Losing power on hills

Wedgetail

Wedgetail

Member
I have a 40 Fordor, and it loses power under full throttle especially on a steep hill. I floor the accelerator, it accelerates well for 3-4 seconds and then the power cuts down drastically. Let off the pedal and you can do it again, but getting up a hill is a losing deal. 1/2 throttle is great. And by the way, the spark plugs are covered in soot, so I know it is running rich.
 
i would be thinking fuel starvation if it happened to me, and it has happened.

in my case i searched every where i could in the fuel system from tank to carb and couldn't find any blockage, until i took another look in the engine compartment and noticed partially hidden rubber fuel hose about four inches long leading right to the carb (this was NOT on a vintage Ford BTW) and so i removed it and took a look in one end and couldn't see light at the other end! turns out there was some kind if insect larvae in there! fuel could get through but not enough when a load was put on the engine, like ascending hill or entering a freeway. smh
 
It does feel like fuel starvation. I took the hose off the carb and pressed the starter button and got a reasonable blast of fuel out of the fuel pump. Can I measure that to see if it is enough? Or if it looks like a lot, that isn’t the problem? It was enough to knock over the cup I aimed the tube at.
 
It could be a slipping clutch disc...
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Wedgetail said:
It does feel like fuel starvation. I took the hose off the carb and pressed the starter button and got a reasonable blast of fuel out of the fuel pump. Can I measure that to see if it is enough? Or if it looks like a lot, that isn’t the problem? It was enough to knock over the cup I aimed the tube at.
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can't say...but if i google "how do you test a 1940's ford mechanical fuel pump for volume", i get an AI response that outlines how one might go about it.

and if i found the volume per unit of time insufficient, i might think it userful to remove the fuel pump and check for leaks and/or a clogged fuel filter that i've heard tell is in and around the fuel bowl on most vintage ford mechanical fuel pumps.
 
Why not start with addressing your fuel mixture? Take it one step at a time. You’ve identified one issue, track that down with adjusting your carburetor, then if that doesn’t fix, check float level, check fuel pressure.
 
Also look for potential fuel pipe leaks which allow air to be sucked in. I had this happen on my 57 Thunderbird and a piece of fuel hose was failing. I could drive but only at a modest pace. On the early fords it can be the metal lid on the fuel pump. Make sure the gasket is good there. Also check the vent on your fuel cap is working.
Mart.
 
A partially collapsed flex line will lean out your mixture as your float bowl level gets critically low. You say thus happens on upgrades, but it can also reduce your top speed.
 
Lots of things to think about here. Fritz, when you say to adjust the carb, do you mean to change the jets? I have not been able to find any other adjustments to make it more lean. And Mart, I did just change the gas cap, if the new one is not vented, that would be hilarious. It also sounds like it might be time to change the inlet hose to the fuel pump, just in case. The fuel pump looks like a new one, so I’m suspecting the previous owner might have come across this problem and I somehow made it just a bit worse so it showed up again.
 
If it’s an all metal pump there should be a screen filter on the top of the pump.
If it has glass bowl there is a screen above the glass bowl.

weak spark can also limit power
 
How old is the flex line to the pump? Have you changed it? If its old I would remove it and closely inspect it. It may be time for a new one.
 
I do have a Holley carb, the only settings I have seen are the idle and the summer/winter settings, I’ll have to check that I have that set correctly. And the fuel flex line is old and somewhat suspicious, although not obviously leaking. I will change it as a precaution.
 
Wedgetail said:
I do have a Holley carb, the only settings I have seen are the idle and the summer/winter settings, I’ll have to check that I have that set correctly. And the fuel flex line is old and somewhat suspicious, although not obviously leaking. I will change it as a precaution.
Click to expand...

A leaking flex line is never obvious: You can’t see a dribble of air entering a leaking flex line. The same is true all the way back to the gas tank, should you have a rust pinhole in the supply line or a leaky spring wire clip (these always leak) on a fuel filter.

A moderate leak can go un-noticed for miles and miles until you start on an upgrade, which requires more gas than your pump can deliver while also pulling air.
 
IME, the use of the phrase "mixture screws" WRT the screws on the back of the 94 is and was very misleading. especially for one with extensive experience with other carbs. :)
 
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