Should my ab valve have fuel in it?

[None_zero]

Asking for a friend.

[None_zero]

Not really asking for a friend but I'm wondering if this might be somehow the reason my air/fuel mix is so unresponsive, the only response being it improves slightly when all the way closed.. last night I hooked up the the new tachometer only to discover that the old tach was telling the truth. Unless they are both lying? Anyway I set the engine speed as low as I possibly could maybe 800 probably more like 900 and set the timing. It was idling along for quite a while as I was tinkering with it and every thing was hunky dory then today I leave for work and it has that muted combustion sound of plugs that are completely fouled. Normally after driving a short distance that will clear and it will pick up horsepower. But today that did not clear and after 6 miles it was still dragging arse down the road. Cylinder 1 3 and four plugs were black and sooty cylinder 2 was wet and black. After messing with it and cleaning the plugs I did manage to get to work but it was still running like an old man with arthritis. So I was pulling things off and checking here and there and I just so happened to pull the ab valve and noticed it had a lot of build up in the lines and when I sniffed it. Straight gas. You can shake it and hearing sloshing in there.... this can't be normal 

Edited March 29, 2023 by None_zero

[datzenmike]

Solve and fix the over rich. AB valve will be fixed by fixing the over rich. This the Chinese carburetor? You had this apart and rebuilt it?

 

Why not below 800??? should be able to get 600.

 

Float set too high?

Needle valve dirty not closing?

If primary and secondary jets were out were they swapped by mistake??

Is choke on/part on??? after 10 min warm up??

 

Look down carburetor while idling. See gas dripping??

[Thomas Perkins]

Rule number one.If you have a 720 Nissan.Get a Weber.If you have no money to buy one.Go door to door and see if you can cut their grass.Less than a week.You will have a new Weber,or do like everyone else,hold a sign up and beg for money.720 carbs are junk.Just look in the Dictionary,but make sure it is spelled right..Also no one including me knows how to spell on this site..We used to many years ago I think.I stayed stoned in school,so I have a excuse.Lost many brain cells,but I do try.Man versus 720 carb.The winner is,Weber...Even the Nissan service center told me to get a Weber.People in California are catching hell keeping there 720 Alive.Us in Georgia,let our hair grow out and cut them cats off.Dire Straits is changing their I want my MTV to I want my Weber...And no little faggots as they say...Never heard a 720 stock Carb is better,but a Auto Zone Alternatoris is...On my casket when I leave ya'll,it will say, couldn't spell but tried.Don't take this junk mail too serious,but do get a Weber.I never got pass a C in English in school.But I had the best weed..Remember this,roll roll roll a joint,Take a  hit, then pass it to a friend,back in the 70 saying's here.The stock carbs are like the stock heating and air,Too many parts hooked up to it to keep it working.Japanese were taking too many rice breaks when they designed the 720.Even got confused with the Datsun name and replaced it with Nissan.Don't be a yoyo...

 

 

Edited March 29, 2023 by Thomas Perkins

[None_zero]

Lol wow that's a lot to take in. 

[None_zero]

21 minutes ago, datzenmike said:

Solve and fix the over rich. AB valve will be fixed by fixing the over rich. This the Chinese carburetor? You had this apart and rebuilt it?

 

Why not below 800??? should be able to get 600.

 

Float set too high?

Needle valve dirty not closing?

If primary and secondary jets were out were they swapped by mistake??

Is choke on/part on??? after 10 min warm up??

 

Look down carburetor while idling. See gas dripping??

