Carb going dry while driving. Why?
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Lead Driver
Joined: Jul 2011
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From: On the Edge of the Desert
Originally Posted by CougarJohn
351, if you still have the filters you took off, try blowing through them. If you can't or it is hard to do, you probably found your problem.
You may have to pull the tank but not yet. Easy things first.
You may have to pull the tank but not yet. Easy things first.
Originally Posted by TeachNlive4ever
Pull the air horn off the top of the carb and see if there is any rust in the carb?
Fleet Mechanic
Joined: May 2001
Posts: 1,396
Likes: 4
From: Cupertino
Toothless Jake taught me that.
Hotshot
Joined: Mar 2013
Posts: 14,255
Likes: 199
From: Phoenix, Az.
Yes, but the jets won't like that.
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Lead Driver
Joined: Jul 2011
Posts: 8,679
Likes: 191
From: On the Edge of the Desert
Problem still there.
Thinking about it more.
It's not high speed driving that causes it, its high engine load at moderate engine speed. Such as towing, or driving fast.
It happens when running above 2,000rpm at lower vacuum levels. 10" or less.
The one thing I find rather peculiar is that it will not recover once it starts. It doesn't die out unless it gets really bad, but it will not go back to running normally until it sits for a few minutes and "cools". Although I don't know what would be getting "hot" now that it's winter time.
I had a suspicion that it was the fuel pump somehow acting up, but as I previously mentioned, a new fuel pump didn't make any difference.
My only suspicions now are that
A) there is something loose in the tank that is (not so randomly) obstructing the pickup tube,
B) the stock fuel pump can't keep up with the high fuel demand,
C) something is FUBAR and I'll be running in circles forever....
With my luck, it's going to be option C...
Thinking about it more.
It's not high speed driving that causes it, its high engine load at moderate engine speed. Such as towing, or driving fast.
It happens when running above 2,000rpm at lower vacuum levels. 10" or less.
The one thing I find rather peculiar is that it will not recover once it starts. It doesn't die out unless it gets really bad, but it will not go back to running normally until it sits for a few minutes and "cools". Although I don't know what would be getting "hot" now that it's winter time.
I had a suspicion that it was the fuel pump somehow acting up, but as I previously mentioned, a new fuel pump didn't make any difference.
My only suspicions now are that
A) there is something loose in the tank that is (not so randomly) obstructing the pickup tube,
B) the stock fuel pump can't keep up with the high fuel demand,
C) something is FUBAR and I'll be running in circles forever....
With my luck, it's going to be option C...
Cargo Master
Joined: May 2015
Posts: 2,350
Likes: 7
From: Garland, Tx
Problem still there.
Thinking about it more.
It's not high speed driving that causes it, its high engine load at moderate engine speed. Such as towing, or driving fast
It happens when running above 2,000rpm at lower vacuum levels. 10" or less.
The one thing I find rather peculiar is that it will not recover once it starts. It doesn't die out unless it gets really bad, but it will not go back to running normally until it sits for a few minutes and "cools". Although I don't know what would be getting "hot" now that it's winter time.
I had a suspicion that it was the fuel pump somehow acting up, but as I previously mentioned, a new fuel pump didn't make any difference.
My only suspicions now are that
A) there is something loose in the tank that is (not so randomly) obstructing the pickup tube,
B) the stock fuel pump can't keep up with the high fuel demand,
C) something is FUBAR and I'll be running in circles forever....
With my luck, it's going to be option C...
Thinking about it more.
It's not high speed driving that causes it, its high engine load at moderate engine speed. Such as towing, or driving fast
It happens when running above 2,000rpm at lower vacuum levels. 10" or less.
The one thing I find rather peculiar is that it will not recover once it starts. It doesn't die out unless it gets really bad, but it will not go back to running normally until it sits for a few minutes and "cools". Although I don't know what would be getting "hot" now that it's winter time.
I had a suspicion that it was the fuel pump somehow acting up, but as I previously mentioned, a new fuel pump didn't make any difference.
My only suspicions now are that
A) there is something loose in the tank that is (not so randomly) obstructing the pickup tube,
B) the stock fuel pump can't keep up with the high fuel demand,
C) something is FUBAR and I'll be running in circles forever....
With my luck, it's going to be option C...
My my buddy has a 69 F250 that absolutely will not run in the manual fuel pum and runs an electric to back it up. 25 years it’s the same way. Don’t give me any suggestions on what it could be or is. It WILL not run/ drive on the manual pump alone.
