Vapor lock ?
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Cross-Country
Joined: Sep 2011
Posts: 91
Likes: 6
Vapor lock ?
Hi here is my issue. I have a 1956 F250 v8 (272) I have aluminum radiator with a electric fan. I can only go 2 or 3 miles and the truck dies. No gas in the fuel filter. Try pouring a bit of gas in the carburetor still no go. This has happened 4 times in the past week. I put on a vented gas cap. Still no go.im hearing I need a electric fuel pump. If I let it sit about a hour or so it will start.Any suggestions would be great. Thsnks
Parts Nerd Extraordinaire
Joined: Sep 2010
Posts: 4,383
Likes: 1,791
From: Western NY
An electric fuel pump is not a silver bullet.
Let's identify the real issue before we try solving things blindly.
First, You shouldn't vapor lock in 2-3 miles. You more likely have a problem with your fuel line.
Make sure your tank pickup isn't obstructed with rust or debris. There may also be a shutoff valve under the tank - be sure it is fully open and not obstructed. Be sure that the lines are good and tight and free from leaks. There can be vacuum leaks in them that don't weep fuel but still suck air that can diminish the pumps flow.
This makes the most immediate sense to me as your symptoms could correlate with using up fuel that has slowly entered the fuel line and immediately available to the pump. When the fuel line is emptied, the restriction prevents adequate fuel flow to keep the engine running. Letting it sit allows for the fuel line to be slowly refilled and so it runs again after an hour or so.
You can disconnect the fuel pump and remove the gas cap and lightly pressurize the system with compressed air into the fuel line and see if you can clear any restrictions and make the gas in the tank bubble.
You already mentioned use of a vented gas cap. You can always do a test drive with the cap off.
Another thing that we can sometimes embarrassingly overlook - Is it as simple as having a too low fuel level in the fuel tank?
If dead set on considering use of an electric fuel pump, consider the following points:
*The electric pump must be compatible with your 6V positive ground power or 12V negative ground source as applicable.
*~4 psi fuel pressure. Much higher will overcome the carburetor float.
*Safety shutoff - you will need a safety shut off. This usually involves the addition of an oil pressure switch and crank override electrical circuitry.
*Do not use an electric pump to move fuel to or through the original mechanical pump. You risk filling the crankcase with fuel.
Let's identify the real issue before we try solving things blindly.
First, You shouldn't vapor lock in 2-3 miles. You more likely have a problem with your fuel line.
Make sure your tank pickup isn't obstructed with rust or debris. There may also be a shutoff valve under the tank - be sure it is fully open and not obstructed. Be sure that the lines are good and tight and free from leaks. There can be vacuum leaks in them that don't weep fuel but still suck air that can diminish the pumps flow.
This makes the most immediate sense to me as your symptoms could correlate with using up fuel that has slowly entered the fuel line and immediately available to the pump. When the fuel line is emptied, the restriction prevents adequate fuel flow to keep the engine running. Letting it sit allows for the fuel line to be slowly refilled and so it runs again after an hour or so.
You can disconnect the fuel pump and remove the gas cap and lightly pressurize the system with compressed air into the fuel line and see if you can clear any restrictions and make the gas in the tank bubble.
You already mentioned use of a vented gas cap. You can always do a test drive with the cap off.
Another thing that we can sometimes embarrassingly overlook - Is it as simple as having a too low fuel level in the fuel tank?
If dead set on considering use of an electric fuel pump, consider the following points:
*The electric pump must be compatible with your 6V positive ground power or 12V negative ground source as applicable.
*~4 psi fuel pressure. Much higher will overcome the carburetor float.
*Safety shutoff - you will need a safety shut off. This usually involves the addition of an oil pressure switch and crank override electrical circuitry.
*Do not use an electric pump to move fuel to or through the original mechanical pump. You risk filling the crankcase with fuel.
Tuned
Joined: Nov 2024
Posts: 323
Likes: 264
An electric fuel pump is not a silver bullet.
Let's identify the real issue before we try solving things blindly.
First, You shouldn't vapor lock in 2-3 miles. You more likely have a problem with your fuel line.
Make sure your tank pickup isn't obstructed with rust or debris. There may also be a shutoff valve under the tank - be sure it is fully open and not obstructed. Be sure that the lines are good and tight and free from leaks. There can be vacuum leaks in them that don't weep fuel but still suck air that can diminish the pumps flow.
