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Discussion Starter #1
Need a hand please trying to figure out a fuel delivery issue that's driving me nuts!

Background is, I have a new fuel tank, cap, new sending unit, cleaned out the fuel line between tank and pump, mechanical SBC pump, and a filter up by the carb, carb is a Holley 4160. The tank does pressurize as I get a pressure release when I drive to a station and remove the gas cap.

Only change in the past few years is that I changed the sending unit as the previous one was leaking when the tank was full (the solder around the pickup tube was cracked). When I replaced that, I checked inside the tank to make sure everything was still clean (it was), and blew out the fuel line (the hard line from tank side by the frame rail up to the end of the hard line near the mechanical fuel pump) with compressed air for kicks.

So here’s the problem….. It started one night a couple months ago, when I parked the Nova facing uphill at an angle, after driving it 30 minutes to get somewhere. During the drive over, I had filled the tank up to full. It sat for about 3 hours. When I hopped back in, I fired up the engine as usual. While it warmed up, it ran out of gas in the carb. Popped the hood, and there was no fuel in the filter. We rolled the car back to level ground elsewhere in the parking lot, and cranked the engine for a good long while with no fuel showing up. Called a tow, the driver showed up and had a small fuel jug, so we tried to pour fuel down the carb a few times to see if running the motor a bit would get the fuel to come back to the front, and no luck there either. So we flatbed towed it back to my place, and left the car in my shop. The following morning when I went to troubleshoot it, the filter was full of fuel, and the problem seemed to have gone away.

A few drives around town later, with no issues, I tried to reproduce the problem at home. I parked the fully warmed up Nova in the driveway where it angles up slightly, and let it sit for 30 minutes. I forgot to check under the hood, but as I drove the dirt road out the car ran out of gas again, with no fuel in the filter. I tried to use the fuel in the accelerator pump to bang it over a little, and that worked after a couple tries, it fired up and the filter was full of gas again, and I was on my way.

Having reproduced the problem, I went to get a new fuel filter. When I was going to exit off the freeway, there was a long bumper to bumper line to exit. Ran out of gas there again, this time while the engine had been running fine. I had to bump the engine over and pump the gas to get it going again, after letting it sit for a few minutes on the shoulder.

I eventually got home and replaced the fuel pump with a new Delphi pump. The old one I think I put on in 2002 was an old Carter unit, and it visually looked fine. Putting the new one on, I checked for leaks, and took it for a spin. Filled it with gas, and drove home. To enter my shop, I have a little incline uphill to get to the roll up door. Shut the car off, opened the roll up, then hopped into the Nova and started it. Drove it inside, and left it running. I got out, popped the hood, and saw that the fuel filter was empty again with no fuel coming in. I revved the engine some, and the fuel eventually and slowly started filling the filter again.

I don’t think this is a fuel pump issue anymore since I had replaced it with a new one. As I type this out, I think this is narrowing down to a possible bad sending unit or dirt in the line, maybe some weird vapor lock issue (since I can reproduce the issue when it is facing uphill), or perhaps an issue with the needle and seat valves or stuck floats not letting fuel into the carb somehow?

I had one suggestion of installing an anti-drain back valve in the line somewhere, to keep the fuel from draining backwards through the line but don’t think I should have to. Especially since the issue once happened on level ground waiting to exit on the freeway.

What do you guys think?

Thanks!

:confused::turn:
 

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Need a hand please trying to figure out a fuel delivery issue that's driving me nuts!

Background is, I have a new fuel tank, cap, new sending unit, cleaned out the fuel line between tank and pump, mechanical SBC pump, and a filter up by the carb, carb is a Holley 4160. The tank does pressurize as I get a pressure release when I drive to a station and remove the gas cap.

Only change in the past few years is that I changed the sending unit as the previous one was leaking when the tank was full (the solder around the pickup tube was cracked). When I replaced that, I checked inside the tank to make sure everything was still clean (it was), and blew out the fuel line (the hard line from tank side by the frame rail up to the end of the hard line near the mechanical fuel pump) with compressed air for kicks.

