Hi everyone,
Just finished cleaning my 69' 500L carburetor. Changed gaskets, washers, filter, and that delicate thing that is pressed under the float.

Did everything by the book (as much as I am aware). The process was pretty smooth, used carb cleaner and a tooth brush to clean.

When I put everything back together and tried to start the engine, it sounded like a tool fell inside the engine and is rattling inside. Needless to say that the engine is not holding for more than a few seconds.

Link to video:

https://drive.google.com/file/d/1oh3xlgWy-gDeCOUiM3MF3NPP_Uc903WA/view?usp=drivesdk

Any ideas? [emoji20]

Did you cover the intake hole with a rag when you took the carb off? See if you can get access to a flexible shaft camera and take the plugs out and have a look in the cylinder head. Did you take the valve cover off? Look for something that may have dropped in the rocker area. I would also remove the carb and check for anything missing no matter how small. Especially look for 2 small screws holding the butterfly flap to the spindle. There’s not much else that can fall from the carb. I’m only recommending this because it’s the last thing you were working on.

Having said that it sounds more like something is down in the fan impeller and getting flung around. I would expect the noise to be more rhythmic if something got sucked into the engine. Might be a nut or washer that dropped in there. Did you have the rubber plug covers off or do you even have plug covers installed?

Regardless of the cause I would not run the engine again until you find it.

Veloman518 said:

Did you cover the intake hole with a rag when you took the carb off? See if you can get access to a flexible shaft camera and take the plugs out and have a look in the cylinder head. Did you take the valve cover off? Look for something that may have dropped in the rocker area. I would also remove the carb and check for anything missing no matter how small. Especially look for 2 small screws holding the butterfly flap to the spindle. There’s not much else that can fall from the carb. I’m only recommending this because it’s the last thing you were working on.

Having said that it sounds more like something is down in the fan impeller and getting flung around. I would expect the noise to be more rhythmic if something got sucked into the engine. Might be a nut or washer that dropped in there. Did you have the rubber plug covers off or do you even have plug covers installed?

Regardless of the cause I would not run the engine again until you find it.

Click to expand...

Thanks.

I had only the carburetor off and covered the intake and the passage from the air cleaner. I'm trying to understand what could be dropped and can't think of anything that I have used.

The plugs have the rubber covers and stayed on during the entire time.

Do you have a picture of these two screws holding the butterfly flap? If they were to get lost, wouldn't the flap just fall out?

What is the easiest way inside the fan area?

Tomer

If only one of the screws holding the butterfly intothe shaft fell out, the other screw would still retain it in position. To get at the fan, you remove the top cover, but to see right into the fan shrouding, the rear section of the shroud needs to be removed---it is an 'engine out' job.
I completely agree with Joe (Veloman)--you need to find the cause before you run the engine again, and again as he suggested, if something dropped into the engine, you would expect a more continuous, rythmic noise--it does sound like a something is being spat-around on an irregular basis.

tmrsgv said:

Thanks.

I had only the carburetor off and covered the intake and the passage from the air cleaner. I'm trying to understand what could be dropped and can't think of anything that I have used.

The plugs have the rubber covers and stayed on during the entire time.

Do you have a picture of these two screws holding the butterfly flap? If they were to get lost, wouldn't the flap just fall out?

What is the easiest way inside the fan area?

Tomer

Click to expand...

I don’t have a picture handy but it will be obvious if you look at it. The flap slides into a split on the shaft and there are 2 very small screws holding the flap in place. They are readily visible. If you see daylight through one then the screw is missing ?. And as Tom pointed out if one is still tight the flap would stay in place more or less. You’re probably going to need to pull the carb anyway to look around so may as well check this. And to do that you need to pull the valve cover where I would look thoroughly again for a loose washer or some such that may have landed in there.

The reason I’m thinking impeller is it sounds like something being thrown and then working it’s way back down to be thrown again. It may eventually jam itself in the impeller and then you have big problems.

