Vacuum line questions.

[Jordan_J]

Ok for as long as I can remember the vacuum lines going to and from the MAP sensor have been broken. What problems would this cause? Also what do I do with these lines?

There is the first pic...you can see the line coming from the MAP sensor stops right at the other two vac lines coming out from the firewall that I placed next to the accumulator. Speaking of which what do I do with those two lines coming out from the firewall? The small segment on top of the accumulator just looks like it's a broken segment from what used to be. I've found smaller ones before but never thought anything of them.

Another view.

 

[wb's87]

it looks to me that the vac line going to the map is still connected. any vacuum leak even slight is not good for turbo cars. usually you will get a rich running condition, poor gas mileage and poor performance. are those lines active??if they are producing vacuum i would plug them off for now and see what happens. how does the car run??

 

[Nick Micale]

The MAP sensor only has one vac line running to it.

There are 2 lines going into through the firewall to the dash.

One is the supply vac for the AC/heater controls, the other is a vac line back from the switch to control the heater control valve.

 

[Jordan_J]

it looks to me that the vac line going to the map is still connected. any vacuum leak even slight is not good for turbo cars. usually you will get a rich running condition, poor gas mileage and poor performance. are those lines active??if they are producing vacuum i would plug them off for now and see what happens. how does the car run??

Umm last I knew the car was running fine other than the cam going back and before that lean due to a vacuum leak but I thought I found it elsewhere. There is a hose on the vacuum block that is blocked off and I am unsure if the previous owner has done something with those lines. The map sensor isn't connected at all, the edge of it's line is right where those two under dash lines are where they meet. I do recall extra poor gas mileage on a big road trip with the car though. The heater and AC seemed to work still even when the lines weren't connected, does that sound right?

If I decided to hook them up where would each line go at? Could I just unplug the blocked of port and connect them to that? I may call up the previous owner and see what he says on the matter. He may have done something with the lines.

Thanks guys!

 

[Scott87]

The hard line is I think 5/32" line. The connection comes off this line from the intake.

Another shot of the spot it comes from on the intake.

You could use all rubber hose to make the shot over to the MAP sensor and remove the stepdowns or you can buy new stepdowns. I would suggest if your going to do that take the little rubber peice off the MAP sensor so you can match it up from the auto parts store.

 

[Jordan_J]

Awesome, thanks for the pics Scott! Upon reading I found the vacuum line to the MAP sensor is for the boost gauge, does it do anything else? I'll connect it still even though I have an after market gauge connected.

 

[bmackinnon]

The map sensor does nothing other than run the factory boost gage in the dash.... has no effect on engine management....

 

[hesermon]

http://i216.photobucket.com/albums/cc31/earl87gta/86 Buick GN/vac_federal.jpg

This is how I got mine figured out. These cars are very funny about vacuum. There may be way to bypass or block of lines and get your car running but I think you'll find the best way is the right way.
On the diagram:
"To HVAC" means run that line to one of the lines that go down inside the finderwell and through to the AC control head.
(the other line from that location goes back to the heater control valve in the heater hose against the firewall.
"To Sensor Gauge" is the one that connects to the MAP sensor. Again it only runs the indash boost gauge so it could be capped off if you don't want the gauge to work.
Everything else is pretty self explanatory if you print it out and compare it to your engine. Location of check valves is also very important.
The only thing not pictured is the location of the vacuum reserve canister or "ball". I left mine off at first and every time I got into the throttle my a/c would blow warm. It is needed by the a/c control head to keep the vents operating properly. (BTW it has a check valve built into it)

Hope this helps

 

[Scott87]

Very cool Hesermon. Nice little diagram complete with the location of the check valves makes it easy for someone who may have the car second hand and can use it to check missing items.

 

[hesermon]

Can't take the credit, just re-posted from when someone on here helped me out when I was putting mine back together!

 

[bmackinnon]

http://i216.photobucket.com/albums/cc31/earl87gta/86 Buick GN/vac_federal.jpg

"To HVAC" means run that line to one of the lines that go down inside the finderwell and through to the AC control head.
(the other line from that location goes back to the heater control valve in the heater hose against the firewall.


The only thing not pictured is the location of the vacuum reserve canister or "ball". I left mine off at first and every time I got into the throttle my a/c would blow warm. It is needed by the a/c control head to keep the vents operating properly. (BTW it has a check valve built into it)

Hope this helps

To clarify this a little... the vacuum reserve 'ball' does not have it's own check valve, is considered part of the HVAC, and is supplied by a 'Y' in the line labeled hvac on that diagram.... post check valve.... :wink:

 

[Jordan_J]

Everything else is pretty self explanatory if you print it out and compare it to your engine. Location of check valves is also very important.
The only thing not pictured is the location of the vacuum reserve canister or "ball". I left mine off at first and every time I got into the throttle my a/c would blow warm. It is needed by the a/c control head to keep the vents operating properly. (BTW it has a check valve built into it)

Hope this helps

Very helpful! Is this the vacuum reserve canister?

While re routing wiring and making the engine bay look nicer and less cluttered I saw this had a rubber line in bad condition (the one in the picture coming out of it) going straight up and ending shortly after getting above where it's mounted. I don't think I have any check valves at all, unless I missed some, looks like I"ll have to work on them to get my AC and everything working right!

 

[bmackinnon]

That's it, and yep, that line is one of the first to deteriorate...

 

[Jordan_J]

That's it, and yep, that line is one of the first to deteriorate...

Is the line specific to that part or can I get any vacuum line and throw it inside? So all that part does is keep a vacuum reserve?

 

[1984 t-type]

I recentley asked the same question about the purpose of the map sensor and got the same answer ( that it only controls the factory boost gauge ) well with that being said i am wondering why you need a map sensor if you are running a alky kit, after all it only controls the boost gauge right?

 

[hesermon]

http://i216.photobucket.com/albums/cc31/earl87gta/86 Buick GN/vac_federal.jpg


The only thing not pictured is the location of the vacuum reserve canister or "ball". I left mine off at first and every time I got into the throttle my a/c would blow warm. It is needed by the a/c control head to keep the vents operating properly. (BTW it has a check valve built into it)

Hope this helps

My 85-before conversion had a vacuum reserve that is not actually a ball. It is plastic but about 6 inches long and about 3 inches across. On one end it says "check valve this end". That is what I was referring to. On the other end it says "to HVAC" Sorry about that.

 

[bmackinnon]

I recentley asked the same question about the purpose of the map sensor and got the same answer ( that it only controls the factory boost gauge ) well with that being said i am wondering why you need a map sensor if you are running a alky kit, after all it only controls the boost gauge right?

The map only runs the boost gage on a STOCK setup. The alky kit uses a 3-bar map (stock is 2-bar) to feed the boost signal to the alky controller to regulate the amt of alky injected...

 

[bmackinnon]

Is the line specific to that part or can I get any vacuum line and throw it inside? So all that part does is keep a vacuum reserve?

Regular old vac line from the store.... yes, holds a reserve to maintain hvac setting in boost. Without the check valved reserve, the hvac will switch to defrost / hot (default positions) whenever you hit boost....