I've got an odd problem with the 65 - It seems to build excessive fuel pressure after it's shut off. Doesnt matter if the engine is hot or just warm, about 5 minutes after you shut it down the passenger side primary venturi just dumps fuel down the carb throat. I blew out the standpipe vent so it's clear, and took the tank cap off, it still does it. Just now as it was doing it, I pulled line fuel line off the front of the carb (car off) and there was enough pressure to send a burst of fuel back to the cowl and windshield. I pulled the carb top off, checked the floats for floatiness, set the min and max travel and checked the needles and seats. Nothing wrong. I'm not surprised as it did it with the prior carb too. As it's doen it with two different carbs, it would really appear that the line pressure is getting past the needle and seat. This is a Non-Air car with no return line, and I'm using a honest AC GF-94 filter. Any ideas on whats going on? Thanks, It just seems the fuel line pressur
Forgot to add - the car did this before I replaced all the fuel lines and hoses, and there is no electric fuel pump, just the mechanical pump which shows no leaks or seepage.
A bad float??? A defective pump???? Install a fuel pressure regulator after checking fuel pressure. A stock pump shouldn't be any more than 6-7psi.
Thanks for the responses - I dont have a guage, but I cant imagine a stock AC pump making that much pressure??? I'll see I can borrow a guage from my buddy.....
Rhett, what is happening is that the fuel pump pulls the fuel into its self under suction,,,,then when the fuel gets past the check valves in the pump, the situation changes... the fuel is then under pressure... usually 6 to 8 psi....all the way up to the inlet needle and seat... where all the pressure is depleted.... then when you shut the engine off , the heat from the block causes the fuel to heat up and expand.... raising the pressure more.... causing the effects that you see and are experiencing.... The real cure is to either insulate the fuel pump from the heat by putting a 1/8th spacer between the block and pump made of a non heat conducter, or installing a electric pump back at the tank and not using the mechanical pump....
Bowl vents are the 4 holes in top of the carb AND the 4 brass pipes. It's highly unlikely they're all blocked...or even one side. Either there's too much fuel in the bowls due to leaky needle/seat (and check the gasket and seal surface under the seat assembly!), or gas in the carb is boiling after shutoff (at what temp will it do that?). Put a gauge on it and observe pressure during operation and after shutoff.
It's not blocked vents that I can see, and I don't think it's bowl boiling, cause that wouldnt send that kind of pressure back to the line. I borrowed a gauge, that should give me a pretty good idea of whats going on. I had a long talk with Doc, and I'm sold on the insulator idea, at least giving it a shot. However, by the reasons we discussed (heat soak, oil temp, etc..) all of our cars should be doing this, and my 455 Pontiac too....but it doesnt. I'll get to the bottom of this, maybe even this week.
Doc - is the material you're thinking of Phenolic Resin Laminated Sheets? If so, it looks like my local Grainger carries them. Will this stuff cut clean with tin snips or do I have to use a cut off disc?
When you say "dumps" you mean it's dripping correct? I would say the needle is not seating and the bowl is simply over filling. I know you said you checked the float level but based on experience with the same problem here i would say check it again. Is it dripping both sides or just one? Mine was dripping from one side only and turned out i needed to adjust the one float just slightly to fix the problem. This was after installing a new kit so i knew the needles and exc-pump were all good. Gary
thanks again - To answer, it's just one side..and I think you're right. I got a gauge, and learned that even 2 lbs of pressure will shoot fuel as far as the cowl! The pressure stayed at a steady 5 while running and dropped slowly after shut off, eventually to zero as the passenger venturi dripped... I'm gonna take the carb top off again this am, and check everything again. I initially adjusted it to the specs from the service manual, which (as I recall) showed 3/8 at the top with a drop to 3/4 at full float travel, and check the needle/seat again, make sure there's a seat gasket, etc... At least it's just the carb, so thats good news. I still like Doc's idea of the insulator too, so I'll be doing that as soon as I get the sheet from Grainger. Thanks again -
I didn't use any measurement to adjust the floats. Instead at the suggestion of my brother I blew into the inlet holding only the top side in my hands. You can hear the air blowing through it and adjust the float until it seats the needle and the float looks about parallel with the top. Use a little trial and error with very small amounts of bending. <QUOTE> Had this happened to me a couple of times when i was switching out fuel filter....sure does shoot out! Gary
BTW, you don't need to remove the whole carb from the engine, you can just remove the top part of the carb, adjust it, reinstall and test. Gary
I ha a similar problem with my Special Wagon. Fuel between pump and carb remained pressurized after shut off, then would come out the throttle shafts like the needle would not hold it back. I ended up putting a return line in, problem solved for me. Just need a pin hole in the return to bleed off the pressure.
Ok - I'm officially at a loss ... I took the carb top off and notice the passenger bowl fuel level 1/2 inch higher (to the bottom of the baffle notch) Both floats are the same brass construction, dry, have free travel and adjusted correctly - 3/16 top and 3/4 at drop per manual specs - doesnt look like there are specific left or right applications. both needles and seats good, no scoring and seat correctly (hold air). both have gaskets. (I do notice these needles are full brass, no rubber tip like on my other carb) Both top vents and tubes clear I guess the next step is to switch needle/seat assemblies from side to side to see if the problem follows. then do the same with the floats.
Was it the passenger side that was dripping on yours???? If so you can clearly see that this side if filling up higher. Still think it's the float adjustment but i'm no expert. I don't know if this could be a problem but mine had the rubber tips (carter AFB 9321).
NAPA did sell needle/seat assemblies, and even some gaskets separately, but their website has gone downhill in the past year.... if you have a local store, give them a call.
