school me on fuel pumps...

[Dart_Guy]

I know very little about fuel pumps and have something on my Dart that has me curious. When I bough the car, a 69 340 Dart, it had a mechanical pump and an electric pump which had a toggle switch on the dash to turn it on and off. Before tearing it down, I noticed no difference with it on or off...

So my questions,
1. Why would this be done?
2. Should I just remove the pump and go with the mechanical? With no difference noticed is it worth keeping the electric?

Thanks in advance!

 

[slantsixdan]

I don't like electric pumps on carbureted applications; see here for explanation.

 

[Johnny Dart]

If the electric pump was inline with the mechanicl pump,it is known as a booster pump.
For anything but an all out race car you should get rid of it.There are plenty of high quality mechanical pumps out there that will keep your 340 plenty happy.

 

[67Dart273]

Dan doesn't seem to like much of anything. I like electric pumps "sometimes." They can help with vapor lock problems, which has been aggravated by todays alky gas.

You definately want to put an oil pressure safety on the engine, and an inertia "crash" switch doesn't hurt, either. Thanks to our new EFI cars, finding usable oil safety switches or crash switches is real easy. Ford Rangers are one source of crash switches. Toyota used to use an oil pressure switch that was easy to deal with.

You really should run the pump through a relay, so all these additons are easy.

Here's one diagram, showing one generic way to add a pressure switch. In this case, they are not using a relay, so the item marked "pump" would be the "pump relay. Here's how this one works. The connection to the starter solenoid goes to the nc (nomally closed) contacts. So when you are "on the starter," current feeds from the starter solenoid, through the nc -c (common) contact to operate the pump. If pressure should happen to come up, either from the engine firing or "on the starter," pressure will change the switch over to the n.o. (normally open) to c (common) contact and this power comes from the "igition run" circuit.

On Moparts, "ignition run" is dead during crank, so the pump will actually QUIT if you are cranking and the engine develops enough pressure to trip the switch.

This should be no problem, because the pump should already be primed, and there should be enough fuel in the bowl to run for the .00000000001 to 2 seconds that this is going on.

Back "when I was a kid" I used to run series pumps as you describe, and they worked OK. The purpose was to give a little boost for the 440 back then. It actually saved my a$$ one time when the mechanical pump failed. Just bypassed 'er and used the electric pump.

Incidently, running series pumps OF CERTAIN TYPES does not jack up fuel pressure. This is because the older "pulser" pumps build pressure the same way as the mechanical pumps---they pump gas on a spring. So the camshaft "cocks" the mechanical, the electric solenoid "cocks" the electric, and the spring inside returns the piston or diaphragm, pumping the gas. This means that fuel pressure is regulated by the spring, not the solenoid, and that as the electric pump builds pressure, the mechanical simply "floats" the arm off the cam and stops pumping.

 

[slantsixdan]

Dan doesn't seem to like much of anything.

Looks like somebody needs a nap…!

Dan likes lots of things. Dan backs up his assertions and preferences with explanations and references. Dan doesn't care what 67Dart273 thinks of him, so Dan's going to keep on giving solid advice he's qualified to give, and keeping his mouth shut (or at least ending his sentences with question marks) when he doesn't know what he's talking about. Dan hastens to remind 67Dart273 that this board has an "Ignore user" function that works very well. Dan's going to stop talking about himself in the 3rd person now.

 

[Dart_Guy]

Thanks for the great input! I know far more about fuel pumps than I did when I woke up for work this morning... Gotta love the internet, a productive day work coupled with a lesson on my car. I figure I will have a lot more questions as put the car back together.

I will, for now, go with the mechanical only. Just to avoid adding all the safety items as mentioned above. But I will keep this information in case I decided to add one later on.

 

[Johnny Dart]

Looks like somebody needs a nap…!

Dan likes lots of things. Dan backs up his assertions and preferences with explanations and references. Dan doesn't care what 67Dart273 thinks of him, so Dan's going to keep on giving solid advice he's qualified to give, and keeping his mouth shut (or at least ending his sentences with question marks) when he doesn't know what he's talking about. Dan hastens to remind 67Dart273 that this board has an "Ignore user" function that works very well. Dan's going to stop talking about himself in the 3rd person now.

Dan also likes stock grocery getters. And Dan knows that in some aplications more fuel will be necessary where a stock mechanical fuel pump just aint enough.

 

[slantsixdan]

Dan also likes stock grocery getters. And Dan knows that in some aplications more fuel will be necessary where a stock mechanical fuel pump just aint enough.

True and true.

 

[Johnny Dart]

Dan.......You suprised the heck out of me....Kudos to you.

 

[slantsixdan]

How? There is no point arguing with facts; they will stubbornly remain facts.

 

[green1]

lol, how true; facts are facts. Bench racing is non-factual.

 

[3forty]

Leave that electric pump in,reason being if you decide to 1/4 mile your car,you hit the switch and go. When your driving around town the mechanical pump will do its job by itself.

