Secondary Barrel Not Opening (1 Viewer)

[mvisio]

Hello All,

My 5/85 FJ60 wasn't idling well after a road trip. I ended up taking off the factory carb and rebuilding it via Pinhead's videos. Too my surprise, it looked as if the secondary barrel had not been used in years. The secondary diaphragm was torn and wouldn't hold vacuum. The power piston was completely seized as well. I dipped the carb and replaced the torn diaphragm. Blew it out and ran fishing line through all the jets. Hooked the carb back up and went for a test drive. It idled successfully again.

I did the paperclip test on the secondary diaphragm and it only moves as far as the mechanical advancement allows, it never completely opens via vacuum. I took the carb back off, bent the linkage tab out so the secondary would open a little more mechanically, but this still didn't solve the problem.

I am at 8500'-9000', my vacuum at idle is 13", which I believe is normal considering my elevation. Is there anything else I can try to get this secondary working? Am I at such high altitude that no matter what, I'll never have enough vacuum to open the secondary? My FJ is a dog going up hills. I always chocked it up to being high altitude, but I don't think it helps that I've been running primarily on one barrel. Would appreciate any advice!!

 

[CruiserTrash]

Following because I’m at 5200’ elevation. I know my choke opener does not fully open the choke with vacuum and I figured that was due to lower vacuum at altitude.

 

[OSS]

Since the air is thinner at altitude and the engine can’t create as much vacuum, everything vacuum related (diaphragm actuators) will have less force applied to them.

Maybe take a drive down to lower elevation some time and test it out down there where the air is thick and engine vacuum high. If the secondary works correctly at sea level, then it’s doing what it’s supposed to at elevation.

 

[3_puppies]

Pagosa Springs? is there still a guy who has a smoker, sells in a parking lot, he does cheese balls? can't remember his name.
He also does some welding/fab work.
I'd ask about the feed store but I thought it was gone.

 

[jcj_78FJ40]

Builds - The Rushing Turdle - https://forum.ih8mud.com/threads/the-rushing-turdle.873488/page-9

See post #170 on swapping out the vacuum secondary spring for a lighter one. This worked for my desmogged 60 but I'm under 1000 ft elevation. Might be worth a try.

 

[CruiserTrash]

Builds - The Rushing Turdle - https://forum.ih8mud.com/threads/the-rushing-turdle.873488/page-9

See post #170 on swapping out the vacuum secondary spring for a lighter one. This worked for my desmogged 60 but I'm under 1000 ft elevation. Might be worth a try.

That’s a good idea for high elevation folks like myself and OP. But I wonder what implication that has on vacuum advance.

 

[cps432]

That’s a good idea for high elevation folks like myself and OP. But I wonder what implication that has on vacuum advance.

Probably none. The larger diaphragm on the vac advance adds up to 12* and the smaller is 6*. If you are de-smogged and your dizzy has been recurved then you need to use the larger diaphragm on the inner nipple of the vac advance. The smaller diaphragm is for the HAC… etc. The dizzy is retarded from the factory because of the EGR system. When you ditch that you need to recurve the dizzy. The quick fix for this if you don’t recurve is to switch the vac advance lines. Running the Holley sniper I don’t have a secondary. But I desmogged and recurved my dizzy. It was a massive improvement but I was still havin major issues with power climbing hills. I had the vac advance line hooked up to the smaller diaphragm at 6* which essentially retarded the recurve I performed. Switching to the 12* diaphragm allowed the recurve to shine and now this truck has more pep than ever before. I don’t know that the secondary would have any effect on advance unless you also recurve the dizzy and ditch the smog crap. Maybe it would change the point at which the advance begins to kick in? I’m not certain.

 

[CruiserTrash]

Probably none. The larger diaphragm on the vac advance adds up to 12* and the smaller is 6*. If you are de-smogged and your dizzy has been recurved then you need to use the larger diaphragm on the inner nipple of the vac advance. The smaller diaphragm is for the HAC… etc. The dizzy is retarded from the factory because of the EGR system. When you ditch that you need to recurve the dizzy. The quick fix for this if you don’t recurve is to switch the vac advance lines. Running the Holley sniper I don’t have a secondary. But I desmogged and recurved my dizzy. It was a massive improvement but I was still havin major issues with power climbing hills. I had the vac advance line hooked up to the smaller diaphragm at 6* which essentially retarded the recurve I performed. Switching to the 12* diaphragm allowed the recurve to shine and now this truck has more pep than ever before. I don’t know that the secondary would have any effect on advance unless you also recurve the dizzy and ditch the smog crap. Maybe it would change the point at which the advance begins to kick in? I’m not certain.

I guess the ported vac for the main advancer diaphragm comes off the main carb barrel, eh? I was trying to puzzle out the fact that the secondary opening would drop manifold vacuum, thus sending less vac to the diaphragm ... but I don't think that's how it works.

I have to be fully smogged (daily driver, Denver), and I do have my HAC hooked - I verified it works, too. If it ever stops working I can just cap the vac line to the second diaphragm and add 4-7* of permanent timing beyond the base timing of 7*. Obviously if I went below ~4000' I'd set the timing back to the BB.

 

[mattressking]

First-off there are two parts to this, it isn't just the secondary vacuum diaphragm. Before you replace a spring, verify the mechanical linkage for the secondary is correct. Years and years of opening/closing bends the arm on the secondary butterfly and by this point if not adjusted, barely opens, rendering it very difficult to open.

1. Verify the mechanical opening of the secondary opens enough for vacuum to take over. You need to set the opening of the secondary butterfly to 25*. This is done by removing the carb, opening the primary butterfly completely then checking the secondary. There is an arm that opens the secondary and needs to be bent to increase or decrease opening.
2. Verify your vacuum secondary holds vacuum, which you need to remove and use some method to pull vacuum such as a hose to the port and seal it tight then pull, or push the arm inward, cap the hole and release the arm. Once you release whatever is capping the hole - you should see the arm release. If nothing holds, the diaphragm is torn or leaking, or your test method wasn't air tight (pun intended).
3. Ensure gasket is in good condition/new between vacuum secondary and carb body and lower linkage is connected to butterfly.
4. Last but not least, there's two diaphragms, a straight arm and offset arm. 60 series carbs require an offset arm. I find that is something to note as carb rebuild kids include the 40 series, not the correct 60 series version.

 

[micruz60]

4. Last but not least, there's two diaphragms, a straight arm and offset arm. 60 series carbs require an offset arm. I find that is something to note as carb rebuild kids include the 40 series, not the correct 60 series version.

^^^ T H I S ^^^

 

[mvisio]

Appreciate all of the helpful comments from everyone. FWIW, I did put an offset-arm new diaphragm on the carb, along with a new gasket. I tested the vacuum secondary before re-installing the carb and all was well. I've played with the "opening tab" once. I may need to bend the tab to open the secondary a little more. I have ~3mm of opening at WOT.

As luck would have it, I ended up driving the 60 down to Midland TX for the week. I plan to do the paperclip test at this lower elevation (2800') and see if the secondary opens (although it may be tough finding a suitable hill to put the 60 under load....Midland is pan flat LOL). I'll report back with my findings.

I can tell a pretty major power difference at 2,800' versus 8,500'. I can actually squeal the tires if I gun it in first gear going around a turn; this was impossible at altitude.