Almost ready for smog but...

[A guy named Rick]

Well, I went to adjust float level a bit higher to see if it will idle a bit better and stripped the bottom screw. 💩 I have a few carbs (some in pieces) so I'm taking it off and if I can't get the screw out I'm going to just rebuild one of swap out the middle section this weekend. Should be fun. This is my daily so I have a deadline to have it done Sunday night.

 

It's strange, it will start up and idle fine, about 10 seconds after it will start to idle a bit up and down. Idle switch is functioning properly. No choke. It's about 10 seconds into starting it warm. I was hoping it would smooth out if I raised the float level a tad and then it stripped.

[datzenmike]

There are 4 screws holding the bottom to the main body. The front and rear screws are not the eaxct same. The front one is hollow and must go in the front.

 

 

 

It's for the vacuum signal to the power valve and will run fine at full throttle if wrong but will run even better if correct!!!!

[A guy named Rick]

On 5/12/2023 at 2:32 PM, datzenmike said:

There are 4 screws holding the bottom to the main body. The front and rear screws are not the eaxct same. The front one is hollow and must go in the front.

 

 

 

It's for the vacuum signal to the power valve and will run fine at full throttle if wrong but will run even better if correct!!!!

I'm in California though. I just looked at the carburetor I'm rebuilding currently and there isn't a screw with a hole in the center. And BTW this one was never opened. I think this is the one I found in a truck with 200,000 miles on it too. Every screw was a real PITA to get off. I opened it up and the top of the middle section was shiny like brand new. Honestly it wasn't in too bad of shape too. But I can tell judging by the screw heads, gaskets, even the float needle, nothing was ever touched!

 

I wanted to ensure the accelerator pump will work and cracked open the flathead screw plug on the internal side. I've always had trouble getting these open. I don't have a screwdriver that will break it free without busting up the plug head... until I made my own today:

 

 

i ground down an old school straight edge ruler to fit snug, and used an adjustable wrench. Broke the thing free.

Edited May 14, 2023 by A guy named Rick

[A guy named Rick]

Is there a way to measure backpressure to the BPT to determine if I have too much, i.e. a clogged cat? If cat is clogged, I'm assuming would signal BPT to open EGR too early, causing a stumbling premature lean condition. 

 

I also noticed I had to adjust the BCDD because when shifting I think it was going rich on deceleration, so coming into the next gear you can feel it lagging out a second like the ecm is playing catch up going lean to cancel out. Turning the screw clockwise on the BCDD helped remedy this, and with a muffler that's not stock I can hear some nice pops in the exhaust now. Thoughts??

[A guy named Rick]

Anybody know what I can rig up on my pedal to hit my clutch switch? The pin it's supposed to press just goes through a hole. Never had anything there, just a hole so now everything is hooked up right but the truck thinks it's got the clutch pressed in and messes with the fuel cut taking off from a stop or releasing the gas pedal slightly after having been accelerating makes it act all jerky. I have the port capped for now but I need to smog this thing this week. 

[NC85ST]

You can use just about anything to cover the hole, think bolt or glue a penny over it. As long as it contacts the switch, you’re good. I had that happen with the brake switch. The little rubber? piece deteriorated and the brake lights would stay on. Unfortunately I don’t remember what I used to fix it and my truck is about 2 hours away.

[A guy named Rick]

1 hour ago, NC85ST said:

You can use just about anything to cover the hole, think bolt or glue a penny over it. As long as it contacts the switch, you’re good. I had that happen with the brake switch. The little rubber? piece deteriorated and the brake lights would stay on. Unfortunately I don’t remember what I used to fix it and my truck is about 2 hours away.

I have some JB weld if it comes down to that! 🤣 I was thinking something along that line, a bolt, but I like the penny idea. 

 

It runs so much better with the switches bypassed. I just wish I could feel the secondary kick in a bit better and I'd be happy. It's amazing, I've been chasing a vacuum leak for a month almost just to find out it's been that switch the whole time!! The rpms would flutter up and down +/- about 15-20 rpm with a slightly rough/misfire but not so bad. And when you take off the EGR opens a bit and was causing a lean effect because the fuel was cutting too. It idles so smooth now 😎 glad I don't have a crusty leaking EGR internally. 

