fuel starvation
12-20-2007 | 08:36 PM
#1
Guest
Posts: n/a
fuel starvation
Hi, excuse me my bad english. This is my problem:
I have a 318, weiand intake, 274 comp cam XE, Crane Hi6 ignition, mechanical factory pump. I start the engine with no problems.. when the car get the temperature (around 80 C) and after a run at full throttle. The car stop, i have a fuel filter between the pump and the carb and in the filter i dont see fuel. I let rest the car for 10 minutes and the car runs but only for a little time. I check the fuel pump: the valves and diapraghm are ok. The tank has gasoline. The next day on the morning the car runs without problem again and the fuel filter looks full of gasoline.....
Any ideas?? Thanks.
I have a 318, weiand intake, 274 comp cam XE, Crane Hi6 ignition, mechanical factory pump. I start the engine with no problems.. when the car get the temperature (around 80 C) and after a run at full throttle. The car stop, i have a fuel filter between the pump and the carb and in the filter i dont see fuel. I let rest the car for 10 minutes and the car runs but only for a little time. I check the fuel pump: the valves and diapraghm are ok. The tank has gasoline. The next day on the morning the car runs without problem again and the fuel filter looks full of gasoline.....
Any ideas?? Thanks.
12-21-2007 | 12:12 PM
#2
Mopar Lover
Joined: Nov 2007
Posts: 2,424
Likes: 248
This sounds like a case of what in the U.S. we call "vapor lock" which can have several causes.
The general situation is that heat causes the fuel to tend to boil. Because the normal fuel pump is engine mounted up front, the entire fuel line from the tank to the pump is under reduced pressure (suction) caused by the pump. THIS FACT causes the fuel boiling point to be lowered, and the fuel can "flash" or boil right in the fuel line, causing vapor which "won't pump", hence the name "vapor lock".
There are several things you can do to solve the problem.
First, inspect carefully the condition of the line. Start at the tank, and inspect the rubber connector, as well as the one at the pump. If these appear to be at all crimped, flat, soft, or damaged, replace. Inspect the metal line for damage, such as large dents or flattened. Look to see if the tube is close to heat, exhaust/mufflers, etc.
In some cases, the filter or tube in the tank can be damaged, rusted up, plugged, which causes a restriction.
It might just be the pump itself is weak. Just because you installed a new pump does not mean that it is working properly, or is of good quality.
I did not see your car model listed. Some cars, and Jeeps, have a "vapor return line" in the fuel system. This consists of a can or filter which is inline at the output of the pump, with a small bleed hole at the TOP of the can, returning to the tank through a second tube. This can collects bubbles and vapor and returns them to the tank
My '70 Roadrunner, which came from the factory with a "440 six pack" had this right from the factory. My '69 383 car did not.
One sure fire way to cure this problem is to install an electric pump RIGHT AT THE TANK, where the pump can "push" rather than "pull."
Take a GOOD look at all your fuel line, and isolate, move, or insulate it from exhaust and engine heat as best you can.
Don't wast time with wive's tales concerning "cow magnets" or other clip on devices--they don't really work.
Here is a diagram of a "universal" vapor return filter. IT IS UPSIDE DOWN. The small return fitting should be UP at the top.
http://www.autozone.com/images/cds/gif/small/0900823d8005150b.gif
The general situation is that heat causes the fuel to tend to boil. Because the normal fuel pump is engine mounted up front, the entire fuel line from the tank to the pump is under reduced pressure (suction) caused by the pump. THIS FACT causes the fuel boiling point to be lowered, and the fuel can "flash" or boil right in the fuel line, causing vapor which "won't pump", hence the name "vapor lock".
There are several things you can do to solve the problem.
First, inspect carefully the condition of the line. Start at the tank, and inspect the rubber connector, as well as the one at the pump. If these appear to be at all crimped, flat, soft, or damaged, replace. Inspect the metal line for damage, such as large dents or flattened. Look to see if the tube is close to heat, exhaust/mufflers, etc.
In some cases, the filter or tube in the tank can be damaged, rusted up, plugged, which causes a restriction.
It might just be the pump itself is weak. Just because you installed a new pump does not mean that it is working properly, or is of good quality.
I did not see your car model listed. Some cars, and Jeeps, have a "vapor return line" in the fuel system. This consists of a can or filter which is inline at the output of the pump, with a small bleed hole at the TOP of the can, returning to the tank through a second tube. This can collects bubbles and vapor and returns them to the tank
My '70 Roadrunner, which came from the factory with a "440 six pack" had this right from the factory. My '69 383 car did not.
One sure fire way to cure this problem is to install an electric pump RIGHT AT THE TANK, where the pump can "push" rather than "pull."
