Can somebody explain to me how fuel pumps function (specifically on my Volare) and if/how one that is failing could affect an engine's idle?
Thanks guys..

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<i>D'Artagnan</i>
<img src="http://img.photobucket.com/albums/v432/stephaniexchaos/dart/th_IMG_0326_zpsumhhfxi0.jpg">

will it could have low pressure and not fill the bowl in the carb when a load is placed on the engine and cause it to run lean or it can have a internal leak and pump gas into the base and hurt the bearings,also low flow can keep the level in the bowl so low that fuel is not metered properly and affect idling.what is the problem?

I'd rather not get into it quite yet cos I'm not sure I understand everything quite right, and I want to understand the functions of parts I think are involved so I can make sure I explain things correctly.

However, I should have specified, I meant to say affecting the engine's idle only when fully warmed up, not at any other time.

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<i>D'Artagnan</i>
<img src="http://img.photobucket.com/albums/v432/stephaniexchaos/dart/th_IMG_0326_zpsumhhfxi0.jpg">

They work a lot like the pump on an old squirt gun. There are two (or more) check valves. One valve allows fuel into the pump through a fitting and the other allows fuel to leave the pump from another fitting. Depressing the arm or on the pump pulls the pump diaphragm away from the valves causing a partial vacuum in the pump cavity. The outlet valve(s) are held closed by the vacuum and the inlet valves open. Atmospheric pressure acting on the fuel in the tank pushes fuel into the pump. Releasing the lever allows the spring in the pump to act on the diaphragm and push fuel out the outlet valve(s). The spring and the area of the pump diaphragm determine the fuel pressure assuming the pump is not starved for fuel.

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Joshua

Thanks Josh.
So is it reasonable to think that, if the spring is failing, there might not be enough pressure to get enough fuel to the carb when the engine is warm (and so fuel line is warmer, requiring more pressure), causing the engine to partially starve and idle really rough, even stall, and starve the carb completely at W.O.T. on the track?

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<i>D'Artagnan</i>
<img src="http://img.photobucket.com/albums/v432/stephaniexchaos/dart/th_IMG_0326_zpsumhhfxi0.jpg">

If it's only affecting it after warm-up I'd check the carb and choke :shrug: maybe it's sticking

Choke is disconnected completely...

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<i>D'Artagnan</i>
<img src="http://img.photobucket.com/albums/v432/stephaniexchaos/dart/th_IMG_0326_zpsumhhfxi0.jpg">

Your fuel pump is not affecting your idle quality. When a fuel pump is not putting out enough fuel to meet the engine's needs, the engine starves at high speed/load when it needs the most fuel, not at low (idle) speed when it needs very little fuel.

Look elsewhere for your idle problem...I found one in a really interesting place this evening on my Dart (will make a separate post).

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

It more likely that there is a restriction on the inlet side starving the pump. If the fuel is warm enough and there is enough vacuum the fuel will boil and vapor lock the pump.

I would make sure that there isn't a restriction in the line from the tank to the pump and that there isn't a vacuum in the tank.

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Joshua

Ok, this is why I was being confused. Because the engine has starved and nearly stalled at high speeds/load as well, so I wasn't sure if the two problems were connected.
Ok, sounds reasonable. I'll check it out if/when I have a chance.

Thank you!

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<i>D'Artagnan</i>
<img src="http://img.photobucket.com/albums/v432/stephaniexchaos/dart/th_IMG_0326_zpsumhhfxi0.jpg">

fuel pump output is pretty easy to check. if you take the outlet hose from the pump and pour it into a container, then start the engine, you should see a good stream of fuel coming out of it. be very cautious that no fuel gets on your ignition system, run a longer hose from your outlet fitting so it dumps well away from the ignition system. your pump should put out a few pounds of pressure, verify this either with a gauge you dont have, or by firmly holding your thumb over the outlet and cranking the engine with a remote starter (watch your eyes).

as stated it's doubtful this is your problem since you have idle issues. check base timing, dwell (points ignition) advance operation, spark quality with adjustable spark tool, heat riser operation, and valve lash (drool tube head) before settling on the carb.

if this is the same motor with faltering oil pressure you may have sticking rings or valve issues or cracks somewhere showing themselves at operating temperature. but if youre still taking this car to the track and racing it when you know youre trying to sell it and need the money, well... why not just keep both cars, race one and drive the other? if you drag race a car it's inevitably going to break. if you have another car to get you around---you wont find yourself in a panic.

just tryin to help..........

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

Bad idle + high-speed stalling + disconnected choke suggests your carburetor is faulty and/or has been hacked.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I'm actually wondering whether the fuel problem and the oil pressure problem are really one and the same. Since the pressure problem only shows up during rough idle, I would think that if the engine is faltering due to fuel problems, then the pump drive gear wouldn't be spinning fast enough for the pump to put out correct amounts of pressure.
Is that reasonable?
I took the car to the track a week after I got it - it's what I raced at the last Redding race, and that's where the stall at W.O.T. occured - luckily, I didn't stall completely, backing off the pedal for a second and then pumping it a bunch brought it back to life, but it wasn't happy (and I didn't get past the first round. )
The problem with keeping both cars is one of space - I live in an apartment complex with two other people who both have cars, and we only have one assigned space. I don't have enough room to work on one car, let alone own two. Plus, I do have Chris's Duster to fall back on in the event my car is down for a while - he doesn't need it to drive to work, or to be any place regularly.

I'm just not one to know there's a problem and not try to fix it. So I'll probably keep working on it here and there until it does sell.
Ok. I'll swap the carb from Audrey onto the Volare and see what happens.

Thanks for the suggestions and guidance!

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<i>D'Artagnan</i>
<img src="http://img.photobucket.com/albums/v432/stephaniexchaos/dart/th_IMG_0326_zpsumhhfxi0.jpg">

If Audrey's the '65 Dart, that swap won't work. Wrong linkage hookup, too many vacuum fittings not present on the '65 that you need for the '78 car.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Dan,

Audrey (the '65 Dart) and the Volare both sport Super Six induction.