 

The secondary spring that holds the flap closed, can I put a softer one on it? Maybe that will help it open by needing less vacuum? 🤔 🤔

Edited May 16, 2023 by A guy named Rick

[A guy named Rick]

JB welded a penny there, don't like the hesitation I sometimes feel taking off. Adjusted idle mixture a bit.

Do I really need the fuel cut feature?? Am I better off without the vac switches?? Will it affect smog at all?? Someone let me know please.

[A guy named Rick]

With Vacuum switch A and B hooked up, the idle is a bit rough and a bit up and down. With the line plugged off, it's fine. I know my throttle switch works and is adjusted to come on like 1400rpm, temp sensor works, why on earth would my idle be affected by the vacuum switch? It stumbles a bit off idle too with it hooked up. Without then, it runs amazing. Thoughts?? 

[datzenmike]

The idle cut solenoid helps reduce run on or dieseling after hot shut down. On Z24 engines there is a fuel cut feature on deceleration. Remember that when foot is off the gas when slowing down the carburetor is at idle and fuel is still being sucked into the intake. This fuel is completely wasted out the exhaust. This feature actually saves you gas and reduces HC emissions.

 

 

What are vacuum switches A and B??? Where are they?

[Stoffregen Motorsports]

I haven't really been following along here on this thread, but the comment about - it runs great without the vacuum switch connected - make perfect sense to me.

 

CA emissions controls were in their infancy in the '70s, and did get better in the '80s but just barely, especially where carbureted vehicles were concerned. It does not surprise me at all that connecting the vacuum switches make the truck run worse.

 

I can give some useful advice, but it will take some learning on your part. Learn what the carious switches and devices do and how they work and you'll be able to make the truck run well and still pass smog. You may need to pre-test a couple of times before it's ready. Chances are, your smog tech won't know how the parts are supposed to be hooked up, so if it passes the pipe and there aren't any vacuum caps on anything, it will probably pass.

 

It's been a long time since I've owned a car'd vehicle that needed to pass, but I did pick up a '77 Cherokee a year and a half ago. It had been sitting for almost 20 years and had obviously been worked on and changed over the years. By learning the function of the various vacuum switches, and combined with a couple different vacuum diagrams, I was able to get the Jeep to run great and pass a smog test. Two of the vacuum switches had been replaced at some point with switches that looked the same, but did not function the same. Some close when hot, some open when hot. Others, with three way, close and open when hot. I was able to figure out what the engine wanted at what temp.

 

Yes, I've cheated here and there on other vehicles (small ball bearings inside of vacuum hoses), but again, if it passes the pipe, he/she probably won't care.

[Stoffregen Motorsports]

Apologies for the long winded response...

[A guy named Rick]

7 minutes ago, Stoffregen Motorsports said:

Yes, I've cheated here and there on other vehicles (small ball bearings inside of vacuum hoses), but again, if it passes the pipe, he/she probably won't care.

😉 😉

[datzenmike]

8 minutes ago, Stoffregen Motorsports said:

Apologies for the long winded response...

 

It's who we are. It's what we do.

 

What switches? There is a vacuum switch to turn the exhaust side plugs off, but only under full throttle conditions and another shuts off the idle cut solenoid when decelerating. Neither should affect any vacuum they are closed systems so if they affect the idle. Look for vacuum leaks on the hoses to them. Pinch off the hoses to them one at a time. If you can isolate the leak to the switch then the switch is the fault.

[A guy named Rick]

29 minutes ago, datzenmike said:

The idle cut solenoid helps reduce run on or dieseling after hot shut down. On Z24 engines there is a fuel cut feature on deceleration. Remember that when foot is off the gas when slowing down the carburetor is at idle and fuel is still being sucked into the intake. This fuel is completely wasted out the exhaust. This feature actually saves you gas and reduces HC emissions.

 

 

What are vacuum switches A and B??? Where are they?

They are the 2 round ones on passenger inner fender. It's California model, does one control the fuel cut and the other controls spark plug switching? Or does the Cali model even switch plugs? I have no 3rd round vacuum switch on driver's side which in the FSM is for spark switching.

