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84 Chevy 305 Vacuum Lines diagram


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ShellnLeo
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Apr 3, 2005, 5:06 PM

Post #1 of 22 (45038 views)
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84 Chevy 305 Vacuum Lines diagram Sign In

I have an 84 Chevy Silverado 4X4 that's been sitting for 6 years. Restoring now, but rats and squirrels ate most of the vacuum lines. Anyone got a diagram of this? Think I have most of them back on, except for one that comes off the intake manifold in the front (it actually has 4 lines; 2 goes to the passenger side and 2 goes to the driver's side but I'm not sure where the bottom driver's side one goes to) It will crank up now but idles rough. When my new transmission gets put in, this'll be the only thing keeping me from taking my 4 yr. old MUD RIDING!!!! HELP!


Tom Greenleaf
Ultimate Carjunky / Moderator


Apr 3, 2005, 6:15 PM

Post #2 of 22 (44909 views)
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Re: 84 Chevy 305 Vacuum Lines diagram [In reply to] Sign In

The running rough could be the choke pull offs or vac lines to them. There should have been a diagram on a sticker underhood but you probably can't read it anymore at it's age. There are diaphragms everywhere on that year and they need to be checked for leakage as any vac leak will cause some troubles.

I could do them all from memory if that was in front of me. DanD (hope he catches this) has found some neat diagrams and posted them here. Got to find out where he finds them. The books are expensive!!!

EGR may be sticking too, spray some carb cleaner at it and see if the idle changes, if so check it's diaphragm and try cleaning it up off car as they are kind of expensive if they can just be cleaned to working right again. Good luck, and hit back if your having trouble and I'll come up with something,
_________________________________________
Long retired now


DanD
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Apr 4, 2005, 7:48 AM

Post #3 of 22 (44874 views)
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Re: 84 Chevy 305 Vacuum Lines diagram [In reply to] Sign In

Sorry But there is 55 different diagrams on my system for that year of vehicle and it would almost be impossible to figure out which one is for yours with out you telling us the calibration code for your truck. It may also be called an emissions code, it’ll be made up of three letters starting with an X.
Check the glove box door sometimes you’ll find a decal there and it may have the code, along with paint, trim and may other codes.
There are so many due to all the different applications, even altitude is taken into consideration when these trucks were built, alone with Federal or California Laws. You name it they had to modify it to keep everybody happy.
Dan.

Canadian "EH"






ShellnLeo
New User

Apr 10, 2005, 6:46 PM

Post #4 of 22 (44550 views)
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Re: 84 Chevy 305 Vacuum Lines diagram [In reply to] Sign In

I think it might be XDH.

Thanks for all the help.

Shell


ShellnLeo
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Apr 10, 2005, 6:51 PM

Post #5 of 22 (44555 views)
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Re: 84 Chevy 305 Vacuum Lines diagram [In reply to] Sign In

Thanks for the input Tom.

We know there's one line for sure that we're not sure where it goes. Trying to figure it out. I went to our local Chevy dealer to see if they could pull up a diagram and of course...since they want to do the work they said THEY COULDN'T PRINT IT OUT...BS I'm sure. But I did see on his screen where a lot of the ports that some of these vacuum lines hook up to are now DISCONTINUED. But we haven't given up yet. Still trying to get all these vacuum lines hooked up right.

And you're right...none of the diagrams on the truck are legible.

Shell


Tom Greenleaf
Ultimate Carjunky / Moderator


Apr 10, 2005, 9:25 PM

Post #6 of 22 (44549 views)
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Re: 84 Chevy 305 Vacuum Lines diagram [In reply to] Sign In

Earlyish 80s were vacuum hose city!! If you know what is being controlled by what it can be figured out by looking which we can't really do well on computer.

The veh has either a 2 or 4 barrel carb, and the vac lines go everywhere! As you know. Some sense temp near the thermostat and wait to send vac to a device until engine is warm. Some sense "Manifold Actual Pressure" and some sources are mid carb that sense air speed for timing and perhaps some other items. DanD - who has been magic at finding stuff out there said there were a lot of different configurations. Many from that vintage can just be plugged off (Probably not legal) with no effect on engine performance, but several really count! In general the ones that go to the air cleaner housing are for cold air to warm air introduction called ThermAC.


The book on this stuff would break your foot if you dropped it!!!! Some of this is a real pest. When replacing vac hose from plastic vac trees, best to cut the hose with a razor and peel them off - as I have had no luck glueing them back together. Good luck, Hit back if I/we can help. Best, Tom,
_________________________________________
Long retired now


DanD
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Apr 11, 2005, 7:31 AM

Post #7 of 22 (44550 views)
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I found this one hope it helps, sorry for the quality but that’s how bad they were right out of the manual.
Dan.


Canadian "EH"






bobland
New User

Apr 15, 2005, 3:42 PM

Post #8 of 22 (44489 views)
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Re: 84 Chevy 305 Vacuum Lines diagram [In reply to] Sign In

I have been looking for information about my own 84 k-10 with a 305. It was encouraging to find someone asking about the emission diagram.

