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Discussion Starter #1
OK, so I've been going crazy trying to fix my stalling when at fully warmed up operating temperature problem. I rebuilt and adjusted the carburetor, replaced the fuel filter, gas cap, coil, points, condenser, rotor, cap and plugs. Set the the dwell and initial timing at 6 deg BTDC (since everything is factory correct in this car I figure the factory setting should be fine).

Replaced the generic aftermarket mechanical fuel pump with a new Airtex mechanical pump that is closer in design to the original Carter. This got the fuel line away from the cylinder head (where it was actually touching before). I put an insulating sleeve on the fuel line from pump to carb. It is touching the P/S and A/C brackets, but not touching the engine/intake/etc. It was touching the coil so I temporarily put a clothes pin on it to give it a little space.

I'm pretty darn confident that it's vapor lock because it only happens when fully warmed up. After it stalls, if I let it cool off, it will restart after a fair amount of cranking. The last time it stalled I took out the primary bowl sight plug and the primary bowl was completely empty. Secondary bowl seemed a smidge low but OK (I did set the floats after re-installing the carb after rebuilding). There is a factory correct spacer under the carb. I haven't checked the positioning of the fuel line at the back of the car where it crosses the exhaust pipe to see if it might be too close, but I doubt it. It definitely seems to be related to engine compartment heat.

I'm using 93 octane fuel with the Sta-Bil 360 additive. There's no gas stations anywhere near me that offer ethanol-free fuel. :mad:

Any suggestions? I'm stumped at this point.
 

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I am not sure if there is there a screen on the fuel tank pickup tube in 1969??? ... or cracked or collapsing hose from tank to fuel line?
 

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Discussion Starter #3
If that were the case then why would it run fine when cold/warming up? Also this problem was not occurring as much when the outdoor temps were in the 40's or below.
 

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Discussion Starter #5
I recently replaced all the rubber portions of the fuel line proactively. What was there was relatively new and fine however.
 

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This is the most important part of the whole post:

"The last time it stalled I took out the primary bowl sight plug and the primary bowl was completely empty."

This sounds like a packed in fuel filter. If it happens again, the way to check it is really easy. Disconnect the fuel line at the carb. Point it into a can to catch the fuel. Have some one turn over the engine and you should see gas spurting into the can. If you don't see that then some where in the fuel line or filter you have a blockage. Keep in mind that fuel lines rust from the inside out so a great looking line on the outside means nothing.
 

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Good thought there Bill.....also you might consider putting in a phenolic spacer under the carb. It will insulate the carb from the intake heat - and keep the fuel from boiling away from heat soak. Most vapor lock problems are from the car sitting and the heat rising up and causing the trouble. If it's happening while your moving - I think Bill's thought is more likely.
 

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Discussion Starter #9 (Edited)
This is the most important part of the whole post:

"The last time it stalled I took out the primary bowl sight plug and the primary bowl was completely empty."

This sounds like a packed in fuel filter. If it happens again, the way to check it is really easy. Disconnect the fuel line at the carb. Point it into a can to catch the fuel. Have some one turn over the engine and you should see gas spurting into the can. If you don't see that then some where in the fuel line or filter you have a blockage. Keep in mind that fuel lines rust from the inside out so a great looking line on the outside means nothing.
I guess I'm confused as to why it would be a packed in fuel filter or blockage somewhere else in the lines. It appears to be heat related. It starts when cold and runs fine, through all the kickdowns of fast idle to curb idle. It smooth idles at curb idle speed until it gets hot (with car sitting in driveway this takes probably 20 minutes from a cold start). Then it begins to rough idle, then stalls. If allowed to cool down, it will restart and run some more until again it gets hot, then starts to rough idle, then stalls again. Last time I fiddled with it, I let it run up to full operating temp. It began to idle rougher and rougher until it stalled (over the course of 1-2 minutes). I waited about 30-40 minutes. Restarted the car. When it began to rough idle again, I pushed the throttle up to about 2,000 RPM's. Seemed OK at 2,000. Shortly after I took my foot off the gas, it idled very rough then stalled. If the fuel filter or line were blocked, wouldn't it not run at all?

When this has happened in the past, it's been while driving down the road at a steady speed (doesn't seem to matter what speed--it's happened on the interstate at 65 and also while cruising down a side street at 35). There's no warning, all of a sudden there's just a total loss of power (as though the car has just run out of gas). When this has happened, I have found you can pump the gas pedal and get a few short bursts of power but not enough to maintain speed. It's never stalled under acceleration.

As far as a carb spacer goes, there is one already in place. Not sure what material it is made of. However I don't really have any room to deviate from the existing spacer's thickness due to the ram are intake.....
 

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Hmmm. If the fuel bowl is going dry - it's gotta be either not getting there, or boiling away, or running out somehow. I don't suppose you ever have a heavy raw gas smell when you roll up to a stop or anything when it's hot? Wondering if something is expanding as it gets hot enough...?

Check this out https://www.youtube.com/watch?v=EppSYI8s3nI
 

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Discussion Starter #11 (Edited)
We have noticed a raw fuel smell when the car is hot at a stop light or while traveling at lower speeds like 25-35 MPH. More so with the top up and heat on than the top down. Last time it stalled while actually driving we did notice the raw fuel smell shortly before and during the stalling and coasting into a nearby parking lot.

Do you think it would be OK to run the car (in the driveway) with the primary sight plug removed to try to see if I can observe if the fuel is indeed boiling inside the primary bowl? I'd like to try to nail down the source of the problem before continuing to take shots in the dark to try to fix the problem. I feel like I've wasted so much time and money replacing stuff that likely didn't even need replacing only to find that I still have not fixed the problem.
 

