First drive in the Z, Backfiring and sputtering.

[messenger]

Well as some of you may have read I picked a "72 Z a few weeks back. The car sat for 5 years in a garage. I got it towed home changed all the fluids, got a new cap, rotor, plugs, wires, fuel filter.

The car started right up and ran great. I drove it for about 5 miles and it was running like a dream. Then it was like someone flipped the "run like $^!# switch". First the car started to really hesitate and fall on it face under part throttle, then it started to back fire under throttle. It would run ok under steady throttle, not great by anymeans but good enough to get me home.

I think that the car is running a bit rich. The orginal plugs I removed looked pretty fouled out. When I got home I pulled the new plugs that had about 5 miles on them, they where all ready pretty sutted up looking. Plus the back fire under throttle leads me to believe richness.

I checked the timing that seemed to be in check.

My first assumption is that something is wrong in the carb department. The thing is I don't know jack $^!# about carbs really. All the cars I have had prior have all ben fuel injected controlled by afc's.

I have done some reading up on adjusting the carbs, it seems a bit foreign to me right now. One more small note I did check the fluid level in the carbs and it seems to be in check.

What do you guys think is going on?

[Zedrally]

Are all the plugs fouled the same?

Also try a compression check, after all the sitting a ring may have frozen, causing oil fouling.

[MikeW]

It's possible that one of the carb float bowl needles is stuck causing you to not get any fuel to half of your cylinders. Do all 6 plugs look the same?

[EScanlon]

....."72 Z ............ car sat for 5 years in a garage. I got it towed home changed all the fluids, got a new cap, rotor, plugs, wires, fuel filter.

The car started right up and ran great. I drove it for about 5 miles and it was running like a dream. Then it was like someone flipped the "run like $^!# switch". First the car started to really hesitate and fall on it face under part throttle, then it started to back fire under throttle. It would run ok under steady throttle, not great by anymeans but good enough to get me home.

STOP!!

BEFORE YOU ADJUST YOUR CARBS AND GET A MORE SERIOUS PROBLEM.

That it "started right up and ran great" then shortly thereafter "someone flipped the 'run like $^!# switch'", to me, is a clear indication that something ELECTRICAL is what's wrong.

The only thing you haven't checked is if it will IDLE ok, but just not let you accelerate unless you do it V E R Y S L O W L Y. if THAT is what it is doing, your problem is in the Distributor Vacuum Advance plate.

This little plastic plate with a couple of ball bearings on it, is what the vacuum advance solenoid actuates. When this goes bad, the exact symptoms you describe happen.

Take a look at that BEFORE you go making adjustments everywhere else.

2¢

Enrique

[messenger]

Thanks for the replys this far guys. I got home late its dark here so I only pulled one plug out. I will pull all 6 tomorrow to take a look. I also plan on doing a compression check.

Mike, Im not familiar with the frozen ring theory. Do you mean the ring froze to the cylinder wall while the piston kept going? Thus I am missing a ring?

Enrique, How would i be able to tell if the distrubutor vaccum plate is bad?

I forgot to mention one thing. This may or may not discredit the distubutor plate diagnosis. The first night I got the car I was dying to start the car up. So I checked all the fluids topped them off got a new battery and it started up. It was running slightly rough. I never drove it like this, I just started it and let it run for a few minutes and revved it up to about 3 grand. It did seem to miss or hesitate like it is now, of course I can't be 100% sure it was the same problem as I did not drive the car like that.

Once I did the tune up the missing and hesitating went away........... well for a little while.

[Zedrally]

Gee, isn't it difficult to advise someone when you know precious little about the car in question!

Zeds are like women, they need TLC, this will be the start of a life long affair, sorry to hear it hasn't started off with a bang!

Messenger, where all having a stab in the dark here. Problems that have been known to create running difficulties,these may not be the solution or in the worst case scenario, they all may be...hope not in this case.

Try a compression test first, should be around 160/180 IIRC in all cylinders.

It's really the difference between the pots that will give a ring problem away. Remember though, fouling if equal between all plugs would indicate rich running, although 5 mins and fouling would indicate something more serious such as a ring or valve stem seals. The comp test will give you a much better idea as to where to go next..

Good luck

MOM

[seerex]

I had the same issue twice , did it start running poorly just after the choke was turned off < pushing down the choke handle? If so you might have it stuck and that will give you that kind of issue somewhat . Also check the gap in the points as well as the points , acts just like that. Good luck

[Bambikiller240]

When you changed all the fluids, did you drain ALL of the gas out of the tank, and lines, change filter and replentish with fresh gas? Sounds to me like possibly a fuel problem from sitting for so long with stale gas.

[Fun_in_my_z]

Thats what i was thinking Carl 5 years is a long time to leave gas sitting

[messenger]

I did not drain the tank. I know I should have, but I guess i just figured hey the car started right up on it its fine. There was maybe only 1/2 gallon of old gas in the tank im pretty sure I idled through it before I even drove the car. It does have a few fresh gallons of 93 and redline fuel system cleaner in there now.

I just pulled all the plugs, they where all sooted pretty evenly. They were gapped at .030 I just regapped them to .040, I was reading that helps in over rich conditions.

I checked the distrubutor vaccum plate. It seemed to work fine, I sucked on the hose and it moved roughly .125 or so.

The car still idles and runs like &#036;^&#33;# this morning.

Can anyone point me in a good spot that has info about the points on these cars? Basically how to adjust them. Ive done some searching but have not found much.

Thanks again.

[Bambikiller240]

1 question, how do you arrive at a estimate of fuel in the tank? How much of that old gas was jelly and rust, crud, etc (that could now be plugging your fuel lines and filter? In addition to the filter on the passenger-side engine bay, there are filters in the (both) inlet fitttings at your carb float bowls.

Setting points is pretty basic stuff, if you have a dwell meter, and timing light. Any shop manual (Factory, Haynes, Chiltons, etc) should have it. It's a bit difficult to describe briefly in a forum.

[messenger]

I arrived at that estimate by looking at the gas gauge, it read below E and it does work. I also shook the car and listened to the gas slosh around in the tank. It is defitently and estimate but I think it was a decently accurate one.