Engine will not idle after a good run

robinsbd

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Before touching the choke, I played with the throttle a bit. I pushed it all the way down and back as I have done in the past. Only this time something different happened, the choke plate opened to about 1/8 inch gap and it stayed that way even when I moved the throttle back to neutral.

So, it seems like something in the linkage on the carb changed so that now the choke plate holds with 1/8 gap.

I think it has something to do with the linkage and cams on the side of the carb. I'm not sure what would have changed to make the plate go full closed, and now it has correct gap.

I went ahead and removed the water separating fuel filter as requested. I poured the contents into a glass jar for inspection. I think the gas looks good. I attached a couple pics.

 
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alldodge

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Gas looks fine, if it smells like gas your good to go. Choke also appears to be working correctly.

Only thing left is your idle and that comes from the idle circuit, this may need to be cleaned
 

robinsbd

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Do you have any suggestions on how to lubricate the linkages and cams on the side of the carb?
 

alldodge

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Do you have any suggestions on how to lubricate the linkages and cams on the side of the carb?

In most cases the carb linkage needs no lubrication, there is slop built into the linkage so it should move easy. Things that can cause them to drag is rust, paint and grease build up. If it looks a bit cruddy I'll take some carb cleaner and spray it down
 

robinsbd

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Yes, you guys are most likely right on here. A good carb cleaning should be done.

I verified the choke adjustment is fine and the linkage seems to be working fine. I think all signs still point to the idle circuit.

I was able to get it started again and it dies at idle, but if I give it a little throttle, it catches itself and actually starts surging. It stays running, but surges some. I took a video of this and posted to YouTube.

https://youtu.be/WSrsOD-33VY

Please take a look.

If we're still set on carb cleaning, i will go down that path.

Thanks for the help guys.
 

FreeBeeTony

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I assume when the engine is warm (like it was in the video) and you try to reduce the RPM's the engine dies.
I would try that again and see if you can keep it running buy manually closing the choke..........this will help prove it's the idle circuit.
The fluctuation of the voltage is strange............
 

robinsbd

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Yes, the voltage fluctuation has me concerned. On one of the previous times I started the engine, I could not get RPMs to increase very much when I pushed the throttle. At that time, the volt gauge was reading less than 12 volts and the needle was bouncing a little but always under 12 v.

The latest run, is what you see in the video.

Also, I uploaded another video of what happens when I pull the throttle back to idle.

Please check it out here: https://youtu.be/jmK8sGrG5yE
 

FreeBeeTony

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Seems like the engine dies immediately when you throttle down.......almost like you shut the ignition off.
What is that switch you shut off w/ the green light?
 

robinsbd

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The switch with the green light is the blower for venting the engine bay. I know that during my testing, I had the engine bay cover open so venting probably wasn't needed, but I am trying to simulate a normal startup procedure.
 

alldodge

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Still looks like fuel but I would suggest turning the blower off once started. Have not heard a blower that loud in a long time. the engine is shut off and I still hear nothing but the blower.
 

robinsbd

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I removed the connections from the back of the alternator to inspect and clean the connections. I attached a pic of the diagram for my alternator.

I found a couple of interesting things: ​

1. Someone had put an insulating washer directly underneath the orange output lead 'd'. So on mine from the bottom up, there is an insulating washer at the very bottom of the terminal post to insulate from the alternator housing. Then, there is the ring lug for the capacitor followed by the nut that holds it down. On top of that nut, there is another larger insulating washer (not sure if this is needed or causing an issue). The ring lug for the orange output wire sits on top of the insulating washer and then its nut holds that lug tight against the insulating washer. It seems like the washer under the output lug is not required. Just wondering if you guys have ever seen that before or if that could be an issue. The diagram does not show an insulating washer there. I attached a picture of the insulating washer for reference.

2. The nut and ring lug for the purple excitation lead 'a' were rusted together and to the post. When I turned the nut, the ring lug of course turned with it. I was able to get it off Ok.


The other wire connections seemed good. The sensing lead 'b' looked fine, the ground lead 'c' looked fine, and the electric choke connector was fine.

I had purchased a new alternator last season, but I didn't get around to installing it. Now that I have all the wires disconnected, I plan on installing the new.

​Wondering what your thoughts are on items 1 and 2. Thanks!
 

robinsbd

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No Title

Here is the diagram.
 

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Bondo

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Ayuh,.... Yer #2 could be a problem,....

Yer #1, the washer is sometimes used to hold the little boot in-place, the connection is still made through the stud, 'n nut,.....
 

alldodge

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+1^, and will add the only thing I read that's different, is the two insulating washers. In most cases there is only one on the bottom for the boot to fasten to
 

robinsbd

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I successfully installed my new alternator over the weekend. The volt gauge reads more stable now. It's not bouncing around like it was before. It still fluctuates slightly, but that seems normal. That was quite a job putting the new alternator in without dropping anything into the bilge. I cleaned all the wire connections at the alternator and the connections at the battery.

After getting the belt back on, I started it up. It ran Ok while the choke plate was mostly closed. As soon as the choke plate opened up to almost full open, the RPMs came down and the engine stalled. I started it again, and I revved it up to 3K RPM and then as soon as I backed off, it stalled again. So, it seems to be stalling after the choke opens.

If this is the idle circuit, is there anything I can adjust to get things moving again. Is there a needle I can adjust or remove for cleaning?

On my outboard engine, I removed the idle mixture screw, cleaned it, and reinstalled. That seemed to resolve the issue I had with that engine.
 

alldodge

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You can pull the idle screws out and try cleaning them just like an outboard, it may help, probably not. Won't hurt
 

robinsbd

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During one of my tests, I noticed fuel dribbling down from the venturis to the throttle plates? Is it normal to be able to see gas dripping there?
 

alldodge

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During one of my tests, I noticed fuel dribbling down from the venturis to the throttle plates? Is it normal to be able to see gas dripping there?

No, this is a no dribble area, should see a slight spray kind of, from the air being pulled past the plates. Either float, float level of needle seat is weak
 
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