complicated slightly when I dropped one of the attaching nuts into the intake manifold (Protip: don't drop stuff in the intake). But it wasn't too far in and I managed to gingerly fish it out and reattach the carb and all its vacuum hoses and such.

Then, the big moment came as I cranked the engine and waited for it to fire. It took a little while, probably because the end of the fuel line and the carb were empty and had to be primed. It finally caught on, and already the engine sounded better. I looked down into the carb to make sure everything looked right. I noticed that it looked to be using less gas than it did previously. It may be the case that if it's running so much leaner that you can SEE the difference, it must have been pretty bad off before.

Bonus: the garage no longer smells like gasoline fumes.

DISCUSSION (5)

desertdog5051 > AncientOfDays
05/05/2014 at 17:16

As a veteran of rebuilding carbs, I can say you put together a very good post on it and some of the problems you may encounter. The biggest pain is tuning after the rebuild. They are all different and each vehicle has its own quirks and needs. Well done.

AncientOfDays > desertdog5051
05/05/2014 at 17:25

Thanks! I had a feeling that tuning it might be its own special challenge. If I can get the idle to sound right, without the engine stalling when I hit the brakes, I'll be more than pleased with my results.

BoulderZ > AncientOfDays
05/05/2014 at 18:26

Parts bag and tag. Method of champions and professionals everywhere! Looks very similar to the rebuild kit and instructions from a rebuild I did on my 22R. It was distasteful enough that when I needed to do it again 10 years later, I turned it in to a 22RET instead.

Bad Idea Hat > AncientOfDays
05/05/2014 at 18:34

Do you want to hate yourself and manufacturers in general, and suddenly have a mild personality crisis? Mess around with a lawnmower carb.

It was much less in the way of parts, but they were all parts for ants. It was like a carburetor for ants.

Damn you, Mugatu!

AncientOfDays > Bad Idea Hat
05/05/2014 at 18:41

haha... This carb should be at least... 3 times bigger than this!