propane troubleshooting...

[altfuel1991]

photo bucket broke, so no pics

That pin was 1/16 above the edge. LPG is still coming out with just the key on though. I repositioned the end of the lever with the rubber pad since it didn't seem to sit flush, but neither seemed to help since I still had a leak (smaller than before!) while the key was on. I removed the top again and turned the key on, and I can see that the gas is pushing that whole arm up. Not sure how heavy the spring is supposed to be, but is it possible the gas pressure is too high? Is that little silver metal thing near the inlet supposed to seal up or reduce pressure?


Edit: I wedged another spring under the arm. Still leaked, but slower. I went and pushed down on the orange flapper and it took quite a bit of pressure to seal it off. Not from leaks/cracks/holes, but to overcome actual pressure. I removed my other spring and slowly let off, but it still had quite a bit of force that the stock green spring would not be able to seal.

So... should I be running some sort of regulator? I have the AFC 121 lock off, and the nut on top was barely tight. This looks like it can be turned down quite a bit. What does it do? Google was surprisingly not helpful

The lever height is definitely too high. When you put the cover back on that will automatically push the lever down. Also if yo can see the pressure lifting the seal up and blowing past then there is way too much pressure. You probably just need to rebuild it and reset the lever height. Sounds like someone really jacked this system up before you got it. But good news it is correctable. You said there is a green spring under the secondary arm. There should be a blue or orange spring only. If there is a green spring it came out of a the top of a 425 mixer and is the wrong one. You should have a blue spring when running a model "E" with a 425 mixer. The one on the photos looks blue. The color does matter.

 

[jakec69]

in for reference later.

 

[patman]

I'll double check the springs when I get home. Maybe they were reversed?

Should I do anything to reduce pressure? Does the AFC 121 have any adjustability?

 

[altfuel1991]

The IMPCO vaporizer is a regulator/vaporizer assembly. If it is not regulating the pressure something is wrong internally. It will take full tank pressure. You should not need anything else.

 

[patman]

The IMPCO vaporizer is a regulator/vaporizer assembly. If it is not regulating the pressure something is wrong internally. It will take full tank pressure. You should not need anything else.

I think I found the issue, or just another problem.



The silver thing (what's it called?) has a circular wear mark on top of it, and the bottom of the rubber stingray that goes near the gas inlet has what looks like a corresponding mark. The body of the regulator has a hole between the two and it looks like a pin is supposed to be in there. Is this correct? Is there anything special about it or can I just make a replacement if I know the correct length??

Btw, the spring is blue, just missing most of the finish

 

[altfuel1991]

The pin is in the housing in your earlier photos.

 

[patman]

The pin is in the housing in your earlier photos.

****....

found the pin and put it back. Engine runs and sounds good. No leaking when motor is off as well. Did have some issues getting it going when I first attempted, but once warmed up it restarted instantly.

Dumb question 2: I adjusted the idle mixture screw on the carb to give me the highest idle, then lowered the idle adjustment on the throttle cable. The engine was running in my garage, and if I get near the exhaust for an extended time, my eyes started to burn. I know breathing in exhaust fumes is bad, but is that expected? Or a sign of something else? No real stench of propane, so I don't think it's rich

 

[altfuel1991]

If it is burning your eyes it is way too rich. Unless you are burning oil as well. When adjusted properly, unless you have a big cam in the engine, you should be able to start the engine and let it run with the garage doors down. It should run that clean. Think about warehouses running propane forklifts, in the winter they keep the doors closed to keep the heat in with no extra ventilation. I would check for vacuum leaks at the throttle body and manifold. See if the throttle shaft will move around in the base. If so the idle mixture will be rich to compensate for the air leak.

 

[patman]

If it is burning your eyes it is way too rich. Unless you are burning oil as well. When adjusted properly, unless you have a big cam in the engine, you should be able to start the engine and let it run with the garage doors down. It should run that clean. Think about warehouses running propane forklifts, in the winter they keep the doors closed to keep the heat in with no extra ventilation. I would check for vacuum leaks at the throttle body and manifold. See if the throttle shaft will move around in the base. If so the idle mixture will be rich to compensate for the air leak.

Motor is stock. I'll check for leaks and play in the throttle shaft.

Which way should I turn the idle adjustment on the impco carb to lean it out if I find nothing else?

 

[altfuel1991]

Motor is stock. I'll check for leaks and play in the throttle shaft.

Which way should I turn the idle adjustment on the impco carb to lean it out if I find nothing else?

Turn the idle screw in(clockwise) to lean it out. Normally we turn it out until you can hear the rpm drop a little, then turn back in about 1/4 turn.

 

[patman]

Turn the idle screw in(clockwise) to lean it out. Normally we turn it out until you can hear the rpm drop a little, then turn back in about 1/4 turn.

Engine started up immediately tonight, and also restarted immediately after it was warmed up. Still running rich, and I can turn the idle mix screw all the way in clockwise without a noticeable difference. Couldn't find any air leaks around the base or any connections.

I'm guessing the vaporizer or carb needs a rebuild. Is there a way I can narrow it down to a specific problem so I know what is being fixed?

 

[altfuel1991]

Remove the idle mixture housing from the side of the mixer. It has four screws that hold it on. There is a very thin diaphragm under it that might be split. Normally when the idle screw doesn't change anything that is the problem.

 

[patman]

Removed idle cover. Diaphragm looks good, no tears. The bend that fits inside the cover, is this extreme or normal?

Aside from the rich idle, the setup worked great on my test run

Sent from my SM-G900V using Tapatalk

 

[altfuel1991]

That looks normal. Just make sure when reinstalling it that the idle screw goes inside that bend and not on top of it. You might want to check the mixer housing for excessive wear. With the air/gas valve in the down position see if if will move sideways in the housing. There is only about .002" clearance between the air/gas valve and housing so if you can see it move it has too much clearance. This can make it hard to turn and usually run rich. There is no fix for a worn housing other than replacing it.

 

[patman]

With the air/gas valve in the down position see if if will move sideways in the housing.

I'm trying to understand this statement... do you mean with everything turned off and no gas coming through that the moving piece I can access through the opening (covered by the air filter) shouldn't have any wiggle room? Or the cone piece only accessible by taking the top of the carb apart?

 

[altfuel1991]

With engine turned off and air filter removed, take your thumbs and fore fingers on each side and hold the air/valve between your fingers and see if it there is any side to side movement within the housing. The air valve should move up and down freely but not have any side movement when in the resting position.