Non return valve in fuel lline question
Thread Starter
Racer
Joined: Mar 2002
Posts: 406
Likes: 1
From: Maroochydore QLD
Non return valve in fuel lline question
I know the small in carby fuel filter has a non return valve in it and even though I have replaced this filter many times my car still takes 10 seconds of cranking when cold before it fires. I have researched this problem and everyone I have spoken to including Lars tells me that it is not leaking plugs in the fuel bowls on a late model C3 Rochester but syphoning of fuel back in to the fuel tank. If left long enough (overnight) you have to crank long enough to refill the carby.
Has anyone ever fitted some kind of external non return valve that stops this from happening?
I am concerned that I am putting undue wear and tear on my starter, ring gear, electrical system and battery.
Any ideas?
Thanks, Dennis.
Has anyone ever fitted some kind of external non return valve that stops this from happening?
I am concerned that I am putting undue wear and tear on my starter, ring gear, electrical system and battery.
Any ideas?
Thanks, Dennis.
Le Mans Master
Joined: Aug 2006
Posts: 7,413
Likes: 1,552
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
You can test the well plugs by putting same paper on your work bench then put a few sockets on the paper and put the carb on the sockets and pour a shot glass of fuel into the vent tube. If that's all good then reinstall the carb.
Choke:
After the car sits overnight remove the air cleaner and just crack the throttle a little and make sure the choke is closed and that the fast idle cam is in the correct step.
Next open the throttle fully and see if fuel squirts out from the accelerator pump movement.
If not the fuel pump check valve may be bad.
To check that: Start the engine confirm the carb is full and go under the car and clamp the return line closed.
See if you still have fuel in the carb the next day.
Choke:
After the car sits overnight remove the air cleaner and just crack the throttle a little and make sure the choke is closed and that the fast idle cam is in the correct step.
Next open the throttle fully and see if fuel squirts out from the accelerator pump movement.
If not the fuel pump check valve may be bad.
To check that: Start the engine confirm the carb is full and go under the car and clamp the return line closed.
See if you still have fuel in the carb the next day.
Le Mans Master
Joined: Oct 2010
Posts: 6,914
Likes: 836
From: melbourne florida
2023 C3 of the Year Finalist - Modified
i had the same problem and the same concerns as you i fixed it with a Holley.i know others swear by the q jet but I'll never ever change back
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
All you have to do is use a seat with no windows (needle and seat). Then the fuel filter check and pump check is irrelevant. Gas can't travel uphill since the bowl is vented.
Best way to check for well leakage is to shut the car off hot, let sit a few hours, carefully remove carb without moving linkage or tilting and checking intake for gas. Have found it in there when the bench/paper method does not.
It's not that big a deal to plug the wells properly anyway with screws and epoxy.
Ethanol speeds up the evaporation greatly, but overnite is a little much.
When cold, give it 2 pumps to the floor before touching the starter.
Mine will start in less than 1 revolution even without a choke.
Best way to check for well leakage is to shut the car off hot, let sit a few hours, carefully remove carb without moving linkage or tilting and checking intake for gas. Have found it in there when the bench/paper method does not.
It's not that big a deal to plug the wells properly anyway with screws and epoxy.
Ethanol speeds up the evaporation greatly, but overnite is a little much.
When cold, give it 2 pumps to the floor before touching the starter.
Mine will start in less than 1 revolution even without a choke.