My 84 still has the diagram intact under the hood. Since my son and I replaced the engine and moved all of the ports and fittings to the new (actually used) block I have had trouble getting all of the vacuum hoses plugged into the right places. I can interpret most of the diagram, but I still have leftover ends and objects coded on the drawing which I can't identify under the hood. The problem began with trying to use an Edelbrock carburetor without all of the emission connections that are present on the Rochester. I have replaced the Rochester and now too many things have been changed. The Haynes Chevy truck book doesn't go into enough detail about the emission system for me to find all of the items that need to be connected. Being an old school, backyard mechanic, I don't know the names or functions of many of the emission parts. The Haynes book covers several years and not all of the pictures are specific enough for me to follow.

Are there other resources that I could use?

Bob


DanD
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Apr 15, 2005, 6:01 PM

Post #9 of 22 (44477 views)
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There are only two types of vacuum sources that are generated by an engine above or below the throttle plates. One is manifold that is somewhat constant (below throttle plates) then there is ported (above throttle after throttle is opened) both depending on what loads are on the engine.
With the carb being changed you’ll have to somehow figure out what device originally required what vacuum, ported or manifold.
All I can say is good luck, I’ve never seen anything that will tell you what source is for what device, unless it was documented before the original carb was removed.
If you can tell us what isn’t connected or what’s not functioning maybe I’ll be able to help with derivability problems and or emissions devices.
Dan.


Canadian "EH"






Tom Greenleaf
Ultimate Carjunky / Moderator


Apr 15, 2005, 7:15 PM

Post #10 of 22 (44473 views)
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Bob - I think we can help here. There are a couple vac ports, for the various items, as Dan said. A lot go thru temp control devices to delay vac delivery. The couple items that matter the most would be the EGR and the distributor. In a 1984 you could do without a lot and still run well. Choke pull offs need to be correct, with vac or veh will run aweful. I'll help where I can, good luck,
_________________________________________
Long retired now


bobland
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Apr 15, 2005, 11:33 PM

Post #11 of 22 (44466 views)
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Re: 84 Chevy 305 Vacuum Lines diagram [In reply to] Sign In

Thanks for your prompt response! The Rochester carburetor I just put on the engine is the original from the old engine. My son and I worked on the truck this afternoon and got all of the connections together except the "decel valve". There are 3 lines ready to plug in once we figure out what and where it is. Not being able to find this item made things much more confusing. It may be possible that I didn't transfer the "decel valve" from the old block, but its not on the old block now. The diagram on my truck is coded XDR. Would this be useful in finding out where this valve would be located or what it looks like? Also, can you help me out with what the decel valve is and what it does?

Thanks for your help.

Bob


Tom Greenleaf
Ultimate Carjunky / Moderator


Apr 16, 2005, 3:59 AM

Post #12 of 22 (44463 views)
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Re: 84 Chevy 305 Vacuum Lines diagram [In reply to] Sign In

Hi Bob,

I just checked everything I own (books) and surfed for your answer. ???? From now dusty memory the decel valve held idle up for the duration of decellerating and or advanced timing as an emmission control. Not used in all cars/vehicles and probably first in CA emmissions. I'm totally open to anyone's better ideas here, hang in there,
_________________________________________
Long retired now


DanD
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Apr 16, 2005, 12:24 PM

Post #13 of 22 (44468 views)
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I wont be back to the shop until Monday, when I get a chance I’ll have a look and see what I can come up with. Even after you get all of them reconnected you’ll have to go through and see if they are still functioning.
They were always screwing up and most times we just bypassed them, it was just too hard to find replacements for them 10-15 years ago. I can only imagine that it’ll be just about impossible now at 25 years. Most of the parts guys probably have never even seen a thermal vacuum switch let alone know what you’re talking about. LOL
Dan.


Canadian "EH"






bobland
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Apr 16, 2005, 5:51 PM

Post #14 of 22 (44452 views)
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Thanks Tom and Dan! I appreciate your efforts in getting me rolling on this. You were right, the parts stores in town didn't know what a decel valve was or what it did. When they looked it up in their database the decelleration valve was listed, but they couldn't order it. I only went to 2 parts stores before I went to a Chevy dealer. The desk clerk was clueless and the manager had to ask the guy in the shop who had worked on 80's Chevy's during the 80's (he was about my age). Enough about all that, I found a deceleration valve and installed it.

