I have a 327 chevy 4 barrel carb. New mechanical fuel pump, I have a clear gas filter and after it sits a couple weeks the filter goes dry. I know the pump is supposed to have a check valve but I didn't think it was doing its job, so I installed a one way valve in fuel line to keep gas from running back to pump . My question is will this keep to much pressure on carb and cause it to flood. I drove it around some and carb started flooding took it off still flooded so I replaced float needle seat doesn't flood now but would like to put valve back in line . I don't know if that was a coincidence or not , thanks mike
If the one way valve in the pump is not working, it will not pump. I don't think you need to add another valve. Modern gasoline evaporates rather quickly. If I don't drive my cars every day or two, the fuel evaporates out of the carb, and I have to crank it a while to get it going again. That's with everything working as it should.
What squirrel said. Just todays gas. All carbureted, mechanical fuel pump engines have the same problem. If you want to alleviate the problem, an electric fuel pump is the answer. Turn the pump on for a few seconds before turning the key, all should be fine. Mike
Q-jets are notorious for percolating after being shut off , especially if the intake is carboned up and/ or the base gaskets are wrong application or damaged ...
As mentioned by Jim (squirrel) and Mike above, probably evaporation. This issue is sufficiently serious enough that we added it to the troubleshooting section of our website: http://www.thecarburetorshop.com/Troubleshooting.htm#Hardstartcold Jon
I had the same issue with the fuel evaporating, and that plus having a Qjet with an internal leak (fixed), made it a true pain in the butt to start after the truck had been sitting for a week or more. I installed an electrical pump between the tank and the mechanical pump. This solved the problem. Bob
The engine should still start right up if the float bowl is full. Q jets had a problem with the soft plugs in the bottom of the bowl would leak and the bowl would drain all fuel if the car sat for a time. If the the bowl is empty after sitting I would suspect those plugs. You used to be able to buy rubber plugs that went between the bowl and the base plate that prevented the leak. The other fix is to clean and seal the plugs with epoxy.
What make model pump did you use and do you leave it running and does mechanical pump still pull gas thru thanks mike
Hot Rod mag recently had article re: fixing dribbling Qjets with kit from Ohio shop. Also fix for throttle plate wobble. Sent from my iPad using The H.A.M.B. mobile app
Yeah sounds like well plugs leaking. Quick fix? Get a little toothbrush style wire brush and jb weld. Pull bottom plate off carb, use wire brush to clean the crap out of the plugs then some carb cleaner, let dry good and then mix up some jb weld and cover the plugs really well. One thing to be careful of is using too much. So after coating the plugs wait about 5 minutes and try putting the bottom plate on, make sure that the jb weld isnt to thick to allow the plate to seal. If all checks out let it set over night and put back together the next day and enjoy... One note, after you do this you can throw the stupid foam "seal" away that comes in kits for the well plugs.
One guy wondered where the gas was going so he set the carb on the bench, filled it up, came out the next morning and the crap gas they sell us had evaporated
They do make a paper fuel filter with a check valve built in, for the inside of the carb . Make sure you have the spring behind the filter. They worked keeping the bowl from emptying before ethanol was around.
I bought the electric pulse type pump on ebay. It is a solid state unit, and I have also been running the same pump on my excavator with no issues. I am using the pump to feed the mechanical pump, and the setup is working great. After the truck has not been used for a couple of weeks, all I have to do, is turn the ignition on, count to ten, and everything is primed and ready to go. If the electrical pump was to fail, the mechanical pump will pull just fine. I tested this, my having the electrical pump plumbed into the circuit and disconnected the power. There were no issues with starting or driving, even at full power. Bob
My vote is also evaporation, sometimes we look for a problem when there isn’t one. I have the same issue if I don’t drive them every day or two as well, just like squirrel said. I just know it’s going to crank awhile. Sent from my iPhone using H.A.M.B.
If your plumbing the electric thru the mechanical one and using it full time there is a possibility of the diaphram cracking on the mech pump and the electric filling the crankcase with gas, this is not a pretty picture.
I agree that what you state is possible, but it is not probable. The mechanical pump is fairly new, and the pulse pump is not a high pressure pump. I haven't checked the pressure of the electric pump myself, but I am not concerned. Bob
I have electric pump in back and SBC with mechanical pump. I have a manual switch on electric pump. When car has not been started for four or five days, I switch on electric pump. Wait a few seconds. Click the auto choke on by touching accelerator oecal. Start cranking. Usually fires in less than ten seconds. Once it is started I turn electric pump off and run on mechanical pump. Occasionally I get a vapor lock stall on the highway. Switch on electric pump and it restarts itself. Might then have to leave electric pump turned on until next scheduled stop. I try not to overwork electric pump. Carter 4070. Phil
Good idea, I will do the same, because the only thing I am really using the electric pump for, is for the first cold startup. The rest of the time, the engine fires up immediately. I don't know why I didn't think of it, because that is the exact setup I have on my plane, a Lake amphibian. Bob
I believe I have the electric pump on a circuit with a ten amp fuse. The toggle switch I believe is rated somewhere above 20 amps. Also have one of those plastic flip covers on the switch. Phil
Thanks for all of the replys , one thing that has not been Addressed that was asked in my original post is [ will the inline 1 way valve hold to much pressure at the carb] it is between the carb and pump which keeps fuel filter full when engine is not running . Which keeps carb primed
It's not possible to keep the carb primed with today's oxygenated fuel. The fuel evaporates much more quickly than anyone would think. That's why the carb needs to be re-primed if it sits for a few days. Unlike a mostly air sealed efi system, most of the carb internals are open to the air. Phil
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