PLEASE HELP!!! Carb secondary still not opening (1 Viewer)

[Stumpalama]

I have a persistant pinging/knock at WOT or near WOT, especially when climbing a moderate grade incline and I have to back off to half throttle to get the ping to stop, then I'm slower than dirt going up hill. It comes on immediately at 60-65+ when I mat the pedal, but there is a delay at lower speeds... I attribute this to fuel demand exceeding supply more quickly at higher RPMs, thus an INOP secondary (Y/N?)

Motor specs: 81 2F with all smog (all working except the speed sensor due to aftermarket speedo and deleted VSS), smog headers, 2.25" exhaust with cat and flowmaster Hushpower muffler (no leaks), MSD 6A with blaster 2 coil, Denso W14EX-R plugs gapped to .032, 1984 FJ60 distributor (vac advance checks SAT) set to 11 deg BTDC with 20"Hg steady at idle of 660-ish, FJ60 stock carb with 1.47 primary and 2.00 secondary jets. Oh, yeah, I'm running 35's on 4.11 gears with stock 4spd, which will happily roll down the road at 70 mph all day... in Kansas (no appreciable incline).

To diagnose this, I pulled the distributor, checked the operation of weights and springs, as well as the pick-up. I thought maybe I was getting too much advance at the high end, but all seems OK. I reinstalled the distributor and set intitial timing at 11deg BTDC. As I said, the vac advance works (it pulls somewhere around 22 deg of advance when vacuum applied with hand pump at idle).

Moving to the carb, like I said, this is an unmodified stock FJ60 carb that I installed a while ago. I ran through the on-engine tests for secondary operations and it moved freely, I adjusted the throttle linkage to ensure the throttle was reaching 90 deg at full pedal and that the secondary moved freely. I changed out the secondary diaphragm as a matter of course. I also checked the carb float level by running at full throttle then shutting the engine off and pulling over. The level was normal in the sight glass. Following this work, I did the “paperclip test” (thanks to Pin-Head and his videos and posts) and got little to no movement despite a good long pull at WOT up hill at 50+ mph (I thought I felt a momentary mini surge but could have been imagining it, not to mention the paperclip told me otherwise).

So, I pulled the carb and did a mini rebuild, cleaning the vacuum passages with carb cleaner and blowing them out with compressed air, pulling and cleaning the jets and slow jets, replacing the power valve and the top gasket. I checked all vacuum ports and confirmed they were clear. I also checked the throttle position and secondary “touch point”, in so much that the primary throttle moves to near 90 degrees before tipping the secondary a bit (no angle measurements) and that once it tipped, the secondary was clear to open and did open freely.

I reinstalled the carb, retuned the timing to what is stated above, set the paper clip and made several runs… with negative results. At this point I filled up with 93 octane (previously running 87) since I needed fuel. It seemed to suppress the pinging a bit, but it is still there with s no apparent secondary movement.

What am I missing!?!?! I am all out of ideas. PLEASE HELP!

 

[Stumpalama]

Bump Bump. Need some help.

 

[Pin_Head]

I don't know. It should open at WOT with high engine load. If it isn't opening, check the mechanical secondary opening and adjust it to open a little wider.

 

[Stumpalama]

Pin_Head, Thanks for looking. It's got me stumped. I was thinking of bending the tab a bit "flatter". Just to be clear, the one I want to bend is the wide flat one on the secondary that is contacted by the "hammer" on the primary linkage, correct?

 

[Pin_Head]

Sounds about right. It is the tab on the secondary that the primary opens. Make it open more mechanically and see what happens. You can always bend it back.

 

[subzali]

Just a thought, maybe you have a bushing problem?
http://risingsun4x4club.org/forum2/showthread.php?t=16462&highlight=carb

 

[Pin_Head]

That is a good possibility too. I didn't think of that, but the primary has to be open nearly all the way before the secondary can open.

 

[subzali]

I'm wondering though if the secondary not working has anything to do with the pinging sound. Isn't pinging usually a timing issue or a fuel octane/engine compression issue?

 

[ducktapeguy]

I went through the all same issues with my first carb trying to troubleshoot the vacuum secondary. After multiple (10+) rebuilds, snaking out passages, many cans of carb cleaner and compressed air to figure out the inner workings of the puzzle, the way I solved it was by switching to a spare carb.

