Boat engine backfire, with sound clip.

[KeepItSimpleStupid]

That smoke seems to be too much fuel when accelerating. A faulty accelerator pump is usually really bed hesitation.

Check the vacuum hoses.

With the head rebuilt, it's possible that the carb needs to be adjusted. There is a really easy way of doing it correctly the first time.

The general problem is that the throttle position sets the idle system and it's difficult to uncouple the two.

Get yourself a small propane torch and cut the torch part off. Attach an on/off ball valve and then to vacuum hose size.

You want the engine at operating temperature if possible. The choke needs to be fully open and not in fast idle.

Attach the propane to manifold vacuum. Turn off both propane valves. Attach a tach. Start the engine.

On/off valve on. Add propane so you reach max RPM. Too much will decrease RPM,

Basically what you want is the ability to be able to turn on and off the propane and get very little change in the RPM (i.e 25 RRM) at the idle speed. You will be adjusting the mixture and idle speed screws to attain this.

Once you have that, the throttle plates are positioned in the idle system.

A primer:

When the engine is cold. A push on the accelerator will close the choke and set the fast idle cam.
if the engine is warm, the fast idle cam doesn't get set.

As the engine warms the heater on the carb and/or a linkage to the manifold temperature slowly starts to move the fast idle cam.

When when car starts, the "choke unloader" is pulled off by a vacuum linkage. This opens the choke plate a small amount. That could cause more fuel if the unloader is not functioning. Usually it's a diaphram attached to full engine vacuum that yanks on the choke plate/

Some cars added heated air to the air cleaner controlled by a vacuum door.

All of the mechanical stuff has to set first. fast idle cam. choke unloader. As the car warms up, the fast idle cam moves.

Finally, wide open throttle opens the choke plate independent of everything. That's your flooding fix.

So, the hardest part is getting the throttle plate positioned so the carb is in the idle system. if you enrich the mixture there should be no change in idle speed except for the fact that you can add too much propane and drop the RPM.

You start with the suggested initial mixture settings. Full seat and back off x.y turns. (e.g. 1.5 turns)

EVERYTHING HAS TO WORK TOGETHER.

 

[KeepItSimpleStupid]

I had one of those engine fires too. I had a Holly Economaster Carb and occasionally, the accelerator pump linkage would fall off..
Ended up with fuel in the engine compartment somehow. I grabbed my jacket (which i still have BTW) and smothered the fire I did damage the jacket. The propane enrichment WAS REQUIRED to get that carb working,

 

[SimonTHK]

That smoke seems to be too much fuel when accelerating. A faulty accelerator pump is usually really bed hesitation.

Check the vacuum hoses.

With the head rebuilt, it's possible that the carb needs to be adjusted. There is a really easy way of doing it correctly the first time.

The general problem is that the throttle position sets the idle system and it's difficult to uncouple the two.

Get yourself a small propane torch and cut the torch part off. Attach an on/off ball valve and then to vacuum hose size.

You want the engine at operating temperature if possible. The choke needs to be fully open and not in fast idle.

Attach the propane to manifold vacuum. Turn off both propane valves. Attach a tach. Start the engine.

On/off valve on. Add propane so you reach max RPM. Too much will decrease RPM,

Basically what you want is the ability to be able to turn on and off the propane and get very little change in the RPM (i.e 25 RRM) at the idle speed. You will be adjusting the mixture and idle speed screws to attain this.

Once you have that, the throttle plates are positioned in the idle system.

A primer:

When the engine is cold. A push on the accelerator will close the choke and set the fast idle cam.
if the engine is warm, the fast idle cam doesn't get set.

As the engine warms the heater on the carb and/or a linkage to the manifold temperature slowly starts to move the fast idle cam.

When when car starts, the "choke unloader" is pulled off by a vacuum linkage. This opens the choke plate a small amount. That could cause more fuel if the unloader is not functioning. Usually it's a diaphram attached to full engine vacuum that yanks on the choke plate/

Some cars added heated air to the air cleaner controlled by a vacuum door.

