Vacuum hose routing/ diagram?

[Jeepwm69]

Yesterday I started replacing all the original rotted, cracked vacuum hose under the hood.

A few weeks ago the truck started hesitating and sputtering, and someone here suggested it sounded like the vacuum advance hose might be off. I looked, and sure enough, the hose was rotted and had broken off. I cut the end loose and stuck it on and it ran fine.

I ordere new hose, and started routing yesterday. At some point in the past someone has obviously blocked off a few of the hoses, so not sure where everthing goes. For example, in pic #1, this was on the front of the motor right up top, and the middle and top right holes went on the two prongs on the motor, while the other two hoses weren't on anything.

In pic #2 you'll see where it connects in the bottom right of the pic. This is how I hooked things up following the same routing as before, but eliminating some of the extra hoses that didn't appear to be hooked up to anything. That little 4 way block....is that a check valve of some sort?

Pic #3 shows the distrubutor and another one of these connectors on the back of the block right at the base of the distributor.

So basically I eliminated that 4 way plug in pic #1 because it was rotted beyond help, and there weren't any male fittings to slide new hose onto. The truck now runs like it did when I had the vacuum leak with the vacuum advance, so I'm thinking that something isn't right, possibly that 4 way connector in pic 2 if it's a check valve.

Does anyone have the simplest vacuum diagram one can use on one of these older trucks? This one doesn't have any emission crap on it anymore and I want it to be as basic as possible. On my Jeep I eliminated everything except the vacuum advance and PCV valve, and would like to so something similar for this truck.

It looks like I have a vacuum hose going to the A/C area, which I assume is for the climate controls. I obviously need one for vacuum advance. Could I run straight from distributor to carb? The EGR and the two little connectors (are they CTO valves) on top of the engine are what I'm not sure about, and there is also a hose going to the grill to what looks like a charcoal canister for fumes.

Sorry for the wordy post, just trying to get as much info out there from the get go. Any suggestsions on running these hoses?

[Jeepwm69]

Anyone?

[sambrutay]

What year Truck are you working on?

[hatzie]

The GM service manuals I have in my library don't have vacuum hose diagrams even tho they allude to the existence of some mythical tome with that information. That's one thing the Chilton Big Books are sometimes good for. Go to a Half-Price Books or the local Library and look at one.

I assume the Vacuum hose diagram on the radiator mount or the air cleaner is among the missing. Worst case... Year One and Classic Industries reproduce some underhood emission labels a few of them came with the vacuum hose routing diagram.

[Jeepwm69]

Originally Posted by sambrutay

What year Truck are you working on?

Crap! All that info and forgot the year. 83 GMC with 305.

Not necessarily trying to put it back to stock. There is no cat converter on it, and I'm trying to get it to the best running shape with as few vacuum lines as possible.

[hatzie]

Google is your friend...
https://www.google.com/search?q=83+G...=2554&bih=1476

[Jeepwm69]

Originally Posted by hatzie

Google is your friend...
https://www.google.com/search?q=83+G...=2554&bih=1476

That helps, but how much of that crap can I get rid of given that the emissions stuff is gone?

I know on a mid 80's CJ you can get rid of everything but the vacuum advance and PCV valve and it runs better without the 12 miles of old dryrotted vacuum hoses.

The problem is, my vacuum stuff has obviously been modified to some degree over the years, and something like that 4 hose plug able to be duplicated easily and mine is rotted.

[hatzie]

Start with just those pieces and go from there.
If you have a TH350 you'll need the vacuum modulator and TCC controls in the mix too.
Get a kit of rubber vacuum line caps to close off all of the unused pips. Don't go ghetto with hose and screws.
http://www.amazon.com/Piece-Rubber-Vacuum-Quik-Sel...

[Jeepwm69]

It's an SM465 so no worries on that.

I found a post from a google search that appears to show that 4 plug vacuum harness above as being plugged into a two port EFE/ Distr TVS so that would leave the two small hoses unattached to anything. Is that correct?

