PLEASE HELP!!! Carb secondary still not opening

[FJ40Jim]

They don't come loose on the 74-later carbs because the body is a much harder aluminum alloy. On the 70-73 carbs, the venturis fall out all the time, because the lead-zinc alloy body won't hold shape or hold the stakes.

And don't try to remove the 75-later venturis without first removing the brass vacuum jets that are pressed in through the body and into the venturi. Driving the venturi out without removal will scissor the vac jet and make a mess. It means I hafta throw your carb body in the recycle pile.

 

[Stumpalama]

There are two separate issues here.

The distributor that is currently in the truck has a disintegrated governor limit bushing, which allows too much timing advance & steepens (sp?) the advance curve. Additionally, the base timing is advanced 4*. The result is 11* plus 26*, a total 37*, or 9* more timing than stock which gives audible spark knock.

What is so frustrating is I had the same issue with the timing at 9*. As far as advance goes, I got a vacuum advance of 22* (what is standard vacuum advance? though I don't see how Vac advance can be limited).
I thought it could be too much advance at the top end, so I added a bushing on the advance limiter pin (I saw one of the FSM photos with a bushing over the pin, which gave me the idea) in an attempt to reduce the overall mechanical advance. The bushing is essentially a plastic vaccum cap with the end cut off slipped over the advance limit pin to reduce the amount of total mechanical advance. Should this limit bushing be thicker? The one in the FSM looked pretty thick.
I also compared the springs from an earlier (small cap) electronic distributor and used the small cap short spring because it appeared a bit beefier, though I didn't use a spring test tool to compare them.
So, stock advance numbers are: 7* plus 21*, for a total 28* (plus vacuum), totalling 50*?
The spark knock comes on after a second or so when accelerating in 3rd gear when I am flooring the pedal, but the knock comes on instantaneously above 60-65mph (tach broken). This may be a stupid question, but, can the combination of lack of fuel supplied from secondary coupled with too much advance create the condition for spark knock? Meaning, the advance curve would be fine for a healthy carb, but is too much for a carb with a bad secondary?

The secondary is not opening because they don't open much on a stock, smogged 2F. Like Pin said, adjust the bump linkage so when the "hammer" hits the secondary tab, it bumps the secondary open to a higher angle. Even if the secondary doesn't open under vacuum, at least there will be a small increase in airflow through the cracked open secondary.

Understood. What are the potential symptoms of the secondary opening, but no fuel flow into the secondary?
I don't want to chace my tail anymore than I already am (I learned the yo-yo effect when trying to diagnose my idle when I first got the truck and learned what effect a cracked intake manifold over the stock exhaust can have).
Thank you to everyone who is contributing to this thread. It is humbling to be on the other end of the advice discussion.
I look forward to hearing the responses to my latest questions.

 

[FJ40Jim]

What is so frustrating is I had the same issue with the timing at 9*.

That's because 9* is more than 7*.

As far as advance goes, I got a vacuum advance of 22* (what is standard vacuum advance? though I don't see how Vac advance can be limited).

Correct vac advance is 20-22*.

I thought it could be too much advance at the top end, so I added a bushing on the advance limiter pin (I saw one of the FSM photos with a bushing over the pin, which gave me the idea) in an attempt to reduce the overall mechanical advance. The bushing is essentially a plastic vaccum cap with the end cut off slipped over the advance limit pin to reduce the amount of total mechanical advance. Should this limit bushing be thicker? The one in the FSM looked pretty thick.

The bushing should be thick enough to give 21* mechanical advance.

I also compared the springs from an earlier (small cap) electronic distributor and used the small cap short spring because it appeared a bit beefier, though I didn't use a spring test tool to compare them.
So, stock advance numbers are: 7* plus 21*, for a total 28* (plus vacuum), totalling 50*?

Yes.

The spark knock comes on after a second or so when accelerating in 3rd gear when I am flooring the pedal, but the knock comes on instantaneously above 60-65mph (tach broken). This may be a stupid question, but, can the combination of lack of fuel supplied from secondary coupled with too much advance create the condition for spark knock? Meaning, the advance curve would be fine for a healthy carb, but is too much for a carb with a bad secondary?

