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Discussion Starter #1
I have a 472 caddy in my commando. Have a new VFF30 vacuum lockoff, used model E regulator, and a used 425. When I try and start it, I get a large whoosh and it dumps a cloud of propane out of the 425. The venturi rises when it dumps the propane.

I pulled the top off the 425 and the diaphram seems fine, has a spring in it to keep the venturi down. Wondering if I have a vacuum line routing problem.

Kind of at a loss right now.
 

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Discussion Starter #2
I went and messed with it some more. I can get it to run briefly. If I open the throttle all the way and crank it, she will start and not dump propane out the mixer. Can only do this if I open the tank, let the system pressurize, then shut the valve. Once I get it running, I can keep it running for a minute or so, by just barely cracking the valve. If I try opening the valve to much, it kills it.

Initially it fired and ran at 2000 rpm. Tried slowing it down with the idle speed, and got it down to about 1500 rpm. Anything below that and she quits. I know I have to mess with the timing and such, but no idea why it dumps propane out the mixer with tank valve wide open.

Probably need to rebuild the mixer and regulator.

Any ideas?
 

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the reg is stuck wide open.
that reg has some extra stuff glued to the top that I am unfamiliar with.
did you get the lever into the slot in the diaphram or is it pushing the diaghram down?
 

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I see what looks like frost on the outlet of the regulator, this means there is a good chance it is stuck open.

Your issues could also be woth it being airbound and not passing coolant.
 

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Discussion Starter #5 (Edited)
Thanks for the help. I'll pull the regulator in the morning, and see what I can find. That is indeed frost that you see in the picture. When it dumped the propane out of the mixer it left frost everywhere.

The regulator is a model E, it does have some funky crap on it that you can see. I pulled the covers off, looks like accelerator pumps in there. There is a diagram of it on www.teecoproducts.com
Just go to carburetion, dig around and you should find a link for technical crap on Impco regulators. And they have a exploded diagram for the crap on mine. I just plugged the things.

Really need to get this pile running in the next couple of days. Little town I live in is having it's centennial, and I want to be able to drive it. Here's a pic of my pile.
 

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Problem is in regulator somewhere, I'm willing to bet. Open the front cover and inspect the diaphragm in there. It looks like the previous owners has bolted that crap on the outside of it, which would mean they drilled a hole in the cover. I bet they may have screwed something up when they did that. Once you open it up and look inside it will become obvious how it works and you will probably see something wrong.

You should only need the one vacuum line going to the lock-out valve, the big fuel hose to the carb, and the two coolant hoses to the reg. If you have any others, you probably don't need them.

J. J.
 

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i had the same problem. look at the pivot arm inside the regulator to make sure its not bent. also see if rubber valve is torn or obstructed.
 

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Discussion Starter #8
That regulator is factory Impco. Not stuff somebody bolted on. But the diaphram in it was shot. No rebuild kit's locally. So I ordered up a brand new Model E without the extra crap on it.

Put the new regulator on, and she fired right up and runs like a champ. Took her on it's maiden voyage tonight. I'm loving the big caddy. Thanks for the tips.
 
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