[69heavychevy]

If you don't need the emissions then all the vacuum hoses you need are PCV, vacuum advanced, and brake booster.

[Liberty]

I had the same engine in my 82 C10. Here is my diagram.

[Liberty]

On a side note, the only emissions equipment the GM Master Techs suggested I keep was the vapor canister.

Also sputtering and hesistation could be caused by a failing ESC Module, which sucked even when it was new.

[Jeepwm69]

Originally Posted by 69heavychevy

If you don't need the emissions then all the vacuum hoses you need are PCV, vacuum advanced, and brake booster.

What about the vacuum motor on the air cleaner?

So I can delete the EGR, the EFE/Distr/TVS?

Thinking run distributor straight to carb nipple on front, leave purge hose and signal hooked to EGR (or how can I hook up the vapor cannister as simply as possible?), hook air cleaner vacuum motor to manifold vacuum source, and get rid of everything else. Would that work?

I've never seen all the "delay valve" and "check valve" crap but I think the way I tried to bypass that 4 hose plug ont he EFE/DIST/TVS is the problem with my hesitation.

It was running ok before I started replacing hoses, but the old hoses were stock and started to fall apart. A few weeks ago it started running like crap and I found a leaking hose, so I replaced that one and it was running fine. I figured I might as well replace the rest since they were all original.

[Liberty]

I highly recommend you keep the vac motor on the air filter operational. I have mine running off manifold, which the diagram calls for anyway.

EGR can be completely deleted. You will need those delays, and you need to keep a hose going to your ESC.

I'll take a pic of my vapor can. But really its pretty much straight forward simple commections if you follow the diagram.

[Jeepwm69]

Originally Posted by Liberty

I highly recommend you keep the vac motor on the air filter operational. I have mine running off manifold, which the diagram calls for anyway.

EGR can be completely deleted. You will need those delays, and you need to keep a hose going to your ESC.

I'll take a pic of my vapor can. But really its pretty much straight forward simple commections if you follow the diagram.

ESC? Don't see that on the diagram. Thank you for your help.

[Liberty]

It will be a switch mounted on the passenger Side of the firewall with a vac line running to it. You can run it right off manifold vac.

That switch sends signals to your Electronic Spark Control which controls your timing and carb.

[hatzie]

Originally Posted by Liberty

It will be a switch mounted on the passenger Side of the firewall with a vac line running to it. You can run it right off manifold vac.

That switch sends signals to your Electronic Spark Control which controls your timing and carb.

I think ESC started in '84 or '85...

[Jeepwm69]

Ok, messed with this some more yesterday. Apparently that delay valve OR the 4 hose plug in the first pic that I tried to eliminate is still causing some issues, so let me try this step by step.

I have the EGR plumbed like it is in the diagram with a line going to J on the carb, and another going to the canister, but it looks like at some point in the past the EGR Purge TVS was elmiinated, so what effectively I have is the EGR going to the canister. Should I leave that alone, or cap off the EGR and the canister?

I have the Distributor/ Vaccum Advance plumbed straight to the carb. Do I need that Distributor delay valve? It runs better than it did, but I'm still getting some hesiatation that wasn't there bofore I started messing with all this stuff. If I plumb the vacuum advance through the delay valve as pictured, what goes on the other two outlets on the dist delay valve?

I have the rear manifold vacuum source going to the air cleaner but am not sure whether the other end of the line should go on the EFE/ DISTR/TVS or what. If I run the rear manifold vacuum source to the air cleaner with no T, would that work? If I do it that way does that check valve need to be between the air cleaner and the rear manifold vacuum source?

So bascially that only leaves the 4 connections to the EFE/DIST/ TVS. I only have two nipples on this, and again, looking at the plug in the first picture I posted, it appears that two of the 4 hoses went on those two nipples, and the others were just open. It looks like two of the 4 go to either side of that Distributor Delay valve, and one goes to the EFE back on the passenger side bottom of the engine, and the last one T's into the rear manifold Vacuum source. Can I just cap all this crap off?

