[Leonard Welch]

Hey All,

Anyone out there familiar - I mean really familiar with the 1971 TCS system?

Here's my story. I've had this car for almost three years and I've been unable to fix this problem. I can't get the system to work. My car idles high due to a constant vacuum advance caused by the inoperability of my TCS system. Strange thing is that the fuse pops at each cold start. This fuse also contains the radio and idle stop solenoid circuits in addition to the TCS system. Warm starts will not blow the fuse. Strange thing is that once the car is warm and the fuse is replaced, the TCS system still doesn't function as it should - which is (per the Service Manual) no vacuum advance unless abnormal operating temperatures (under 80F and above 220F) or transmission in 4th gear (I have a 4 speed 400).

I've made sure that the vacuum hose routing is per the Service Manual (because there are two hose outlets - one is plugged).

I've replaced all of the TCS components - the three-prong temp sending unit, transmission sending unit and the TCS diaphragm itself. I've even replaced the engine wiring harness and the sending unit jumper (car has rally gages).

Since the fuse pops at cold start only (I can make it pop just by turning the key on without starting it), I think that this points to the temp sending unit - or something to do with it.

Any troubleshooting ideas?

[Leonard Welch]

Hey All,

Anyone out there familiar - I mean really familiar with the 1971 TCS system?

Here's my story. I've had this car for almost three years and I've been unable to fix this problem. I can't get the system to work. My car idles high due to a constant vacuum advance caused by the inoperability of my TCS system. Strange thing is that the fuse pops at each cold start. This fuse also contains the radio and idle stop solenoid circuits in addition to the TCS system. Warm starts will not blow the fuse. Strange thing is that once the car is warm and the fuse is replaced, the TCS system still doesn't function as it should - which is (per the Service Manual) no vacuum advance unless abnormal operating temperatures (under 80F and above 220F) or transmission in 4th gear (I have a 4 speed 400).

I've made sure that the vacuum hose routing is per the Service Manual (because there are two hose outlets - one is plugged).

I've replaced all of the TCS components - the three-prong temp sending unit, transmission sending unit and the TCS diaphragm itself. I've even replaced the engine wiring harness and the sending unit jumper (car has rally gages).

Since the fuse pops at cold start only (I can make it pop just by turning the key on without starting it), I think that this points to the temp sending unit - or something to do with it.

Any troubleshooting ideas?

[Carl]

Disconnect the sending unit wire from thew sender when its cold. If the fuse still blows the the tcs vaccum soleniod is bad,if it doesnt then the sender is bad. You should have ignition power there when the key is on. The sender on the trans puts the ground in when you shift to 3rd and 4th gear. What I did on my 70 was to disable that system and run ported vaccum to the distributor. The car runs alot better this way also. Hope this helps you Carl

[Carl]

Also I dont know if you are aware but there is a little electric coil in the sender. If it draws too much power or it is contacting ground it will also blow the fuse. I went threw this when I first got my GTO and said the hell with it and converted it to ported vacuum. When you do it this way you get advance in all gears. Carl

[Leonard Welch]

The latest. While the engine was cold, I disconnected the temperature sending unit and turned the key on. Fuse didn't blow. I replaced the temperature sending unit with another one that I had hanging around and...incredible...no more fuse popping. Unbelievable that it was a bad sending unit. One strange thing is that the numbers were different on the two sending units - bad one is AC 85M-220B-253M, good one is AC 95M-220B-253M. The 85 and 220 happens to correlate to the two extreme operations of the TCS system - below 85F and above 220F. Coincidence? I wonder if the one I replaced it with - the one that doesn't cause the fuse to blow with the 95M - is incorrect.

Anyway, even though the fuse doesn't blow, it still seems that I'm getting vacuum all the time. There are two 'out' vacuum ports on the TCS solenoid. Either one gives me vacuum all the time. You mentioned that you converted to ported vacuum. I'm assuming you have a carb with a ported vacuum source. Mine doesn't - it only has a manifold vacuum connection - no ported source since it is a 4-speed car.

Is there a way to check the solenoid to see if it's getting power? Warning - I'm an electrical novice. I do have a multitester, however.

[Carl]

You should have ignition power to one of the terminals on the solenoid. The other terminal should be the ground from the transmisson. Yes my carb has ported vacuum because it is from a 69 gto. forgot that 70 and up has no ported vacuum source. With power off you should not have vacuum threw the solenoid. The onlt time you should have vacuum threw there is 3rd and 4th gear. Is it the right solenoid for the car. Is it defective. Ther is a way to make a ported vacuum souce from that carb. Email me and i will give you all the details. Carl

[Leonard Welch]

An update...although by changing the TCS temperature switch the fuse doesn't blow any longer, I still get vacuum advance all the time. To diagnose the sitautiong:

Changed the TCS vacuum solenoid to see it it was broken. No change.