There are a bunch of Cruisers driving around with bad (effectively 1-bbl) carbs. They don't rattle, they just don't make power above 2500RPM.

What are the potential symptoms of the secondary opening, but no fuel flow into the secondary?

The engine will fall on it's nose, lose vacuum and close the secondary.

If the ignition timing is set to the stock setting, with a stock distributor, and it still rattles, then it is likely a problem w/ insufficient EGR flow, FWIW.

 

[Stumpalama]

Jim,
Thank you for answering my questions. I'm sure it can be frustrating answering, often, the same questions over and over again. I hope someone else can get some value out of the answers provided in this thread.
I got your point: Set the timing at stock setting and go from there. I am going to try to measure my mechanical advance, more to determine how far the mechanical advance is going. In the meantime, I'll get my spare distributor to you for a recurve... do you require a vacuum advance module? Or do you assume vacuum advance is a constant and focus on the mechanical?
If I cannot get it to stop pinging at 7* I will have to dig deeper into the EGR system.
I'll report results back when I get a chance to adjust the timing.
Thank you again.

 

[FJ40Jim]

To recurve the dissy, a vac advance module needs to be in the hole, to lock in the breaker plate. Without it, the plate would try to spin around inside the dissy.

 

[Strait Cruisin]

What are the potential symptoms of the secondary opening, but no fuel flow into the secondary?

The engine will fall on it's nose, lose vacuum and close the secondary.

If the ignition timing is set to the stock setting, with a stock distributor, and it still rattles, then it is likely a problem w/ insufficient EGR flow, FWIW.

I think you should look at your EGR as well. Engine ping is usually either too much advance, too low of octane in the fuel (could be old or contaminated) or an inoperative EGR valve. (the idea of an EGR valve is to introduce exhaust gases into the intake manifold, reducing combustion temperatures and NOx emmissions. As a side effect of lower combustion temps, the engine will tolerate more advance without pinging)

The secondarys would have very little to do with a ping though. Too much air and too little fuel just makes the engine drop into a lean misfire condition. It will slobber, cough and die but it wont ping....

 

[Pin_Head]

Except the EGR is supposed to close on high load WOT conditions which is when it pings.

 

[Stumpalama]

I'm gonna set the advance to 7* BDTC and see what happens. I am also going to delve deeper into my EGR system.

 

[Strait Cruisin]

Except the EGR is supposed to close on high load WOT conditions which is when it pings.

Some of them had back pressure modulators and vacuum cans, but yeah, when manifold pressure approaches atmospheric, the valve closes. I dont exactly remember the smog system on my 40 though.

Speaking of back pressure, does it have any? plugged muffler / smashed pipe?

 

[Stumpalama]

No restrictions that I now of. good exhaust cat and muffler.

 

[edwjmcgrath]

Once you figure out the cause of your pinging, I'll bet that you'll want to figure out why your secondary is not opening. I just went through the same thing and I would recommend following pinhead and jim's advice above. Namely bump up the mechanical secondary more. I had to open mine a lot more than the FSM says to get the vacuum secondary to kick in. See this discussion:
https://forum.ih8mud.com/40-55-series-tech/612961-tuning-vacuum-operated-secondary.html

 

[Pin_Head]

I must have missed the end to that thread. It seems to confirm that opening the throttle wider helps to work the vacuum secondary. Good to know thanks.

 

[Stumpalama]

I will definitely be working on the secondary issue. Fortunately I shouldn't need the secondary for this weekend's wheeling since I finally have a trailer to tow the FJ40 to the trial-head.

