Vacuum line diagram? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

kcackler · 03-13-2009, 11:31 AM

We just purchased an 86 GMC Sierra 2500 that runs, but does a pretty crappy job at it.

What we discovered is that there are 2 vacuum lines disconnected. One of the lines comes from the carb and splits into a "T". One side of the T goes down into the carb or engine somewhere, but the other side of the T looks like it's been ripped apart. When cranking, there is some suction on the line, so it obviously needs to go somewhere.

The other disconnected line comes FROM the breather, but we don't know WHERE it goes. There is an unoccupied male connector connected to the distributor, but we're not 100% that's where this second hose goes (Although when we put the breather on, the hose does sort of rest next to the distributor)

So is there a diagram of where all the hoses go from our breather?

Kevin

EDIT: Pictures of our question hoses are attached.

The PURPLE hose is one of our question hoses. I think it connects to the male connector on the distributor (WHITE), but I'm not 100% sure on that.

The RED and BLUE hose connector at a Y and a single hose goes down to the carb area.

The GREEN hose is our broken hose that has suction when we turn on the truck. We just don't know where it should go, and we can't find any other open male ends..just the one on the distributor. The GREEN hose's "T" is on the "B" port of the carb.

maxreps · 03-13-2009, 01:53 PM

I'd say the one marked in green should go to the male on your distributor to control vacuum advance...

454HO · 03-13-2009, 02:12 PM

There is over a dozen different vacuum diagrams for '86 V8 engines. Need to know the engine size and usage before you can pick which one matches your truck. Hopefully this will help you out...

http://www.autozone.com/shopping/rep...00c1528004c3cb

kcackler · 03-13-2009, 02:17 PM

Didn't realize there were so many configurations. The truck is a 3/4 ton 2500 with a 5.7L V8, but we don't know any of the other details (California emissions, etc...)

Where can we find out exactly which engine we've got?

kcackler · 03-13-2009, 08:27 PM

Looked through all of the 350 diagrams, and http://www.autozone.com/shopping/rep...00c1528004c3cb looks closer than any of them. If I'm right, according to that diagram, the hose marked in green above should in fact go to the distributor. Can anyone confirm or deny this?

heavychevy79 · 03-13-2009, 08:50 PM

It should be one of the lower ones.
Since all of the vac lines have been messed with, you set it up like an older
model and delete all of the extra emissions junk.

Hey, did you have another thread about this allready?

kcackler · 03-13-2009, 09:05 PM

I'm about to give up on this mess and hire someone to come over and hook it up right. I don't know what the PO did here, but it's a mess for sure.

And no prior threads - I'm keeping each issue to its own thread.

dswancutt · 03-13-2009, 10:00 PM

There should be an emissions label on the core support with the vacuum diagram. GM started that in 81 I believe. Also look for a code if you can find it. I know on my 77, it is CM which is the light duty 350 emissions class.

kcackler · 03-13-2009, 10:25 PM

I've got the emissions label (I think), but there is no wiring diagram there. The only number/letter codes I could find were:

YLF - In the top left of the label
GGM060.0GEA2 - In the right middle of the label

heavychevy79 · 03-13-2009, 11:36 PM

It should still run good enough to drive it somewhere, even with the choke unhooked and vac lines plugged.

Most of those things can be capped off, and it's easy to figure out which one
is the ported vacuum on the carb, you can feel it when it's running and you
give it some gas, it will suck your finger, while the other ones suck all the time.
And you can get keyed power from alternator if one of those wires in the pic don't work. Or just adjust the choke so it's open a little, which you prob need to do anyway.
But don't give up, you can do it!

heavychevy79 · 03-13-2009, 11:42 PM

Quote:

Originally Posted by dswancutt

There should be an emissions label on the core support with the vacuum diagram. GM started that in 81 I believe. Also look for a code if you can find it. I know on my 77, it is CM which is the light duty 350 emissions class.

Some are on the air cleaner. But it's prob been discarded for one of those chrome ones that everyone's just gotta have on their engine.