 

[805moparkid]

Leave that electric pump in,reason being if you decide to 1/4 mile your car,you hit the switch and go. When your driving around town the mechanical pump will do its job by itself.

while staying on topic i pose another question

ive heard that some electric pumps will not allow a mech to suck the fuel thru if the electric is not on...

is this true on just some styles of elect pumps or not true at all?

 

[3forty]

I have a carter electric pump at the rear and a mechanical pump on the engine, with the electric off and cruising around, no problems.

 

[67Dart273]

Looks like somebody needs a nap…!

Dan likes lots of things. Dan backs up his assertions and preferences with explanations and references. Dan doesn't care what 67Dart273 thinks of him, so Dan's going to keep on giving solid advice he's qualified to give, and keeping his mouth shut (or at least ending his sentences with question marks) when he doesn't know what he's talking about. Dan hastens to remind 67Dart273 that this board has an "Ignore user" function that works very well. Dan's going to stop talking about himself in the 3rd person now.

"We" are quickly getting tired of Dan and his snide remarks You seem to have grown fond of accusing "us" of being

stupid

uneducated

inexperienced

"not knowing" what "we" are talking about.

along with a few other things. If you cannot be civil to "us" maybe YOU should be the one considering "keeping one's mouth shut."


Not agreeing with someone, "buddy" is not grounds for this kind of behavior.

I wasn't born just yesterday, and I didn't fall off the truck. In my younger days I've logged thousands of miles in these cars, and used to know them very well. I've done my own driveline work, built engines, suffered failures, as well as lots of good times. You have absolutely no grounds for this sort of attitude. Claiming that everything you post is abosolute fact and that someone else who might have a different approach "needs a nap" is quickly getting more than tiring.

If you cannot keep a civil tone with me, here, it's very possible that YOU are the one who should go take a nap.

I take issue with your assertion that you "explain your assertions" and use "references". I've actually read some of your favorite links after you've asserted that the "Mad" site is run by a bunch of "Chevy heads" (because as you know, according to you, Chevy heads know nothing at all). Some of the links you've posted here are nothing more than references to other posts with references to other links with references to other................................................

Sometimes, Dan, there IS more than one way to skin a cat. Just because you know two ways, doesn't make everybody else incorrect, stupid, or "needing a nap."

 

[805moparkid]

buddy[/B]" is not grounds for this kind of behavior.

ok "chief"...

if you dont know what im talking about don't worry about it... lol

 

[AtomicWedgie]

They could have used the electric pump as a starting pump then when the car is running flip it off. Saves the starter from excessive cranking. I have heard of this before.

AtomicWedgie is done posting now because I am tired.:bootysha: Sorry I couldn't help myself.

 

[Dart_Guy]

more good info and even some drama to boot... I am more worried about the possible safety issues. This car is my first restoration and intended to be a fun crusier car as the Dodge Dart is my dream car.

My next project, I will step up my learning and try to make something with big horsepower... so all this information will be good for when that happens. (That also hinges on me getting a bigger garage.)

Thanks again, and if someone needs a hug, well, I ain't into huggin guys, so good luck, I hope you guys sort out your issues.

 

[AtomicWedgie]

i would ditch it. A good mech. pump is all that is needed for a cruiser. There are plenty of brands to choose from. I always thought using a electric and mech pump together is kind of a rinkie dink way of doing things.

 

[slantsixdan]

You seem to have grown fond of accusing "us" of being stupid uneducated inexperienced "not knowing" what "we" are talking about.

Is that so? Please find where I have even just once accused you or anyone else of being stupid, uneducated, inexperienced, or not knowing what you're talking about.

maybe YOU should be the one considering "keeping one's mouth shut."

Er…yes. That's exactly what I said: When I don't know what I'm talking about, I keep my mouth shut. Go scroll up and read it again a little more carefully and you'll see.

Claiming that everything you post is abosolute fact

Find where I've ever said any such a thing. I dare you.

Sometimes, Dan, there IS more than one way to skin a cat.

Yes. Definitely. Take a look in this very thread where I agreed on that very principle...as stated by someone without your sort of chip on his shoulder.

and that someone else who might have a different approach "needs a nap"

No, I said it looks like you need a nap because you took a gratuitous, unwarranted potshot at me because you're still sore about my knowing more voltage regulator options than you seem to (which is, admit it, kind of a silly thing to be bent outta shape about). Not because you have a different approach.

Welcome to my ignore list. If you're so sick and tired of reading my posts, I suggest you go ahead and add me to yours.

 

[3forty]

i would ditch it. A good mech. pump is all that is needed for a cruiser. There are plenty of brands to choose from. I always thought using a electric and mech pump together is kind of a rinkie dink way of doing things.

Not rinkie dink!!

 

[oldkimmer]

...............The reasoning behind using an electric pump into the mechanical is that the mech can attain its free flow capability........all pumps have a pressure and flow drop when restricted..........kim...............