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I have a 69 Cutlass with a Fa 455 in it. I'm wondering what the plugged line from the fuel pump is for and if it should be connected to something? Is this a replacement part that fits a wide variety of engines and years and not 69 specifically?
Fuel pumps come in two flavors: with a return line and without a return line. Both are essentially the same except for the return line The appropriate pump depends upon the specific application.
Cars with air conditioning used a pump with the return line. The purpose of the return line is to constantly circulate fuel to the tank (keeps the pump and fuel a little cooler) and more importantly, to vent fuel pressure back to the tank after shutting off the engine.
Imagine driving the car with the A/C on in 100 degree temp. You **** off the engine, the fuel in the pump will continue to heat and boil. Without the return line, the fuel pressure will continue to rise enough to force the needle off the seat in the carb, flooding the engine. That obviously makes hot restarts difficult.
Typically, fuel return was used on applications that were at risk of percolation due to high underhood temperatures. This includes A/C cars and high performance models, among others. Recirculating a portion of the hot underhood fuel back to the tank to cool helps with fuel temps. Whoever did the swap pulled that 455 from an A/C car and couldn't be bothered to change the fuel pump. It won't hurt anything to cap the line.
Typically, fuel return was used on applications that were at risk of percolation due to high underhood temperatures. This includes A/C cars and high performance models, among others. Recirculating a portion of the hot underhood fuel back to the tank to cool helps with fuel temps. Whoever did the swap pulled that 455 from an A/C car and couldn't be bothered to change the fuel pump. It won't hurt anything to cap the line.
Joe, curious on your opinion or thoughts on the rationale (from the table and my past experience) on why a 350 with 4 bbl, AC and AT would not have a return line and the 2 bbl version of the same combination would ?
Joe, curious on your opinion or thoughts on the rationale (from the table and my past experience) on why a 350 with 4 bbl, AC and AT would not have a return line and the 2 bbl version of the same combination would ?
I've only had a couple of cars with 2GC carbs, but I've found them to be sensitive to percolation. It might have been in response to that. Otherwise, I got nothin'.
Joe, curious on your opinion or thoughts on the rationale (from the table and my past experience) on why a 350 with 4 bbl, AC and AT would not have a return line and the 2 bbl version of the same combination would ?
My 72 Supreme has AC and the original 350 4BBL. It does not have a return line.
My 72 Supreme has AC and the original 350 4BBL. It does not have a return line.
Based on the table, yes that would be a correct setup. I was wondering why GM thought that a 2 barrel version of the exact same combination would need a return line; the opinion being that carb would be more sensitive to percolation.
Based on the table, yes that would be a correct setup. I was wondering why GM thought that a 2 barrel version of the exact same combination would need a return line; the opinion being that carb would be more sensitive to percolation.
To answer your question of where to plumb that return line; it depends. Cars that were originally equipped with a vapor return line had two fuel lines running parallel to each other from the tank to the fuel pump. The '69 442 had a 3/8" main fuel line and (I think) 1/4" return line. If your car was not originally equipped with the vapor return, you only have the single fuel line running the length of the car from the tank to pump so there wouldn't be anywhere for you to plumb that capped line into - unless you wanted to retrofit a new vapor line in the car. Hardly worth it.
Sounds like your car was not originally equipped with a return line and, as mentioned above, whoever installed the 455 brought the fuel pump with it and just capped that line. A little sloppy but won't hurt anything.
Sloppy for sure. That looks ridiculous, the PO took the time to chrome plate all brackets, pulleys, and valve covers, and he leaves that! I just ordered the correct one from Rock for $18.
Echo on A/C cars having the return line and non-A/C having no return line. I work on one of each.
I like the Carter brand of fuel pumps. They seem to last a long time & send something like correct fuel pressure to the qjet’s I use.
I don’t like the die cast chrome Holley pumps. At all.
Here’s why: out on I-5 in CA, between nowhere & nowhere, in the 80’s, one of them just cracked apart on me at freeway speed. A broken diecast fuel pump made a 5 hour trip into a 12 hour odyssey complete with zip-tied electric fuel pump rigged directly to the battery. I’m not even going to mention the two drunk guys who gave me a ride to the nearest gas station. Or the station attendant who laughed in my face (in the 80’s) and said “A Sixty what?”
The electric replacement worked, but to this day I carry a spare fuel pump in the trunk of each car, just in case. With hoses, clamps, the whole bit.
Catastrophic failure leads to improved preparation. Occasionally.