Let me see if I can address these less political comments in truck functionality lol. Ok float set too high? Maybe I did raise it before the fuel pump swap and lowered it and raised it again because gas was dripping. Haven't seen gas dripping lately bit I did notice when I goose the gas while looking down the carb it does tend to be a bit irregular as in sometimes its mist and other times it becomes more liquid but while idling no drips that I've seen. Needle valve dirty I don't think so the seat maybe I only just briefly hit the seat with compressed air one time so maybe it's dirty up in there. 800-900 is what I'm getting if i back the fast set screw completely off to where it stops changing anything and turn the mix screw all the way in to the highest rpm while idling (which is closed) I did manage to get it down a bit by backing my throttle cable off some bit not much. Choke is open when warm. As to the jets I've never taken them out though I can't swear they've never been taken out. And yes I think it is a Chinese knock off of the original and it is a pos no doubt Thomas I've had to rig a couple of the mechanisms on the back side of it to keep it going. I haven't rebuilt the carb no and I've tried to disassemble it as little as possible. The one thing i haven't done yet is fiddle with the running mix but this seems more like the issue is just with the idle fouling up the plugs. I swapped the distributor cap back to a previous one a few days ago but there was no immediate loss of performance from that. I wonder if the issue is one of voltage. Maybe something is making my spark weak? Also my gas Gauge is out right now which isn't uncommon it comes and goes i think the connection at the fuel level indicator is faulty but normally it starts again before i stop driving and this time it's been out for several days or a week even 

Edited March 29, 2023 by None_zero

[None_zero]

I could maybe get the rpms down further but not and have the truck continue to idle 

[bottomwatcher]

What's your gas milage been like? 

Any other clues to weak voltage like slow wipers or dim headlights? Do lights dim when operating turn signals? Only asking because if your fuel guage is having a voltage issue your ignition could be too. You mentioned fuel pump replacement. Maybe the pressure is too high?

[None_zero]

Lights are pretty dim yes but I don't think they dim further when signals flashing wipers pretty slow but I think they always have been but what's weird is (and I forgot this until just now) the fuel gauge reads empty but it's getting power because it rises to empty when I cut the truck on , even if the tank is full. And normally when it goes out it drops lower like it just has no power 

[None_zero]

35 minutes ago, bottomwatcher said:

What's your gas milage been like? 

Any other clues to weak voltage like slow wipers or dim headlights? Do lights dim when operating turn signals? Only asking because if your fuel guage is having a voltage issue your ignition could be too. You mentioned fuel pump replacement. Maybe the pressure is too high?

As to fuel pump pressure too high not a chance Mike made me go back and return the one that the parts store sold me and get a different one that was correct 

[None_zero]

Which was super awkward 

[None_zero]

So I was tinkering with it at work today and cleaned all the plugs tightened the back of the valve cover where that pain in the butt moon was back there leaking a little turned the choke all the way lean. And even though this breaks the do one thing rule I hooked up the vac advance again. When I started it to leave work it fired right up was idling pretty welI and after letting warm for a couple minutes  rolled it back out of the parking space and put it in first and just got all over it. She took off like a shot haven't felt it give all 88 horses like that for a long time seems like. Anyways little ways down the road it starts getting noisier and I'm thinking let me check the timing again real fast. Pulled off and checked it with rpms 750-800 any lower and it dies. I checked and it was a little advanced maybe so I dialed it back just a touch. Got back on the road. Few miles later I'm listening to the engine and I'm noticing it sounds rough like it's way too lean. So I pull off and adjust the choke back a bit and take off it sounds a little better. Up the ridge into the town next to mine speed limits are really low and it started making a definitive knocking sound after stopping at the light though it backed off a little and I pulled down to this park and pulled off again. I guess I'm gonna disconnect the vac advance again and check a couple plugs just to see if im fouling. But I don't like that knocking sound even one tiny bit. It sounded beautiful when I left work a short 12 or so miles back and hell my gas gauge even started working again and was pretty close to full (always a nice surprise) hope that's not like telling someone you love em right before you die in a trucks language? Thoughts?

[NC85ST]

I don’t remember from any of your posts, have you checked the compression on this engine? It does sound carb related and for all the time that you have spent on this carb, I would replace it with a Weber.

