Topic: 1981 turbo trans am map sensor hookup

[78w72]

i know this isnt for a 78 400 w72 etc....but i also own a 1981 nascar t/a with 301 turbo. i'm in process of trying to get it running a little better & have found that the 2 map sensors mounted on the drivers fenderwell area have vaccum hoses going to them, as well as electric connectors. the elect is fine but the vaccum hoses are not right.
 
From what i can find the vac diagram for a 301t (at the 301 Garage website) shows the vac line going to a metal line in the turbo system. one of the map sensors is hooked there, but the 2nd one goes to nothing at the monent.

The question is: where does the other sensor hook to? is it another location, or should there be a T-fitting at the sensors & they then both hook to the one point in the turbo line?

Just seeing if anyone has or is familiar with the 81 301t vac routing etc.

Thanks in advance.

[jjr]

 I'm familiar... <grin>

 It doesn't get connected to anything. It's the baro sensor, so it's
looking at the barometric pressure of the surrounding air. The MAP
sensor runs to a manifold connection (on the side of the compressor).

 The computer is comparing the surrounding air to that in the manifold
to make decisions.

 Make sense?

 Joe R

[78w72]

hey a fellow 81 pacecar'er on the 78ta site!! ahh yes, the barometric pressure sensor. makes perfect sense. thanks! one sensor is connected to the manifod vac next to the turbo, i think it's the sensor closest to the firewall. is that the correct sensor to have vac hooked to? the "front" one looks the same & has the same vac hose fitting, but that hose just runs to nothing. just want to make sure the correct one is hooked to the vac source.
Also, does the baro sensor need to have a hose on it -- if so, where should it be routed to be correct?

& by any chance could you send me or post a few pics of the engine & vac/electric lines? i think most of the stuff is hooked up correctly, i just want to have a good example to compare it to. the car runs but has always seemed to run crappy. although i did just identify a possible major problem, the secondary top plate was stuck. it would barely open, & when it did it would stick open. i sprayed some wd40 on the shaft & readjusted it slightly, works like new now. that should help alot for anything beyong about half throttle.

thanks again for the help.

[milly]

jjr runs the 301 Garage site that you visited. So you probably have already seen most of his pics. 

[jjr]

> hey a fellow 81 pacecar'er on the 78ta site!!

  Actually, I'm a 301 - 301T'er... owning both a '80 and '81
 pace car. And as Milly's told ya, 301 Garage is me.

> i think it's the sensor closest to the firewall. is that the correct
> sensor to have vac hooked to?

  I'm just getting in from traveling all weekend, I'll verify all that
tomorrow and look for the part numbers.

> the "front" one looks the same & has the same vac hose fitting,
> but that hose just runs to nothing. just want to make sure the
> correct one is hooked to the vac source.

  That's right, they look nearly identical (almost)

> Also, does the baro sensor need to have a hose on it --
> if so, where should it be routed to be correct?

  While I've seen short lengths on them some times, no.

> & by any chance could you send me or post a few pics of the
> engine & vac/electric lines?

  Lemme ask you first... do you have the Pontiac service manual
for your car ($20 for one of Brett's CDs)?

  A no-kidding must for a '81 Turbo car.

  So you want pictures of an '81 engine bay... I'll look.

> i think most of the stuff is hooked up correctly, i just want to
> have a good example to compare it to.

  I see.

> the car runs but has always seemed to run crappy.

  Ah... might need a bit more to diagnose possibilities.

  If your secondaries were that stuck, I'm thinking the rest of the
carb may need attention too.

  78w72,

  There's no reason your car can't run decent. There are more Turbo
folks than myself, help is available.

  Most of my posting has been on TAC, which seems to have somewhat of
a concentration of turbo folks on it. And there is a rather large 301
thread over there that you may find useful as well.

  Joe R

[78w72]

the turbo t/as are nice cars for sure, cruisers. my 78 w72 t/a is not too nice on gas. but i love them both.

i dont have the cd manual, but plan to get one real soon, before i dig much deeper into this mysterious, technical wonder that is the 301 turbo.

i looked all through your 301 site, & while it is packed full of info & pics, i cant seem to find one that shows the complete vac & elect routings. again, just wanted something to compare to, some of my vac lines are plugged off &/or go nowhere.

the carb was "rebuilt" for lack of a better term, by a local garage a ferw years ago. dont think it was ever tuned/setup correct though. the plates look as if they were just misaligned when put back together.

thanks for all the help & i may have a few other ?'s after i start looking deeper into repair/tuneup of this motor. it is actually a low mile original rust free car from az. just was very neglected in its life.

i have looked at the tac site for quite awhile now, just not signed up yet. i'll make a point to do that. i can give you my email address if you can send me some vac/elect specific pics.

thanks again.

[jjr]

 My research has proven inconclusive. While the parts catalogue
does show separate part numbers, I don't  see that in practice.

