Ben85Z28

My car is a 1985 Z28 LG4 Canadian model. I believe the car is stock (previous owner was an older women that I knew). Is it possible that there is no ECM from manufacture? (because I don’t have one) Does this mean that my carburetor (Rochester Q-jet) and my HEI distributor are non-cc? There is only one electrical wire going to the carburetor on the passenger side (I think it’s for the choke – looks like a bowl on the side) Have you guys ever heard of this before? Is all this possible?

I followed the route of the electrical harness coming from the passenger side. There are only 4-5 wires in the harness. One is going to the alternator another one is disappearing under the distributor and one is going to the O2 sensor. There are two wires going to the driver side in what I would call a “vacuum sensor” on the firewall. From that sensor a vacuum line is going to the charcoal canister. What is that thing?

Last question. I want to get rid of that charcoal canister and all those vacuum lines related to it. Is this a good idea or should I leave all of this intact. I don’t have to worry about emission test anymore because next year the car will be 20 years old and no tests are required after 20 years. If I go for it can somebody tell me what I need to do with all those vacuum port on the carburetor? Cap them all off? What about the EGR valve?

Thanks guys!

five7kid

iTrader: (14)

Canadian LG4's by all accounts were not computer controlled.

Leave the charcoal canister in. It also vents the tank.

Ben85Z28

Thanks five7kid.

I guess it’s a good thing that the car is non-computer controlled. One less thing to worry about and troubleshoot.

Too bad I can’t get rid of the charcoal canister and all the vacuum line it would clean the engine bay and look much nicer. Isn’t there another way to vent the tank?

Anyone out there no what that vacuum thing on the firewall does?

Thanks!

84 Z28 5.0 HO

you can alway rerun them and hide them(as well as you can)

Ben85Z28

Nobody here ever got rid of the charcoal canister but kept the Q-jet and the intake manifold? If so what did you do with all the vacuum port?

83_1/2 L69

I don't think a non ECM, Canadian car would use an O2 sensor.

five7kid

iTrader: (14)

I missed that O2 sensor part.

The carb should have a solenoid for the two-stage accelerator pump. The power is switched by a coolant temp switch on the front of the intake manifold.

The "vacuum sensor" on the firewall is probably a temp switched vacuum to purge the charcoal canister. But, that's a huge guess, I've never heard mention of it before.

Apeiron

On the firewall behind the brake booster? It's the vacuum switch for the torque converter clutch if you have an automatic.

Peter82Z28

What can that make if it is not to connect?
What problem that can it bring?

five7kid

iTrader: (14)

Must "tee" to the canister purge vacuum source, then, correct?

Ben85Z28

I just double-checked everything and here how it is.

You were right 83_1/2 L69 there is no O2 sensor. The wire is connected to what I believe is a temp switch on the driver side head between the first two plugs.

five7kid the solenoid you are talking about could it be that “bowl shape” thing I was asking about in my original post thinking it was related to the choke?

About the vacuum thing on the firewall. There’s 3 electrical wires going to it then a vacuum line “teeing” on one side to the canister and on the other side to the coolant temp switch on the front of the intake manifold that five7kid was talking about. From there a vacuum line is going to the EGR valve.

83_1/2 L69

That should be the dash Temp gauge sender.

five7kid

iTrader: (14)

The conector is on the top front passernger side corner of the carb. Looks just like a CC carb mixture control solenoid connector.

Apeiron

I think so. I'd have to look at the VECI label on my car to be sure, which is kind of hard to do when it's 500 miles away, but as I recall it goes to a port on the vapor canister. Purge vacuum and EGR vacuum come from a TVS on the water neck, which may also have an electrical connector for the M4MED's double-capacity accelerator pump. There's also a vacuum delay valve in the ported vacuum line to the distributor, which may have it's own TVS, I don't really remember.

Apeiron

By the way, an excellent source of service information on the Quadrajet is available at: http://www.tocmp.com/manuals/Carbs/R...QJet/index.htm

Ben85Z28

Sorry, but the one and only connector on the carb is for the electric choke (thanks to Apeiron web site!!)


By the way how can I tell which model of Rochester carb I have (M4M, 4MV, ...)? The tag number indicates 17085580.

Apeiron

It's an M4ME.

Before 1970 Q-jet model numbers begam with 4M, after 1970 mechanical models began with M4M and computer controlled models with E4M. The next letter indicated the type of choke, E for electric, C for hot air and V for divorced coil. There can be another letter after that if it had the double-capacity accelerator pump (D), or an aneroid compensator (A), or a few other options, I think there was a C too, but I don't remember what it was for.

Ben85Z28

Thanks Apeiron for the info. BTW what is the purpose of the double-capacity accelerator pump and aneroid compensator? I'm asking the question because I am presently rebuilding the carb and notice that I don't have neither of them.

Apeiron

They appeared on some cold-climate or high-altitude models. The double-capacity pump increased the volume of the pump shot until the engine warmed up, and the aneroid compensator would change the mixture in response to changes in atmospheric pressure with altitude.

jess

about taking out the charcoal canister i have a 85 Z it dont have any emmisions left on it or a computer for that fact the gas tank has a vent in the top of it. it will run better with out all that crap.

but thats my to sense