I bought an inexpensive bore camera from Depstech on Amazon. It has a few feet of flexible fiber optic cable and connect to an app on your phone (or tablet if you have old eyes like mine) via WiFi. I had actually dropped a nut inside mine and used the cam to find it and it has a magnetic tip as well so fished it out. Handy little tool.

Ok. A fiber optic camera is a good idea.
I'll try to get one, take off the carb and look if something is there.

Hope to update soon

*update*
Took off the carb and tried to probe with a flexible magnet and flashlight. Seems like there's nothing in the intake.
Question 1: if a m6 washer fell to the intake, there's no possibility that it got inside the pistons, right?

Taking your advice, considering something fell and got to the fan impeller, I'm trying to figure out how it might have gotten there.
So I don't really understand the airflow path from the fan impeller to the piston cooling fins and to the air filter.
My best guess at the moment is that there is a clear path between where the spark plugs sit to the fan impeller. There are the spark plugs rubber boots but they do not completely cover the opening.
So... question 2, is it possible that something fell through that opening and got dow to the fan?

Attached two pictures, does it make sense?

Thanks!

tmrsgv said:

*update*
Took off the carb and tried to probe with a flexible magnet and flashlight. Seems like there's nothing in the intake.
Question 1: if a m6 washer fell to the intake, there's no possibility that it got inside the pistons, right?

Taking your advice, considering something fell and got to the fan impeller, I'm trying to figure out how it might have gotten there.
So I don't really understand the airflow path from the fan impeller to the piston cooling fins and to the air filter.
My best guess at the moment is that there is a clear path between where the spark plugs sit to the fan impeller. There are the spark plugs rubber boots but they do not completely cover the opening.
So... question 2, is it possible that something fell through that opening and got dow to the fan?

Attached two pictures, does it make sense?

Thanks!

View attachment 212847

View attachment 212848

Click to expand...

You are correct. All the black tinwork is just a shroud around the engine. Think of it as a big open box surrounding the engine. The large fan sucks air in from the large intake pipe and moves it through that shroud around the engine and then back out the opening on the right side by the distributor. Anything dropping through the spark plug openings can go straight to the impeller fan...ask me how I know.

Couple of thoughts while tinkering with mine this morning. If you are pretty confident it’s in that area I think that top cover piece can come off without moving a lot of other stuff. It’s a ton of bolts and maybe disconnect the accelerator and air intake. That would give you a pretty clear view in there and might even allow it to fling the offending bit out by just turning the engine. I wouldn’t stand to the side because it’s going to come out like a bullet.

Yes, the top cover for the fan housing can be removed as a seperate item. You need to first disconnet the throttle link to the carb. You then have the bolts+nuts round the edge, and 4 small machine screws into the cylinder head. I think that you might also have a screw at the top of the cover into the ends of the cylinder head (trying to remember at gone 11.00pm in my study)---if you would like me to double-check tommorow morning I will. With the top off you will gain better access to the fan, and might even be able to put a magnet down around the fan. If not, try starting the engine, but as Joe (Veloman) suggests, keep your head well out of the way!

Thanks, appreciate the great info! I will give it a try.
I think I'll wait for the camera to do it once with the proper tools (don't have much free time to work on it anyway [emoji20])
Will update soon i hope

Often when I have dismantled engines I have found foreign bodies inside the small cover that fits between the bottom of the fan housing and the sump. Held in place by two of the sump bolts. I would look for debris or clues in there.

Based on my experience, you can also easily undo 2-3 bolts on the bottom of the tin work and pry it apart with a screwdriver enough to recover a bolt. Easier than removing the top cover.

tmrsgv said:

*update*

Question 1: if a m6 washer fell to the intake, there's no possibility that it got inside the pistons, right?

Click to expand...

I cannot see where this has been answered but for clarification yes a washer could go down the intake and when the inlet valve is open drop through into the cylinder on top of the piston or at least wedge in the valve.