 

I get the concept of reducing the wasted fuel, but it seems active at idle and should not be if throttle is closed with an idle switch adjusted properly, transmission in neutral and the clutch released, there should be no reason it would make the truck go from a smooth idle to a noticeable miss and slightly fluctuating idle. Also jerky when rolling between idle and when it becomes closed circuit. 

[A guy named Rick]

1 minute ago, datzenmike said:

 

It's who we are. It's what we do.

 

What switches? There is a vacuum switch to turn the exhaust side plugs off, but only under full throttle conditions and another shuts off the idle cut solenoid when decelerating. Neither should affect any vacuum they are closed systems so if they affect the idle. Look for vacuum leaks on the hoses to them. Pinch off the hoses to them one at a time. If you can isolate the leak to the switch then the switch is the fault.

I have isolated it there. When the line is capped off, it's fine. I can pinch the line, but then I have to undo one hose to the switch to release the vacuum from the switch. I've tested them with a vacuum hand pump with gage and they operate fine it seems per FSM spec. Vac lines are new.

 

It should be noted when my hand pump vac gauge is connected to that port to manifold at idle is about 20ish and rapidly bouncing up and down a few in/hg. but that could be the gauge bouncing since it is a brake bleeder hand pump after all.

[A guy named Rick]

Also while at idle I've tried this with both gauges: drawing vacuum to where they would be engaged. Timing light on exhaust side. Rev engine and still getting timing light flash from exhaust side plugs. 

[datzenmike]

 It will run fine even if both these functions don't work. Separate them. Find out which one when connected is causing the bad idle.

[A guy named Rick]

5 minutes ago, datzenmike said:

 It will run fine even if both these functions don't work. Separate them. Find out which one when connected is causing the bad idle.

Oh yeah no doubt it runs fine. Just bugging me not knowing what's going on.

 

Can't wait for Datslocos tomorrow, Manteca CA. Just wish my 720 was looking good enough to not just sit in the parking lot. 

[A guy named Rick]

So made a breakthrough. I mentioned that my anti-dieseling solenoid had to be grounded through the 2 wires that are grounded on the intake below the carburetor. Previous owner must have known there was a ground issue because one of those ground wires' coat is stripped and twisted with the truck side of the black wire on the 6 wire connector. Without this connection, the anyi-diesel solenoid doesn't work. I found a ground wire near the battery that is loose, not screwed down so I secured it and guess what? Have ground to the solenoid now. I want to see what effect this has with vac switch A and B, I'm thinking possibly I don't have a working neutral switch so need to test that theory, possibly check my temp sensor (seems it may be going closed-loop when it's cold and shouldn't be).

[A guy named Rick]

Loose red wire, thick jacket like the black wire that goes to the distributor, which is grounded near or on the vacuum advance. Where does the red wire go or is it extra?? 

 

And one more thing: is it possible the LED inspection light on the ECC control unit has burned out after all these years? No light flashing 4 times in 10 seconds like it says in the FSM that it should.

 

Edited May 21, 2023 by A guy named Rick

[A guy named Rick]

I attempted smog again and my truck is now classified as a gross polluter. It ran severely rich, worse than the first time. Second time was lean once I realized the idle switch wasn't activated because the little spring came off. This time I tried another carburetor I rebuilt but I forgot Vac switches A and B were plugged. I believe this caused it to run in open loop, and the mixture solenoid jet is larger on this carburetor resulting in an even richer mixture than before.

 

I need some help understanding Vac switches A and B. When connected is when the idle will go up and down a tiny bit, which is not a problem, it's not by much at all. The problem is taking off and when around town I let the gas pedal go and start accelerating again it's often jerky in the lower ram's until the idle switch is off above 1500. I understand there is a fuel cut function for the idle circuit, why is it doing something when still on the idle circuit? 🤔 it runs fine in the running circuit. I'm wondering if the idle cut solenoid is partially activated at idle? My understanding is if I leave it plugged, the computer thinks it's under WOT and will be in open-circuit, per the FSM. If I have it connected, it's very annoying around town. My next guess is float level, but this doesn't make sense to me because in open-circuit it idles and runs perfect. Just that it's insanely rich. I'm out of ideas 💡 

[A guy named Rick]

What does the green light flashing on the ECC control unit mean? I went back to old O2 sensor and it's more of a consistent flash vs new one which was more rapid but more time green light on.

