No Gas to the Carb When Engine Warms Up

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Money Pit

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I have a stalling problem. I found the problem but I don't know why. I have a 70, 225, with a Holley 1920. I've read many threads on this subject and subitted one myself. I got a lot of great advice. When the engine is cold, the filter (clear plastic) is 3/4 full. After letting the engine idle with the hood open, for 15 min, outside temp about 75 degrees, the level of the fuel in the filter, goes to almost zero. The temp guage is on the first mark. The gas cap is off. I tried to put a foil pan between the engine and the filter. The filter is relatively cool but the gas lines are warm. I'm new to slant six's but not to MOPARs. I had a 340 Cuda with headers and have never had a problem like this. Do I need to insulate the gas lines and get a metal filter? The fuel pump is new and I just adjusted the float level. Is is common to slant six's? Thanks everyone in advance.
 
Sounds like the fuel pump is giving up as it warms up.
 
The previous fuel pump did the same thing. The filter is new and checked the pick up today. The tank is new and I drained the tank. I filled it with fresh gas.
 
Here's a true story...... I had a friend who had a car that he drove everywhere. One day as he was driving along the car started slowing down and finally died. He would have to wait a few minutes then it would start again and run real good but then later on it would start slowing down until it died again. He had a good idea that it was engine was running out of gas but didn't know why. He drove the car like that for months trying different things to fix it, fuel pump, fuel filter, gas cap, carb filter. One day he got really pissed off and pulled the gas tank. He found that someone had stuffed a shop rag down into the tank. The rag would float around until the pick-up sucked it up. Once the engine died the rag would float away and he could drive again. I'm not saying that you have this same problem:
If you turn the engine off for a few minutes then restart does the fuel filter get full again??

Treblig
 
Not so much "warming up" as "engine running time". Original tank and sender?Might be time for a fuel system overhaul. New everything including lines. I replaced everything on my 66 10 years ago and haven't had a fuel issue since.
 
You're chasing your tail. The fuel filter appearing to be almost empty of fuel is normal and does not indicate a problem (and really, you should be running a metal filter, preferably repositioned as per the Fuel line mod).

You'll get some good advice about the stalling problem if you'll tell us about the stalling problem—all you've told us is just one sentence ("I have a stalling problem") but then a lot of description about the visible fuel level in the fuel filter. Tell us more about the stalling problem: only when the engine's cold and you try to accelerate? Only when the engine's hot and idling? When, where does it happen? Can you work around it? How? That info will help us help you.
 
Sounds like it is pulling a vacuum from the tank. Possible clogged vent line. Try it with the gas cap off/open to verify. The other possibility could be a section of rubber fuel line collapsing internally.
 
Money Pit said:
The previous fuel pump did the same thing. The filter is new and checked the pick up today. The tank is new and I drained the tank. I filled it with fresh gas.
Click to expand...
How did you check the pick-up?
Do a fuel flow test with a warm engine. The engine will run waaay long enough to do the test, if the fuel bowl is full at the beginning of the test. If the engine stalls you can refill the bowl through the bowl vent using a tiny funnel.
1 qt, in 1 minute or less, at idle.
If you don't get it, it doesn't mean the pump is bad; it could still be a restriction between the pump and the gas in the tank.
If you get air coming out, well, that's not supposed to happen.
 
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The car stalls after driving for 15 min. When you step on the gas, no response. it won't restart, no fuel in the filter, no gas to the carb. if I let it sit over night, the filter is full. it starts right up and idles well, accelerates well, no problem on flat or hills.
My question is, why is it normal for there not to be gas in the filter? There's gas in the filter for about 15 min, then nothing. I guess that's why I didn't give more info about the stalling because I was concerned about the gas in the filter. Sorry for the confusion.
 
Tried it with the cap off, checked the pick up, the tank is new, the fuel pump and pick up are new, the hose from the tank to the fuel line is new fuel injection hose. Should I use a rubber hose>
 
Money Pit said:
The car stalls after driving for 15 min. When you step on the gas, no response. it won't restart, no fuel in the filter, no gas to the carb. if I let it sit over night, the filter is full. it starts right up and idles well, accelerates well, no problem on flat or hills.
My question is, why is it normal for there not to be gas in the filter? There's gas in the filter for about 15 min, then nothing. I guess that's why I didn't give more info about the stalling because I was concerned about the gas in the filter. Sorry for the confusion.
Click to expand...

If the filter is horizontal it will trap a pocket of air. Air is compressible. As long as the engine is running, and the pump is pumping fuel, everything works. As soon as you shut off the engine, the pressure will begin to fall and the air-pocket will expand. If the float valve opens, the compressed air will force the fuel up into the bowl. If the float valve remains closed, the pocket will try to force the fuel backwards thru the pump. That's not supposed to happen.
If the pump is sucking air somewhere, It will drive it up to the bowl , until the pump is sucking nothing but air.
IMO, your pump either cannot deliver enough fuel or it is not delivering pure fuel, and in either case, the fuel flow test will determine the next course of action. You, or we , can keep guessing at the solution til next Tuesday, but no one can move ahead with authority until the flow-test results are in. And that's my opinion.
 
AJ/FormS said:
How did you check the pick-up?
Do a fuel flow test with a warm engine. The engine will run waaay long enough to do the test, if the fuel bowl is full at the beginning of the test. If the engine stalls you can refill the bowl through the bowl vent using a tiny funnel.
1 qt, in 1 minute or less, at idle.
If you don't get it, it doesn't mean the pump is bad; it could still be a restriction between the pump and the gas in the tank.
If you get air coming out, well, that's not supposed to happen.
Click to expand...
Did a visual. The filter was clean, no cracks in the tube, tube wasn't plugged.
 