I had it happen once to me on a VW flat 4 engine, it turned out that there were 2 washers on one of the manifold studs......as it was a horizontal engine imagine the mess made with the washer laying flat in the cylinder as the piston went about it's stroke...........

The Whitakers said:

I cannot see where this has been answered but for clarification yes a washer could go down the intake and when the inlet valve is open drop through into the cylinder on top of the piston or at least wedge in the valve.

I had it happen once to me on a VW flat 4 engine, it turned out that there were 2 washers on one of the manifold studs......as it was a horizontal engine imagine the mess made with the washer laying flat in the cylinder as the piston went about it's stroke...........

Click to expand...

Wow, hope this isn't the case here. Sounds like a mess...
I had a look with a flashlight but it wasn't perfect, I'll need to verify with better inspection tools

I listened to your video and doubt anything (6mm washer or whatever) has gotten into an engine cylinder, the noise sounds, as others have suggested, like possibly a washer bouncing around inside the cooling fan housing.

(I worked in a Fiat dealership in the '70's and know full well what an errant nut or washer inside an engine cylinder sounds like.....)

You might try tapping on the bottom of the fan casing/engine shrouding with a rubber mallet or block of wood (with the engine stopped) - if there's a stray washer inside, you'll likely hear it bouncing around. If so, you could try doing as JumpJet suggests i.e. try removing the lower shrouding bolts and pry apart.

Back in my day, we didn't have 'inspection cameras'. I used to employ a small rod type magnet ('borrowed' from a Mini sump drain plug) inserted into a length of plastic fuel pipe to 'fish' around a hidden recess to hopefully retrieve what I had dropped, it usually worked. I also used a small mirror in conjunction with a torch/flashlight/inspection lamp to try to see where an errant nut etc. might have become lodged. Nowadays, there are available, inexpensive small mirrors and magnets on extending wands that would serve the same purpose.

:idea:
I suppose you could always affix a strong magnet to the bottom of the fan housing/engine shroud to hopefully prevent the errant washer from bouncing around. (o.j. )

Al.

tmrsgv said:

Wow, hope this isn't the case here. Sounds like a mess...
I had a look with a flashlight but it wasn't perfect, I'll need to verify with better inspection tools

Click to expand...

Try poking your camera through the spark plug hole maybe.......

*update*
Opened the airbox upper cover to reveal a line of sight and access to the fan.
Poked inside with a flexible magnet and also tried to have a peek with a flashlight. Nothing came up other than a lot of black gunk [emoji58]

Off topic, any suggestions on how to clean inside the fan area? With what materials?

I have to note, don't know if its normal but when I'm trying to rotate the engine by hand (gripping by the dynamo pully), it has a hard spot once every few turns. Is that normal?

And so, the adventure continues!

tmrsgv said:

Off topic, any suggestions on how to clean inside the fan area? With what materials?

I have to note, don't know if its normal but when I'm trying to rotate the engine by hand (gripping by the dynamo pully), it has a hard spot once every few turns. Is that normal?

Click to expand...

I would leave the dirt alone; it will be a mixture of road dust and oil vapour. Apart from the fact that it might come partly from a gasket or seal leaking somewhere and may therefore come back straight away, cleaning it wouldn't be very comprehensive with the cowlings assembled. You might dislodge something that could clog the air-filter or shift dirt which might bypass it to block a part of the carburettor. If you do clean it and use the right sort of degreaser available these days, it will be water-based and rinse water will also be a risk to the carb..(been there). :bang:

The engine compression is what you are feeling and that's normal. You could remove the fan-belt and try rotating the generator pulley to get a better way of listening for anything catching...it might even be the fan itself.

tmrsgv said:

*update*
Opened the airbox upper cover to reveal a line of sight and access to the fan.
Off topic, any suggestions on how to clean inside the fan area? With what materials?

Click to expand...

For your own comfort I would recommend that at some stage you remove and clean that fan cowling. With what you describe you will always be driving with the aroma of stale oil in the car if the heater flap is open.