1983 720 Z24 Power Issue

[AustinSink1]

Hey there,

So I have a 1983 720 4WD with a Z24 motor. Everything is completely stock on the engine. I don't know how much power these trucks are supposed to make, but this one is just slow. I mean slow. On hills, it can barely hold 45. Sometimes it drops to about 40 then you have shift into 3rd to make it up. If you are cruising in 5th at 55, and come to a hill, neither 5th or 4th will hold 55. You will drop down to around 50 with your foot on the floor. Does this seem accurate to what these trucks are supposed to be putting out? I understand its a small engine and being 4wd has a little more weight to move, but I would at least expect it to maintain steady speed. Is there anything I can do on the current setup, or should I consider swapping to the Weber carb?

 

If you need pictures, I can get some uploaded of the truck.

 

[datzenmike]

No, they're capable of any freeway speed. In no order some things to check are....

 

1/ Look down the carburetor with a flashlight and depress the gas pedal. Is the throttle butterfly opening fully, Is the throttle cable too loose?

 

2/ With the throttle at least half way open, pull up on the vacuum secondary linkage. It's the round thing on the bottom right with the cone shape on the bottom in the picture below. The rod sticking out the bottom should be stiff but free to push upwards into it. If it won't move chances are the secondary won't open because it's stuck.

 

3/ One at a time pull one intake and one exhaust side plug wire off and put any old spark plug in the end. Lay the plug on a grounded surface and try starting the truck. Are both sides intake ans exhaust side plugs firing??? If only one side check the first fuse on the left side of the fuse box.

3a/ Is the ignition system in good shape? Wires clean, plugs clean and gaped? (use only NGK BP6ES intake and BP5ES exhaust) Distributor cap and rotor clean and free of moisture, cracks or carbon tracking? No carbon tracking on the coils?

3b/ Timing at 5⁰ ?

 

4/ Head gasket may be blown. This is a common problem on the Z24 but it is preventable after it's fixed. Does this engine need to have the coolant topped up regularly? Is the oil gray or milky color? Is there unexplained steam in the exhaust? does it smell like antifreeze? A compression test may show two adjacent cylinders with low numbers.

 

5/ Has the valve lash been checked and set? to 0.012" on all?

 

6/ Has the fuel filter been changed? in the last 3 years?

 

[AustinSink1]

1) How far open should the butterfly be. Should it go from flat to vertical?

 

2) The secondary appears to be bone dry, but I can push up on it when throttle is half way. It is stiff, but it does move and I hear a compression sound in doing so. 

 

3a) All plugs and wires have been replaced. They were not gapped however. The distributor and distributor cap were also replaced. 

 

3b) Timing was upped from 3 to 5 at idle.

 

4) I do not have to add coolant regularly and oil looks fine. Have not done compression check however. 

 

5) Valve lash has not been check or set.  I do not know how to do that. 

 

6) Fuel filter and most fuel lines have been replaced in the last few months. 

[AustinSink1]

1) Update. Yes it is wide open. The second butterfly does open as well when pushed. Is there a way I can check to make sure that fuel is actually entering the second barrel?

[datzenmike]

Throttle plate should go vertical.

 

Check your wires all go to the correct plugs, it's so easy to mix them.

 

 

It's hard to get enough load on the engine without driving it to see the secondary open. Have someone with ear protection watch the linkage on the vacuum diaphragm (the round thing with the cone shape bottom) Rev it up, then suddenly hold the throttle wide open...... if you have a tachometer, not above 6K. The secondary should pop open briefly.

[AustinSink1]

Okay, will give the secondary trick a try. Plug wires were all in correct positionings. Throttle plate opens all the way, and linkage all moves ad it should. Waiting on engine to cool down, then will do a compression check. Will update results here. Thanks for the help so far!

[datzenmike]

One other thing first. I re-read you forst post and there is another possibility. The secondary jet may be plugged. It's hard to get at on the vehicle.

 

They are on the front of the carburetor under a plug with the primary away from the valve cover and the secondary closer to. Once the cover plug is unscrewed a narrow screwdriver will lit up inside. I ground down a stubby screwdriver and got them out but it wasn't easy on the car.

 

The jet looks like this...

A primary will be around 100 and the secondary around 170. Use something soft like a toothpick to dislodge anything plugging it.

[AustinSink1]

Compression results were good. 