 What I do see is the handling of the sensor used for MAP. As
you would expect this is the one "hose" connected to pressures
in the manifold. As such, it's connected to the electrical connector
for the MAP reading. "If" your harness still has discernible connector
colors this would be the orange coded connector.

 When I looked for a picture of the engine showing wiring and (or)
vacuum I realized why there wasn't one yet. The '81 setup is pretty
complicated and any "easy" shot of same all but impossible.

 Most shots show the engine fine, but the wiring and vac is mostly
hidden. So, I went back to how I verified mine when I did it...

 The manual.

 Using numerous illustrations in the manual, I eventually checked everything
and moved on. While I don't mind scanning in a illustration or two, right now
the whole, complete, where does it go project will take a good deal of time
since I really cannot just repo that much of the manual.

 1981 is in many ways a one year only version. The computer isn't like anything
after. The concepts are very close as the 80's moved on, but '81 is all by itself.

 For me, I found some software "Diacom" that enabled any computer the ability
to watch the '81 computer and it's sensors. That's not the only package that
is capable though.

 So let's do a question at a time and get you back to cruising '81 Turbo style...

 Joe R

[78w72]

i'll have to find that software, is it a large program, maybe you could email it to me???

how about i tell you what i need pics of? i think most of it is ok, mainly i need a shot of the air/smog pump area. there is a small plastic elect/vac sensor (mine is red) suspended over the manifold on a bracket, (i'm sure you know just what i mean) near that is a black plastc "thingy" attached to the smog pump with a larger vac hose going to it, then at the end is a very small vac port. both of the previously mentioned components are plugged at the small vac ports. seems like they should go somewhere. possibly hook to each other? on one end of the 'suspended" sensor, the vac line goes to the front carb port. a pic of that whole area would help alot.

so besides the map/baro sensors (thanks again) i'm pretty close to complete. computer works, have got the codes, it read a bad o2 sensor, 54 or 55 i think. i replaced the o2 recently. will check the codes again after i rehook the bat & drive it a bit.

also a pic or info on the choke pull off & back area of carb. specifically, where does the choke pull- off hook to. i have mine to one of the small ports on the rear vac fitting of the carb.

let me know what you can find.

thanks again
scott

[78w72]

oh & my map sensor is hooked to the orange connector.

after looking again at the smog pump area, there are actually 2 "little suspended" elect/vac sensors. the one i'm refering to is the upper red one. the 2nd one is set lower down under lots of things, it seems to be hooked up as per factory.

i can also send you pics of areas i need, & then you could send back the same pics, but of your car of course.   

[jjr]

 I know you asked for pictures, but I think these diagrams may be
better.

 First is the detail and part numbers for the sensors.



 The connector you are trying to place is the EGR solenoid I believe.



 The SVB hose is shown as a part of a hose assembly.



 This is what shows on the emissions label, it's the only
place a vacuum diagram appears.



 Please review this material and hit me with what you need
next.

 Joe R

[78w72]

thanks so much joe. this really helps. i spent hours last night reading at the tac site. i read the entire 301 sticky & many other threads i found using "turbo" & "301" as a search. you really do spend ALOT of time & effort helping us ametuer 301'er's out. i'd like to say THANKYOU again.

 the egr sensor is what i was refering to. i think i can make sense out of those diagrams. (i will get the manual soon too)

the only thing left is the air mangmnt valve. wher does it hook to. it's kinda hard to tell from the emission diagram.

i'll get registered at tac so i can bug you over there about my 301t stuff. this site seems more for the 78's & 400's etc.

thanks
scott

[78w72]

i was just looking at my engine bay comparing it to my new diagrams  i have noticed that the egr sensor is NOT the sensor i was refering to. there is another sensor above the egr, that is what is unhooked on mine. the egr setup looks good.

the egr sensor is mounted to one of the bolts for the thermostat housing, this sensor is mounted to a metal line it seems & is above the egr sensor. that looks like the last item that not hooked up.

if i could figure out how to post a pic here, i could just show you what i meant. can ya help with that too???

[jjr]

 Scott, you're welcome.

 78ta and TAC share a lot of the same folks.

 TAC isn't better, just has a little different mix of folks.
I don't know why exactly but more turbo folks seem to
go there.

 You can ask your questions there or here, I just might
see it a little quicker there though.

 Ok, so focus on air management valve and connections...

 Joe R

[78w72]

i noticed you seem to hang out there a little more. i agree neither place is "better" & if you own a 78 w72 & a turbo 301, they are bothequally valuable!

i think everything should be ok thus far (short of a shot turbo) just need the air management routings. also can you re-explain how to "t" in a boost gauge on an 81? i have the vac/press gauge.

thanks 

[jjr]

 Ok, detail on air management valve...

 From manual:



 From Car:



 Valve itself:



 And about "T"ing in a boost gauge. Now, I've used very
short hoses to show the idea. The one to the gauge itself
would have to be longer to see from driver's position.

 Adding the "T" before:



 Adding the "T" after:



 Joe R