Author Topic: primitive wonders about fuel tank pumps  (Read 1858 times)

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Offline franksolich

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primitive wonders about fuel tank pumps
« on: April 05, 2008, 07:11:20 PM »
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=310x138

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arkie dem  (279 posts) Sat Mar-05-05 09:23 AM
Original message

Could someone please explain to me the purpose of
   
in the fuel tank fuel pumps on newer FI autos?

Had one quit on the wifes car, and I about fainted when pricing a new pump.

This is a phenomenon new to me.

Do Ford Tauruses have such things?

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HamstersFromHell  Donating Member  (1000+ posts) Sat Mar-05-05 11:03 AM
Response to Original message

1. Older cars with engine mounted pumps...
   
were also carbureted rather than fuel injected. Carbs. only require somehwere around 2-4 psi of fuel pressure, so the system was designed more so that the (mechanical) fuel pump could draw gas from the tank up to the engine, then push it the short distance up to the carb. under low pressure. The float in the carb. then kept the fuel level in the carb. at the correct level against a low pressure source.

Today's FI systems put it in the tank because it's easier to build a pump which doesn't have to draw fuel uphill a long distance and then pressurize it as well to the 35-50 psi needed to operate an injector. These systems also have a fuel pressure regulator as well as a return line back to the tank (this is where the excess fuel goes). Since FI systems can't have a "bowl" to store fuel locally close to the engine.

Mechanical pumps supply one "squirt" of fuel per 2 crankshaft revolutions (they usually run off a lobe on the camshaft, running at 1/2 crankshaft speed). This pulsing would cause no end of problems in maintaining a constant pressure in the fuel lines and accurate metering and control of fuel delivered to the cylinders with a FI system. In contrast, a electric pump running all the time supplying a constant regulated pressure insures very exact metering of fuel...something good performance and good emissions require.

Note also that Honda used electric low pressure pumps mounted at or in the tank for their carbureted cars for years...with a similar price to today's FI pumps.

Hope this helps!

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arkie dem  (279 posts) Sat Mar-05-05 11:21 AM
Response to Reply #1

2. Thanks
   
I understand the reasoning behind pushing the fuel instead of the pulling effect of the old mechanical pumps.

Why can't the manufactures mount the electric pumps between the tank and the fuel rail? This in the tank business seems unneccesary and an extra labor expense.

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HamstersFromHell  Donating Member  (1000+ posts) Sun Mar-06-05 08:18 AM
Response to Reply #2

3. Don't quote me on this but...
   
I think it's done for two reasons.

Cheaper to make. (Don't have to pull gas any distance at all, so no need to have a check valve to keep the pump from losing "prime".)

No need to "armor" the pump to make it resistant to road objects...this would also reduce cost a bit more. It's relatively "safe" inside the tank.

Just my thoughts on it anyway, for what they're worth.

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CO Liberal  (1000+ posts) Sun Mar-06-05 11:08 AM
Response to Original message

4. I Agree They Can Be Expensive
   
I had one go out on my '96 Isuzu Hombre pickup - the garage said Isuzu wanted $600 for the part!!! I asked them if a Chevy part would fit, since the Isuzu Hombre was based on the Chevy S10. They checked and found out the pumps were identical, except the Chevt pump was only $150!!

Needless to say, my Isuzu went back on the road with a Chevy fuel pump in its gas tank.

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arkie dem  (279 posts) Sun Mar-06-05 12:10 PM
Response to Reply #4

5. Thats Insane
   
I know it happens seems like the part suppliers like to gouge on the foriegn auto parts.

I called several parts stores concerning the fuel pump for my wifes car. The AC Delco pumps were $100 higher than the Delphi pumps. Considering Delphi was once owned by GM I figured all the pumps were made by Delphi, but who knows...???

The consumer takes in the shorts again...!!!

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CO Liberal  (1000+ posts) Sun Mar-06-05 02:16 PM
Response to Reply #5

6. You Have to Shop Around
   
The garage I took My Isuzu was willing to work with me. The Chevy dealer wanted $200-plus for the pump, but when I called around I found the exace same pump at Auto-Zone for $150. I went and got it and the garage installed it for me.

Now, isn't this a no-no?

I always thought that when one hired a mechanic, one wasn't supposed to bring his own parts, since the underpaid mechanic makes a little bit of money on the mark-up for the parts.

Just a simple courtesy to those humble hard-working workingmen.

I was surprised however about a year ago, when my mechanic suggested I go to an automotive junkyard and get a used alternator myself, for him to put in.  I did that, and he charged only ten bucks.

Later, I found out he was pressed for time, too many jobs, and as I had more time than he did, that was why.