[datzenmike]

Open loop means no O₂ control of the mixture ratio solenoid and does not occur during warm up, full throttle, starting and deceleration.

 

 

 

The function of the idle cut is to have a means of shutting off fuel to the idle circuit. The solenoid is on, has to be, at idle. It's generally on all the time but when suddenly decelerating at higher speeds the vacuum switch detects the high intake vacuum and with transmission and clutch switch and other conditions inputs this info to the ECU and it decides if the idle cut is turned off to save wasted fuel. There are a clutch and a transmission switch to defeat this when shifting or if in neutral so the engine does not stall. You can disconnect this vacuum switch and won't notice a thing.

 

The other vacuum switch detects low intake vacuum signaling heavy throttle use such as passing or climbing a steep hill. This turns off the exhaust side spark plugs and advances the timing to compensate for single plug running. Again if disconnected you really won't notice anything much, perhaps a little more engine noise.

 

Neither of these are on or active at idle (or shouldn't be) so can't affect idle. If it runs better disconnected then run disconnected. The pollution test does not check for full throttle or deceleration.

 

Most likely the vacuum switch hoses are miss connected.  Not hard to believe as the under hood looks like a basket of snakes. 

 

 

 

 

1 hour ago, A guy named Rick said:

What does the green light flashing on the ECC control unit mean? I went back to old O2 sensor and it's more of a consistent flash vs new one which was more rapid but more time green light on.

 

The inspection lamp only has to flash more than 4 times in 10 seconds.

[A guy named Rick]

16 minutes ago, datzenmike said:

Open loop means no O₂ control of the mixture ratio solenoid and does not occur during warm up, full throttle, starting and deceleration.

 

 

 

The function of the idle cut is to have a means of shutting off fuel to the idle circuit. The solenoid is on, has to be, at idle. It's generally on all the time but when suddenly decelerating at higher speeds the vacuum switch detects the high intake vacuum and with transmission and clutch switch and other conditions inputs this info to the ECU and it decides if the idle cut is turned off to save wasted fuel. There are a clutch and a transmission switch to defeat this when shifting or if in neutral so the engine does not stall. You can disconnect this vacuum switch and won't notice a thing.

 

The other vacuum switch detects low intake vacuum signaling heavy throttle use such as passing or climbing a steep hill. This turns off the exhaust side spark plugs and advances the timing to compensate for single plug running. Again if disconnected you really won't notice anything much, perhaps a little more engine noise.

 

Neither of these are on or active at idle (or shouldn't be) so can't affect idle. If it runs better disconnected then run disconnected. The pollution test does not check for full throttle or deceleration.

 

Most likely the vacuum switch hoses are miss connected.  Not hard to believe as the under hood looks like a basket of snakes. 

 

 

 

 

 

The inspection lamp only has to flash more than 4 times in 10 seconds.

My truck is California emissions so I don't have the switch that turns off exhaust side coil. That's done through the distributor icm. I have 2 switches on passenger side connected by a T off the intake port that has 2 nipples, the other going to the AB valve. Through the FSM I gather the ECC control module gets signal of low intake vacuum, decides which switch to go based on engine temp and goes open loop, so if I leave it disconnected like I did it failed horribly on emissions. 

 

Basically the computer thought the engine was under WOT because of the low vacuum signal. The first 2 times I had this connected, I failed because the spring on the idle switch arm. The second time was my TVV drawing air warmed up, destroying vac signal to the EGR. This third time I failed because was rich worse than the first time (different carb, different MC solenoid) and only thing different was plugged the line going to vacuum switches A and B because it ran way better.

 

 

I understand the light has to blink 4 times or more in 10 seconds, but I'm curious if it is an indicator of either rich or lean state? The pulse changed having switched back to the old 02 sensor and taking off from idle improved somewhat. So I'm wondering if my new O2 (sane brand and part # Bosch) was defective.