it still backfires & now running rich (pics)

[ekoms]

I had bad float /needle problems were it would flood itself every time I shut the car off cold or hot, so I rebuilt the the top hat of the carb. put in new floats, needles & seats. new gasket & o-rings everywhere. replaced the plugs, wires, coil, cap, rotor, & the distributor with a used low mileage one. the car runs awesome now, idling @ 1000 warm & 750 with the headlamps on. it starts great besides the choke not working on cold starts (choke heater doesn't work or not getting a signal). I adjusted the timing afterwards & its perfect. I cant get it any better, +2 with vac advance plugged @ 750 with lights on. so now it still Backfire through the exhaust when shifting or decelerating in gear & is running rich. it does not hesitate or stutter at all, but the tail pipe is turning black & you can smell that the car is running rich & its not smoking any (my exhaust guy mentioned it too) oh I also got the exhaust fixed to yesterday, no more leaks. my power is back but I lost mileage. 3/4 tanks used & only @ 180 miles the only mod it has are a custom exhaust (all striaght piping & glasspack) installed by the Previous Owner.

so here are my ?'s, should I adjust the a/f screw ? how would I know when it is set proper ? I'm guessing in the middle of turning it both ways. what about the removal of the vac system (my #14 line has gas running through it from the blackbox) ? will it effect mileage, good or bad ? I understand it is only for emissions & I should gain some power from it's removal. all the vac guides on here are for the later carbs, what about the earlier 82-83 Keihin 3 barrel carbs

Thanks,
ekoms

[2ndGenGuy]

Honestly, I don't think you're going to fix anything by doing a devac. I don't believe that you really gain any power by pulling all that stuff off, since it all runs on engine vacuum. As far as setting your air-fuel ratio, I don't know if there is an adjustment screw on those carbs. I was under the impression that they're a feedback carb and have a mixture solenoid that loops off of the O2 sensor. But I really have no idea.

As far as the running rich goes. I bet money it has to do with that line you were talking about that's full of fuel. That should most definitely NOT be full of fuel. You have some sort of leaky gasket or diaphragm in the carburetor, and it's probably sucking that fuel in and burning that up too. I would trace that line back to the carb and replace whatever you can that's near it. It's probably sucking that fuel into the intake and burning it in addition to the regular mixture...

[ekoms]

well right now I have the port on the carb that #14 went to plugged (some diaphragm right below the main float bowl I changed with rebuild) & the 14 line runs to a metal line that I have plugged also. Im just going to have to rip in to the black box & fine everything its tapped in to. Ive pulled all of the lines & its the only one I can find with fuel running through it.

[ekoms]

ok after messing with the black box today #14 didn't have any fuel in it. so it must of been the diaphragm right below the main float bowl that was leaking before & now since I changed that diaphragm with the rebuild, it no longer leaks. I ran the car to operating temp with both plugs off & there was no fuel leaking anywhere. the #14 line ran to the P.J. cut solenoid valve which tapped into the Cranking leak solenoid valve & the #18 vac lines. so the new diaphragm fixed that, but it still is running rich. Im pretty sure there is a A/F screw on the backside of the carb (towards the firewall like the other carbs) but I need some input from other people that have messed with these carbs.

thanks

ekoms.

[Ichiban]

I'm still curious about that line with the fuel being drawn through it. When I did the heads on my chevy, I mistakenly connected an EVAP line to a float vent on the carb, and it was drawing fuel out of the bowl, through the canister, and dumping it into the intake. Properly routing the lines, obviously, made it run properly. I'd make sure I knew where the fuel was coming from before determining the problem fixed.

I had a problem on my Toy where it would dump the float bowl into the intake after shutting it off. Turns out it was a totaled powervalve, which conveniently wasn't included in the rebuild kit, or sold separately. A $300 reman carb fixed that.

The choke looks fully open, which is what you want when engine=hot. If it's not closing try checking the action of the return spring. As far as I know, a spring holds the choke closed, and the choke heater opposes the spring with a force proportional to engine temperature. In effect, the choke heater is a "choke opener".

Looks like the float levels are bang on. Running rich might be caused by a missing/failed o-ring or gasket allowing fuel from the bowl directly into the carb. As far as I know, these carbs weren't set up to allow adjustment for part throttle or WOT mixture adjustment. Only the Idle mixture is adjustable, via the screw you mentioned. I'll post up the procedure in a minute.

[ekoms]

I'm still curious about that line with the fuel being drawn through it.

well i literally took the black box completely apart to determine where the #14 line ran to & what was tapped in to it. disconnected every line one at a time and no fuel was in any of them. im pretty sure its fix with the new diaphragm. check the vac diagram I posted for its routes.

I had a problem on my Toy where it would dump the float bowl into the intake after shutting it off. Turns out it was a totaled powervalve

I know that it was my needles & seats that caused the flooding as they where really worn & the AUX float had a tear in the lower seat o-ring.

try checking the action of the return spring

ok will do.

