z22 vacuum help??

[Snoopy76]

I need some help... Well, maybe lots of help.... Anyway, i just purchased a 81 720 with a z22 engine, and I'm having issues getting it running. Sadly I dont have any repair manuals on this beast yet, so I thought I'd ask for some help from the people who might have the right answers. I purchased this fine vehicle from some redneck retreads who probably shouldn't be allowed to own tools. What seems to have been done is some of the vacuum circuits have been deleted. It also seems that some of the important carburetor parts have been misplaced. Sadly i haven't been able to find a thread here to help with what i need. What i need is a decent vacuum diagram, or pics of proper routing and placement of hoses. I would also like to ask for some decent pictures of the proper carburetor for this year and model. Any help would be much appreciated. thanks in advance.

 

BTW, it's a 1981 720 KC 4x4. I think it may be a CA smog vehicle, if the sticker under the hood is correct.

[datzenmike]

Try this one, I think it's for the Z22.

 

 

[Snoopy76]

Thanks for the great start there DatzenMike. I think im gonna have to run to Horrible Freight and buy a vacuum pump so I can test some of these circuits for proper function.

 

I have another question regarding the electrical/ignition circuits when trying to start the truck. when cranking the engine over it doesn't seem to be firing the spark plugs, but will sometimes catch and sputter along when I roll the key back to the run position. Could this be a problem with an ignition module? Or a relay?

 

One more question, which is the preferred repair manual, and where do people get them??

 

thanks

[datzenmike]

Pull the coil wires off the cap and stick a plug in them and lay on a grounded surface. Crank it over ... is there spark?? No sense chasing something that may be there.

 

A vacuum pump might check the hoses for leaks or just visually inspect them. Some vacuum hoses are only active when motor is warmed up and off idle.

[ggzilla]

when cranking the engine over it doesn't seem to be firing the spark plugs, but will sometimes catch and sputter along when I roll the key back to the run position

 

That's a wiring problem. It means it's not getting full voltage during starter draw, but the Voltage jumps back up when the starter stops. Maybe a partially corroded terminal somewhere.

 

Or possibly someone put a 620 ignition switch in the 720 -- it causes that exact symptom

[datzenmike]

Another is no power while cranking but it does in the run position when releasing the key. Check the coil + wire with a test light or meter with the key in the ON and START(cranking) positions. Should have 12 volts in both positions

[ggzilla]

yes, that's what the older switch causes. newer 720 IGN switch supplies 12V in both Start and Run positions.

 

Note is not the KEY cylinder, but the switch that bolts behind the cylinder.

[Snoopy76]

Ok, so after much parts chasing, and a little frustration. Some with my local Lithia Nissan, some with the local auto wreckers, and some with the parts houses, I made smoke today!!! And in a good way!! I'm kinda thinking my starting issue was a low battery, but I haven't done all the tests like you fine people have suggested. After charging the battery and changing most of the vacuum lines we got it fired up. It ran kinda rough at first, and was idling around 2000-2500 rpm. It also wouldn't run without the choke, or a hand partially covering the top of the carburetor. We kinda figured out some of the carburetor adjustments, and have it idling around 1200-1600 at the moment.

[ggzilla]

Nice to hear!

 

Adjust the choke so it starts cold and runs by itself. It shouldn't run without the choke with engine cold unless it's over 60 degrees outside.

 

Oh yes I forgot if battery is weak it will crank slowy and only catch when you stop cranking. Jump start time.

[Snoopy76]

Adjust the choke he says....... Did I mention some of the previous owners shouldn't own tools??? Somebody modified the choke, and it's now a manual choke. I'm trying to find some good forums on carb adjustment.

 

If I'm leaning over the passenger fender looking at the carb, is the idle adjustment screw in the lower plate between two vacuum ports? And the throttle adjustment screw is on the linkage, right?

[ggzilla]

That sounds about right.

 

Manual choke, just pull knob out to start, then push in partway immediately when it starts, then as it warms, keep pushing in more when engine starts loading up.