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arkie dem  (279 posts) Sun Mar-06-05 02:48 PM
Response to Reply #6

7. That's great to find a garage willing to do that. Most make big bucks of parts mark-up. My wife found a shop that would replace the pump for $120 plus the list price of the pump, which is what I would have paid for it. I'd be willing to bet the shop buys the same pump for around half of what list price is. Had her car towed there yesterday, no way I would change it for $120. The difference between working in your driveway with set of jackstands and having a well equipped shop with a nice lift...!!!

Well, the okie primitive proves it; he's more interested in saving some bucks, than in giving a mechanic a chance to earn a living wage.
apres moi, le deluge

Milo Yiannopoulos "It has been obvious since 2016 that Trump carries an anointing of some kind. My American friends, are you so blind to reason, and deaf to Heaven? Can he do all this, and cannot get a crown? This man is your King. Coronate him, and watch every devil shriek, and every demon howl."

Offline Carl

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Re: primitive wonders about fuel tank pumps
« Reply #1 on: April 05, 2008, 07:24:36 PM »
Yes Frank,your Taurus probably has a pump in the tank and also they had an inertia switch to shut the pump down in the event of an accident.
These can be kind of sensitive sometimes and will trip if you hit a severe bumb or dip,stalling the vehicle after a few feet.

The reset button is in the trunk.

Beside that it would seem the primitives comments are pretty accurate about the fuel pump.

To operate a modern garage requires 10s of thousands of dollars of equipment and training while maintaining a living for the employees,taxes,social security,various insurances,bookkeeping..the list is long.
Even though the per hour rate seems high (40-70) they often can`t bill all the time that a given job may require.
One broken bolt can take an hours time to extract properly without damaging the vehicle or other parts for example.

They make some money off the parts to survive while also having to deal with slow payment and bad checks at times.


Offline franksolich

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Re: primitive wonders about fuel tank pumps
« Reply #2 on: April 05, 2008, 07:37:44 PM »
You know, Carl, of course I know that most automotive mechanics aren't struggling, but one has to think of the conditions endured doing the job.

I always compared it with welding.

Welding is a difficult job, done under difficult circumstances, and yet most welders I know manage to produce things of Old World Craftsmanship.

I don't know about other parts of the country, but in Nebraska, even in Omaha and Lincoln, welding is basically a little-more-than-minimum-wage job; even store clerks make more.

I used to supervise welders (second-shift supervisor) at a manufactory of basketball equipment, and was stunned to learn I, an unskilled person, was making more money than these welders, working in hot weather and cold weather, working in dirt and oil, working exposing themselves constantly to physical peril and injury,

I of course confronted no such difficulties in doing my own job there.

And the same for automobile mechanics.

I've used a lot of automotive mechanics, and I've never been stiffed once.  Not one single time.

I know this, too, because of a certain, uh, vulnerability of mine (being deaf, and so not knowing a whole lot about things), which compels me, after something's done, to inquire of a hearing person if that was the right thing, the thing that was done, and if the charges were reasonable.

They always were, and I suspect sometimes I was even undercharged.
apres moi, le deluge

Milo Yiannopoulos "It has been obvious since 2016 that Trump carries an anointing of some kind. My American friends, are you so blind to reason, and deaf to Heaven? Can he do all this, and cannot get a crown? This man is your King. Coronate him, and watch every devil shriek, and every demon howl."

Offline Carl

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Re: primitive wonders about fuel tank pumps
« Reply #3 on: April 05, 2008, 07:45:58 PM »
You know, Carl, of course I know that most automotive mechanics aren't struggling, but one has to think of the conditions endured doing the job.

I always compared it with welding.

Welding is a difficult job, done under difficult circumstances, and yet most welders I know manage to produce things of Old World Craftsmanship.

I don't know about other parts of the country, but in Nebraska, even in Omaha and Lincoln, welding is basically a little-more-than-minimum-wage job; even store clerks make more.

I used to supervise welders (second-shift supervisor) at a manufactory of basketball equipment, and was stunned to learn I, an unskilled person, was making more money than these welders, working in hot weather and cold weather, working in dirt and oil, working exposing themselves constantly to physical peril and injury,

I of course confronted no such difficulties in doing my own job there.

And the same for automobile mechanics.

I've used a lot of automotive mechanics, and I've never been stiffed once.  Not one single time.

I know this, too, because of a certain, uh, vulnerability of mine (being deaf, and so not knowing a whole lot about things), which compels me, after something's done, to inquire of a hearing person if that was the right thing, the thing that was done, and if the charges were reasonable.

They always were, and I suspect sometimes I was even undercharged.

It would be hard to guess what amount of compensation I would want to work on a modern vehicle.
Eight or more hours a day trying to cram my arms into spaces no where near large enough to fit into,starting a nut in one of those places with your fingertips all the while being caked with grease and dirt.

One thing goes wrong or a diagnosis doesn`t pan out (it ain`t a perfect world and lots of times things go wrong just because) and you are giving away hours of billable labor.

They indeed can do okay but they are like any entrepreneur,risking much to be in business.