03-13-2009, 11:31 AM	#1
kcackler Registered User Join Date: Feb 2009 Location: Russellville, AR Posts: 164	Vacuum line questions We just purchased an 86 GMC Sierra 2500 that runs, but does a pretty crappy job at it. What we discovered is that there are 2 vacuum lines disconnected. One of the lines comes from the carb and splits into a "T". One side of the T goes down into the carb or engine somewhere, but the other side of the T looks like it's been ripped apart. When cranking, there is some suction on the line, so it obviously needs to go somewhere. The other disconnected line comes FROM the breather, but we don't know WHERE it goes. There is an unoccupied male connector connected to the distributor, but we're not 100% that's where this second hose goes (Although when we put the breather on, the hose does sort of rest next to the distributor) So is there a diagram of where all the hoses go from our breather? Kevin EDIT: Pictures of our question hoses are attached. The PURPLE hose is one of our question hoses. I think it connects to the male connector on the distributor (WHITE), but I'm not 100% sure on that. The RED and BLUE hose connector at a Y and a single hose goes down to the carb area. The GREEN hose is our broken hose that has suction when we turn on the truck. We just don't know where it should go, and we can't find any other open male ends..just the one on the distributor. The GREEN hose's "T" is on the "B" port of the carb. Attached Images __________________ Blue - 77 Chevy Scottsdale Last edited by kcackler; 03-13-2009 at 12:53 PM.

03-13-2009, 01:53 PM	#2
maxreps Registered User Join Date: Jan 2009 Location: greensboro, nc Posts: 174	Re: Vacuum line diagram? I'd say the one marked in green should go to the male on your distributor to control vacuum advance...

03-13-2009, 02:12 PM	#3
454HO Registered User Join Date: Apr 2005 Location: Austin, TX Posts: 1,224	Re: Vacuum line diagram? There is over a dozen different vacuum diagrams for '86 V8 engines. Need to know the engine size and usage before you can pick which one matches your truck. Hopefully this will help you out... http://www.autozone.com/shopping/rep...00c1528004c3cb __________________ - Greg

03-13-2009, 02:17 PM	#4
kcackler Registered User Join Date: Feb 2009 Location: Russellville, AR Posts: 164	Re: Vacuum line diagram? Didn't realize there were so many configurations. The truck is a 3/4 ton 2500 with a 5.7L V8, but we don't know any of the other details (California emissions, etc...) Where can we find out exactly which engine we've got? __________________ Blue - 77 Chevy Scottsdale

03-13-2009, 08:27 PM	#5
kcackler Registered User Join Date: Feb 2009 Location: Russellville, AR Posts: 164	Re: Vacuum line diagram? Looked through all of the 350 diagrams, and http://www.autozone.com/shopping/rep...00c1528004c3cb looks closer than any of them. If I'm right, according to that diagram, the hose marked in green above should in fact go to the distributor. Can anyone confirm or deny this? __________________ Blue - 77 Chevy Scottsdale

03-13-2009, 08:50 PM	#6
heavychevy79 Cheyenne Super Join Date: Nov 2008 Location: Dallas Texas Posts: 545	Re: Vacuum line diagram? It should be one of the lower ones. Since all of the vac lines have been messed with, you set it up like an older model and delete all of the extra emissions junk. Hey, did you have another thread about this allready?

03-13-2009, 09:05 PM	#7
kcackler Registered User Join Date: Feb 2009 Location: Russellville, AR Posts: 164	Re: Vacuum line diagram? I'm about to give up on this mess and hire someone to come over and hook it up right. I don't know what the PO did here, but it's a mess for sure. And no prior threads - I'm keeping each issue to its own thread. __________________ Blue - 77 Chevy Scottsdale

03-13-2009, 10:00 PM	#8
dswancutt Registered User Join Date: Jul 2003 Location: Franklin, NE Posts: 387	Re: Vacuum line diagram? There should be an emissions label on the core support with the vacuum diagram. GM started that in 81 I believe. Also look for a code if you can find it. I know on my 77, it is CM which is the light duty 350 emissions class.

03-13-2009, 10:25 PM	#9
kcackler Registered User Join Date: Feb 2009 Location: Russellville, AR Posts: 164	Re: Vacuum line diagram? I've got the emissions label (I think), but there is no wiring diagram there. The only number/letter codes I could find were: YLF - In the top left of the label GGM060.0GEA2 - In the right middle of the label __________________ Blue - 77 Chevy Scottsdale

03-13-2009, 11:36 PM	#10
heavychevy79 Cheyenne Super Join Date: Nov 2008 Location: Dallas Texas Posts: 545	Re: Vacuum line diagram? It should still run good enough to drive it somewhere, even with the choke unhooked and vac lines plugged. Most of those things can be capped off, and it's easy to figure out which one is the ported vacuum on the carb, you can feel it when it's running and you give it some gas, it will suck your finger, while the other ones suck all the time. And you can get keyed power from alternator if one of those wires in the pic don't work. Or just adjust the choke so it's open a little, which you prob need to do anyway. But don't give up, you can do it!



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