I've got a problem with too high fuel pressure on my 57 wagon....I have 11 lbs pressure at idle and 16 lbs at a fast idle (1500-2000 rpms).I've replace the mechanical pump twice and put the third pressure regulator on it. I can set the pressure at 4.5-6 lbs. and it will hold there for a day or so then back to the high pressure.. The pump is for a '69 chevy 350, which is the engine in the car...The pressure gets so high that gas will come out of the vent on carb and pour into engine. Before the regulator goes bad it will start leaking...Any ideas from anyone ??????
I would say you need a higher quality regulator or need to adjust the float level on the carburetor accordingly I had a Stromberg rebuild kit that the float stop actually did not allow the needle to seat and close off so it would flood out all the time before I modified the float stopper Sent from my iPhone using The H.A.M.B. mobile app
cheap ass fuel pumps 2 in a row at 10 lbs, had to add a regulator, to lazy to try a 3rd...never had this problem before....delco's to boot
I've rebuilt the carb and float which didn't help...I'm using Holley regulators..I just today changed from stock cast iron intake and 2 barrel Rochester to eldebrock aluminium intake and 600 carb ...I know this wouldn't fix high pressure but wondered if eldebrock carb would handle it better....it didn't. My biggest question is why would a stock fuel pump put out that much pressure and how to correct it....
I've read this is a problem with offshored parts. Measure it. If it's bad, take it back. If it takes 10 pumps to find a good one... If everybody sent them a labor charge bill @ $100 an hour for R&R of defective, shitty parts this wouldn't happen. One thing you can try is add an extra gasket or two. Probably won't bring it diwn from 10psi to 4.5psi but maybe some. This was a tip somebody brought up here at the H.A.M.B, it moves the pump arm farther out from the eccentric on the camshaft.
No , the pump has no return line....the problem just started overnite...car was running fine one day and the next it was flooding .....that's why I changed the fuel pump thinking that was problem..2nd pump did same thing so on to 3rd thinking I got bad one ...same thing....why would a stock replacement pump put out so much pressure?
Try buying a different brand of pump. I had this happen with a pump I bought at NAPA, 16 psi. retuned it, 2nd was 13 psi. Got one from the Zone, works fine. Quality control at some china factories isn't so great I guess...
All 3 pumps came from Advance auto....I did notice that all 3 had really stiff springs on the arm ..could that cause pressure spike ?
Agree 100%, and also agree with trying another brand pump. You say you got it at Advance, but what brand is it? Maybe try a Holley pump or another name brand.
The cure used to be an AC pump. They would give a uniform 5-6 lbs. every time. This may or may not hold true today. I learned this lesson w/ an Airtex good for 18 1/2 lbs.
I wonder if you put a filter with a return and plumbed it to a tee before the pump would it work the same as a return to the tank? Sent from my LG-TP450 using The H.A.M.B. mobile app
I suspect the regulator failed. A regulator with a return to tank is less likely to fail as it is only subject to the pressure it is set to. Returning fuel to the tank also keeps it cooler as it has a constant flow. The spring in the pump determines the pressure unless the pump has a bypass.
Very entertaining to read all the add on's required for a devise that didn't need add on's ever before.
How the heck can a mechanical fuel pump deliver too much pressure? Is your gauge calibrated? Considering that you have tried several fuel pumps, and regulators, maybe the fault is not in the pumps. The amount of pressure that a mechanical fuel pump can deliver is determined by the diaphragm spring. So a manufacturer would have to install the wrong spring, i.e. one that is twice as stiff as the correct one, to cause the problem you have. I would have thought this almost impossible, but maybe in China heavy springs are cheaper than light springs. How about getting an early, rebuildable fuel pump and a current manufacture rebuild kit for it. That way the pressure will be what it was when that pump was made.
I've always had good luck with Carter mechanical fuel pumps. Some of the higher end pumps are rebuildable also.
That auction site has a pretty wide selection of complete rebuild kits to include Viton diaphragm, for period fuel pumps, that are supposed to be Ethanol tolerant. They cost about twice what a new fuel pump costs though. If you don't need all the springs & gee-gaws maybe Viton sheet can be made to work. Fuel pump pressure (and volume) is an important specification, because every further adjustment or setting downstream of the fuel pump on a carburetor is based on the assumption that the fuel pressure is within limits, not too high, not too low. Replaced the pump on the ole' Y-Block with an Airtex FE style pump that has the integral filter, and really had to crank the float down quite a bit to get the wet fuel height in the carb bowl right. I bet if I checked the pressure, it's too high.
the regulators are Holley and the pumps are Carquest from Advance Auto. Changing fuel pump is a pain as there is no room to work . I've checked all the local parts stores and there are no AC Delco pumps on the shelf...all have to order..
That new Edelbrock won't like the higher fuel pressure either, it will push fuel right past the needles.
Laugh all you want but a ball valve tee'd off the pressure line onto a return line to the tank has proven it's cheap cost over high dollar regulators greatly. Not advised for street use so don't do it.
both of mine were ac delco……..its just no more q/c I guess, never had that problem before, and I have changed out many
"Laugh all you want but a ball valve tee'd off the pressure line onto a return line to the tank has proven it's cheap cost over high dollar regulators greatly. Not advised for street use so don't do it." Lots of vehicles had a return system with a carburetor. It would have a restrictor in it, about 1/32" or 1/16".
https://www.jalopyjournal.com/forum/threads/a-couple-of-questions-sbc-fuel-pressure-problems.860941/ This may help, from a thread I started a few years back.
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