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I have a 69 with a rebuilt 383 stroker. The original fuel delivery setup had the regulator placed directly next to the carb. One in two out style regulator.
I experienced issues recently. Bucking when shifting from low speeds. Slight hesitation when cruising. When it first happened I noticed my fuel pressure was low (around 3 but was set at 6) But starts just fine. Also, this car has the same fuel delivery setup for nearly 30 years.
I assumed it was the pressure regulator (has manual pump). I redid the fuel delivery by moving the regulator away from the carb. I experienced the same issues. So, I replaced the fuel pump with something similar. I installed a Holley 1232711.
The car is still having the same problems but not as bad I suppose. I feel like it has less power. Also, when adjusting the regulator, the fuel pressure barely wants to change. It remains around 4.5-5psi. I’m not sure why I cannot adjust the pressure. I’m assuming just a bunch of air is in my lines? Also, I blocked off one outlet on the regulator to make it one in one out. Not sure if they’re an issue. Maybe vapor lock but that doesn’t make sense giving how long this car ran before with the same setup. I do realize the pump I have says it doesn’t require a regulator.
St. Jude Donor '05-'06,'11,'13-'14,'16,'18,'19,'24, '25
Look at the supply side to the pump also, one issue that caused the exact issue for me was the rubber lines passing over the frame at the fuel tank.
They get missed as far as maintenance goes and will get brittle and crack allowing the pump to draw air along with fuel leaks and fuel odor.
I can't find a drawing on the 69 fuel system to verify that it has the same setup as the 77 so just throwing this out there if it does I would check it out.
Look at the supply side to the pump also, one issue that caused the exact issue for me was the rubber lines passing over the frame at the fuel tank.
They get missed as far as maintenance goes and will get brittle and crack allowing the pump to draw air along with fuel leaks and fuel odor.
I can't find a drawing on the 69 fuel system to verify that it has the same setup as the 77 so just throwing this out there if it does I would check it out.
Neal
I’ll inspect it this week. It’s AN fittings but I really don’t remember how or where I have it converter from the tank to AN.
Well if the pump is only giving 5psi with the reg wide open then you may need to inspect the pump......I assume it is a high performance unit or else the regulator would not be needed.....if so, most are the pancake type with all of the screws around the outside holding it together.......you can rebuild those......
Also....good suggestion on the debris in the inlet/supply of the pump.......check this first.
Well if the pump is only giving 5psi with the reg wide open then you may need to inspect the pump......I assume it is a high performance unit or else the regulator would not be needed.....if so, most are the pancake type with all of the screws around the outside holding it together.......you can rebuild those......
Also....good suggestion on the debris in the inlet/supply of the pump.......check this first.
Jebby
it will be at 6 or 6.5 on start up. After running it will drop. Either way, the regulator doesn’t seem to control pressure. The problem has been the same with the old pump and old regulator.
There are no other filters before the input of the pump. I have a manual shut off before the input. There is an oily substance at the connector from the tank to the anfitting. Does not smell like gas tho
You don't need the regulator with that pump as you already know, get rid of it to eliminate it as a problem.
Can you use the original GF432 style fuel filter with the built in return line?
Going down a different line of thought, if you temporarily disconnect distributor vacuum advance does the problem go away?
If the pressure is up to 6-6.5 psi when the engine starts, how long does it take for it to drop to the 5 psi?
Is the fuel supply line from the tank to the engine the original?
Try running a temporary rubber fuel line from the tank up to the fuel pump to see if the problem goes away.
If so, replace the oem fuel line, they have been known to corrode on the inside.
Also check the fuel sock inside the tank, it could need replacing as well.
One more thing to check is make sure your fuel tank is properly venting.
These are just additional things to check other than what’s already been discussed.
If the pressure is up to 6-6.5 psi when the engine starts, how long does it take for it to drop to the 5 psi?
Is the fuel supply line from the tank to the engine the original?
Try running a temporary rubber fuel line from the tank up to the fuel pump to see if the problem goes away.
If so, replace the oem fuel line, they have been known to corrode on the inside.
Also check the fuel sock inside the tank, it could need replacing as well.
One more thing to check is make sure your fuel tank is properly venting.
These are just additional things to check other than what’s already been discussed.
Usually when it got to operating temperature it would drop pressure.
To your advice and ran it without the regulator. No symptoms like before. Pressure varied around 5.5 at start up to 4.5 warmed up at the end of my test drive. Is that normal for pressure to vary without a regulator?
Usually when it got to operating temperature it would drop pressure.
To your advice and ran it without the regulator. No symptoms like before. Pressure varied around 5.5 at start up to 4.5 warmed up at the end of my test drive. Is that normal for pressure to vary without a regulator?
if you installed the pump number listed earlier it is much lower than the rated number of 6.5 to 8. Is your gauge accurate?
if you installed the pump number listed earlier it is much lower than the rated number of 6.5 to 8. Is your gauge accurate?
Yea. I have two gauges I verified both at good. I’m going to replace all fuel lines. They’re over 20 years old and probably falling apart.
EDIT: Recommendations where to buy a new sock? I may replace the line first and see if that resolves the issue. I also forgot to mention to vacuum advance.
Last edited by Jonscazz; May 10, 2023 at 06:43 AM.
Complete fuel line replacement on these cars is no simple task with the body on the chassis.
It can be done but difficult.
I would do simple stuff first.
Replace the fuel pump, and the mechanical rod (they do wear out), and the regulator.
Set the pressure to Holley’s specs, and go from there.
When you replace the fuel lines be sure to prepare for Ethanol. Your older AN lines might not have had the Teflon (PTFE) tube inside that resists the Ethanol in today's gasoline. Your regulator may have been affected by the ethanol as well as it damages the Rubber components inside the regulator. How close is your regulator mounted to heat generating devices?
I ran an Aeromotive external Fuel pump and had the regulator up front on a fender-well at first. I do not remember any varying of the fuel pressure. My fuel pressure stayed at 6 psi all the time and did not vary according to the gauges I used. Later on I moved the regulator to the area near the fuel pump so the pressure going forward in the fuel lines was already regulated. Relocating the regulator helped cool the parts since sitting inside the engine compartment of a hot running Big block.
Today I have an EFI system and my fuel pump and regulator are both inside the fuel tank and the pressure is rock steady. I also ran the fuel in from over the bell housing to help keep the fuel cooler.
Fuel Pressure Issues