So here’s the problem….. It started one night a couple months ago, when I parked the Nova facing uphill at an angle, after driving it 30 minutes to get somewhere. During the drive over, I had filled the tank up to full. It sat for about 3 hours. When I hopped back in, I fired up the engine as usual. While it warmed up, it ran out of gas in the carb. Popped the hood, and there was no fuel in the filter. We rolled the car back to level ground elsewhere in the parking lot, and cranked the engine for a good long while with no fuel showing up. Called a tow, the driver showed up and had a small fuel jug, so we tried to pour fuel down the carb a few times to see if running the motor a bit would get the fuel to come back to the front, and no luck there either. So we flatbed towed it back to my place, and left the car in my shop. The following morning when I went to troubleshoot it, the filter was full of fuel, and the problem seemed to have gone away.

A few drives around town later, with no issues, I tried to reproduce the problem at home. I parked the fully warmed up Nova in the driveway where it angles up slightly, and let it sit for 30 minutes. I forgot to check under the hood, but as I drove the dirt road out the car ran out of gas again, with no fuel in the filter. I tried to use the fuel in the accelerator pump to bang it over a little, and that worked after a couple tries, it fired up and the filter was full of gas again, and I was on my way.

Having reproduced the problem, I went to get a new fuel filter. When I was going to exit off the freeway, there was a long bumper to bumper line to exit. Ran out of gas there again, this time while the engine had been running fine. I had to bump the engine over and pump the gas to get it going again, after letting it sit for a few minutes on the shoulder.

I eventually got home and replaced the fuel pump with a new Delphi pump. The old one I think I put on in 2002 was an old Carter unit, and it visually looked fine. Putting the new one on, I checked for leaks, and took it for a spin. Filled it with gas, and drove home. To enter my shop, I have a little incline uphill to get to the roll up door. Shut the car off, opened the roll up, then hopped into the Nova and started it. Drove it inside, and left it running. I got out, popped the hood, and saw that the fuel filter was empty again with no fuel coming in. I revved the engine some, and the fuel eventually and slowly started filling the filter again.

I don’t think this is a fuel pump issue anymore since I had replaced it with a new one. As I type this out, I think this is narrowing down to a possible bad sending unit or dirt in the line, maybe some weird vapor lock issue (since I can reproduce the issue when it is facing uphill), or perhaps an issue with the needle and seat valves or stuck floats not letting fuel into the carb somehow?

I had one suggestion of installing an anti-drain back valve in the line somewhere, to keep the fuel from draining backwards through the line but don’t think I should have to. Especially since the issue once happened on level ground waiting to exit on the freeway.

What do you guys think?

Thanks!

:confused::turn:
Next time it happens, remove the fuel cap. Shouldn't it be vented on a '69, or the filler neck have a vent tube? Everything so new and sealed, a little air needs to get in to let the gas out, even under the suction of the fuel pump.
 

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Pinch the fuel supply hose between the fuel line and pump with a clamp or vise grip that won't damage the hose. Test it with the front end elevated to see if it drains back. You may have an air leak on the suction side of the pump.
 

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You need to vent the tank properly. Is your cap vented? Is your fuel line routed as factory? Have you looked at the fuel pump pushrod for wear? If you pull the pushrod, change it to a lightweight arp one. Good insurance for a performance engine.
 

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Discussion Starter #5
Thanks for the replies. I checked my cap and it is indeed vented - it has a plastic cylinder on the backside with holes in it. It's only a few years old, I'm guessing that it might be bad/clogged?

When I replaced the fuel pump, I just looked in the hole at the pushrod in case it looked funny, I didn't notice any visual wear on the pump end. I didn't remove the pump backing plate to remove it though.

Fuel line - it is all as run by the factory. When I replaced the tank a few years ago I blew out the fuel lines. Before that, I daily drove it for years with no prior issues or gunk in the lines/filter.

I think I'll try replacing the cap in case it's not venting into the tank under negative pressure.
 

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My brother had an issue similar to yours. Believing the fuel pump was no good he replaced it. A week later there was no fuel going to the engine. Took that pump back and got another. Sure enough the engine ran out of fuel again later on. Time for a full inspection of the fuel system. He found the problem. Between the fuel tank and the steel line is a rubber line with a crack in it. Seems the crack would open up and the pump would draw the air rather than the fuel. Replaced the rubber fuel line and never had a problem since.
 