However, I suspect my problem was the venturis. This is just a wild guess on my part, but the venturi liners on my first carb were slightly loose. They are just staked in place, and I'm thinking somehow that was either leaking vacuum or somehow preventing enough vacuum to form. It's the only difference I can see between the two carbs, because I'm still using the same secondary diaphragm and it works fine. One of these days I've been meaning to take a closer look at the old carb and troubleshoot it, but since I have a working carb now, the motivation isn't really there.

 

[Stumpalama]

I'm wondering though if the secondary not working has anything to do with the pinging sound. Isn't pinging usually a timing issue or a fuel octane/engine compression issue?

Normally, I'd agree but in this case, I believe the pining is a result of too lean a mixture (caused by the lack of secondary supply at high rmp and high advance) at that specific amount of advance.

The venturi situation intrigues me. It is extremely frustrating because EVERYTHING else is great regarding the engine, it's just this ONE THING and I HATE that.

Perhaps it needs to be sent to a professional following the wheeling season, but I'd still like to solve this myself.

 

[Pin_Head]

Pinging is usually low octane or advanced timing for the engine load (which depends on throttle).

The venturis are cast into the carb bowl, so they are not staked and they can't come loose.

The main nozzles are what some people call venturis, because they sit in the middle of the venturi. They aren't staked, but they could get loose. The nozzles don't have any thing to do with the operation of the secondary unless they are so loose that the engine won't run properly.

 

[Stumpalama]

I just wish there was another way to diagnose the secondary.

 

[Pin_Head]

What is complicated or difficult about the paper clip test?

Jump in and get it done.

The vacuum has to be high in both the primary and secondary for the vacuum secondary actuator to kick in. It the primary or secondary does not open enough mechanically, then that won't happen.

 

[Stumpalama]

I did the papaerclip test woth negative results. What I meant was an easy way to see flow through the secondary. As far as an on engine test, where should fuel enter the secondry? Is it the lower port? I will block the primary open, then move the secondaryand look for fuel entering.

What is complicated or difficult about the paper clip test?

Jump in and get it done.

The vacuum has to be high in both the primary and secondary for the vacuum secondary actuator to kick in. It the primary or secondary does not open enough mechanically, then that won't happen.

 

[ranger]

How do you know the secondary is not opening while driving?
Seems like you have everything else spot on, but like mentioned earlier, more likely a timing or ignition issue.

 

[77mustard40]

I did the papaerclip test woth negative results. What I meant was an easy way to see flow through the secondary. As far as an on engine test, where should fuel enter the secondry? Is it the lower port? I will block the primary open, then move the secondaryand look for fuel entering.

I'm not going to question the operation (or lack there of) of the secondary, but I'm also questioning the cause if the ping. If the primary jet and PV are properly sized for the Venturi and the secondary never opens, my question is how do you have a lean mixture at WOT? This layperson is still looking for the ping culprit (too far advanced etc) at the same time I'm trying to fix the secondary. Not much of a contribution, just my thoughts. Best of luck solving your issues.

 

[Pin_Head]

As far as an on engine test, where should fuel enter the secondry? Is it the lower port?

Like the primary, fuel is delivered to the secondary by the main nozzle. There is also a "transition" slot just above the throttle plate that provides fuel during the initial opening to prevent bogging down. If the secondary butterfly does not open far enough, it will not pull fuel out out of the main nozzle. Just like the primary, the amount of fuel depends on the vacuum in the venturi. In summary, doing the paper clip test is good enough to get an indication of how much fuel is flowing in the secondary.

 

[ducktapeguy]

The venturis are cast into the carb bowl, so they are not staked and they can't come loose.

The main nozzles are what some people call venturis, because they sit in the middle of the venturi. They aren't staked, but they could get loose. The nozzles don't have any thing to do with the operation of the secondary unless they are so loose that the engine won't run properly.

Maybe the FJ60 carbs are different, but I'm looking at mine and it definitely appears to be a separate sleeve inside the carb held in place by 4 stakes on the casting.

In this picture you can see the stakes around the 3:30 position in each barrel.

http://74.53.10.34/~rs4x4/forum2/showthread.php?t=13593&page=2

Like I said, that's what I suspect was causing my problem, but it's just a gut feeling, I have no proof that it was the actual cause.

 

[FJ40Jim]

There are two separate issues here.

First, the engine is pinging because there is too much timing advance. The stock timing is 7*BTDC, w/ 21* of mechanical advance available for a total of 28*. 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.

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.

 

[Pin_Head]

I can see what you mean on mine. They may indeed be pressed in. I thought that they were just casting marks, but there is a rim all the way around on the top and the bottom. I have never seen one loose and I would guess the bowl should be replaced if one is loose.