Being fine cold and bad warm leads to the air/fuel mixture being too rich. You can run a rubber hose from a propane bottle up to the throat of the carburetor. Then while driving get the problem to occur and then turn on the propane slightly. If the engine picks up speed it was too lean, if it gets worse it was too rich.

 

That one video from inside the cab while driving, it sounds like a bad ignition misfire. It could be the carb, but doubt it.

If it were my truck, I would focus on the misfires. Check plugs, wires, cap, rotor, duaraspark box, etc...

Many times with weak spark it will run at idle, but as soon as you put a load on it and raise combustion chamber pressure, the spark that was marginal at idle will be totally insufficient under load.

 

Hey, thanks in advance! Its my feeling to, ill check the whole ignition on tuesday.
Any good Suggestion for the spark plug?

It does a lot of missfiring when the car is cold and i but a little more throttel (more than 30% i would guess). IT was always like the and the Phänomen disappeared when the engine was getting little wärmer. Where could it come from?
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Ill also check the carb things as written above.
I also got the feeling it could be a problem with the fuel supplie because i had slightly equal Problems with a Harley when the internal fuel tank Filter was dirty.
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​​​​​​Here the plugs, same Layout like they are assembled. Anything to See I dont recognize? For me looks ok.

 

They look fouled to me, with modern gasoline blends spark plugs should burn very clean. It takes some experience to distinguish between different fuel, oil, and ignition characteristics, but the spark plugs always tell the tale.

There is oftentimes no magic wand or silver bullet or a simple tweak of the idle mixture with the golden screwdriver to make everything all better again. Each individual carburetor circuit should be checked, check for a good HOT spark at a plug grounded to a cylinder head bolt. What # spark plug? Sudden rough running and over-rich fuel condition are sometimes a result of a failed power valve (economiser) diaphragm. Rubber components sometimes fail quickly. There are many different things to check, this is why I emphasize the need for the shop manuals and carburetor diagrams, and an organized step by step approach. Fouled spark plugs will not fire reliably.

 

In the next to last picture, the vacuum advance port on the carb is not hooked up. On another picture, the vacuum advance hose is hanging down in front of the water pump. That indicates what the timing problem may be related to. Also, have you been running the truck with the PCV hose disconnected for a while? If the oil soaked plugs came from the passenger side bank, that also could be part of the problems. But, hook up the vacuum advance and it will make a world of difference.

 

Hey, could you Mark it in the pictures, I dont get it.
As it looks for me, everything is connected...

As i understand, just 2 out of 3 habe to be plugged because one is for Emission Controlled vacuum advance and the other one for Not Emission Controlled vacuum i guess?

 

I see what Dan was saying Steven, and have a couple of questions of my own as well about all three images.

In this first image, is the hose I have circled in fuschia a water hose? Is this one, along with the one in the last image connected to the heater hoses and to the spacer under the carb? That's what it looks like but I've not happened to see one on one of these vehicles before.
If so, it's just for cold weather running and might be a good thing.

And just a comment, but it looks like someone created the throttle linkage rod out of all-thread rod. This is not a real problem that I can see, especially if it works. But am just pointing it out so that, along with the carburetor, you know it's not original.

The oval shaped hole circled in orange usually has a rubber plug in it.
The port on the carburetor circled in pink is what Dan was referring to, and must either be capped/plugged/closed, or attached to a tube to the vacuum advance. Where does the hose from the front of your vacuum advance attache to the carburetor?
The green circled hose is just a coolant hose like I was mentioning before?
And a big question here, is the device circled in blue just a hollow fitting? This is where the PCV (positive crankcase ventilation) valve should go and is VERY important here. If this is just a hose with elbow fitting then this is a huge vacuum leak and will cause some of your symptoms. I would say take it apart and find out what is under all that rubber hose and clamps.




Finally, this is the other half of your PCV system. It is where the clean filtered air is allowed into the engine while the dirty air from inside is sucked out through the PCV valve in the other valve cover and mixed in with the fuel/air mixture.
From the factory this is attached to the air cleaner housing directly. Because you have an aftermarket air filter it looks like they just left it off. In this condition is it sucking in dirty air and can damage the engine over time.
See if there is a fitting on the underside of the air filter housing that you can attach it to. If not, I would create one. Or in a pinch you can simply attach a filtered cap to the end of the hose temporarily to keep the air clean.