Running rich might be caused by a missing/failed o-ring or gasket allowing fuel from the bowl directly into the carb.

i guess i will take the top hat back off & check if I missed something.

thanks

[ekoms]

ive been driving it now with the 14 line reconnected for over 70 miles & no fuel in it.

[ekoms]

what else can cause backfire ?

[2ndGenGuy]

Backfire out the exhaust, or backfire through the carb? Out the exhaust tends to be right and out the carb tends to be lean, right?

[ekoms]

Out the exhaust tends to be right

huh ? right = rich ? & yes, she backfires through the exhaust. I'm going to change the plugs again & test wires for resistance. I thing the plugs got fouled from all the flooding. today I also tested the choke leads & the choke heater is only getting 0.03 volts ( @ cold start & @ operating temp). that's not right, from what I understand it should be getting 12-14 volts. my battery is getting 14.6 volts @ idle & if I run a lead from the battery positive to the white/blue stripe for the choke (leaving the red choke wire connected to harness) it opens all the way not halfway open like it is now. how do I fix the choke voltage ?

thanks.

[ekoms]

well I took off the top hat again, checked everything. nothing missing & everything lined up sealed good. I put the old primary o-ring back in & reassembled it. now it doesnt smell like its running rich unless you literally stick your nose inches from the tail pipe. i think its a combo of the choke not working right & fouled plugs. still have to test them.

[ekoms]

Ok I got my timing solved, so back to these issues. I pick up a second carb @ the scrapyard today from an 82 hatch. so I'm going to try swapping the top hat that I rebuilt onto this carb & see what happens. it still has the plug over the A/F mix screw & my current carb does not. so I know @ some point it was tampered with. we'll see.

[ekoms]

Well the carb I got from the scrapyard was worse off. it has a high idle issue. pretty much needs rebuild too. I did remove the a/f screw, counting the rotations & it was set @ 11 1/2. mine is set @ 11, I honestly don't think a 1/2 a turn will make it run rich. can float levels make it run lean/rich ? my pics I posted look good, but I think the levels really are @ the bottom of the dot. can that make a difference ?

thanks.

[2ndGenGuy]

Haha yeah sorry right = rich.

Your choke will definitely cause your car to run rich. If you can't trace that wire back to it's source and find a short or break, then you'll need to run a new wire that just gets power upon ignition. You could run a new one from the fuse box or something like that...

[ekoms]

Ok I'll try & trace the wire down, I also read that the choke runs the same circuit as the alternator & if the battery & brake lights are both/always on the alternator is going to die. well its not the same, but my oil & battery lights never turn off. my battery is getting charged fine. ya think that has anything to do with it ?

[2ndGenGuy]

Well your oil light can only be on for three reasons

1) You have no oil pressure and you're destroying your engine.
2) The wire from your oil pressure switch is broken.
3) You have a bad ground and some other circuit is grounding through that light. Typically that would be more intermittent though.

It sounds like you have a few wires in your engine bay with no connections, I would go over your harness and look for a connector that is not plugged in or has loose contacts, or maybe something that is damaged.

[ekoms]

well I know I have oil pressure cause if I take off the oil cap while its running I can see that oil is getting pumped up to the valves. Ive also replaced the pressure switch too, so my harness must have some faults.

[ekoms]

ok I got the choke working again & now its like the throttle has a dead spot. I have to pussy foot the gas until I get around 2000 rpm, if I hammer on from idle it just dies I don't know whats up.

[2ndGenGuy]

Sounds like Accelerator pump maybe. Check and make sure it's operating. When you open the throttle quickly, you should see a squirt of gas down the barrels... You can do this with the car off, but don't do it too much you might flood it.

[ekoms]

but it didn't do that before & all I did was get the choke working, why all the sudden ?

[2ndGenGuy]

Well what happens is when you open the throttle quickly, there is a sudden drop in pressure, and this causes a lean condition. So the accelerator pump makes up for that by squirting in some extra fuel when you mash the gas pedal. I'm guessing the choke being closed was enrichening the mixture and preventing the lean condition, thus making the car drivable without the accelerator pump.

[ekoms]

Well what happens is when you open the throttle quickly, there is a sudden drop in pressure, and this causes a lean condition. So the accelerator pump makes up for that by squirting in some extra fuel when you mash the gas pedal. I'm guessing the choke being closed was enrichening the mixture and preventing the lean condition, thus making the car drivable without the accelerator pump.

well that makes sense i guess. not sure why it is not working, I replaced its diaphragm & o-rings when I rebuilt it. for now I disabled the choke heater again. fix one thing & another arises

[2ndGenGuy]

Well, I was just speculating. It could be something else too. Maybe your timing is a little off still?

[ekoms]

well I got the accelerator pump in spec & working & its running better, but it only squirts a small amount of fuel. if I detach its lever & press its plunger down with my finger it squirts a larger amount. so I'll have to adjust it beyond spec so it'll squirts the larger amount & see what that does. thats all I can think of.

[2ndGenGuy]

Yeah try it out and see what happens. If it runs right after that, then I don't see what it can hurt.