Old 20R Carb problem - Toyota Nation Forum : Toyota Car and Truck Forums

gijoe985 · 11-11-2009, 07:36 PM

I've got a friend with an old celica, 20r engine. There is a 2bbl carb on it. He was having problems. He was having problems and said that a mech told him that his secondary jet wasn't working and ended up having him get a new carb from schucks. $350 later, just for the part, it is still having problems.

I looked at it for the first time today. Noticed that there was no fuel coming from the secondary jet (on the new carb) I then notice that the secondary butterfly wasn't really opening. After investigating the linkage, the secondary butterfly is only opening about 10% while the primary is at WOT. I looked at the linkage but could not see exactly how it worked. As of right now it plainly only engages the secondary butterfly once you have almost floored the first one. There must be something missing? His mechanic seemed sketchy to me. I wonder if a linkage part fell off his old carb and when the new one was installed it was setup like the previous, hence the same problem with a new carb. Regardless of getting messed over by the previous mechanic, I'd like to help him get it back to a good working order.

Any thoughts would be great. I wish I could see a working version...

stepho · 11-12-2009, 01:44 AM

I'm not familiar with the 20R engine but I'm reasonably sure the 20R carb is similar to the 18R carb.
I have scanned the 18R manual and have placed it here:
http://members.iinet.net.au/~stepho/manuals/
Chapter 8 covers carbs.

The 18R certainly looks very close to the 22R carb in another manual I have (not scanned yet), so its a good bet the 20R carb is similar.

From memory, the secondary butterfly starts to come in when the primary is about a third or half way.
But my memory ain't all that reliable

- Stepho

gijoe985 · 11-12-2009, 09:36 PM

Alright, I haven't found the right page yet, but that's a start. Hopefully I can help this guy out. He's pretty low on cash and I'm just trying to get his car back on its feet...

He got a Schucks replacement for the stock carb, so I wonder if they'd have a diagram for the one he got...

stepho · 11-13-2009, 09:07 AM

Pages 08-45 show how to adjust the secondary opening point (about 60 degrees).
http://members.iinet.net.au/~stepho/.../18R/08-45.JPG

I've never heard of Schucks.
Is that the manufacturer or the reseller?
The manufacturer of the carb would be the best source of information.

- Stepho

gijoe985 · 11-16-2009, 05:59 PM

Schucks/Kragen/Checkers is a parts store in the US, now owned by O'reilys. Similar to NAPA.

So my next question, it looks as if the opening point is about 60 degrees, but does the second butterfly open all the way to 90 degrees. I think that this one is opening at the correct point, but the butterfly doesn't open more than 20% of the way...

stepho · 11-17-2009, 05:57 AM

We're going past my comfort zone but common sense says that both butterflies should get to max (ie 90 degrees) at the same time.

Page 8-46 seems to agree with me.

- Stepho

gijoe985 · 11-17-2009, 10:41 AM

It seems that the second throttle valve opening must mechanically open faster. I assume this because if it doesn't engage until 60% throttle, then it must go from closed to fully open in a 40% range.

Stepho, you've been a big help, I just wish there were two or three more guys on here who could second these opinions.