The PCV system is one of the most important for the long life of your engine. It keeps the contaminants inside to a minimum.
If you do not have a valve in the driver's side cover with all that tubing, you should get one as soon as possible. In the meantime, you can disconnect it from the carburetor and cover the vacuum fitting. Or just plug up the tubing somehow. Then start the engine and see how it runs.
With the tubing blocked so that you no longer have a big vacuum leak, my guess is that the engine will run very differently.
Hopefully there is a PCV valve inside that tubing, but if not I would order one right away.

Paul

 

HI,

thanks for the answers and for the effort to edit the pics. The Blue L Fitting is just a connection which goes from the carb into the blue cover.
The advanced air is connected, it was just disconnected to check the ignition forwarder.

Now everything is connected and cheked and has the same status as it is was before the problem did appear.
Timing is checked an improved a little bit as well.

What I have done so far:

1. compression test -> everything is normal
2. checked the cylinder`s -> no cracks, no damages
3. checked the carb -> no cracks, no damages, no dirt
4. checked the fuel line comming from the pumpe with/without filter
5. checked the timing and adjusted it a little bit

What i guess....:

problem with the fuel supply. I just looked in the fuel tank and found a old rubber ban. I also see a the yellow ball of a "suprise egg"???
Maybe the stuff is closing the intake when it is sucking due to more consumtion.
This would explain, why the first couple of seconds of turning up and acceleration are normal.

Ill check this soon, if it does not change anything I have no idea what to do next....???

 

One way to check for fuel delivery problems.
Get a can of gasoline and clamp it in the bed of the truck, hook up a hose from the can to the fuel pump To by-pass the fuel system and take it for a ride.

 

Then you must replace it with a proper PCV valve for your, or similar engine.
Temporarily you must block it off. Remove the tube and plug it with a bolt, or if you have a vacuum "cap" you can remove the tube from the carburetor and cap off the fitting.

As an experiment, leave it connected, but plug the opposite tube (the one on the other side, in the last picture near the air cleaner) and see if this changes how the vehicle runs.
But either way, you need a properly working PCV valve.

What is the other hose connected to?
In your picture, the fitting on the left already has a rubber hose, while in the picture the fitting on the right does not. You said that now there is a hose there for the vacuum advance. I'm just curious what the second hose is for.

Now you may be on to something! Would love to see pictures of that too if you can get them? Those were great images of the pistons before, can you use the same tool to show inside the tank?
Thanks.

Good luck. But get a PCV valve no matter what.

Paul

 

Have you changed your timing chain? Stock ones had plastic teeth that would brake off and leave you with a bunch of slack. This guy gives you an easy way to check the slack.

 

Checked and OK!

I uploaded a new Video.
I removed the yellow ball and a old rubber tape from the insinde of the fueltank.
I was able to have a not proper right to the gas station (around 3 miles). The Problem still exists.

As you see in the video, it looks like there is something with the fuel supply. Couple of seconds acceleration are quiet ok, after that, problem appears.

I DONT KNOW WHAT TO DO NEXT

 

If you want to diagnose your thought of “low fuel”, you can do a couple things.

1. Get a can of gas. An outboard motor gas tank is handy for this. Tie down can in bed. Run a fuel hose from that new can to inlet of fuel pump.
2. If no change in number 1, check fuel pressure from fuel pump. You will need to find proper specification, then see if you have it. Fuel pumps can go bad over time.
3. If number 2 checks out, then you may have a restriction from fuel pump to carb. Check it all over.

Cannot remember (while typing this) what carb you have. Depending on carb, you could have a helper run motor until it is “low fuel condition”. Then shut off, while you immediately pull fuel line from carb. Then check level of fuel in float bowl. If low, then you found your root issue.

Just remember KISS (Keep It Simple Stupid). Engine needs fuel, air and spark. Try and keep diagnosing simple and try not to go down rabbit holes. Very rarely is the problem something “esoteric”.

Good luck!

 

Please do as I said on post #24 and the one above. Another thing that would be of help is to have a fuel pressure gauge connected in line between the fuel pump and carburetor so that the fuel there should be at least 4-5 lbs of pressure at all times.
I had a marine repair shop for 35 years and this was the only way to diagnose a fuel delivery problem sometimes.

 

I got some pressure gages, so i can just but it in between with a t connector? Does that work?
First i will check all the tubes of the fuel System and go on from there...
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