Now, I am back to my first and most baffling problem. No fuel is finding its way into the carburetor. I thought that perhaps getting the vacuum lines untangled would help. The fuel pump is new and pushes fuel all the way to the carb connection when it is disconnected from the carb. The filter in the front of the carb is new We cleaned up and replaced parts in the Rochester. The problem was the same with the Edelbrock. The odd thing is that we drove the truck home from the shop on base after installing the engine - without problems. The truck stalled several times after that without driver related causes. Sometimes the only way it would start was to put a tablespoon of gas in the carburetor while turning it over. Finally, it stopped running any longer than the gas poured into it would support it. Out of curiosity, after it stopped running, we opened the Edelbrock and found there was only a drop of gas in the float chamber. Gas had been sitting in the Edelbrock for several years before we acquired it, so we cleaned it up and put it back on the truck. Still no gas flow. We cleaned and refurbished the Rochester and installed it with all of the emission control system that wouldn't fit with the Edelbrock. Now I am lost. Fuel is still not reaching the jets of the carburetor.

Can you think of anything that I can do to find out why no gas is getting through the carb?

Thanks for all of your help!
Bob


DanD
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Apr 17, 2005, 7:45 AM

Post #15 of 22 (44445 views)
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When you crank the engine over does the fuel spurt out of the carb inlet line disconnected with some form of pressure?
If so then it has to be the needle and seat that is stuck closed or plugged not to have any fuel in the bowl. I understand that it’s not likely those two carbs would have the same problem, but if they both have been sitting around for a long time it’s a possibility.
I just rebuilt a 750 Holly that was put away wet with fuel and it sat for a number of years. This thing was so plugged up with what looked like varnish inside (and smelled like) it was unbelievable.
I literally had to scrape this crud away before I soaked it in metal cleaner.
If you’re not getting a strong fuel pulse from the pump at the carb (5to 7 lbs.) then look at the supply line from the tank to the pump. I’ve seen it happen before that there is a rupture in the line that is above the fuel level of the tank, it won’t leak fuel but the pump would only suck air.
If the line is ok then check and see if the pump can suck about 3 or 4 inches (up to 7") of vacuum. You should be able to feel this suction with your finger over the end of the inlet side of the pump, while cranking the engine.
One last question, how old is the fuel in the tank?

Dan.


Canadian "EH"






Tom Greenleaf
Ultimate Carjunky / Moderator


Apr 17, 2005, 12:22 PM

Post #16 of 22 (44431 views)
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Gasoline goes bad quickly. I find 6 months is old! There are some solvents and stabilizers that help. Good luck,
_________________________________________
Long retired now


bobland
New User

Apr 26, 2005, 5:38 PM

Post #17 of 22 (43949 views)
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Thanks for the reply. I have been in training and don't get much time to get on the computer. The fuel is part (60%) 18 months old and part (40%) from February. I also added stabilizer in February. Last weekend I took the top off the carb and found that the tiny spring that hooks the valve onto the float was not attached. That could have been the problem but correcting that did not make the truck run.

Also gas flows from the carb inlet line, but I haven't measured the pressure.

I will find the problem some way or another. If you can think of something else to check, let me know. I really appreciate your help!

Bob


Tom Greenleaf
Ultimate Carjunky / Moderator


Apr 27, 2005, 5:28 AM

Post #18 of 22 (43933 views)
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WOW - you found a problem with the float! Just FYI - totally flooded out spark plugs won't work. Either heat them up till glowing hot, or better to just replace them. They can look dry and still not work at all! You can't see it but they seek and find ground without making a spark!! Good Luck, Tom
_________________________________________
Long retired now


Guest
Anonymous Poster

Jul 31, 2009, 10:33 AM

Post #19 of 22 (28588 views)
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well i have a new problem my womans car a 2004 dodge stratis the oil light comes on and the engine acts like it is going to die ,but doesnt


Hammer Time
Ultimate Carjunky / Moderator


Jul 31, 2009, 11:01 AM

Post #20 of 22 (28587 views)
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This thread is 4 years old. You need to start a new question of your own.




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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Guest
Anonymous Poster

Aug 12, 2009, 5:03 PM

Post #21 of 22 (28387 views)
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I bought an 81 fullsize jimmy with a 305, th-350 and original rochester q jet. It was dieseling after i shut it off and the timing was really advanced. I rebuilt the carb and played with the timing. After i put the carb on and played with the timing it will run great for a while then idles rough and wants to die.. I can hold my hand over the front butterfly and sometimes smothering the carb makes it run great others it kills it. I'm assuming my carb rebuild was successful but on the installation vacuum lines were swapped. There is no consistency with it. So far i have replaced the distributors vac. advance (i could blow through it), cap, rotor, coil, plugs, wires, fuel pump nd filter. I'm kind of lost now and torn between fuel or electrical problems... Any ideas or comments would be much appreciated.
Thanks


Loren Champlain Sr
Veteran / Moderator


Aug 12, 2009, 5:23 PM

Post #22 of 22 (28385 views)
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Your symptoms smack of a lean condition. It's very possible that you've got the wrong base gasket. BTDT. Check all possiblities of a vacuum leak. Dieseling is caused by heat. A lean condition causes heat. Carbon particles will glow and ignite the fuel after the engine is shut down.
Loren
SW Washington




84 Chevy 305 Vacuum Lines diagram


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