What is your altitude? As you tune the carb the vacuum should raise but there may be a vacuum leak somewhere.
fresh desmog, no start. DIAG
- Thread starter masonbarnard
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I had a bad VCV that leaked vacuum internally. there was no way to notice it other than knowing my vacuum was low(about 14.5) and I could not locate a leak ANYWHERE. I finally started capping off vacuum sinks one by one till I got to the VCV and bypassed it and all of a sudden I had 19" of vacuum and a steady idle- albeit with a fat mixture from trying to compensate...readjusted and on I went. Look at your dizzy vent VCV...if that tests OK go to the next vacuum sink and bypass it. unbypass if it has no effect and move on...
Just to clarify, you are talking about the white multi-port VCV that is under the passenger side of the air cleaner correct?!
At sea level (61 ft above the sea) the vacuum should be near 20 inHg
Yup I am at 4500(ish)' and mine reads about 16 inHg
- Thread starter
- #46
Just got it to be very steady at 15-16.
Pretty excited about that because the Air filter housing is still off (prob wont change anything?)
I haven't adjusted timing, havent adjusted valves, the EGR inlet gasket needs to be replace, and nipple for the pcv broke the line is plugged for now. AND I haven't fully tuned the carb.
I have not changed manifold gaskets because that vacuum seems pretty good?
three new unrelated problems
- master slave leaking, reservoir is empty, the pedal is soft and barely can get into gear.
- a coolant line behind the belts is leaking... damnit.
- a coolant line near the fire wall going to the rear heater was smoking, but it started to settle down. After idling for 10 minutes.
Pretty excited about that because the Air filter housing is still off (prob wont change anything?)
I haven't adjusted timing, havent adjusted valves, the EGR inlet gasket needs to be replace, and nipple for the pcv broke the line is plugged for now. AND I haven't fully tuned the carb.
I have not changed manifold gaskets because that vacuum seems pretty good?
three new unrelated problems
- master slave leaking, reservoir is empty, the pedal is soft and barely can get into gear.
- a coolant line behind the belts is leaking... damnit.
- a coolant line near the fire wall going to the rear heater was smoking, but it started to settle down. After idling for 10 minutes.
@gregnash, YES...
16"s is ok vacuum for a very big cam...not so good for a stocker...keep looking for vacuum leaks...have you tried the propane trick?
But that is saying 16 inHg at sea level would not be good. If he is less than say 4k' above sea level then there is a vacuum leak somewhere. But again he hasn't done any timing/tuning so it SHOULD go up.
- Thread starter
- #50
Enlighten me on propain trick? Is it similar to brake clean to find leaks. Because I sprayed the manifold with brake clean while it was idling and saw no change.
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Yes, same as using carb cleaner spray to find a vac leak.
Don't use brakleen to find vacuum leaks, it burns to something toxic... Phosgene? Chlorine?
Don't worry about looking for a vac leak at this point.
Finish the carb install & tuneup first: route all vac hoses correctly, set timing, adjust idle speed & mixture, adjust valves, install new OEM air filter, fuel filter, PCV valve&grommet.
Don't use brakleen to find vacuum leaks, it burns to something toxic... Phosgene? Chlorine?
Don't worry about looking for a vac leak at this point.
Finish the carb install & tuneup first: route all vac hoses correctly, set timing, adjust idle speed & mixture, adjust valves, install new OEM air filter, fuel filter, PCV valve&grommet.
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- #52
I already did the pcv / grommet that was dried and stuck. Took like 30
Minutes to get out. Need a new hose for it though. I have a new filter in the air cleaner as well as new seals just haven't put assembly back on.
does it matter if I can't get it above, say 17~18?
I'll put the assembly back together tonight actually and take pics to see if I'm doing anything noticeably dumb with the lines. I don't think I am but I also haven't driven it yet.
Minutes to get out. Need a new hose for it though. I have a new filter in the air cleaner as well as new seals just haven't put assembly back on.
does it matter if I can't get it above, say 17~18?
I'll put the assembly back together tonight actually and take pics to see if I'm doing anything noticeably dumb with the lines. I don't think I am but I also haven't driven it yet.
