Fuel pump failure?
06-16-2018, 08:57 AM
#1
Racer
Thread Starter
Engine flooding!
Been troubleshooting a problem for weeks. Rebuilding my ‘72. Having this problem where the engine is flooding. Car starts but after running for a while it will not restart. We are pretty confident it is not the carb. Is it possible the fuel pump could be causing the engine to flood? We tested the fuel pressure and it holds at 3 pounds. When we last started it we removed the carb, looked in the intake and it was wet. Determined it is not vapor lock as the problem happens when engine is cold. Current plan is to replace the fuel pump. Appreciate any suggestions. This is basically the last thing to fix before I can get this baby back on the road after countless years!!
Last edited by Silver72; 06-17-2018 at 03:50 AM. Reason: for clarity
06-16-2018, 10:10 AM
#2
Le Mans Master
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If the engine is flooding first place I would look is the carb. Probably a faulty float or needle hanging the fuel bowl open. Another cause would be if the pump puts out too much pressure. Typically over 7 psi.
06-16-2018, 10:21 AM
#3
Le Mans Master
Not the pumps fault at 3 psi.
Float level too high, dirt in needle valve, or floats sinking, something along those lines.
Float level too high, dirt in needle valve, or floats sinking, something along those lines.
06-17-2018, 06:48 AM
#6
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If it happens after the engine was hot, you need a spacer. The engine heat is heating the carb and boiling the fuel and its overflowing into the intake. My edelbrock was bad at this until I put in the spacer. I just switched to a Quadrajet and they have the small rubber heat shield gasket but I used a 1 inch spacer like I had on the edelbrock and it works great. I had to buy a special divorced choke but it runs great
06-17-2018, 01:52 PM
#7
Racer
Thread Starter
If it happens after the engine was hot, you need a spacer. The engine heat is heating the carb and boiling the fuel and its overflowing into the intake. My edelbrock was bad at this until I put in the spacer. I just switched to a Quadrajet and they have the small rubber heat shield gasket but I used a 1 inch spacer like I had on the edelbrock and it works great. I had to buy a special divorced choke but it runs great
06-17-2018, 01:55 PM
#8
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crack in the bowl or leaking plug? Ask Lars. He just did my carb and my car is running likes its fuel injected. I cant be happier, the man is a genius with these things.
06-17-2018, 03:33 PM
#10
Dr. Detroit
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Both carbs not functioning properly......
It is a function of engine vacuum to draw the fuel into the intake. If the carb is functioning properly.....then it get what it needs and nothing more.
If it is flooding....then it is the carbs fault....especially when cold.
If these are Q-jet carbs.....I remember years ago that there were problems with the well plugs on some rebuild where they used epoxy....check that out.....and Lars, please pop in here if I am not clear.
Good luck....!
Jebby
It is a function of engine vacuum to draw the fuel into the intake. If the carb is functioning properly.....then it get what it needs and nothing more.
If it is flooding....then it is the carbs fault....especially when cold.
If these are Q-jet carbs.....I remember years ago that there were problems with the well plugs on some rebuild where they used epoxy....check that out.....and Lars, please pop in here if I am not clear.
Good luck....!
Jebby
06-17-2018, 03:46 PM
#11
Racer
Thread Starter
Both carbs not functioning properly......
It is a function of engine vacuum to draw the fuel into the intake. If the carb is functioning properly.....then it get what it needs and nothing more.
If it is flooding....then it is the carbs fault....especially when cold.
If these are Q-jet carbs.....I remember years ago that there were problems with the well plugs on some rebuild where they used epoxy....check that out.....and Lars, please pop in here if I am not clear.
Good luck....!
Jebby
It is a function of engine vacuum to draw the fuel into the intake. If the carb is functioning properly.....then it get what it needs and nothing more.
If it is flooding....then it is the carbs fault....especially when cold.
If these are Q-jet carbs.....I remember years ago that there were problems with the well plugs on some rebuild where they used epoxy....check that out.....and Lars, please pop in here if I am not clear.
Good luck....!
