Savage_One

Okay, a few weeks ago our 86 Pickup's carburetor was acting up, spilling fuel into the barrels until it drained the float bowl, making it hard, and then impossible to start. Took the carb off, inspected then cleaned the $#^% out of it. Was some small debris/chunks in the float bowl and the two diaphragms, but otherwise it was in great shape, gaskets were almost fresh, etc.

Except, there was a gasket installed on the plastic riser that sits in-between the manifold and carb, and the gasket was blocking the vacuum port that the PVC plugs into! I gasket sealed the plastic surface where it meets the carb, after the gasket ripped while trying to just remove enough gasket to uncover the two holes that merge into the pvc/vacuum port. How it ever had any suction from before is amazing to me, now it's almost 100 times more.

Anyway, after getting gas into the tank (gas evaporates more then I would have thought over a 2-3 week period!) and cranking it over, and letting it warm up on the fast idle, it doesn't want to regular idle unless the choke plate is only 1/8 to 1/4 inch open, and it will idle fine, but give it some throttle a few times and it gets rough idle and slowly dies. ??? I've tried raising the warm idle

What are the stock settings for the warm idle (how many turns out from fully closed) and I know the stock mixture is 3-4 turns out, does it just need to be tuned with these idle settings? What is the best tuning procedure?

The rough low-idle might be due to this, but my #2 cylinder spark plug is always fouled with oil-residue/carbon, is it a piston ring, or a valve seal, or burnt valve??? I know it's hard to tell over the internet, but it seems like it has compression (which would make me think twice about piston rings) and when I pulled the valve cover off a month ago, the only valve that needed adjustment was the #2 intake valve, which had loosened until there was no clearance between valve and rocker, while all the others had the proper gap.

Thanks for the help!

abecedarian

one "glaring" thing that stands out to me is that the engine won't run unless the choke plates are nearly closed. That implies a vacuum leak somewhere.

drew303

My guess is on Vac leak to

GEt some starter fluid, while the motor is running, spray it around.. when the motor idles up, you know you got a leak (near whatever you just sprayed)

pretty simple trick. the fluid will be sucked in via the vac leak richening the mixture...

You might have a leak where the carb meets the intake.

Or you forgot to hook up a vac line. Or your PCV valve is shot and stuck wide open. Though even with that vac line off and not plugged the motor shouldnt die.

drew303

could be a cracked vac line... Since you obviously removed them all and put them back.

Few weeks ago my dads yoter whom's motor i just rebuilt 3 months ago, however i kept all the original vac lines, didnt have any with cracks... anyway, the thermo vac line that connects directly into the intake manifold (large line) had cracked where it fits around the nipple. Motor ran like poo and would die. Took 3 hours before I saw it, very faint crack that was on the back of the line.

Also had a coolant line crack when I was replacing it back on a nipple.

just something to think about, and look at =)

Savage_One

Thanks guys, I'll check all the hoses/lines for leaks and see what happens...

Savage_One

Okay, all the hoses/lines look good, don't have carb-cleaner otherwise I would spray it and look for the leak that way.

Just started the truck, after letting it warm up, messed with the throttle and noticed it will rev up about half way with the choke "closed", then I have to open the choke to let the engine finish revving up to it's limit. I'm gonna take the carb off and check the seal between carb and plastic spacer I mentioned in first post, sounds like it's getting extra air from somewhere...

Savage_One

Found belt conditioner and checked the vacuum connections and carb body, nothing leaks, but the choke coil is bad, we needed to adjust the housing faaaar past regular limits to have the right spring tension on the choke plate for it to run right. So the Choke Coil is on the list to buy.

Savage_One

Finally got it running right and wanted to put closure to this thread.

When originally taking apart the carb, I had forgotten which side to put each of those (booster?) tubes that crosses across the air horn under the choke and high-speed plates. I had ended up putting the high-speed one on the choke side and vice-versa! So it was throwing the whole mixture off. And when I unblocked the manifold ports for the PCV system, (PO used a gasket with no holes over them to block flow between manifold and plastic spacer/carb) that was throwing more air into the mix (it ran better re-plugged, even before carb was fixed).

So while still trying to find out the "bogging" problem, one of the brass screw heads from the choke plate popped into the carb while it was running and got into the cylinder squish band

Off comes the cylinder head, and inside #2 is the foriegn metal, with it's traces of impact looking a bit like when a textured hammer hits woods. Lucky the connecting rod survived, as we had thought from the sounds of the engine it was gone for sure. It actually wasn't that bad damage to the head or piston surface, as the metal was soft and conformed to the pressures and the clearance for the piston squish is not that tight.

Cleaned up carbon in cylinder and piston surfaces, lightly "Grooved" my cylinders a la www.Somender-Singh.com, noticed I need to replace valve-stem seal for #2 intake valve, which is causing to suck/burn oil, installed new head gasket (PO had used cheap off-brand, Toyota one looks far superior), and blocked off EGR with aluminum-can-gasket on manifold (i had been running with the vacuum valve disconnected anyways)

So it was running alright once head was put back on, just with a different torque/acceleration curve and a slight hesitation/bog during early acceleration, drivable for sure as we put 200+ miles in the last few days going dirt-bike riding/shooting etc and commuting back/forth, but it was a pain to take-off from a stop and acted iffy...

But now with those booster tubes on the correct sides, a new head gasket replacing a worn cracking one, grooved cylinder head (nice extra torque even with my minimal experiment), zip-tied vacuum connections, it's all set and running prime

Might post pics of impact damages and my groove modification if anyones interested. This has been my most extensive mechanical repair/project, and I'm now in love with toyota's more then I can say