YEP, MIKUNI BLEW UP..haha

So the mikuni that came on truck when i bought it started sucking air from everywhere.

I had some credit at junk yard picked up another oem that says "remanufactured". Truck drives like a different breed. Downshifts has some power! Freeway speeds are a breeze.

I have dialed pretty close but need advice on final tweak. Runs and drives well with choke on. Drives good once warm, but when Come to idle has miss about every 10-15s. Exhaust smells like eggs (brand new cat).

What does everyone think? Too lean or rich?

BTW: ignition all new

Can someone answer this: at idle the jet from the accelerator pump is constantly and steadily squirting, Is this normal? I can't imagine so, I tore the new carb off, took out accel. pump, check it and spring looked good. Put it back on, same thing. I also checked the return line for restriction, Looked ok.

There is 2 supply lines to Carb, main inlet and inlet for accel pump. When I crimp the accel pump line just enough to stop the squirt squirt, it seems to run better. Anyone have some suggestions?

Check your plugs for mixture setting? Try to use new plugs to check them for rich or lean. If you put your face near exhaust it shouldn't burn your eyes with rich fuel, just heat should come out.


defective engine controls could cause the catalytic converter to be flooded with fuel, which contains sulfur, hence the rotten egg smell. If not repaired, the heat generated by the chemical reaction from the increased amount of sulfur passing through the converter will cause the honeycomb shaped filter to melt. Once melted, it will be an obstruction in your exhaust system causing poor engine performance, sluggishness and stalling.
Some things associated with flooding a converter with fuel are: a defective oxygen sensor, a leaking fuel injector, and a defective pressure regulator. Even bad coolant sensors have been known to trick the ECM into sending too much fuel.

Check yer fuel lines! It is a really common problem with plumbing fuel lines on these engines (it gets even more confusing when a fuel recirculation cannister is chucked into the mix) It sounds like you have swapped the primary fuel line and the accelerator enrichment pump feed line - thus the constant overfuelling of the accelerator pump...

Thanks for the help. I think I have it figured out. On the body/bowl housing of the carb (the plastic part) there is a metal pass through that bolts down then the accelerator pump on top of it. On the pass through (not sure if this is the right name) it has a feed from the fuel pump and then on other side a return to tank. After close inspection the body housing of the carb, the edge was chipped so it was allowing passing through pressure to leak past gasket into accelerator pump housing and then through jet.

So After many many dis-assemblies and re-assemblies I was able to use carb kit and the two carbs I have to make one. It seems to work pretty good now. But what a nightmare! First Carb I have ever dis-assembled and last I want to.

I do want to check the vacuum lines existing. Some seem fishy. ON the distributor vacuum advance, it is supplied by a switch on driver side fender well. This I believe is normal, but the switch is supplied from a port on the side of the carb base on the back side of bottom carb plate. The port is on the side between carb and valve cover. The port has a T on it and one goes to Depression Chamber for secondaries and the other for the switch to Distributor. Can some one verify this. I can't find any decent diagrams. Also no vacuum at idle or part throttle, this normal?

I will try to get some pix up later today but its raining right now.

Thanks again for everyone taking the time.

Looks like you had to undo someone else's less than brilliant attempt to fix the carby. The plastic resin bodied Mikuni is tricky to fiddle with - especially for a noob. If you can pull one of these biatches down and get it to run you are on the path to enlightenment. Wait til you play with one that has 3 electric solenoids on it and a throttle sensor on it! You should be getting vacuum at idle and low rpm so my guess is you're checking vacuum from the wrong place. Is there a vacuum barb on top of one of the inlet manifold runners?

Yep this is the one with all the Solenoids and TPS sensor...

Here is the best Vacuum Diagram I could find if someone needs it
Attachment 11720 (mitchell) lets see if I can be opened larger, computer annoying me right now.

I used this along with CAMOITS advice to use the hood diagram. The oem lines are color coded which is nice but all the aftermarket wrong ones and black. It was challenge of patience

.Attachment 11721 original carb from donor before I destroyed. Mikuni Solex 32-35 with water choke, Tps and solenoids