Jebby
When does the fun start?
06-17-2018, 07:16 PM
#12
Race Director
06-17-2018, 09:07 PM
#13
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I've got a fuel pump that only goes to 3.5/ 4 lbs. I got the exact opposite problem. new one is in the mail
06-17-2018, 09:29 PM
#14
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Both carbs not functioning properly......
It is a function of engine vacuum to draw the fuel into the intake. If the carb is functioning properly.....then it get what it needs and nothing more.
If it is flooding....then it is the carbs fault....especially when cold.
If these are Q-jet carbs.....I remember years ago that there were problems with the well plugs on some rebuild where they used epoxy....check that out.....and Lars, please pop in here if I am not clear.
Good luck....!
Jebby
It is a function of engine vacuum to draw the fuel into the intake. If the carb is functioning properly.....then it get what it needs and nothing more.
If it is flooding....then it is the carbs fault....especially when cold.
If these are Q-jet carbs.....I remember years ago that there were problems with the well plugs on some rebuild where they used epoxy....check that out.....and Lars, please pop in here if I am not clear.
Good luck....!
Jebby
If fuel pressure is less than 6psi, and if the engine is flooded out after hot shut-down, there is a problem with the carb allowing fuel to "seep" past the needle/seat and flood the engine. It's most likely a carb problem related to the float or the needle/seat assembly. There are instances of porous carb castings and leaking well plugs in the carb that can cause the same problems, but these issues are rare. I'd be looking at the carb(s) for the problem.
Lars
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Silver72 (06-17-2018)
06-18-2018, 12:42 AM
#15
Racer
Thread Starter
If fuel pressure is less than 6psi, and if the engine is flooded out after hot shut-down, there is a problem with the carb allowing fuel to "seep" past the needle/seat and flood the engine. It's most likely a carb problem related to the float or the needle/seat assembly. There are instances of porous carb castings and leaking well plugs in the carb that can cause the same problems, but these issues are rare. I'd be looking at the carb(s) for the problem.
Lars
Last edited by Silver72; 06-18-2018 at 12:42 AM.
06-18-2018, 07:14 AM
#17
Racer
Thread Starter
Been troubleshooting a problem for weeks. Rebuilding my ‘72. Having this problem where the engine is flooding. Car starts but after running for a while it will not restart. We are pretty confident it is not the carb. Is it possible the fuel pump could be causing the engine to flood? We tested the fuel pressure and it holds at 3 pounds. When we last started it we removed the carb, looked in the intake and it was wet. Determined it is not vapor lock as the problem happens when engine is cold. Current plan is to replace the fuel pump. Appreciate any suggestions. This is basically the last thing to fix before I can get this baby back on the road after countless years!!
06-18-2018, 09:55 AM
#19
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06-18-2018, 10:57 AM
#20
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Lars, what fuel pressure should these quadrajets be running at. Ive read less than 6 psi. I just bought a new 7lb pump and a new regulator as my old pump was only putting out 3.5 and the regulator was 1-4 psi I was going to reduce it to 5/ 5.5.
I was thinking the PO was over pressuring his setup if 2 different carbs were causing the same issue. I'm using a 1 inch spacer and haven't had any percolation problems at all. Just hard starts after it's been sitting for a week. Like its evaporated all the gas off.
with my edelbrock I would have these flooding problems when it was sitting after it was hot after it cooled down overnight. That's why I went to the phenolitic spacer and kept it for the quadrajet. I have an aftermarket divorced electric choke conversion mode to work and it does
I was thinking the PO was over pressuring his setup if 2 different carbs were causing the same issue. I'm using a 1 inch spacer and haven't had any percolation problems at all. Just hard starts after it's been sitting for a week. Like its evaporated all the gas off.
with my edelbrock I would have these flooding problems when it was sitting after it was hot after it cooled down overnight. That's why I went to the phenolitic spacer and kept it for the quadrajet. I have an aftermarket divorced electric choke conversion mode to work and it does
Last edited by Rescue Rogers; 06-18-2018 at 11:02 AM.