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Are you running ethanol 10% at all? I would avoid it if possible....it burns hotter and boils easier. Sounds like it's boiling off. I'd try the spacer and see if it helps.....an aluminum intake wouldn't hurt as you next level of defense. Those big blocks got a lot of surface there and modern fuels are designed for injected cars. If you watch that video you can see it change when he pours the water on the fuel pump. Going to an electric pump might be a better option to consider before the manifold I guess......
 

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Discussion Starter #13 (Edited)
I am running ethanol 10%. There's no gas stations within 40 miles of me that sell ethanol free fuel. Plus I want to be able to drive the car to the Ford Nationals and maybe the CCOA East Coast Nationals so I'll need to be able to use readily available fuel as I'll be lucky to make it 200 miles on a tank of gas.

I just want to figure out if it's vaporizing in the bowl or somewhere before it's getting to the carb (such as in the pump itself or in the pump to carb line). I guess I could try to observe through the sight in the primary bowl--I suspect that very little should spill out the open sight plug while the car is stationary. Perhaps I'll use the temperature feature of my DMM and try to take some temperature readings of the fuel line at the fender, at the pump itself, on the pump to carb line, and at the primary bowl to see what the temp are when the car is at the stalling temp. If it's boiling off in the bowl, I would think that a phenolic spacer and maybe some heat reflective tape on the underside of the bowls might do the trick. If it's happening in the pump to carb line, I suppose I might have to re-route that completely (ugh). If it's happening in the mechanical pump, maybe installing an electric pump near the fuel tank might help by pressurizing the fuel between the tank and pump? I doubt it's happening anywhere before it gets to the pump because the fuel line just isn't really exposed to heat until it gets inside the engine compartment......

Just watched the YouTube video. That looks like an excellent diagnostic tool--a glass fuel filter. I could put it right before the carb to see if I'm getting bubbles from the pump--then I would know it was happening before the carb.
 

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Just don't leave that glass filter in - they can be fire hazards. Yeah, you should be able to run it with the site plugs out - if the float levels are set correct. Just going to take a lot of detective work. The fuel pressure should run 3-5 lbs tops BTW. Good luck!
 

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They also make a set of clear site plugs (got mine at Napa), so you can see the fuel level and adjust it while running and not have to worry about fuel going everywhere. Once finished adjusting, swap back to the metal plugs.


If you are getting a raw fuel smell then you have fuel leaking from somewhere. If the engine is hot, then that leaking fuel can evaporate pretty quickly. So check all of your carb / fuel connections for fuel and residue thoroughly, and tighten up the fittings as necessary. Wipe it all down and keep an eye on it for further leaks.


I would think that if the bowl is going dry while driving then something is not right in the delivery - a clog or restriction in the system somewhere. I like Bill's idea of verifying the pump, and maybe replace the filter.
 

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I think your carb is dumping fuel and causing a stall/flooded condition. Has the carb been gone through since you've had the car?
 

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Discussion Starter #17 (Edited)
I think your carb is dumping fuel and causing a stall/flooded condition. Has the carb been gone through since you've had the car?
Yes, first thing I did to try to resolve this issue was rebuild the carb and replace fuel filter. Found that all gaskets were actually fine, but the primary needle valve o-ring was toast. Smell of raw fuel was pretty persistent all the time. After re-installing the carb I performed all adjustments as outlined in the service manual. Actually, since rebuilding the carb, the stalling issue has become more consistent and less random. I do think the car was running rich and getting too much fuel due to the toasted o-ring (which may have actually been helping to offset the vacuum lock issue). Car kept producing black spots on the driveway under the tailpipes, but those have been gradually reducing since the carb rebuild. I think it'll take a while to blow all the soot out of the pipes.

Now we only get raw fuel smell when the car is hot and as it starts to rough idle and then stall.

Because the primary bowl is empty after it stalls I really think the fuel is either vaporizing due to heat either before it gets to the carb or while it's in the primary bowl. Will research this further on Friday when I have time.

This crapanol blended fuel is a real pain!
 

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Well Doug - you could always move!! lol yeah, it's only gonna get worse as time goes on I'm afraid. Another thought that I had is that sometime the meter blocks warp and it's very difficult to tell. It might present itself more after it heats up. The best way to catch them is lay a machinist rule across the face when you have the carb apart.
 

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Doug,

I am in the same area of the US being in NJ and I kind of doubt the fuel in the bowl is all vaporizing. I just went all the way to Ocean City, Md and back this past weekend and had some warm, humid weather during that time. Guessing you have a 735 cfm factory Holley? I have a SS-750-AN Quick Fuel which is a enhanced design Holley.

Have you gone through the tank and the metal lines? If the car sat for a long time, varnish or worse loose stuff from varnish can wreak all kinds of havoc on the fuel system. Have you tried a clear plastic filter at the sender to body metal line to see what the fuel coming out of the tank is looking like and what might be coming along with it?
 

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Discussion Starter #20
I haven't but perhaps I exaggerated when I said the car sat for a long time in my first post. What I meant was that since restoration, the car has been actually driven very little, but as far as I know, it has always been owned by folks who have taken care of it--i.e. ran it periodically, changed the fluids, etc. So it's not like it's been in a barn completely ignored. It was owned by Don Rush back in 2006 and for the last six years by a classic car collector in Virginia who either kept it in his own climate controlled garage or at the Ford dealership that he owned (also inside either in the service area or on the showroom floor).

When I rebuilt the carburetor I found no signs of varnish inside it.
 
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