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My brother had an issue similar to yours. Believing the fuel pump was no good he replaced it. A week later there was no fuel going to the engine. Took that pump back and got another. Sure enough the engine ran out of fuel again later on. Time for a full inspection of the fuel system. He found the problem. Between the fuel tank and the steel line is a rubber line with a crack in it. Seems the crack would open up and the pump would draw the air rather than the fuel. Replaced the rubber fuel line and never had a problem since.
I had that same thing happen to me a number of years ago. The car died while idling in the driveway which has an uphill slope. The short rubber line had never been replaced, and it had cracked. I replaced it, and the problem was solved. This might not be the OP's problem, but it can happen.
 

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Thanks for the replies. I checked my cap and it is indeed vented - it has a plastic cylinder on the backside with holes in it. It's only a few years old, I'm guessing that it might be bad/clogged?

When I replaced the fuel pump, I just looked in the hole at the pushrod in case it looked funny, I didn't notice any visual wear on the pump end. I didn't remove the pump backing plate to remove it though.

Fuel line - it is all as run by the factory. When I replaced the tank a few years ago I blew out the fuel lines. Before that, I daily drove it for years with no prior issues or gunk in the lines/filter.

I think I'll try replacing the cap in case it's not venting into the tank under negative pressure.

I replaced my gas cap one year ago .... bought a stock "vented gas cap".

When I remove 'THAT Cap' .... I get a Big Pressure release from my tank.

Just last week , I bought a 'New Locking Gas Cap' .... on the computer page -- and the package -- it said this cap IS VENTED. Each time that stopped too gas-up last week-end on our 3 day cruise (FUN-RUN) , I would get that
"pressure - release of air" trapped in my tank.

SO, that's two new caps -- one new cap (new last year) : and, one new cap (new last week) .... both caps were stated as being 'vented caps'.
BUT, I'm still getting Pressure in my tank ? ? ?

However, my Nova IS - NOT 'dying out' ----- I drove home == a 125 mile trip (from Kingman to Chino Valley) ----- and the car never quit or stumpled running.

So, is your tank building 'air - pressure' ?

I'm going to check that "rubber hose connection" (it has to be good , or I wouldn't be building pressure ... but, I know that hose is old).

.... my Car is a 69, also .... jim
 

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My brother had an issue similar to yours. Believing the fuel pump was no good he replaced it. A week later there was no fuel going to the engine. Took that pump back and got another. Sure enough the engine ran out of fuel again later on. Time for a full inspection of the fuel system. He found the problem. Between the fuel tank and the steel line is a rubber line with a crack in it. Seems the crack would open up and the pump would draw the air rather than the fuel. Replaced the rubber fuel line and never had a problem since.
What he said!!!!!!!!!!!!!!!
 

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Vented Gas Tank Cap

From my understanding, a vented gas tank cap has a "one-way" air valve... it will let air into the tank as fuel is used, but it will not let pressurized air out of the tank. It is ok to have some pressurized air in the gas tank, as this will aid in pushing fuel to the fuel pump.
I have always had a vented gas tank cap on my Nova and as long as I can remember, I would relieve some air pressure from the tank when removing the gas tank cap... especially in the warmer/hotter weather (not so much when it is cold out).

P.S. I am not a big fan of the clear glass fuel filters located in the engine compartment. If the glass fuel filter was to ever accidentally hit something in the engine compartment while the engine was running, it could break and leak pressurized fuel onto a hot engine and possibly cause a fire.
 

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I had the original gas cap on my '71 and had no issues for 30 years and then one spring day the vent plugged and I'd get 3 miles from my house and it stalled. Wait 20 minutes and it started and I drove it back home. Took me a few days to figure that one out. Replaced the cap and I was back in business.
 

