I picked up a 1967 Cougar base model with 289 auto that hadn’t been started in years. Before starting, I replaced fuel tank, sending unit, fuel lines, fuel pump and filter. It started and ran nicely when the choke was engaged (auto heat choke). When the engine idled down the carb overflowed with fuel. I rebuilt the carb and replaced the float, needle, etc. Fired it up and it did the same thing. Pushed the float down a bit to engage sooner and it still did the same thing. Any suggestions before I look for a new carb? The new fuel pump is supposed to be at 4.7 PSI but I don’t have a guage to verify.
You already guessed a possible cause being pressure. You need the gauge.
Another possibility is the needle not sealing to the seat. Unlikely given the Viton tip on every float needle I’ve seen over the last 50 years.
Is the seat sealing where it screws into the carburetor casting? There should be a gasket at that joint.
How’s the gas cap? Make sure that it is vented, otherwise the gas tank will build up pressure that can override the needle valves in the carburetor.
The needle is sealing. When I checked the float I pushed it down and residual pressure caused fuel to squirt up when the needle came up. Yes, I put a new seating screw in with a gasket.
Yes, gas cap is vented.
This is pretty strait forward - the only source of fuel is the inlet valve. Either it’s defective (and has a nick to where it may be leaking), or if your test validated otherwise, your inlet pressure is higher than it’s designed for. I’m assuming your floats were intact and NOT full of fuel. It does seem off that it is only at idle (not sure how you’d verify otherwise). The pressure while running should not be lower than when at idle.
Thanks. The pump is from Napa #FUP B0110P and although it does not say the PSI spec, another forum says it is 4.75PSI. Valve and needle are new. I think I am going to just buy a new carb. Any recommendations?
Existing carb is Autolite 2100 C7DF-V.
Checking the float with the cover off is good diagnosis. It is still possible that there is a nick in a sealing surface that allows enough fuel to flood it at idle but is insignificant under load.
Measure that pressure before loading the parts cannon.
Replacement part quality is abysmal. Start replacing more parts without diagnosing first and you compound the number of potentially faulty parts.
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I hear you. I can get a pressure gauge and measure PSI quickly before it idles down and starts overflowing fuel.
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Well, I installed a gauge at inlet of carburetor and it started off at 8 psi and steadily climbed and pegged the gauge at over 15 psi. Then it started bouncing back and forth and shut the car off as gas started coming out of the carb. Sounds like you are right that the (new) pump is putting out way more than 4.7 psi and overpowering the float needle.
I hope NAPA is getting a fuel pump back.
If they give you any grief, post the video.
You should be able to attach your pressure gauge to the prospective replacement’s outlet and manually work the arm to see how much pressure it will generate. I grab the body and push the arm against a bench top to see whether a pump will generate pressure. Attaching the gauge should tell how much.
I haven’t personally tried this with the gauge attached, so at this point it is an experiment.
Now I am back to square one. I returned the pump and put a new one on. Same pump model but Napa assured me it is the right pump for 67 Cougar 289. Fired it up again and the pressure pegs past 15 and fuel overflows from the two vent tubes on carb. Any thoughts on nexts steps? Thanks!
Probably multiple pumps went out of that factory with the same problem. Go someplace else. Not sure where to recommend though. I’ve had good luck with Carter pumps, but have read of the same issues with them recently.
Going to return and try Delphi…
At the beginning of the post, you mentioned that you replaced the fuel pump. Was there anything wrong with it and do you still have it? I would recommend putting the original back on and test your pressure with it
I had this issue on my 66 Mustang. It was a stuck float.
I don’t have a good solution. Despite messing with it repeatedly, it would still randomly stick, so I got tired of fiddling with it and swapped to a GT intake and a Holley 4150.
Just go get a pressure regulator and you’ll be fine. Inexpensive ones are in the $20 - $30 range for a decent one. Make sure you get one that matches what you want - assume perhaps 30 psi inlet pressure, dialing it down to around 6 psi. Precision on this pressure is not critical (i.e. +/- 1 psi is fine).
I threw it away because the car sat so long that I wanted all sources of potential old fuel, rust and debris removed.