I just bought an 87 samurai. It runs great, but on the highway it wont go over 90 Km/hr (about 4000 RPM). I believe this is due to the secondary butterfly in the 2 brl carb not opening. Is the secondary operated mechanically by linkages or is it operated by vacuum. If operated by vacuum, where can I get a schematic of the vacuum lines. I have a hayes manual, but it does not go into details on such matters.
Another issue I am dealing with is when I start the engine it runs slightly rough, but as soon as I turn the running lights on the engine RPM increases to smooth pace. To me this seems to be opposite of what should be happening, because as load is put on the alternator it should produce some drag and decrease the rpm, not increase.
there are only two types as you say.
on the mech, there is special linkages between the two butterly shafts , just look , see.
no, if its vacuum then it must have the large vacuum diaphram on the side of carb and a stroking rod.
this rod will open the secondaries.
I can not tell you how many cars I have hacked the secondaries. I would throw the vacuum chamber of my left shoulder and then say , OUTA HEAR, sucka.
then I'd make up my own custom linkage.
Such that when my primaries were half open the secondaries would start to open.
they would open very quickly, form that point on.
after doing this car would really kick butt.
having old carbi's under bench to steal parts helped.
In the old days , eveyone sold kits to do this.
I spent some more time under the hood today and actually found the probelm. I guess the old owner disconected the vacuum line going to the diaphram and just left all the hoses unplugged. I hook them up again and all works, even got ride of the erratic idling when running lights off.
So I now have a new problem. After putting all the vacuum lines to the right places, the engine runs very rich and sometimes idles high (1500RPM but then drops down to 500RPM after a few minutes). I have adjusted the idle screw after warming up the engine, but it never seems to stay at the same RPM.
Is there an adjustable air screw on the carbs? I have found one at the base of the carb (very hard to adjust though) and is there a specific setting for it?
find all the vacuum leaks.
look for empty nipples, cracked hose/diapharms the pinch all the hose and expect no idle drop.
Normal is when engine is cold the choke goes on and holds idle high.
after the choke warms up this mechanism drops the throttle.
make sure it does , by looking at it.
there are 3 kinds of chokes, water, exh.gas, and electric. (?)
manual is best (i always converted to manual)
the carbi in general (all carbs)
1. boil it out ( clean in side and outside,with GunkBOP or x chem)
2. put in a carb kit
3- set float level.
baring that :
check for vacuum leaks and
make sure there is no carbon below the butterfly plate on the bottom
of the carb (where you cant see)
PCV gases coke up this area. is very common. causing stuck butterfly.
does engine still have EGR valve?
yes, make sure its not stuck open.
what else is missing , besides the body? hah hah.......
ok, so I have checked for leaks, plugged all the empty nipples, adjusted the timing, bought new air filter/spark plugs/spark plug leads, and reconnected the secondary butterfly vacuum diaphram. everything runs well, but now that the secondary vacuum diaphram is connected, the engine idles high and runs very rich. It even seems like it is burning oil (everytime you hit the accelerator it belchs out lots of grey smoke), but as soon as you disconnect the vacuum line to the secondary diaphram it stops smoking and the idle drops to normal.
The only thing I can think of is that the vacuum going to the secondary is too strong and tries to open the butterfly at idle, but the linkages should stop this.
I still have not found any kind of diagram for the vacuum lines.
I am really running out of ideas. so input would be much appreciated.
that's a tough one, and no diagram.
Ill see if i can dig one up. ( go it)
did you check the diaphragm for leaks .
the diaphargm must be connected to the correct port too,
the jets in the secondary circuit might be removed or drilled out.
something missing , maybe:?
put the vacuum unit back on the carbi
and connect the hose.
pinch same hose, does the problem stop?
if it did , then jam the secondary closed with hand, and hose connected.
No, then the diaphram is cracked. (a test , lacking proper mityvac tool)
if the diaphragm is good and the arm is opening when it shouldn't
then you are on the wrong port. ( my map is not clear)
Let me think:
the secondcary , ( long ago, synapsis firing....) must open only under high throttle and only under heavy load. Never in driveway.
well that's my experience , if my brain is working.
that is why many put in progressive linkages and get more torque , sooner.
I once had a 64 GTO with a 6 pack manifold 3 carbs, 2 barrels. fun!
no vacuum. an boy could it light up the tires.
been evil since.
BTW: i think you want the vacuum port closest to the center of the venturi, the point of maximum vacuum under WOT.
The AutoGuide.com network consists of the largest network of enthusiast-owned enthusiast-operated automotive communities.
AutoGuide.com provides the latest car reviews, auto show coverage, new car prices, and automotive news. The AutoGuide network operates more than 100 automotive forums where our users consult peers for shopping information and advice, and share opinions as a community.