This makes the most immediate sense to me as your symptoms could correlate with using up fuel that has slowly entered the fuel line and immediately available to the pump. When the fuel line is emptied, the restriction prevents adequate fuel flow to keep the engine running. Letting it sit allows for the fuel line to be slowly refilled and so it runs again after an hour or so.
You can disconnect the fuel pump and remove the gas cap and lightly pressurize the system with compressed air into the fuel line and see if you can clear any restrictions and make the gas in the tank bubble.
You already mentioned use of a vented gas cap. You can always do a test drive with the cap off.
Another thing that we can sometimes embarrassingly overlook - Is it as simple as having a too low fuel level in the fuel tank?
If dead set on considering use of an electric fuel pump, consider the following points:
*The electric pump must be compatible with your 6V positive ground power or 12V negative ground source as applicable.
*~4 psi fuel pressure. Much higher will overcome the carburetor float.
*Safety shutoff - you will need a safety shut off. This usually involves the addition of an oil pressure switch and crank override electrical circuitry.
*Do not use an electric pump to move fuel to or through the original mechanical pump. You risk filling the crankcase with fuel.
Let's identify the real issue before we try solving things blindly.
First, You shouldn't vapor lock in 2-3 miles. You more likely have a problem with your fuel line.
Make sure your tank pickup isn't obstructed with rust or debris. There may also be a shutoff valve under the tank - be sure it is fully open and not obstructed. Be sure that the lines are good and tight and free from leaks. There can be vacuum leaks in them that don't weep fuel but still suck air that can diminish the pumps flow.
This makes the most immediate sense to me as your symptoms could correlate with using up fuel that has slowly entered the fuel line and immediately available to the pump. When the fuel line is emptied, the restriction prevents adequate fuel flow to keep the engine running. Letting it sit allows for the fuel line to be slowly refilled and so it runs again after an hour or so.
You can disconnect the fuel pump and remove the gas cap and lightly pressurize the system with compressed air into the fuel line and see if you can clear any restrictions and make the gas in the tank bubble.
You already mentioned use of a vented gas cap. You can always do a test drive with the cap off.
Another thing that we can sometimes embarrassingly overlook - Is it as simple as having a too low fuel level in the fuel tank?
If dead set on considering use of an electric fuel pump, consider the following points:
*The electric pump must be compatible with your 6V positive ground power or 12V negative ground source as applicable.
*~4 psi fuel pressure. Much higher will overcome the carburetor float.
*Safety shutoff - you will need a safety shut off. This usually involves the addition of an oil pressure switch and crank override electrical circuitry.
*Do not use an electric pump to move fuel to or through the original mechanical pump. You risk filling the crankcase with fuel.
I had problems very similar to yours, and found I had multiple problems working against me.
Fuel filter running dry. Caused by rust in tank and small leaks in fuel line. If you have a clear filter, run the engine at a high idle and watch for air bubbles entering the filter.
My coil was also going bad. After running for a bit, the coil is normally warm but should not be hot. If it has a getting hot, it’s probably best to replace.
Lead Driver
Joined: Oct 1999
Posts: 6,779
Likes: 557
From: Kalispell, MT
I had a similar strange problem when I started driving my 48.
After trying all the things listed above, I pulled the gas tank and emptied it into a 5 gal bucket. In the dumped fuel I finally noticed a clear plastic label from a can of Heet or Instead-o-lead that had fallen into the tank.
It would get sucked over the outlet and shut things down. After sitting awhile the suction would relax and the plastic would float off the outlet and the truck would start and run until the cycle repeated.
The point of all this is: it might be something really simple.
After trying all the things listed above, I pulled the gas tank and emptied it into a 5 gal bucket. In the dumped fuel I finally noticed a clear plastic label from a can of Heet or Instead-o-lead that had fallen into the tank.
It would get sucked over the outlet and shut things down. After sitting awhile the suction would relax and the plastic would float off the outlet and the truck would start and run until the cycle repeated.
The point of all this is: it might be something really simple.
4wd Low
Joined: Dec 2017
Posts: 10
Likes: 3
I had a similar issue and it ended up being the flex line that goes out from the tank to the hard line. It had a small enough crack in it to suck air and cause a fuel delivery problem.
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Fleet Owner
Joined: Dec 2000
Posts: 25,416
Likes: 5,424
From: Central PA
And, being a 56, a 12 volt electric pump would be needed.