[None_zero]

I do need to replace the carb and I haven't done a compression test. But I have a confession though. @datzenmikeyou know how you told me to disconnect the vac advance like 50 times and i kept saying i did. Well i did sort of. Anyways after reconnecting the vac advance the other day everything seemed pretty good for a while bit I noticed that it would take off fine and then immediately deteriorate so I thought ok something is building vacuum that shouldn't and this is why this is happening. So I tool the vac advance back off except this time it occurred to me that you said "disconnect" the vac advance every time and while I did disconnect it from the carb the rest of it was still connected to the tvv and from there back over to the cannister so instead of doing like I had been I just unplugged the wire and then disconnected the vac line from the vac advance to the hard line. I realized shortly after that I still needed to cap it back to the carb so I capped the end of the hardline and left the vac advance disconnected completely. This let the engine idle a bit lower (maybe even at the 650 mark) and I set timing again. Ever since doing this it has been 100% smoother and drives much much better. Although I am back to getting not awesome gas mileage , not sure exactly where I'm at with that but I'd guess 10-14 mpg and it does slowly idle down until it dies when I stop. Now maybe it's not the cause and this is just a huge coincidence. I did also change the oil and filter and removed rhe oil pain and cleaned it out and put new gasket. The only other thing I notice is it does sound a bit loud when doing up towards 70pmh I assume because the exhaust plugs fire the whole time maybe. I did forget to get the oil you recommended and got 10w-30 I was also buying parts and fluids for a jeep and it takes the same oil I been putting in this so it knocked the Rotella right out of my head 

Edited March 31, 2023 by None_zero

[None_zero]

@datzenmikewhat's up man normally when I say what I think the problem might be the next time I visit rherw you are telling me. No actually that doesnt effect that at all. Does your silence mean I may be right or just you've had enough 😉

[None_zero]

I mean they say a broken clock is right twice a day so I'm just waiting on that time to roll around 

[datzenmike]

I'm here...

 

The AB regulates intake vacuum during deceleration. Vacuum can get exceedingly high when slowing down and this can suck oil up past worn rings and down past the intake valve seals. The AB has a sense hose from the intake and when it exceeds a pre determined amount, it opens and lets filtered air into the intake lowering the vacuum.  Can't see how it would have gas or water in it. Has large hose to air filter and to the intake, and a small hose to intake.

 

 

[None_zero]

Maybe i responded to this in a message?? I confused myself there for a second I think 

[None_zero]

On 3/30/2023 at 10:20 AM, NC85ST said:

I don’t remember from any of your posts, have you checked the compression on this engine? It does sound carb related and for all the time that you have spent on this carb, I would replace it with a Weber.

Regarding this... I've been asked so many times if I've done a compression test on the engine that even though I'm sure it does have compression loss I bought a compression tester yesterday while i was at the parts store for another vehicle just so I could answer yes to this question in the future 😆 

[None_zero]

9 minutes ago, None_zero said:

Maybe i responded to this in a message?? I confused myself there for a second I think 

Well I assumed it was because something was hooked up wrong either before or now. Although it's running pretty great right now just not at idle and consuming too much gas. But I was thinking if something is applying vacuum in a way it shouldn't and gas is getting into the ab valve some how and then that's being injected into the intake at decel that would certainly explain the fouling and the fuel efficiency loss but it's definitely fuel in the ab valve no mistaking that.

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None_zero 106

Replied: 12 minutes ago

But I don't know how it would get there either because the valve is only connected to the intake and the intake vacuum and the air cleaner (I think)but based on the residues in the lines I'd say it's coming feom the main line that connects to the intake. Which has a smaller line coming off the bottom of it which connects to the hardline going to the "purge" on the canister and the canister has a connection to the fuel tank so.. as unlikely as it is that it's drawing fuel through that line it has to at least be a remote possibility 

[None_zero]

For continuity sake I copied my response here 

[None_zero]

The only other thing I can think of is if at some point in my ignorance I hooked the line that's supposed to go to the intake vacuum, to the carb and the fuel has just been in there ever since. Which suggests the ab valve isn't functioning and would also explain the fouling i guess