[teegzjay]

just finished rebuilding the aisin carb on my 92 sierra. it had trouble starting so I dumped some petrol down the throat. now it runs, but the whole garage filled up with white smoke and white smoke poured out the exhaust. hoping it was residual petrol to burn off, grabbed a fire extinguisher and took it for a test drive it was idling OK and then it was like the accelerator was locked on - rpm was up at 3000 the whole time - clutch in, out, accelrator pedal in or out didnt matter. pulled up in my driveway still billowing smoke from under the bonet - and pulled theair intake off the top of the carby. with the engine stopped, I can see white smoke in the carb - down the choke flap barrel. the other side is clear. it is running really rough and the idle is now super high. when it starts it coughs and shudders and works its way up from 0-3000.

the idle problem I can fix probably by playing around with the screws, but I'm really concerns about the smoke. maybe the car will blow up on me? is it normal to have smoke in the carb?
any help will be much appreciated.

[Marko_SJ]

teegzjay wrote:

just finished rebuilding the aisin carb on my 92 sierra. it had trouble starting so I dumped some petrol down the throat. now it runs, but the whole garage filled up with white smoke and white smoke poured out the exhaust. hoping it was residual petrol to burn off, grabbed a fire extinguisher and took it for a test drive it was idling OK and then it was like the accelerator was locked on - rpm was up at 3000 the whole time - clutch in, out, accelrator pedal in or out didnt matter. pulled up in my driveway still billowing smoke from under the bonet - and pulled theair intake off the top of the carby. with the engine stopped, I can see white smoke in the carb - down the choke flap barrel. the other side is clear. it is running really rough and the idle is now super high. when it starts it coughs and shudders and works its way up from 0-3000.

the idle problem I can fix probably by playing around with the screws, but I'm really concerns about the smoke. maybe the car will blow up on me? is it normal to have smoke in the carb?
any help will be much appreciated.

Carbs can be cunce of things. When you did the rebuild, assuming there are no other known issues with the car:

what screws did you play with?

What levers on the throttle mech?

what electrical solenoids on the carb?

What vacuum lines?

Is the auto choke functioning?

[HarryHoudini]

Sounds like a Vacum line incorrectly connected but like in the other thread rebuilding Aisins can cause major problems even for experienced/pro mechanics.

[Marko_SJ]

HarryHoudini wrote:

Sounds like a Vacum line incorrectly connected but like in the other thread rebuilding Aisins can cause major problems even for experienced/pro mechanics.

Hmm, I reckon the shittiest part is the throttle and choke linkages.

I reckon its an auto choke issue my self, or incorrect throttle linkage installation/re-assembly....

[teegzjay]

the auto choke was pinned open by the previous owner - it didn't open I guess vacuum leak at that diaphragm that pulls it open. the rebuild kit came with a new gasket for that diaphragm and now the choke is definatlwy working - fully closed at cold, open just a bit to straight up and down at operating temperature.
I only put a new ring on the idle solenoid.
didn't touch the throttle linkages just the one bolt to take the lever arm off the airhorn
didtn adjust any screws except the ones to take it apart.
and vacumm lines - I put tape on them before I disconnected to make sure they all went back the same way.

if I do have a vacumm line wrong, where would most likely put exhaust smoke back into the carb? egr, pcv, vacumm distributor etc.

[teegzjay]

if anyone has a PIC of a 92 sierra carb g13ba engine showing the VAC tubes in correct position that would be super helpful. at least I know my choke tube is correct at this stage.

[Marko_SJ]

Sounds dumb, but how did it run before you pulled the carb apart?

[teegzjay]

the choke was locked open, so I had to warm it up using the accelerator. it didn't idle at all, so I turned the cold idle up to 1500 to keep it going.
when it got hot it would stall on hard deceleration and backfire under load.
hot idle / when the lights were on would make the revs pulsate up and down between 1000 and 2500, so I turned it up to 1500 too. seemed to be the magic number, the problem stopped.
other than that, it would drive fine. had a mechanic look at it and he said he it was a vacuum leak at the carb - needs a rebuild.
my own check with carb spray and engine running looked like it was an air leak at the base of the carb.
when I did the rebuild, I replaced all vacuum lines + booster line with new hoses one at a time.

[teegzjay]

OK looks like one of the float bowl breather holes was dripping fuel down into the choke side barrel. I pulled the airhorn off and adjusted the float. now its been problem after problem. either the engine runs then dies after 10 seconds and fuel gushes out of the breather holes, or the engine won't start because The carbs not filling with fuel. I've had the airhorn off 8 times today, playing with the float level. I'm at a loss. any suggestions?

[jimny_timmy]

Checked the breathers on the tank?