AJ/FormS said:
If the filter is horizontal it will trap a pocket of air. Air is compressible. As long as the engine is running, and the pump is pumping fuel, everything works. As soon as you shut off the engine, the pressure will begin to fall and the air-pocket will expand. If the float valve opens, the compressed air will force the fuel up into the bowl. If the float valve remains closed, the pocket will try to force the fuel backwards thru the pump. That's not supposed to happen.
If the pump is sucking air somewhere, It will drive it up to the bowl , until the pump is sucking nothing but air.
IMO, your pump either cannot deliver enough fuel or it is not delivering pure fuel, and in either case, the fuel flow test will determine the next course of action. You, or we , can keep guessing at the solution til next Tuesday, but no one can move ahead with authority until the flow-test results are in. And that's my opinion.
Click to expand...
I'll try the flow test tomorrow and let you know. Great info. Makes sense. Thanks
 
Treblig said:
Here's a true story...... I had a friend who had a car that he drove everywhere. One day as he was driving along the car started slowing down and finally died. He would have to wait a few minutes then it would start again and run real good but then later on it would start slowing down until it died again. He had a good idea that it was engine was running out of gas but didn't know why. He drove the car like that for months trying different things to fix it, fuel pump, fuel filter, gas cap, carb filter. One day he got really pissed off and pulled the gas tank. He found that someone had stuffed a shop rag down into the tank. The rag would float around until the pick-up sucked it up. Once the engine died the rag would float away and he could drive again. I'm not saying that you have this same problem:
If you turn the engine off for a few minutes then restart does the fuel filter get full again??

Treblig
Click to expand...
No the engine won't start up. It has to sit over night.
 
toolmanmike said:
Not so much "warming up" as "engine running time". Original tank and sender?Might be time for a fuel system overhaul. New everything including lines. I replaced everything on my 66 10 years ago and haven't had a fuel issue since.
Click to expand...
New tank and pick up.
 
You could easily put a small in-line "flow through" electric pump just outside the tank. I had to do that on one of my cars.

treblig
 
Check the rubber hoses,too much hose causing a kink.
A customer replaced fuel filter himself and somehow managed to kink line. It wasnt bent much but engine would starve for fuel. And this was an efi.

After it stalls-
Stuff a rag around air hose and give it 5 psi (even that may be much) into fuel filler neck.
See if filter fills.
Or set up a jug on fuel pump inlet and see if problem changes.
 
Tooljunkie said:
Check the rubber hoses,too much hose causing a kink.
A customer replaced fuel filter himself and somehow managed to kink line. It wasnt bent much but engine would starve for fuel. And this was an efi.

After it stalls-
Stuff a rag around air hose and give it 5 psi (even that may be much) into fuel filler neck.
See if filter fills.
Or set up a jug on fuel pump inlet and see if problem changes.
Click to expand...
I'll try that after the flow test. Thanks
 
Last summer I had the same problem in my 76 Dodge Aspen with a slant 6 .I went thru the entire car prepping for a 2000 mile road trip.Put in a new fuel pump too.Went on the trip.Everything was fine but the morning after I returned it started to act just like your car is. I checked everything and finally came to the conclusion that the ethanol in the gas wiped out the fuel pump diaphragm . Bought another "new " fuel pump and the problem was solved.Don't assume just because it's new it's good
 
No, a stalling problem like this will not (cannot) be caused by a horizontal fuel filter.

No, you do not need (and really do not want) to go adding electric fuel pumps. You're not having this problem because the car doesn't have an electric fuel pump; once you find and fix the problem it will go away.

Two items not yet mentioned: the rubber hose from the hard line to the inlet of the fuel pump, and the strainer on the end of the fuel pickup pipe inside the tank (part of the sender): new, old, absent?
 
The OP has stated new pick-up, tank, pump, EFI hose tank to line. Was the strainer new with the pick-up assy.??
If the float or needle is sticking, the carb will run dry, and the engine heat will cause a large vapor bubble that will stay trapped until conditions change. The old school way
to check is to tap on the carb body somewhere relatively harmless with a plastic screwdriver handle to see if it frees up, while the car is running poorly & before it quits
running completely.
 
Or a ball of t-tape caught in the inlet. I remember t-tape on quadra-jets being quite popular. Wrong but they done it anyways.

So when it quits,immediately pull fuel line off at carb, slip a rubber hose over fitting and put it in a container. Crank for 30 seconds.
 
Treblig said:
Here's a true story...... I had a friend who had a car that he drove everywhere. One day as he was driving along the car started slowing down and finally died. He would have to wait a few minutes then it would start again and run real good but then later on it would start slowing down until it died again. He had a good idea that it was engine was running out of gas but didn't know why. He drove the car like that for months trying different things to fix it, fuel pump, fuel filter, gas cap, carb filter. One day he got really pissed off and pulled the gas tank. He found that someone had stuffed a shop rag down into the tank. The rag would float around until the pick-up sucked it up. Once the engine died the rag would float away and he could drive again. I'm not saying that you have this same problem:
If you turn the engine off for a few minutes then restart does the fuel filter get full again??

Treblig
Click to expand...
No. I have to let it sit for a few hours before the filter fills. Then it will restart.
 
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