Changed the TCS transmission switch. No change.

Tested the voltage on the TCS temperature switch. No power when cold. Power does come on the blue wire when hot. That blue wire goes over to the TCS vacuum solenoid. Same thing. No power when cold. Power when hot. And I checked the power on the tab of the solenoid itself. So power is making it's way onto the vacuum solenoid.

I also disconnected the TCS transmission switch altogether to see if that was causing a ground all the time (which is what it's supposed to do only in fourth gear) No change.

At this point, I'm wondering if BOTH of my TCS vacuum solenoids are bad since power is making it to them but it's not blocking vacuum to the distributor. The service manual says that when the solenoid is 'energized', the vacuum advance should be blocked.

Is there a way to test and/or fix a broken solenoid?

I'm completely stumped!

[Rocky Rotella]

Leonard, to be completely honest with you, getting those components to work after all these years would be very tough to do. I'd have to agree with Carl in suggesting that you run it the conventional way to a ported vacuum source. I'd say that your solenoid is burned out, which isn't uncommon when dealing with 30 year old parts.

From a drivability and performance stand point, keeping it operational looking is fine, but actually using it is another thing. When people super-tuned their cars back then, that was one of the first things bypassed. Might be worth doing as well.

[BillS]

Leonard,

Some things to try,

Does your voltage tester have a continuity
scale? It's for testing resistance. The symbol for it is an omega symbol. If it does put it across the two terminals of the TSC solinoid. It should read just a few ohms (almost like just holding the two test leads together. If it reads alot or no change the coil in the solinoid is shot. If your meter doesn't have that scale you my be able to get around it.
When the car is warmed up and you have voltage on one side of the solinoid and don't on the other that could mean that either the solinoid is energized (working) and that it's the vacuum part that don't work or the solinoid coil is bad and can't pass voltage. The switch in the trans is closed at all times except in high gear that puts ground at the other terminal on the solinoid. A way to make sure the trans sw and connector and wiring are o.k. is to remove the connector from the transmission and find which one is for the TSC system and connect a wire from it to bare metal on the car with the car warmed up. If this doesn't make any sense or if you have any other questions please call (302) 831-3551

[Leonard Welch]

So I bought another NOS TCS solenoid switch. (That makes three now!)

So is there a way to bench test this thing out of the car? Meaning, is there a way to get it to do what it's supposed to do by introducing voltage to it? I do have a vacuum pump to make life easier. I'm not sure what kind of voltage it would accept...12 volts or less than that?

Also, which port should the 'out' vacuum hose be connected to? The service manual shows the one on the side with the one on the end plugged. Is there a difference between the two? The reason I ask is that I'm getting vacuum from the one that branches off the side all the time when the car is warm. (This is the one that the manual shows it connected to) When I reversed the connections - plugged the one off the side and connected the hose to the one on the end, I would only get vacuum passing when I grounded the terminal on the switch - sounds like that's the way it should work. So I'm wondering why there are two 'out' vacuum ports. Is one supposed to give vacuum full-time while the other gives it only when the internal plunger gets kicked off electrically?

[Leonard Welch]

Here's the latest...

I've performed more troubleshooting. I disconnected two of my TCS vacuum solenoid switches from the car and applied 12 volts to one side and a ground to the other. Both click and work as they are supposed to. The side vacuum outlet does not give vacuum when it is clicked 'on'. Then, I did the same thing on the car. An interesting difference, however. The switch would only click when I applied a wire from the solenoid black wire terminal to a ground on the firewall. All other times - when the car was warm and there was voltage going to the blue wire solenoid terminal - vacuum was being passed through the side vacuum port. Weird.

So I'm wondering. I know that the transmission being in 4th gear does 'ground' the system, allowing vacuum to pass through and at all other times (when the car is warm) the switch should be 'on' (clicked) and no vacuum should pass through. I can only get it to 'click' on when I ground the black negative wire terminal on the switch. Is that strange? I'm wondering if I have a ground problem. The block does have a new ground strap from near the TCS vacuum solenoid to the firewall that works fine. The only other modification that I've made is that I have a Mallory Unilite conversion kit under the stock distributor cap. That does have it's own grounds. I'm just totally baffled. Now I've determined that the TCS vacuum solenoid that I replaced works as it should. It's just that it won't do it's thing while on the car.