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I'm having a similar issue with my 66 station wagon. When I start it up cold the fuel filter next to the carb fills completely. When I drive for a while it will start top stumble and then run out of gas. Let it sit for a while and it will start back up with full fuel filter.
Checked incoming fuel lines for suction side cracks and hoses were in great shape. Changed them just in case. Pulled out the holley mech fuel pump and checked the seals. All in great shape. Bench tested and had great suction and pressure.
Put a gauge on the high side of the fuel pump and cranked the engine over. Went right to 6 lbs. Let it sit and held that for 40 minutes.
Crawled under the car today and while PO put in a vented fuel filler, but the Classic Industries tank is NOT vented, so the filler vent does not connect to anything.
It ha a nice chrome non-vented gas cap. That is my last guess. I'm going to drive around today and, if the filter next to the carb goes dry, or almost dry, I"m going to open the gas cap. If that relieves the vacuum and the filter fills, I know that the culprit is!
 

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I'm having the same issue!

1966 Chevy II Wagon. 350 SBC with a Edelbrock 1406.
When I start it up cold the inline fuel filter fills up completely. Take it for a drive around the block and get it to operating temp (195 or so degrees) and the fuel is now splashing in the fuel filter.
Go for a drive of 15 to 20 miles and it 'runs out of gas' Filter empty. Let is sit for a bit, crank it over and fuel returns to the filter/carb. If I feel it running out of gas I can step on it and run on the secondary for a bit and the fuel gets back to the carb and I can run normally.
I changed all the fuel lines with new clamps. Hard line, gas tank, and sender are fairly new (PO installed). Gas tank is vented.
I removed the Holley mechanical fuel pump and took it apart. Gaskets/seals looked fine. Re-installed and put pressure gauge and it went to 4.5, slowly coming down over about 20 minutes.
I think next step it to check pump output, assuming I can find a spec for that. (any help out there) If volume is low I'll pull the pump and pushrod and see if the rod is worn therefore not delivering enough of a stroke for the pump.
Last think would be to drop the tank and see if there is any crud in there, but since it's a very new tank I don't think that is the problem. Although at this point I am reticent to rule out ANYTHING!
Any help/suggestions would be greatly appreciated.
 

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Discussion Starter #14
Update!

I replaced both the front and rear rubber lines. They didn't look bad at all, I think they should have been new around the time I did the fuel system in 2014. They are all buttoned up pretty good now.

I drove it a couple of times and it seemed alright. Today I was able to reproduce the issue though. It's a very warm and sunny day, I had about 45 minutes drive time on it, parked it facing uphill in my driveway by the house, made sure the fuel filter was full, and went inside the house. I came out ten minutes later to hear a slight popping noise under the hood.

Taking off the air cleaner, I noticed that the fuel filter was almost empty, and the carb was steaming from gas. I saw the primary boosters dripping gas, and the accelerator pump nozzles slowly farting out bits of gas. Not quickly, but it was there.

I relieved what seemed like a normal amount of air from the tank, and I don't think anything changed on the carb side. At that point the fuel filter was empty.

I started the car, which took a bunch of cranking. However, this time, it looks like the fuel filter filled up immediately.

So my thoughts are that I probably had a weak fuel pump, that couldn't recover fuel fast enough before the carb ran out of gas, and/or the rubber lines must have been leaking.

But, is it normal for a carb to be sputtering fuel down the bores? I thought the vent tubes on a Holley 4160 should relieve pressure from the fuel bowls?

Carb is Holley 0-82750.

Thanks!
 

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Thanks for the up-date .... & keep us posted.

Then, I have a Story about "Fuel Problem " ....

I fought this fuel (carb would run dry - engine dies) ... for over a year, it was on my (Ford) work truck (at that time , my main driver ... so, it needed too run right). This truck - w/ 351m V8 4x4 - would run good (I had installed a 'New Long-Block Motor" .. (and, at that time 'was a mechanic' : working on a fleet of Ford Trucks. Meaning, That I did have some Spare (both New & used) parts close by.

Going down th' road (or just driving around town) -- the Truck would die.
I installed a 'clear plastic fuel filter' in the line to the 2bbl carb. That fuel filter would run dry --- I would even remove the top of the carb & the bowl would be dry.

