Author Topic: Fuel leak through air horn gasket  (Read 4143 times)

Offline 1 Fat Cat

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Fuel leak through air horn gasket
« on: July 17, 2016, 07:01:13 AM »
Hi all. I'm looking for a little help with a qjet that I had Cliff rebuild about a year and a half ago. I just got the car running about a week ago after doing a number of upgrades and actually having the time to get it all done. Anyway I got the car running and was very impressed with the quality of the rebuild and how well it ran right out of the box. One thing I noticed right from the get go however is that I could see fuel seeping through the air horn gasket almost immediately with the car running. I've read that this can be common especially if the top plate is warped. I just don't see how that is possible if the fuel level sits below this....  So that makes me wonder if the float level is correct....  I've been hesitant to pull it apart yet because I would think it was set properly with the rebuild. Any thoughts or recommendations on this?

This leads into my next problem. The car starts great when cold by giving it three pumps and will pop right off with a turn of the key when up to temperature. The problem I have is when it's hot and you leave it sit for some time, it's difficult to get that initial start. What seems to be happening is that I can see fuel seep into the primary bores via the air horn gasket.  It even seems to work its way up and around the nozzles and appears wet all around the venturis. This all happens within about 10-15 mins and that's when I experience hard starting. Is this related to my issue above and where do I begin to alleviate this?

Thank you.

Offline Frank400

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Re: Fuel leak through air horn gasket
« Reply #1 on: July 17, 2016, 02:54:25 PM »
A few possibilities here that I can see.  First, your fuel pressure could be too high.  You'd be surprised how many brand new fuel pumps bought from auto part stores have  way too much pressure.  I've seen as high as 13 lbs.  You need not to have more than let's say 6 psi. 
 
   Also, if you have a dead end fuel system, you should seriously consider having one with a return line.  I've seen many many cases where this solved all the hard starting problems while hot.

Offline 1 Fat Cat

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Re: Fuel leak through air horn gasket
« Reply #2 on: July 17, 2016, 04:17:30 PM »
Thanks for the input. I probably should have mentioned my fuel supply. I'm running a full 3/8 line from the tank to carb and 3/8 return from the regulator back. Using a Carter electric pump set to 5.5 lbs pressure.

Offline 1 Fat Cat

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Re: Fuel leak through air horn gasket
« Reply #3 on: August 04, 2016, 09:36:16 PM »
Any additional help on this?

Offline carmantx

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Re: Fuel leak through air horn gasket
« Reply #4 on: August 05, 2016, 05:57:22 AM »
What kind of engine?  Intake?  What is the carb code?  What fuel are you running?
Float may be a little high.
Close off fuel line and run engine until it almost dies from using up all the fuel and open fuel line.  This could help dislodge and particles keeping needle/seat from seating fully.
Today's fuel will boil from heat easily.  Are you running a metal heat block between carb and intake?  This will help.  After engine and carb get hot and you shut it off, the fuel in carb will boil out of the bowl and into intake.
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Offline 1 Fat Cat

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Re: Fuel leak through air horn gasket
« Reply #5 on: August 18, 2016, 05:39:35 PM »
Regarding the fuel leak::

I have confirmed the air horn is in fact warped at the two bolt mounting holes. I proceeded to strip the air horn so I could plane it flat. I used a little heat and a side cutter to remove the brass tubes as seems to be the recommendation. Even though I was careful, I still managed to ever so lightly pinch the smaller two tubes the slightest amount. I assume this is bad, can I get replacements?