One more thing...I did get a 'normal' voltage reading at the blue terminal on the TCS switch when the car is warm.

???

[Half-Inch Stud]

Try a 15 Amp fuse. Then a 20 Amp fuse.

H.I. Stud

[Leonard Welch]

I should try different fuses even though my fuse-blowing problem is resolved? I'm an electrical novice - like you can't tell!

[Carl]

The ground comes from the transmission. It should ground the solenoid in 3rd and 4th gear. Not just 4th. If its not grounding check the switch at the trans with an ohm meter. The system is designed to give vaccum advance in 3rd and 4th gear only. dont take this the wrong way but unless you are going for a 100 point resto you are wasting your time. The car will run better if you go right to either ported or manifold vacuum. Your car will have better acceleration and fuel economy.

[Carl]

One more thing. Even if you get it working properly you only get advance in 2 gears. If you hook it up the way I said to you get advance all the time. Like I said better fuel economy and performance.

[Leonard Welch]

Good point!

But the way I understand it, in the absence of this system, the best way to connect is via ported vacuum, which I don't have in this particular carburetor because it's a 4-speed (7041263).

Right now, I get vacuum advance all the time so I've set the timing at 12 degrees BTDC at 600 RPM with the vacuum advance connected. Idles MUCH better but the performance is lacking.

Also, my service manual says that the system only gives advance in 4th gear and if under 85 or over 220 degrees.

I've thought about putting a 'tee' in the vacuum port that controls the break diaphragm but I don't want to mess around with that, thinking it may cause other problems.

?

[Leonard Welch]

One other thing I forgot to ask. So if I do leave it connected to the manifold vacuum port (back of the carb) what's a good timing setting?

The reason I ask is that when I set it to 12 degrees at 600 RPM with the vacuum advance disconnected (the procedure in the service manual) it shoots up to 800 RPM with about another 8 or 10 degrees. That's why I backed it down to 12 degrees withthe vacuum advance (manifold) connected. Should I just experiment incrementally with a lower limit of 12 degrees with vacuum advance connected?

[78 GHOST]

Leonard- IMHO I think you can get away with using a direct manifold fitting for the vacuum advance source.

I don't know why you shouldn't use the factory timing spec. on your BTDC setup unless you are having pinging problems. I forget your engine combo and what kind of compression you're running. I'd start at the factory spec. then adjust (only to retard) the timing as needed with a light.

Performance wise, you might be better off limiting the vacuum advance and going with more initial and mechanical. Vacuum advance is really a milege feature and should probably be called "Vacuum retard" based on the way it operates. Remember that when you step on it, vacuum drops, the vacuum advance removes the additional timing it added at high vacuum. This is why they say if everything is perfect, you'll hear 1-2 pings only after you hammer it then the pings go away and the car runs as well as possible.

A professional dist. curve would probably be your best route to improving performance.

Best of luck, Matt [img]/infopop/emoticons/icon_smile.gif[/img]

[Half-Inch Stud]

78 Ghost,

Perceptive note there.

My way of tuning the Q-Jet for high-compression relied on listening skills while swapping Primary Piston Valve springs [went firmer].

Secondary Rods were optimized at the track -DG.

I run the Prat-throttle enrichment topplates.

All of a sudden, that Q-Jet became the standard for all the rest of my Q-Jet builds.

[Leonard Welch]

PROBLEM SOLVED!

With the engine at operating temperature, I was able to ground the wire that connects to the transmission switch to the side of the transmission and heard the solenoid click on. When the solenoid clicks on, that is the state where vacuum is not permitted to pass through the side port on that back of the solenoid...no vacuum advance. This confirmed my theory that the normal operation of the solenoid is that when the system is grounded, no vacuum advance occurs.

That means that in every gear except 3rd and 4th, the system is grounded. In 3rd and 4th, there is a movement that takes place in the transmission that passes over the ball at the end of the transmission switch. This allows the ball to extend...breaking ground. At all other times, the ball is compressed and the system is grounded, preventing vacuum advance.

My problem? In addition to the other problems listed above, the transmission switch had a washer on it. This washer was too thick which prevented the switch from being compressed when it should have...which prevented a ground...which allowed vacuum advance at all times. Once the washer was removed, everything works when and as it should.

Awesome! Thanks for your help and if anyone needs assitance with this for their own setup, I'll be glad to help.