Problem with Tri Power - Pontiac GTO Forum
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post #1 of 13 (permalink) Old 08-20-2012, 07:28 PM Thread Starter
 
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Problem with Tri Power

I just put my 455 engine back together and I have run it a fair amount in the garage. I have a Tri Power setup on it. All of a sudden today when I went to start the engine, gasoline started shooting out of the vent tube on the top of the back carburetor. I took off the top to verify that the needle seat was seating and that when I lifted the float and blew air with my mouth when lifted it would shut off the flow of gas. There was no evidence of foreign material in the needle seat area. I put the carb back together and it is still shooting gas out of the back vent tube. It appears to shoot gas in unison with the Fuel Pump as it pumps. The float is brass and did not appear to be heavy as if it had a hole in it. Any body had this happen to them? Any suugestions appreciated.
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post #2 of 13 (permalink) Old 08-20-2012, 07:37 PM
 
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Originally Posted by timmyg View Post
I just put my 455 engine back together and I have run it a fair amount in the garage. I have a Tri Power setup on it. All of a sudden today when I went to start the engine, gasoline started shooting out of the vent tube on the top of the back carburetor. I took off the top to verify that the needle seat was seating and that when I lifted the float and blew air with my mouth when lifted it would shut off the flow of gas. There was no evidence of foreign material in the needle seat area. I put the carb back together and it is still shooting gas out of the back vent tube. It appears to shoot gas in unison with the Fuel Pump as it pumps. The float is brass and did not appear to be heavy as if it had a hole in it. Any body had this happen to them? Any suugestions appreciated.
How high was the fuel level when you took the top off? You sure the float is not sticking mechanically?
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post #3 of 13 (permalink) Old 08-20-2012, 07:54 PM Thread Starter
 
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The float assembly seemed to be free, however the fuel level did appear higher than normal.

Last edited by timmyg; 08-20-2012 at 09:02 PM. Reason: additional information
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post #4 of 13 (permalink) Old 08-21-2012, 06:39 AM
 
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What year Tri-power do you have? I have a troubleshooting and set-up DVD for a '66 tri-power that I got from "Pontiactri-power.com".

I will go through the troubleshooting tonight and see if there is any mention of a fix, or what to check.
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post #5 of 13 (permalink) Old 08-21-2012, 09:20 AM
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Not to be crude, but think of it, literally, as a toilet. Fuel can only get in one way: thru the inlet. The inlet is opened and closed by the needle on the seat, which is activated by the float. Just like a toilet tank. Has to be the needle, seat, or float. The needle is not closing during operation, causing your problem.
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post #6 of 13 (permalink) Old 08-21-2012, 11:34 AM
 
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Get rid of the needle and seats, and install the replacement check ball valves , available from pontiac tripower. com. The fuel which is available now is not good on the old type needle and seats. Also make sure you have brass floats. Check out their website.
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post #7 of 13 (permalink) Old 08-21-2012, 11:52 AM
 
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I had the same thing happen to me once.
1, the brass float sunk. check it prior to installing but when I adjusted the thing, I must of cracked the seal. what a mess that was.
I did install a pressure regulator set at 3.5 lbs.
Good luck
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post #8 of 13 (permalink) Old 08-21-2012, 01:11 PM Thread Starter
 
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My Tri-power is a 66 setup as well.
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post #9 of 13 (permalink) Old 08-21-2012, 03:29 PM
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What kind of fuel pump and how much pressure is it putting out?

I agree with the others - either you've got a problem with the float/needle/seat that's not doing it's job, there's a crack/defect in the carb inlet that's allowing fuel to find its way around the needle/seat completely, or you're making so much fuel pressure that it's forcing the needle open.

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post #10 of 13 (permalink) Old 08-24-2012, 11:37 AM Thread Starter
 
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The problem did end up being the basic thing that was suspected. The float did have a tiny area at the seam between the two halves of the float that was allowing just enough fuel in to weigh it down. Somehow I missed it the first time I removed the top of the carb. Thanks for all of the help and suggestions.
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