Good luck. Go step by step and don't throw money at it aimlessly
Good luck. Go step by step and don't throw money at it aimlessly
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Cargo Master
Joined: Aug 2015
Posts: 2,076
Likes: 101
From: Marana, Arizona
@FortyNiner has a good point. If it doesn't fire with gas down the carb maybe it's ignition related. My truck used to die at the end of the block when I first got it and start again in about 15 minutes and die again at the house. I put in a proper coil, points and condenser. Fresh solid core plug wires and a good cap and rotor and no more dying a block from the house.
Gotta have fuel AND spark. Good luck with it!
Gotta have fuel AND spark. Good luck with it!
Thread Starter
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Cross-Country
Joined: Sep 2011
Posts: 91
Likes: 6
Vapor lock
[QUOTE=Hank65;21597140]I had a similar issue and it ended up being the flex line that goes out from the tank to the hard line. It had a small enough crack in it to suck air and cause a fuel delivery problem
I went out and looked everything over. Sure enough I found the flex hose from the tank to the hard line was bad. Thanks for responding
I went out and looked everything over. Sure enough I found the flex hose from the tank to the hard line was bad. Thanks for responding
Thread Starter
|
Cross-Country
Joined: Sep 2011
Posts: 91
Likes: 6
Vapor lock
[QUOTE=bmoran4;21596930]An electric fuel pump is not a silver bullet.
Let's identify the real issue before we try solving things blindly.
First, You shouldn't vapor lock in 2-3 miles. You more likely have a problem with your fuel line.
Make sure your tank pickup isn't obstructed with rust or debris. There may also be a shutoff valve under the tank - be sure it is fully open and not obstructed. Be sure that the lines are good and tight and free from leaks. There can be vacuum leaks in them that don't weep fuel but still suck air that can diminish the pumps flow.
This makes the most immediate sense to me as your symptoms could correlate with using up fuel that has slowly entered the fuel line and immediately available to the pump. When the fuel line is emptied, the restriction prevents adequate fuel flow to keep the engine running. Letting it sit allows for the fuel line to be slowly refilled and so it runs again after an hour or so.
You can disconnect the fuel pump and remove the gas cap and lightly pressurize the system with compressed air into the fuel line and see if you can clear any restrictions and make the gas in the tank bubble.
You already mentioned use of a vented gas cap. You can always do a test drive with the cap off.
Another thing that we can sometimes embarrassingly overlook - Is it as simple as having a too low fuel level in the fuel tank?
If dead set on considering use of an electric fuel pump, consider the following points:
*The electric pump must be compatible with your 6V positive ground power or 12V negative ground source as applicable.
*~4 psi fuel pressure. Much higher will overcome the carburetor float.
*Safety shutoff - you will need a safety shut off. This usually involves the addition of an oil pressure switch and crank override electrical circuitry.
*Do not use an electric pump to move fuel to or through the original mechanical pump. You risk filling the crankcase with fuel.[
Thanks for responding. I went out and checked things out.i found the flex hose from the tank to the hard line was bad. You have some very good input. Thanks again.
Let's identify the real issue before we try solving things blindly.
First, You shouldn't vapor lock in 2-3 miles. You more likely have a problem with your fuel line.
Make sure your tank pickup isn't obstructed with rust or debris. There may also be a shutoff valve under the tank - be sure it is fully open and not obstructed. Be sure that the lines are good and tight and free from leaks. There can be vacuum leaks in them that don't weep fuel but still suck air that can diminish the pumps flow.
This makes the most immediate sense to me as your symptoms could correlate with using up fuel that has slowly entered the fuel line and immediately available to the pump. When the fuel line is emptied, the restriction prevents adequate fuel flow to keep the engine running. Letting it sit allows for the fuel line to be slowly refilled and so it runs again after an hour or so.
You can disconnect the fuel pump and remove the gas cap and lightly pressurize the system with compressed air into the fuel line and see if you can clear any restrictions and make the gas in the tank bubble.
You already mentioned use of a vented gas cap. You can always do a test drive with the cap off.
Another thing that we can sometimes embarrassingly overlook - Is it as simple as having a too low fuel level in the fuel tank?
If dead set on considering use of an electric fuel pump, consider the following points:
*The electric pump must be compatible with your 6V positive ground power or 12V negative ground source as applicable.
*~4 psi fuel pressure. Much higher will overcome the carburetor float.
*Safety shutoff - you will need a safety shut off. This usually involves the addition of an oil pressure switch and crank override electrical circuitry.
*Do not use an electric pump to move fuel to or through the original mechanical pump. You risk filling the crankcase with fuel.[
Thanks for responding. I went out and checked things out.i found the flex hose from the tank to the hard line was bad. You have some very good input. Thanks again.
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