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For those of you who have installed a check valve between the fuel pump and carb what did you use?
There are several on Amazon for $13.00 for 2. Anyone have any experience using those? Evil seems to be a very common brand on Amazon.
Thanks for the input.
Assuming you’re talking about a Quadrajet. Why not just use a fuel filter with one built in?
I have been using them. Never made a difference. Carb and fuel line still dry after sitting about 16 hours. Used Napa 3052 filter w built in check.
I’m replacing the water pump and it seems a convenient access to install a check in fuel line. I may also remove the float clip as suggested by Lars. Belt and suspenders.
Yes it is a quadrant, 1978 L82. The QJ is a replacement but it is a 1978 vintage and unmolested.
Just seems like an easy, inexpensive solution with no drawbacks.
I have been using them. Never made a difference. Carb and fuel line still dry after sitting about 16 hours. Used Napa 3052 filter w built in check.
I’m replacing the water pump and it seems a convenient access to install a check in fuel line. I may also remove the float clip as suggested by Lars. Belt and suspenders.
Yes it is a quadrant, 1978 L82. The QJ is a replacement but it is a 1978 vintage and unmolested.
Just seems like an easy, inexpensive solution with no drawbacks.
The drawbacks are two extra connections in your pressurized fuel line. That introduces additional fire risk. If the check valve in the carb isn't doing anything, perhaps your problem is elsewhere inside the carb.
And just because this comes up all the time anyway, what is your timing set to? Perhaps you are just cooking the fuel out of the carb with excess engine heat. There was just a thread on this, and some suggested fixes.
I have been using them. Never made a difference. Carb and fuel line still dry after sitting about 16 hours. Used Napa 3052 filter w built in check.
I’m replacing the water pump and it seems a convenient access to install a check in fuel line. I may also remove the float clip as suggested by Lars. Belt and suspenders.
Yes it is a quadrant, 1978 L82. The QJ is a replacement but it is a 1978 vintage and unmolested.
Just seems like an easy, inexpensive solution with no drawbacks.
How did you determine that the float bowl was empty after 16 hours?
Are you aware the fuel pump has a check valve and depending on age of pump may have failed
I had one but I removed it a month later when I realized it was evaporation and not fuel draining back. Because your previous check valve filter didnt work I am willing to bet your problem is also evaporation. I could be wrong
I have ethanol free gas available not far away. When I use it, my car can sit for a week and it will start with 2 pedal pumps. The trade off is the ethanol free gas is lower octane so I need a booster or I have to back off timing. Neither option appeals to me.
How did you determine that the float bowl was empty after 16 hours?
Are you aware the fuel pump has a check valve and depending on age of pump may have failed
I look down the carb. I get one squirt of gas then nothing. Run the starter for a long time then I get fuel and it starts right up . It is cold in WI now, less than 30 degrees and still same issue. Thinking the cold is eliminating evaporation?
Thermostat is cooling system is 190. Is that too high?
I do not have non ethanol gas available.
If I remember correctly my timing is 36 degrees at 2800 rpm. I will recheck that when I get the new water pump installed and running. Probably next week.
I look down the carb. I get one squirt of gas then nothing. Run the starter for a long time then I get fuel and it starts right up . It is cold in WI now, less than 30 degrees and still same issue. Thinking the cold is eliminating evaporation?
Thermostat is cooling system is 190. Is that too high?
I do not have non ethanol gas available.
If I remember correctly my timing is 36 degrees at 2800 rpm. I will recheck that when I get the new water pump installed and running. Probably next week.
Thanks for the good comments
Unrelated to problem but a 180 thermostat would be best and Lars told you the best answer, use correct needle and seat, no window on seat.
Also, shortly after I got the car the fuel pump was replaced. Don’t know what kind. Put a pressure gauge on the supply line and get 6.5 to 7.5 psi at all speeds. Pressure drops to 0 as soon as engine shuts off. If check valve in pump was working would there be at least some residual pressure in the line? If the pump check valve is not working would the pump even pump?
Also, shortly after I got the car the fuel pump was replaced. Don’t know what kind. Put a pressure gauge on the supply line and get 6.5 to 7.5 psi at all speeds. Pressure drops to 0 as soon as engine shuts off. If check valve in pump was working would there be at least some residual pressure in the line? If the pump check valve is not working would the pump even pump?
There are 2 valves inlet and outlet. If outlet leaks fuel can drain back. Again though check the type of needle and seat you have.
Thank You all for your responses and help. Difficult for me to work up the nerve but I took the top plate off the carb. It does have windowed seat. Not sure what size the needle is, no markings on it. However, the rubber section looks very new.
So, I will get a new non windowed seat with .135 orifice. I went to Quadrajet Power. They show non windowed seat with a .134 needle. They also show a windowed seat with a .135 needle. Dumb question looking for an intelligent answer: is .001 a big difference? Should I go through the effort to order a non-windowed seat with a .0135 needle or am I breaking up a mated pair?
Lars - Do you sell these parts? Never Mind - looking through the many papers of yours I acquired over the years you always give resources for parts.
Also, Lars, you have advised removing a clip from the float assy. Are you referring to the sort of "C" clip. Straight on one side and half moon on the other side? I figured that out also, you are referring to the hanger wire on the needle that hangs from the float.
Thanks all for your help and continued help.
Jim
Last edited by biackbenz; Apr 28, 2026 at 01:53 PM.
Here’s one that’s exactly .135. It’s about a .7% difference in area between the two, so nothing to be too worried about, however Cliff is known to have very high quality parts. Shipping is the same no matter how much you get, so it pays to check for other items you might need like an airhorn gasket, accelerator pump, or choke pulloff.
Fuel line check valve
