I have a 1963 Avanti R2. Shortly before I purchased it the owner went to a reputable Studebaker parts vendor and replaced the fuel pump with the correct one for a supercharged Avanti with a fuel return line to the fuel tank. The car ran alright for a few hundred miles and then I had a mechanic do some necessary work on it, including a tune up and fixed the choke. The car then started easily and ran great for the next 3-400 miles. It sat for about a month. I then started it easily, but it would not idle unless I kept my foot on the gas to about 1500 RPM. I did that to the normal operating temperature thinking the rough idle might be temperature related, but to no avail. I shut it off and found that the carb was leaking gas all over the place from the gaskets and accelerator pump. I spoke with a local shop that repairs the Carter AFB carb and he said the needle seats and/or float were probably to blame, but asked me to check the fuel pressure before rebuilding the carb. I followed the shop manual procedure for checking the fuel pressure, including disconnecting the fuel pump-to-supercharger air pressure line at the supercharger. The fuel pressure came in a little over 8 psi. The manual says it should be between 5 ½ to 7 psi and the carb shop said I should be running at a max of 6 psi to avoid overwhelming the carb internals.
I spoke with another mechanic about why the fuel pressure would be high and he suggested that the pump may not be the correct one and/or was not rebuilt correctly. If that’s the case why did the carb not leak for the 500 or so miles it ran with that pump? He suggested that it might have taken that long for the high pressure to overwhelm the carb. He also suggested that the fuel return line may have gotten clogged during the 500 miles thus increasing the pressure. I pinched off the return line rubber hose at the fuel pump before it goes into the metal fuel return line and the pressure went up to a little over 9 psi. I released the clamp while the engine was running and the pressure dropped back down to a little over 8 psi.
Based on the above tests I have several questions to the Studebaker experts:
Even though the pump came from a reliable Studebaker parts vendor, could it be the wrong one and/or rebuilt incorrectly? If that’s the case, could it take 500 miles for the 8 psi pressure to overwhelm the carb? It would seem to me that the carb would leak long before that, but y’all may know differently so please let me know you’re opinion.
Is an approximate 1 psi differential between the fuel return line being open or close normal with the Avanti supercharger set up or should there be a greater differential, suggesting that the return line may be partially clogged? Please note that before I checked the fuel return line I did take off the rubber hose on the fuel return line at the fuel pump and a trickle of gas ran out of the pump fitting which I expected, since the Avanti fuel tank is higher than the fuel pump. I then ran a sewing needle in the fitting and felt it slip through the 40 thousands opening to the fuel return line fitting. A thin stream of gas then flowed out instead of a trickle, so I assume that’s as clear as it could be at the fitting.
If it’s likely that the return line is partially clogged what would be the easiest way to check that and clear it? Compressed air, run a wire through the line or ___? I’m trying to avoid removing the back seat and panel assembly if possible. Even if the psi differential should be 1 more psi, that would bring the pressure down to around 7 psi, which the carb shop is telling me is probably too high long term. What has been your experience concerning a normal pump pressure (with the supercharger air pressure line disconnected) in today’s environment?
I’m trying to determine if the fuel pump is the culprit for the high fuel pressure before I replace it. And even if I replace it will another one correct the problem since the current one came from a reputable Studebaker source?
If nothing else, I could put a proper fuel pressure regulator in between the fuel pump and the carb and reduce the pressure that way. Have any of you had to resort to that set up? Any suggestions on such a set up?
Any suggestions would be helpful. I just want to be able to drive the car again without worrying about the carb leaking fuel all over the place!
Thanks!
I spoke with another mechanic about why the fuel pressure would be high and he suggested that the pump may not be the correct one and/or was not rebuilt correctly. If that’s the case why did the carb not leak for the 500 or so miles it ran with that pump? He suggested that it might have taken that long for the high pressure to overwhelm the carb. He also suggested that the fuel return line may have gotten clogged during the 500 miles thus increasing the pressure. I pinched off the return line rubber hose at the fuel pump before it goes into the metal fuel return line and the pressure went up to a little over 9 psi. I released the clamp while the engine was running and the pressure dropped back down to a little over 8 psi.
Based on the above tests I have several questions to the Studebaker experts:
Even though the pump came from a reliable Studebaker parts vendor, could it be the wrong one and/or rebuilt incorrectly? If that’s the case, could it take 500 miles for the 8 psi pressure to overwhelm the carb? It would seem to me that the carb would leak long before that, but y’all may know differently so please let me know you’re opinion.
Is an approximate 1 psi differential between the fuel return line being open or close normal with the Avanti supercharger set up or should there be a greater differential, suggesting that the return line may be partially clogged? Please note that before I checked the fuel return line I did take off the rubber hose on the fuel return line at the fuel pump and a trickle of gas ran out of the pump fitting which I expected, since the Avanti fuel tank is higher than the fuel pump. I then ran a sewing needle in the fitting and felt it slip through the 40 thousands opening to the fuel return line fitting. A thin stream of gas then flowed out instead of a trickle, so I assume that’s as clear as it could be at the fitting.
If it’s likely that the return line is partially clogged what would be the easiest way to check that and clear it? Compressed air, run a wire through the line or ___? I’m trying to avoid removing the back seat and panel assembly if possible. Even if the psi differential should be 1 more psi, that would bring the pressure down to around 7 psi, which the carb shop is telling me is probably too high long term. What has been your experience concerning a normal pump pressure (with the supercharger air pressure line disconnected) in today’s environment?
I’m trying to determine if the fuel pump is the culprit for the high fuel pressure before I replace it. And even if I replace it will another one correct the problem since the current one came from a reputable Studebaker source?
If nothing else, I could put a proper fuel pressure regulator in between the fuel pump and the carb and reduce the pressure that way. Have any of you had to resort to that set up? Any suggestions on such a set up?
Any suggestions would be helpful. I just want to be able to drive the car again without worrying about the carb leaking fuel all over the place!
Thanks!
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