I'm trying to start a 1968 442 and am having flooding problems flushing the whole motor with gasoline. Float and seat checked, rechecked and then checked again. I'm about to take a sledge hammer to this quadrajet pile. Checked the fuel pressure, although deadheaded to the gauge, and it is 10 to 10.5 psi. I'm on my second napa pump at this point and they both do exactly the same thing. My brother did some research and found some blogs that claim the over pressure can be related to the return/vapor line is plugged causing an over pressure condition (almost twice spec) at the seat. Going to blow back this line today. Thoughts?
I'm trying to start a 1968 442 and am having flooding problems flushing the whole motor with gasoline. Float and seat checked, rechecked and then checked again. I'm about to take a sledge hammer to this quadrajet pile. Checked the fuel pressure, although deadheaded to the gauge, and it is 10 to 10.5 psi. I'm on my second napa pump at this point and they both do exactly the same thing. My brother did some research and found some blogs that claim the over pressure can be related to the return/vapor line is plugged causing an over pressure condition (almost twice spec) at the seat. Going to blow back this line today. Thoughts?
Considering that you can cap the return port on the pump and it will work fine should tell you that this is not a credible failure mode and you should stop getting diagnostic info from the interwebs. 10 PSI is obviously why your carb is flooding, so don't blame the Qjet. And stop getting crappy Chinesium pumps from NAPA. I've has no issues with a Carter M4516 pump. $22 at RockAuto.
I had the same issue with two Carter pumps from NAPA - both pegged my pressure gauge at 10 psi. The third pump was good with around 6-7 psi. This was years ago so I would think the issue had been rectified by now.
Alright gentlemen, here are the results of todays test, irrespective of theory. I installed the pressure gauge on the supply side of the pump and took a line from the return side and put it in a jug. Remember I haven't been able to start the car to this point from flooding. The gauge showed 8-9 psi when cranking. I disconnected the the pressure side and connected it to the carb. With a little tweaking of the timing I finally got it to start. I ran the car for probably 20 minutes. No flooding, and it pumped between 1 and 2 gallons of gasoline into the jug from the return line. This pump is truly working as a return style fuel system and it appears I have a plugged return line somewhere between the pump and the tank. My brother was right with his search on the interweb.
As a side note Fusick has a sender with two lines and they describe the second line as a return line as I would as well. Just thought I would give an update.
Last edited by Ultra Tweaker; July 19th, 2021 at 10:01 AM.
A couple weeks ago my non return pump started leaking out the weep hole. I swapped it w a return line style pump i had in a box. I blocked off the return line and havent had any issues. The car ran fine w the old pump for 10 yrs till it started leaking ( w a sbo n edlebrock and a bbo n qjet). It runs fine w the new ( old ) return line pump.
I just posted this not to discount your experience but to state i had a different experience.
Last edited by RetroRanger; July 19th, 2021 at 03:34 PM.
Intresting thread , was thinking to order a new fuel pump to my 98 -65 without AC. But the old one in
the car looks to be an AC model with 2 threaded connections when looking at Rockauto.
I can see at their website that the AC type Carter M4526 have a min pressure of 9.0 psi and the
non AC type Carter M4871 have a min pressure of 7.0 psi . Guessing that the higher min pressure is
because the fuel return to the fueltank. Seems to have worked in my car with a little higher min pressure
than the recommended fuel pump M4871, too bad
this was out of stock at Rock
I donīt want a Airtex pump , had one in my truck and it failed a couple years later so now i have a Carter
who has worked just fine.
Probably 20 years ago, the original fuel pump started leaking on the 307 in my 81 Delta 88. I think it was factory, I had all the bills from new in 82. The factory was a 2 line in spite of A/C. They gave me a Carter 3 line pump. I was going to return it but just plugged the line. The pump could not keep up with a 307! I don't know if this was a Canadian car oddity or if someone did it. I found a cap with a factory style emissions clamp that requires pliers to open, on a return line in the factory spot, not a regular hose clamp like someone after the fact would have used. I removed the cap and added a clear fuel hose. Fuel flowed through, pump still starved the motor. A bought a proper 2 line pump that worked for a few years. I actually tried it years later in my Olds powered truck, same result, it went in the garbarge. I had a no name pump no keep up running my 8 to 1 Olds 403 in the 1/8 mile. I have bought 2 Carter Muscle car series pumps since, a 2 and 3 line pump. One was track tested with 0 issues. Strange things happen with replacement parts. I also keep a lot of spare parts in my old car, including a fuel pump.
June 26th, 2021, 08:38 AM
