fuel starvation

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jmontav
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Joined: Tue May 24, 2016 11:24 am

fuel starvation

Post by jmontav »

my 57 has started starving for fuel after running along at 40-55 mph and driving for 30 minutes or so. engine feels like it is not getting fuel and the car starts to slow down. I pump the accelerator a few times and it kicks back in, then runs fine for a couple miles, then cuts out again. Fuel filter? Fuel pump (pump is only a year old)? Vacuum?
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55Greg&Amy
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Re: fuel starvation

Post by 55Greg&Amy »

Maybe a sticky float or needle. Could also be a weak fuel pump
Greg Minnich
Kendallville, IN
bobioknight
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Re: fuel starvation

Post by bobioknight »

Something I read, may help you. Bog from a cruise RPM may be caused by a defective advance mechanism, but on 4 barrel carburetors is often caused by the secondary side opening too soon. Most original equipment 4 barrel carburetors have “on-demand” secondaries (I use this term rather than vacuum, as some early 4 barrels used vacuum to accuate the secondary, while most 4 barrels from about 1960 up used either spring tension or weights to control the secondary). The Carter AFB uses weights, and therefore never goes out of adjustment. Other 4 barrel carburetors such as the Carter AVS, Carter TQ, Rochester 4GC, and Rochester Q-Jet have a tensioned secondary spring. As the spring fatigues, the air valve will open too soon, creating an instantaneous lean condition, and a bog. These units, when rebuilt, should virtually always have the tension spring replaced, and adjusted to factory specifications. A defective accelerator pump will rarely cause bog from cruise.

Your secondary advance Rubber or spring may be worn. Both are cheap, easy fixes.
1957 Ford Thunderbird | Black | 312 Y Block | 28,000 miles
2007 Jaguar XK | Green | 18,000 miles
2002 Ford F-350 SD Lariat | Green/Tan | 7.3 Turbo Diesel | 190,000 miles
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bobioknight
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Re: fuel starvation

Post by bobioknight »

jmontav wrote:my 57 has started starving for fuel after running along at 40-55 mph and driving for 30 minutes or so. engine feels like it is not getting fuel and the car starts to slow down. I pump the accelerator a few times and it kicks back in, then runs fine for a couple miles, then cuts out again. Fuel filter? Fuel pump (pump is only a year old)? Vacuum?
I think you would notice a vacuum leak more at idle, I am not sure which carb you have but I think you may want to initially check your float levels to make sure they are allowing enough fuel in the bowls. Could be fuel pump, fuel lines or filter, I have read that some people have rust in their tanks and small particles travel up and plug filters. You should definitely check your filter first thing to make sure this is not your issue. If your carb is starving then I assume it is possible.

If your pumping the accelerator, then your pumping fuel from your primaries using the accelerator pump to keep things going. So you obviously have fuel in the bowl or you would just be adding more air into the system when your pumping. If this is the case then maybe your Vapor Locking. Can you post a picture of your fuel route from the pump to the carbeurator.
1957 Ford Thunderbird | Black | 312 Y Block | 28,000 miles
2007 Jaguar XK | Green | 18,000 miles
2002 Ford F-350 SD Lariat | Green/Tan | 7.3 Turbo Diesel | 190,000 miles
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paul2748
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Re: fuel starvation

Post by paul2748 »

Could also be a fuel line that is sucking air. Check the flex line.
1956 Fiesta Red 312
1954 Ford Victoria 312
1948 Ford Convertible Street Rod 302
jmontav
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Joined: Tue May 24, 2016 11:24 am

Re: fuel starvation

Post by jmontav »

thanks for all the feedback. I have a relatively new edelbrock carb, fuel pump was replaced less than 2 years ago. first thing I did was put a new fuel filter in. I use an in line metal aftermarket fram filter. still have the problem; I have ordered a new pump (airtex). Will see if it helps. In the meantime I pulled the air cleaner and drove the car only a mile or so and it started acting up. why would this make the problem worse... low speed... I thought about vapor lock. Not sure how to diagnose this and / or to reroute fuel line further from the engine surface? will tighten clamps where the rubber fuel line is spliced to the metal........what else?
bobioknight
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Re: fuel starvation

Post by bobioknight »

Well for instance, I had a rubber fuel line that was old, hard and ran up from the fuel pump along the engine block across the intake and up to the carb. I put a small glass fuel filter inline, after a short trip much like you I noticed the fuel would be boiling in the glass filter and the filter would nearly empty itself. I started chasing what I am calling vapor lock (fuel boiling) issues and decided to run new steel fuel line from the pump, up to the carb, with a era correct fuel filter with glass bowl. I run a number of lines until I routed it up far enough away from the engine that it finally ended the boiling issues. If you take a look at a few photos of the the stock route and bends in the metal fuel line, as soon as I mimicked those same bends my fuel issues were over, seriously seems like ½ inch further away from the engine block made a huge difference . Vapor lock could make your engine act like it is running out of fuel & flood the intake.