Again, this is all on an 83 GMC with 305, no emissions needed, and SM465.

Also will add that I left the PCV valve and plumping intact.

[Liberty]

Originally Posted by hatzie

I think ESC started in '84 or '85...

ESC started in the mid 70s for cars, late 70s for the 305 engine only in the Trucks.

My 82 C10 had a 305 with ESC. My buddy had an 80 C10 with not only ESC but a badge on the tailgate proudly stating "ELECTRONIC SPARK CONTROL"

[Liberty]

Take the EGR off, its completely unneeded. Eliminate all connections associated with the EGR. You can completely ignore the TVS.

Run your Canister Purge signal off ported vacuum on the carb, that line will be shared with the TRANS CONV VAC SW. Keep the line running to the air filter to the can, keep the line running to PCV to the can. Keep the vapor line from the carb to the can connected, and keep the can to fuel tank line connected. Keep the line from the distributor connected as well, for winter start-up purposes keep the air filter vac motor on manifold vac. You also have a vac line running to a bowl on your firewall for your Heating and AC controls, keep that on manifold vacuum, and specific to your engine keep manifold vac going to the ESC Switch mounted on the passenger side of the firewall.

These are the only VAC lines you need. You will want these delay switches, it keeps the vac signal steady to these electric switches and to the canister.

[Liberty]

Also my truck does not have an EFE (Early Fuel Evaporation Valve)

This was purely for California emissions, it can be deleted.
Although I'm not sure what effect it has on fuel economy.

Also on those delay valves, I just remembered my Dizzy doesn't have one on the line, so its safe to assume its unneeded. So I'm thinking the Distributor Delay Valve can be removed.

[Jeepwm69]

Ok, thanks for the reply.

So run Canister Purge to carb port

Don't think I have a Trans Conv Vac SW. That for automatic transmission equipped trucks or ???

Leave canister lines alone

Cap off EGR

Run distributor vac advance line to carb port (do I need distributor delay valve?)

Keep manifold vac to air cleaner valve and HVAC controls (rear manifold source by the distributor).

That it?

I've gotten rid of all this crap on my Jeep 258's, so trying to do the same with this truck.

Thanks again for the help.

[Jeepwm69]

Originally Posted by Liberty

Also my truck does not have an EFE (Early Fuel Evaporation Valve)

This was purely for California emissions, it can be deleted.
Although I'm not sure what effect it has on fuel economy.

Also on those delay valves, I just remembered my Dizzy doesn't have one on the line, so its safe to assume its unneeded. So I'm thinking the Distributor Delay Valve can be removed.

Oh yeah, forgot about that one too. The EFE hookup is there. Supposely closes off the right manifold till the truck warms up to keep fuel from pooling in the intake during cold running. That sounds like a problem waiting to happen. So just cap it off too?

Good to know on the delay valve. Never seen anything like that before so I wondered.

[Liberty]

Originally Posted by Jeepwm69

Ok, thanks for the reply.


Don't think I have a Trans Conv Vac SW. That for automatic transmission equipped trucks or ???

Haha forgot you had a standard, so no you don't have that.

Originally Posted by Jeepwm69

Ok, thanks for the reply.

Run distributor vac advance line to carb port (do I need distributor delay valve?)

I don't think you do, I don't have one and it seems to run fine without it.

And to answer an earlier question, yes you need the check valve operating between the air filter housing VAC motor and manifold vacuum or it will never open for fresh air.

[Liberty]

Originally Posted by Jeepwm69

Oh yeah, forgot about that one too. The EFE hookup is there. Supposely closes off the right manifold till the truck warms up to keep fuel from pooling in the intake during cold running. That sounds like a problem waiting to happen. So just cap it off too?

Good to know on the delay valve. Never seen anything like that before so I wondered.

Yes, mine runs just fine without it. I would think a properly tuned carb would prevent that anyway.