1) 160 psi

2) 150 psi

3) 160 psi

4) 150 psi 

 

In order to check the secondary fuel jet, if I am looking at the carb where do I begin?

https://imgur.com/3f7Mb4m

[datzenmike]

 

The hex plug on the right is for the secondary jet.

[AustinSink1]

Okay, just trying to get a time estimate to see if I can attempt this today. How long would you say it takes to unbolt the carb, clean the jets, put carb back on?

[datzenmike]

Probably an hour. I think they are way easier to get at on the Z series engine. Say under 2 hours to be safe. Charlie69 would probably know.

[AustinSink1]

Won't have time to take it off today, want to give myself plenty of time since I've never done that before. However It appears my carb may look a little different than yours. From what I could see/feel I don't have two big hex plugs like that on the bottom. There is some sort of plate with a single Philips. Sorry if I'm asking simple questions, I'm just a highschooler trying to fix up an old truck and learn a thing or two. So I really appreciate your time. 

[datzenmike]

That picture was an L series carburetor but identical to the Z series in placement of the jets.

 

I think I have seen that before, a single screw holds a single cover for the jets. I only have one Z24 carburetor and it's a Candian one.

[AustinSink1]

Ahh, That would make sense. Will do this either tomorrow or Tuesday and update here. Hopefully it's clogged and my issues will be fixed. My great Grandpa bought new in 83. Been in a few fender benders, then sat for about 10 years in a field. I recently picked it up and started bringing it back to life. Got it mostly daily drivable except for power issues and various oil leaks.

 

https://imgur.com/uQt8z9Y

Edited May 25, 2020 by AustinSink1

[datzenmike]

Valve cover is most likely. Oil sender switch under intake above the oil filter can fail and drip, oil pan gasket.

[AustinSink1]

Haven't cleaned jets yet, but I believe we are making progress. On my way to work, it kept breaking up when floored under load. My guess is that the second Barrel was stuck, now that I freed it up from messing with it, it is opening properly. However, since no fuel is coming in that barrel, that's why it's breaking up. Just my assumption. 

[AustinSink1]

Took carb off, got to the jets. Both look clean, nothing clogging either. Put it all back together, still low on power and breaks up at full throttle. 

[banzai510(hainz)]

This is a Hail Mary but rev up the motor pretty good and put your hand on half the carb the main barrel and the 2ndary side vaccum should open the flap.

 

whay  could do with a stock 521 I would get it to run on the 2ndary side once I got the motor up to speed and hold the flap open on the secondary. then I fure it was good.

 

Maybe its getting stock . if anything the looses it spring strength and they prematurely open to soon causing a BOG OUT siutiation.

 

Is this distributor timed correctly?????????Yu try a timing light?

 

cat converter plugged?

 

I see lots of emission hose on this????????????

Edited May 28, 2020 by banzai510(hainz)

[datzenmike]

 

1 hour ago, AustinSink1 said:

  Put it all back together, still low on power and breaks up at full throttle. 

 

Shouldn't break up. Sounds like ignition.

[AustinSink1]

Let me be more specific on my last post. It will rev fine in neutral. Once your driving, all good until 3rd, 4th, and 5th. In those gears, if you put the throttle to the floor, the engine pretty much just cuts out. Barley firing and shaking quite bad. I can try and get a video uploaded if that helps. 

[banzai510(hainz)]

fuel filter???? under load?????

 

Vacuum advance stuck, distributor shaft wobble(im really just guessing now)

 

Edited May 28, 2020 by banzai510(hainz)

[AustinSink1]

Distributor was replaced, so shouldn't be any issues there. Timing as adjusted and carb was tuned by a guy I know that use to work for Dale Earnhardt, so shouldn't any issues there.

[datzenmike]

Well that sounds like no gas.

 

Take for a drive and floor it till it cuts out. The rest you have to do very quickly....

 

Turn the ignition off as fast as possible and get into neutral and pull over to the side of the road. Naturally do this away from traffic where you can do this safely. What I want is to preserve exactly what gas is in the carburetor when this happens. You have an electric fuel pump so it has to be turned off when the problem is happening not later or it will fill the carburetor up.

 

Once safely parked look for the small round glass window on the front of the carb. Can you see the gas level? Where is it????

[AustinSink1]

So when I put the carb back on, running it and idling it, the fuel in the window was below the half way mark. So maybe it must be low on fuel, the question then is how do I get it more fuel?

[AustinSink1]

Took carb back off, adjusted the float, it wasn't level when I opened it up. Re assembled and fuel is still below the dot.