At first, I fought this trying to find out if when the truck would die : was it fuel or ign. my 1st thought was "spark" ... which lead me down the wrong path ..
Because , the motor was new, carb, fuel pump & everything was installed new (but, not the Distrb. ). Plus, those old trucks had those old style ign boxes -- with the "blue-grommets" -- I even installed a new one (plus, changed several times). == WAS NOT an IGN problem.

So, back to the fuel : I even changed the (New) fuel pump (twice, cheap fix -- if it worked) -- it didn't.
Let me say ..... This was "on - going problem" ---------
this stupid truck would Run - Good , for a month or two, then, start the cycle again ... acting-up , for a day .... may-be two days .... then, start running great again... a month, even two months ... crazy !

Bottom Line : : : False indication ... Since I installed almost everything New , when I installed the new 'Long-Block' (including a new 2bbl carb
(from Ford Dealer .. not a rebuilt) .... and, ruled out the 'ign'.
I even changed 'All Rubber Fuel Hoses, fuel tank 'selector tank valve' , gas cap, that clear plastic fuel filter 5, 6, 8 times .... ? ? could it be ? ?

KISS -- Simple -- Don't Over Think It --
While I was always changing out those parts .... I overlooked the simple thing. .......... and, man , does it piss-u-off !

When, I installed that New Carb (Ford Motor-Craft type 2bbl) ...... they have a "metal type screw in fuel filter" that mounts to the fuel bowl .
(which WAS NEW, when carb was installed).
While I was Changing out 'everything that could be wrong : including the 'plastic fuel filters' ...... I never once checked that stock metal filter.
Even 5 guys could-not have enough "blow-power" too blow through that plugged fuel filter. While installing the new 'plastic filters' , I guess the metal filter got plugged, somehow .....

NEVER HAD ANY PROBLEM after that "CRAP" .....

long story --- but, sometimes ----- it's the easy things that get-you

I'm just saying ............. jim

ps : I had / drove that truck for Over 23 years ..... so, may-be I did win .... ?
 

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“Taking off the air cleaner, I noticed that the fuel filter was almost empty, and the carb was steaming from gas. I saw the primary boosters dripping gas, and the accelerator pump nozzles slowly farting out bits of gas. Not quickly, but it was there.”


Sounds to me like a fuel percolation problem. Due the the alcohol in the fuel it will boil at a lower temperature. When the carb bowls get hot the fuel starts to percolate pushing out the air bleeds.
 

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“Taking off the air cleaner, I noticed that the fuel filter was almost empty, and the carb was steaming from gas. I saw the primary boosters dripping gas, and the accelerator pump nozzles slowly farting out bits of gas. Not quickly, but it was there.”


Sounds to me like a fuel percolation problem. Due the the alcohol in the fuel it will boil at a lower temperature. When the carb bowls get hot the fuel starts to percolate pushing out the air bleeds.

good idea .....

op ... do you have a carb spacer on your intake ---------

or ---- maybe you need one ... like a 1" plastic type spacer (would you think that would hurt, anything ........ just thinking 'out loud' ).
They also have a "Heat-Plate' , for that purpose -------

sbc1320 -- he has one -- look at some of his post .. or .. look on Summit & see what I'm talking ?
 

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Discussion Starter #19
Interesting on the percolating fuel. Never had that issue before, even the years I daily drove it. Thinking back, I always ran a 4150 directly on the manifold since 2002, until I sold the car in 2013. It bought it back the following year in 2014 with a Summit M2008 carb and a 1/4" phenolic spacer that were both trash. Amongst the many things that happened, I replaced the leaky carb with the new 4160 HP Holley that sits directly on the manifold now.

I think I'll get one of those phenolic isolator spacers again.

Also, I just remembered that over the winter my engine temp was way low even when driving this January, so I figured I had a stuck thermostat. I bought a replacement 195* thermostat, because I figured that's what I had. Upon remove/replace, I found the old one was indeed stuck (I was driving at 155*) and the old part was stamped with "180". Should I have stuck with the 180*?

This is turning out to be quite the conundrum for me.... :D but better now than in the 95* full heat of power tour 200 miles from home :turn:
 
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