I am still working on my intake vacuum leaks which could be your problem as well, have you tested for vacuum leaks along the carb and intake?

Pictures are worth a thousand words, I have had guys point out possible problems because of something they could see in a photo.
1957 Ford Thunderbird | Black | 312 Y Block | 28,000 miles
2007 Jaguar XK | Green | 18,000 miles
2002 Ford F-350 SD Lariat | Green/Tan | 7.3 Turbo Diesel | 190,000 miles
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jmontav
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Re: fuel starvation

Post by jmontav »

breakthrough!!! vapor lock! turns out that I had rearranged the fuel line as part of my engine restoration project in November. The carb inlet on the edelbrock carb allows the underside of the air cleaner to "bump" into it such that the air cleaner will not fasten all the way down on the passenger side where the inlet is. I solved that by installing a nice edelbrock fitting whereby the fuel line runs along the side of the manifold then turns 90 degrees up to the inlet (banjo fitting). nice installation BUT I had not driven other than short local trips in cool weather until a couple weeks ago when the problem occurred. I had forgotten this and when the vapor lock question came up I remembered the fuel line change. I rerouted it as it was before, with lots of spacing between the fuel line and engine surface. took the car for a long highway test drive and it runs great. THANKS or calling this to my attention!!!
bobioknight
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Re: fuel starvation

Post by bobioknight »

Your welcome, I had the same issue when adjusting the banjo fitting too much. Fixing these little thing makes driving so much more enjoyable. Love those victory laps.
1957 Ford Thunderbird | Black | 312 Y Block | 28,000 miles
2007 Jaguar XK | Green | 18,000 miles
2002 Ford F-350 SD Lariat | Green/Tan | 7.3 Turbo Diesel | 190,000 miles
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adg57
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Joined: Mon Jul 11, 2016 6:27 pm

Re: fuel starvation

Post by adg57 »

Resurrecting this thread. My 56 has started similar behavior, seemingly starved for fuel after the car warms up. This happens under load, i.e. uphil. However the car dosn't just bog down, the rpms start fluctuating wildly. Usually when I pull over for a couple seconds, the car is back to normal as long as I don't accelerate too hard.
Was thinking this is probably vapor lock, engine gets warm (it's mid-90's here, but not above 180-190 coolant temp. Gas is not bubbling in the glass fuel bowl & just replaced the fuel filter. However the fluctuating rpm makes me think might also be the secondares "fluttering" or opening early. Is that even possible ::?
Appreciate any thoughts.
Andy
1956 312
voltron
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Re: fuel starvation

Post by voltron »

The flexible fuel line connecting the fuel pump inlet to the steel tubing on the frame from the fuel tank has been known to get flimsy and suck shut. At least one of the Tbird suppliers sells a replacement made with a coil spring inside the hose to prevent it from collapsing.
ICON 1956
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Re: fuel starvation

Post by ICON 1956 »

I'am not hijacking this thread but could this problem also be cause by the Ethanol additive ? By what I have read the additive can cause damage to the carburetor floats rubber gaskets, etc..... my 2 cents worth ::?
1956 Thunderbird Sage Green
1953 Ford Custom Liner Hot Rod With Flat 8 Motor with Henderson three 2 barrel Carbs
VTCI Member # 12309
adg57
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Re: fuel starvation

Post by adg57 »

Thanks, I did order a new fuel flex line. Current one doesnt look bad but it's worth a try.
Re ethanol - what I've read indicates it might make vapor lock problems worse, in addition to being tough on gaskets/hoses.
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Re: fuel starvation

Post by ICON 1956 »

Well it happened to me first time....I took my car to a cruse night only to find out that I ran out of gas ! I thought the gas gauge had a quarter of gas left I guess the gauge is off , I noticed that I was losing power and the car just coasted to a stop.needless to say I called my wife to bring a gallon of gas, In the meantime I had to stand far behind my car to signal to the on coming traffic to turn to the next lane. Since these cars have no emergency flashers. The Police did show up to assist with their lights flashing. I felt embarassed..... :oops:
1956 Thunderbird Sage Green
1953 Ford Custom Liner Hot Rod With Flat 8 Motor with Henderson three 2 barrel Carbs
VTCI Member # 12309
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