Throw an electric pump on there and see what happens. DO NOT but an Oreilys one. It only lasts 3 weeks.
Ask me how I know...
Laughing Gas
Joined: Mar 2013
Posts: 1,027
Likes: 5
From: Garner NC
I'd pull the sender from the tank and look in there to see if you have a bunch of sediment in the bottom of the tank. Get the gas real low first so you can get a decent sample of whats on the bottom.
Cargo Master
Joined: May 2015
Posts: 2,350
Likes: 7
From: Garland, Tx
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Laughing Gas
Joined: Mar 2013
Posts: 1,027
Likes: 5
From: Garner NC
Trace the line and see if it got kinked anywhere between the carb and the tank. The hard line on my wife's Mustang was in the 'early' location which made it vulnerable to getting crushed by a floor jack, which it was. A pinch will reduce flow greatly, and will also collect crap quickly.
Fleet Mechanic
Joined: May 2001
Posts: 1,396
Likes: 4
From: Cupertino
Try this:
Get a suction gun and a short length of copper or steel line to fit the rubber. Check flow at the tank end of the pump. Put the gun on the line and suck as hard as you can. Check flow after.
You may be able to crud that is obstructing the line.
That a stock fuel pump cannot supply enough fuel for your need sounds implausible to me.
Get a suction gun and a short length of copper or steel line to fit the rubber. Check flow at the tank end of the pump. Put the gun on the line and suck as hard as you can. Check flow after.
You may be able to crud that is obstructing the line.
That a stock fuel pump cannot supply enough fuel for your need sounds implausible to me.
Hotshot
Joined: Mar 2013
Posts: 14,255
Likes: 199
From: Phoenix, Az.
I think the problem is in the tank. Whether it be crud on the bottom, sender, sender's sock, or maybe the hose clamped on to the sender. When the engine is under load it's carb is in the "power" circuit. Which makes the carb go through a lot of fuel. So there is more fuel flow coming out of the tank. If the fuel filter is open maybe just enough to flow then it is partially plugged. Whatever that partial plug is, it came from the tank.
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Lead Driver
Joined: Jul 2011
Posts: 8,679
Likes: 191
From: On the Edge of the Desert
Originally Posted by JEFFFAFA
"Maybe just not enough"
I think the problem is in the tank. Whether it be crud on the bottom, sender, sender's sock, or maybe the hose clamped on to the sender. When the engine is under load it's carb is in the "power" circuit. Which makes the carb go through a lot of fuel. So there is more fuel flow coming out of the tank. If the fuel filter is open maybe just enough to flow then it is partially plugged. Whatever that partial plug is, it came from the tank.
I think the problem is in the tank. Whether it be crud on the bottom, sender, sender's sock, or maybe the hose clamped on to the sender. When the engine is under load it's carb is in the "power" circuit. Which makes the carb go through a lot of fuel. So there is more fuel flow coming out of the tank. If the fuel filter is open maybe just enough to flow then it is partially plugged. Whatever that partial plug is, it came from the tank.
The fuel system is too simple to have a complicated problem.
Based on what we "know"
-It's not carb related. The engine runs fine at full throttle past 5,000rpm. That's maximum flow there.
-the line to the carb from the pump is new, clean, and clear.
-the fuel pump is a new unit. OE style mechanical, same kind used on the hefty BOSS 351 engines and the 400. So it should be more than capable of supplying enough fuel.
-The filter in front of the pump is new, clean, and clear.
So, that only leaves the line(s) going along the frame and to the tank.
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Lead Driver
Joined: Jul 2011
Posts: 8,679
Likes: 191
From: On the Edge of the Desert
Gosh dang it done did it again!
However, this time the problem was quite evident. Fuel filter before the pump was dry. And when I pulled the fuel line off on the tank side, there was an obvious vacuum that have been created by the pump. Blowing back to the gas tank with lung power revealed a plugged up line i'm assuming at the pick up tube. But a couple of hard blows and I was able to clear it.
So, now I have something to go off of.
However, this time the problem was quite evident. Fuel filter before the pump was dry. And when I pulled the fuel line off on the tank side, there was an obvious vacuum that have been created by the pump. Blowing back to the gas tank with lung power revealed a plugged up line i'm assuming at the pick up tube. But a couple of hard blows and I was able to clear it.
So, now I have something to go off of.
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