All of the mechanical stuff has to set first. fast idle cam. choke unloader. As the car warms up, the fast idle cam moves.

Finally, wide open throttle opens the choke plate independent of everything. That's your flooding fix.

So, the hardest part is getting the throttle plate positioned so the carb is in the idle system. if you enrich the mixture there should be no change in idle speed except for the fact that you can add too much propane and drop the RPM.

You start with the suggested initial mixture settings. Full seat and back off x.y turns. (e.g. 1.5 turns)

EVERYTHING HAS TO WORK TOGETHER.

I see that you write, that a push on the accelerator will close the choke, does it normally close the choke, when you accelerate?
Thank you

 

[shortbus=]

The general problem is that the throttle position sets the idle system and it's difficult to uncouple the two.

Thank you for explaining this. Many people that don't know keep moving the idle speed screw to keep an engine running, then readjusting the idle screws. But by not having the throotle plates where they belong to start off with, the transition jets/ports are exposed and not doing their job as designed. So the engine stumbles on acceleration.

The carb has a "beginning" set up, so many turns on the idel screws and so many turns on the idle speed from throttle blades completely closed. With those not set correctly you can't even begin to make thing right, tune up wise.

 

[SimonTHK]

Thank you for explaining this. Many people that don't know keep moving the idle speed screw to keep an engine running, then readjusting the idle screws. But by not having the throotle plates where they belong to start off with, the transition jets/ports are exposed and not doing their job as designed. So the engine stumbles on acceleration.

The carb has a "beginning" set up, so many turns on the idel screws and so many turns on the idle speed from throttle blades completely closed. With those not set correctly you can't even begin to make thing right, tune up wise.

A stumble on accelerating, would that also be a backfire or BANG with smoke outta carburator?

 

[Pommie]

Assuming multi cylinder and multi coil, this is exactly what I experienced on a land cruiser and it turned out to be a faulty coil. Just saying.

Mike.

 

[SimonTHK]

Assuming multi cylinder and multi coil, this is exactly what I experienced on a land cruiser and it turned out to be a faulty coil. Just saying.

Mike.

Has also been changed!

 

[shortbus=]

I'm going to ask a question that's not been asked yet, what make of engine is this?

After watching the video again, I'm going back to my earlier diagnosis of a bad camshaft. One or more of the exhaust lobes is worn out. Or the timing chain is off one tooth. Really hard to diagnose something from a bad video at a distance.

 

[gophert]

I'm guessing a vacuum leak. Check all vacuum hoses. Also look for exhaust manifold leak (easiest at night looking for a slight glow). If the valves were just replaced and the head was off, then a reassembly error is a likely cause (forgotten vacuum hose or lose vacuum hose or failure to replace the exhaust manifold gaskets).

 

[SimonTHK]

SOLVED
I dunno what it is called but not CDI. But still something that controls the timing. I belive a CDI does not require a power distributor, which is on this machine.
So it has a power distributor and hall sensor. So some kinda CDI part, thatis called ignition module. Like this:
**broken link removed**
Almost similar.
Also it was allready tested with 2 similar but not completely alike ignition modules. These and like CDI´s has to be the exact correct model to work.
Thank you all for you time and help.
Best regards Simon

 

[KeepItSimpleStupid]

shortbus= The Propane enricement method of adjusting mixture was in the Holley Carb manual.

I think I used it 3x when re-built carbs:
1) 1968 Chrysler 8cyl
2) 1965 Ford 6 cyl. The simplest of all.
3) 1973 Chevelle 8 cyl Holley Economaster replacement carb
4) 1982 Celica. 4 cyl That carb had nearly 120 parts and you had to drill out the mixture caps. I made one mistake and I had to take the carb apart again. Float valve was loose so the bowl would not stop filling. original problem - an internal port had a piece of vacuum port in it.
Extremely complex carb,

 

[shortbus=]

I always just did it the old fashion, set it for factory set up and tune from there.