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Use this chart to de-rate vacuum readings according to altitude. Use the difference between Maximum Value Attainable and your altitude. Subtract that number from 20.
Example: At 2000 ft, the vacuum drop is 2.12 inHg. 20-2.12=17.8 inHg vacuum on a perky engine
Example: At 2000 ft, the vacuum drop is 2.12 inHg. 20-2.12=17.8 inHg vacuum on a perky engine
- Thread starter
- #54
I know the gas filter should have a legit plug but why didn't extra plugs come with Jims desmog kit... lines are all new McMaster Carr.
With intake. I need a hose for the it.
My pcv hose is dry and has a very very small crack, don't judge by all the tape I went all out. it's very temporary.
Line leading left from the carb is for the vacuum gauge from the gas filter
I need to mount the passenger side vacuum switch and vcv better and the engine bay needs a good cleaning up.
i also just threw the air cleaner on for a pic, obviously things need securing.
I need to mount the passenger side vacuum switch and vcv better and the engine bay needs a good cleaning up.
i also just threw the air cleaner on for a pic, obviously things need securing.
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Thanks for posting the chart - I always wondered how well my stock '76 FJ40 (~64,000 original miles) was doing vacuum-wise after a complete tune-up and adjusting everything by the book. It purrs like a kitten at idle, and has pretty good power, but I can't get any better than 14 inHg. Now I feel a little better: 20 - (29.92 - 22.88) = 12.96 (my driveway is right at 7,240 feet). I never took the time to check for vacuum leaks using carb cleaner or propane - now that I'm curious I might give it a shot tomorrow (no snow on the ground and ~47*F for a high).
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- #56
I'm pretty good at math and but i have no idea how you guys are getting the vacuum loss number you subtract 20 by...
i'm at 600ft. Will maybe go above 2000 at most, but prob never. that's why i used the first diaphram on the dizzy, and thats also why i dont have HAC. i still have it incase i want to move to back to colorado though.
i'm at 600ft. Will maybe go above 2000 at most, but prob never. that's why i used the first diaphram on the dizzy, and thats also why i dont have HAC. i still have it incase i want to move to back to colorado though.
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That's a pretty sanitary engine bay. Compared to some cruisers, it's not covered in mud & rust & PS oil. Keep up the good work! 
Minor notes:
The rubber carb to air cleaner seal actually snaps into the neck of the air cleaner, then the AC lid is carefully dropped onto the carb.
Because the ICS is permanently grounded to a carb screw, there is no need for vacuum switch. Either rewire ICS back to stock config (ignition hot & computer ground), or remove vac switch & engine computer.
Where is the volt regulator on the alt? Looks like an old external regulated type.
Minor notes:
The rubber carb to air cleaner seal actually snaps into the neck of the air cleaner, then the AC lid is carefully dropped onto the carb.
Because the ICS is permanently grounded to a carb screw, there is no need for vacuum switch. Either rewire ICS back to stock config (ignition hot & computer ground), or remove vac switch & engine computer.
Where is the volt regulator on the alt? Looks like an old external regulated type.
That's a pretty sanitary engine bay. Compared to some cruisers, it's not covered in mud & rust & PS oil. Keep up the good work!
Minor notes:
The rubber carb to air cleaner seal actually snaps into the neck of the air cleaner, then the AC lid is carefully dropped onto the carb.
Because the ICS is permanently grounded to a carb screw, there is no need for vacuum switch. Either rewire ICS back to stock config (ignition hot & computer ground), or remove vac switch & engine computer.
Where is the volt regulator on the alt? Looks like an old external regulated type.
@FJ40Jim Are you talking about the block booted switch in the very last photo that connects to the carb? At the bottom, close to dead center of the pic? I had to ground mine when I rebuilt the top end this time last year but didn't realize you could delete the Emissions computer (right?) and that switch.
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Yes, to waste even more gas than stock, remove the vac sensor switch & computer, disabling decel fuel cutoff.
Sweet! Looks like I got a mini project while it is freezing out... Wonder if this has something to do with the sudden fuel consumption problem I am having.