Take a GOOD look at all your fuel line, and isolate, move, or insulate it from exhaust and engine heat as best you can.
Don't wast time with wive's tales concerning "cow magnets" or other clip on devices--they don't really work.
Here is a diagram of a "universal" vapor return filter. IT IS UPSIDE DOWN. The small return fitting should be UP at the top.
http://www.autozone.com/images/cds/gif/small/0900823d8005150b.gif
Last edited by 440roadrunner; 12-21-2007 at 12:26 PM.
12-26-2007 | 09:35 PM
#3
Guest
Posts: n/a
This sounds like a case of what in the U.S. we call "vapor lock" which can have several causes.
The general situation is that heat causes the fuel to tend to boil. Because the normal fuel pump is engine mounted up front, the entire fuel line from the tank to the pump is under reduced pressure (suction) caused by the pump. THIS FACT causes the fuel boiling point to be lowered, and the fuel can "flash" or boil right in the fuel line, causing vapor which "won't pump", hence the name "vapor lock".
There are several things you can do to solve the problem.
First, inspect carefully the condition of the line. Start at the tank, and inspect the rubber connector, as well as the one at the pump. If these appear to be at all crimped, flat, soft, or damaged, replace. Inspect the metal line for damage, such as large dents or flattened. Look to see if the tube is close to heat, exhaust/mufflers, etc.
In some cases, the filter or tube in the tank can be damaged, rusted up, plugged, which causes a restriction.
It might just be the pump itself is weak. Just because you installed a new pump does not mean that it is working properly, or is of good quality.
I did not see your car model listed. Some cars, and Jeeps, have a "vapor return line" in the fuel system. This consists of a can or filter which is inline at the output of the pump, with a small bleed hole at the TOP of the can, returning to the tank through a second tube. This can collects bubbles and vapor and returns them to the tank
My '70 Roadrunner, which came from the factory with a "440 six pack" had this right from the factory. My '69 383 car did not.
One sure fire way to cure this problem is to install an electric pump RIGHT AT THE TANK, where the pump can "push" rather than "pull."
Take a GOOD look at all your fuel line, and isolate, move, or insulate it from exhaust and engine heat as best you can.
Don't wast time with wive's tales concerning "cow magnets" or other clip on devices--they don't really work.
Here is a diagram of a "universal" vapor return filter. IT IS UPSIDE DOWN. The small return fitting should be UP at the top.
http://www.autozone.com/images/cds/gif/small/0900823d8005150b.gif
The general situation is that heat causes the fuel to tend to boil. Because the normal fuel pump is engine mounted up front, the entire fuel line from the tank to the pump is under reduced pressure (suction) caused by the pump. THIS FACT causes the fuel boiling point to be lowered, and the fuel can "flash" or boil right in the fuel line, causing vapor which "won't pump", hence the name "vapor lock".
There are several things you can do to solve the problem.
First, inspect carefully the condition of the line. Start at the tank, and inspect the rubber connector, as well as the one at the pump. If these appear to be at all crimped, flat, soft, or damaged, replace. Inspect the metal line for damage, such as large dents or flattened. Look to see if the tube is close to heat, exhaust/mufflers, etc.
In some cases, the filter or tube in the tank can be damaged, rusted up, plugged, which causes a restriction.
It might just be the pump itself is weak. Just because you installed a new pump does not mean that it is working properly, or is of good quality.
I did not see your car model listed. Some cars, and Jeeps, have a "vapor return line" in the fuel system. This consists of a can or filter which is inline at the output of the pump, with a small bleed hole at the TOP of the can, returning to the tank through a second tube. This can collects bubbles and vapor and returns them to the tank
My '70 Roadrunner, which came from the factory with a "440 six pack" had this right from the factory. My '69 383 car did not.
One sure fire way to cure this problem is to install an electric pump RIGHT AT THE TANK, where the pump can "push" rather than "pull."
Take a GOOD look at all your fuel line, and isolate, move, or insulate it from exhaust and engine heat as best you can.
Don't wast time with wive's tales concerning "cow magnets" or other clip on devices--they don't really work.
Here is a diagram of a "universal" vapor return filter. IT IS UPSIDE DOWN. The small return fitting should be UP at the top.
http://www.autozone.com/images/cds/gif/small/0900823d8005150b.gif
I look the fuel line and tank and are ok... Y protect the line from heat and i install another mechanical pump.. nothing works.. today i installed a electric pump close to the tank and is the same problem.. i installed a holley carb instead of my carter AFB and the same problem hehehe.... any other idea? thanks
12-27-2007 | 08:44 AM
#4
Mopar Lover
Joined: Nov 2007
Posts: 2,424
Likes: 248
You might try a "hot run" with the fuel filler cap removed. You might have an incorrect cap, or a vent plugged up---you might be developing a vacuum in the tank
How did you inspect the tank?