 

[firestopper]

Stumpalama,
Just finish reading your issue (on going). I too was chasing the pinging under similar conditions.
I spent almost ten months trying to find the cause. I had purchased my 2-82 running very poorly as well as other mechanical issues a thirty plus old "week end warrior" goes threw.
Just to be clear, the FJ is now my DD. Any how, about the preignition. I went through every conceivable possibility, fuel,carb,EGR,vacuum leak etc. and what I found was inside the dizzy. I found the best way to diagnose a factory stock smogged F2 is to put all adjustment back to FSM specs (timing in your case).
Inside the dizzy I found warn pivot pins weak spring and excessive end play on shaft. Without access to a distributor machine, I chose to simply replace the dizzy assembly with a reman for $170.00. It also cost me another $100.00 in core as I decided to keep and rebuild the original as these thing a getting sort of hard to find.
My secondary fuel delivery was in-op as well but never really was the cause of pinging, although it sounds plausible in theory. Like Jim said, two separate problems. I was able to restore the secondary issue by replacing the diaphragm and adjust the linkage but at a cost of lower MPG. The rig make more power now and climes grades without the problems I was experiencing.
At this point I can run advanced a bit without the pinging to suit my altitude and needs.
Keep in mind, the fuel sold during winter months suck in my opinion, so I use premium when all you can find is "oxygenated" fuels.
I hope this helps.
firestopper

 

[Stumpalama]

new development: smog pump and check valve shot.

UPDATE!

So on our last wheeling trip (GSMTR) my engine developed a scream at 2500+ RPM then through almost the entire RPM range. With that I was getting hesitation at WOT, or near WOT under load and acrid exhaust smell.
I surmised it was the smog pump and bought a reman'd one from Rock Auto and bearings to rebuild the old one as a spare. When I pulled the old one apart, needle bearings fell out and the rear bearing had disintegrated. From reading other smog pump related threads I decided to check the air rail check valve... It was destroyed as well. Fortunately I previously noticed it was burning the paint off it for a while and figured it was an issue of running lean, so I bought a new/used one to replace it. So I will replace that as well with a good check valve attached.

My question: could the check valve and smog pump bearing failure cause pinging and hesitation? Could it affect my tuning process so as to contribute to my symptoms of over advanced timing and pinging under load issue?

I am also rebuilding my PS pump as a probable cause for the smog pump failure.

 

[FJ40Jim]

No, the AIR system is all about aftertreatment of exhaust gas. It has no effect on in cylinder events.

 

[Stumpalama]

No, the AIR system is all about aftertreatment of exhaust gas. It has no effect on in cylinder events.

Well shoot! I thought if the ABV wasn't functioning properly and the check valve was blown open, that the system would be pumping air into the cylinder. So the AI system injects air into the exhaust as it exits to the manifold.

I'm going to go through the whole system tho ensure it's all working.

 

[Stumpalama]

UPDATE: In an effort to start from scratch, I rebuilt my 1981 carb with 147/65 main jets and 200/90 2ndary jets. Adjusted carb per FSM for butterfly positions (bumped the secondary bump linkage as you suggested @FJ40Jim) etc... adjusted valves (they needed it) and reset distributor (I installed an advance stop bushing that is discussed elsewhere on the forum). I set idle using vac gauge and lean drop method. I am holding a steady 18 in HG at 650RPM.

Interestingly, when I reset the distributor as per the FSM, with the flywheel at TDC compression and pointer pointing at 22* when fully seated (cut a piece of cardboard @ 22* to confirm this) the minimum advance I can get is 10* BTDC.

It appears the ping is gone and power seems fine.

So, the new issue is my max speed is 65 MPH with the pedal floored. (I adjusted linkage to ensure I am getting full range of motion of the carb linkage). The secondary is still not opening. I tested a few times accelerating from 50 MPH to 60 MPH flooring it going up a slight grade. When I hit my max, it doesn't fall flat, it just seems to not have anymore in it and just holds that speed.

I know I am but what am I missing?

 

[edwjmcgrath]

Is the secondary diaphragm intact and working? Does it pass the suck test? Did you verify that the vac passage is open?
How much did you kick up the secondary kickup?
I found that I had to bump mine up way over the factory spec to get it to open. 2.5mm or 33*.
If it's not opening, I'd bump it up more.

 

[Stumpalama]

The carb was dipped and blown out. I confirmed all passages are open. i will try bending the secondary kick a bit more. vac diaphram is new and functioning.