The very least you should do is disconnect the fuel line from the tank and with a short scrap of hose, try blowing through the tube to see if it "feels restricted."
A BETTER method and the only sure method, is to actually remove the tank, remove the sender/ pickup assembly and inspect it. As old as all these cars are getting to be, the filter IN THE TANK as well as the pickup tube could be rusty and plugged
Another thing you might do is to "rig" a fuel pressure gauge as near to the carb that you can, and temorarily fasten (tape?) where you can see it, say, to a wiper arm. See if and how much the fuel pressure drops down
Now that you have an electric pump either:
You have a serious restriction in the line, or a plugged vent, or else it is NOT fuel, but rather, ignition or some other cause.
How did you inspect the tank?
The very least you should do is disconnect the fuel line from the tank and with a short scrap of hose, try blowing through the tube to see if it "feels restricted."
A BETTER method and the only sure method, is to actually remove the tank, remove the sender/ pickup assembly and inspect it. As old as all these cars are getting to be, the filter IN THE TANK as well as the pickup tube could be rusty and plugged
Another thing you might do is to "rig" a fuel pressure gauge as near to the carb that you can, and temorarily fasten (tape?) where you can see it, say, to a wiper arm. See if and how much the fuel pressure drops down
Now that you have an electric pump either:
You have a serious restriction in the line, or a plugged vent, or else it is NOT fuel, but rather, ignition or some other cause.
12-27-2007 | 12:46 PM
#5
Guest
Posts: n/a
Hi!!
I removed the tank, and the sender and looks fine.. i clean the filter inside the tank and looks good... i disconected the tank and put some air with my air compressor and there is no restriction or vent....
Just seconds before the car was run out of gasoline..i disconect the fuel filter near to the carb and sounds like a vapor coming out, after all vapor coming out, the filter start to be filled with gasoline....
I removed the tank, and the sender and looks fine.. i clean the filter inside the tank and looks good... i disconected the tank and put some air with my air compressor and there is no restriction or vent....
Just seconds before the car was run out of gasoline..i disconect the fuel filter near to the carb and sounds like a vapor coming out, after all vapor coming out, the filter start to be filled with gasoline....
12-28-2007 | 03:59 PM
#6
Mopar Lover
Joined: Nov 2007
Posts: 2,424
Likes: 248
Here's a few other things
First, did you try leaving the fuel cap off? This would tell you whether you have a vacuum/venting problem. That car should have a vent system tied in with the engine breather, so you might even have a hose incorrectly hooked to intake vacuum, when it should be hooked to the open breather. (Originally should have been a huge multiport breather on one valve cover, with several hose fittings)
You must not have a leak on the suction side of the line (from original pump to tank) because you did put an electric pump at the tank.
All I can suggest at this point is to take a real good look at the relationship between the hot exhaust and the fuel line.
Make sure you run a pressure / volume test of the pump. For a volume test, the pump should deliver AT LEAST a quart in a minute or less, at slow idle.
According to my old '70 book, the fuel pump should deliver 5-7PSI, but just about anything above 3 1/2 PSI should be OK.
Where are you, Rulito? I spose you use Kpa's for pressure?
First, did you try leaving the fuel cap off? This would tell you whether you have a vacuum/venting problem. That car should have a vent system tied in with the engine breather, so you might even have a hose incorrectly hooked to intake vacuum, when it should be hooked to the open breather. (Originally should have been a huge multiport breather on one valve cover, with several hose fittings)
You must not have a leak on the suction side of the line (from original pump to tank) because you did put an electric pump at the tank.
All I can suggest at this point is to take a real good look at the relationship between the hot exhaust and the fuel line.
Make sure you run a pressure / volume test of the pump. For a volume test, the pump should deliver AT LEAST a quart in a minute or less, at slow idle.
According to my old '70 book, the fuel pump should deliver 5-7PSI, but just about anything above 3 1/2 PSI should be OK.
Where are you, Rulito? I spose you use Kpa's for pressure?
04-28-2008 | 11:29 PM
#8
Guest
Posts: n/a
Fuel Problem
This sounds stupid, but I presume the filter arrow is pointed towards the carb and not reversed. Run a temporary hose from the fuel tank to the carb laying next to the car. Water in a tank or line will act like air and may not move from where it is at, but it may move to a fitting or restriction and block the passage of fuel. Put a lot of alcohol or dry gas in the tank, this will combine with the fuel so it moves thru the system and passes thru the carb and is burned up. Without something to combine with, a little bit of water will cause a lot of problems. The CARB WAS NEVER THE PROBLEM.
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