If a frame-mount fuel injection pump works - why the need for in-tank fuel pump?

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Old 08-08-10, 02:36 PM
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If a frame-mount fuel injection pump works - why the need for in-tank fuel pump?

I was watching one of those hot rod car shows on tv this morning. The host showed how you can get rid of your carb and switch over to a 2-barrel throttle body injection. Then, rather than use your mechanical pump(because that will not work, with this modification), you surface mount a fuel injection pump somewhere. You also need this brainbox to go with it.

If this works, why strap us with the hard to service, diagnose, and replace........ in-the-tank fuel pumps? ???

Or - WILL it work - and it's just that they allow such methodology to slide for the relatively few hobbiests out there - but will not allow such external pump location outside the tank for all the vehicles on the road, for car crash purposes or ?
 
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Old 08-08-10, 03:00 PM
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A couple of reasons.

First off, Most electric pumps ....PUMP...But arent very good at Sucking....So they are immersed in gasoline , so there is an ample supply of Static (Stationary, or Standing still) fuel. Second , is for cooling purposes. The pump itself is cooled by the fuel it pumps. If the car were to run out of fuel, the pump ran dry. and cooked itself.

Now ...I hear what youre saying....If a frame mounted pump can suck up all the fuel it needs, and is designed not to overheat itself, Why do the MFR's still use in tank pumps...???

Well....What they didnt show you on TV...is that frame mounted pumps are noisy as hell..., And are not by a stretch reliable for any distance or daily use....130 miles a day, 5 days a week, transportation to work is out of the question. Hot rods and Race cars, that arent used on a daily basis...Yep..Neat little toy...For a "Grocery Getter"...forget it.
 
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Old 08-08-10, 03:01 PM
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Better to push than pull.
I'm sure if I say the term "vapor lock" you'll remember.
I think the mod was done like that since retro fitting a gas tank that didn't originally have an in tank pump would be a tall order.
The pump they used was probably not an OEM type pump.

Or they didn't wanna hide the chrome fittings.
 
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Old 08-08-10, 03:15 PM
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Thanks guys. Your explanations seem to cover it all.
 
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Old 08-08-10, 03:27 PM
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Originally Posted by ecman51` View Post
If this works, why strap us with the hard to service, diagnose, and replace........ in-the-tank fuel pumps? ???
Also many manufacturers (specifically the one I work for I might add) are making a 10" hard rubber fuel pump access cover in the floor pan under the back seat to provide easy access to the pump assembly. You can clean the pickup, change the pump, check the sending unit, check the electrical, etc all without removing the tank.
 
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Old 08-08-10, 03:39 PM
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Originally Posted by mickblock View Post
Also many manufacturers (specifically the one I work for I might add) are making a 10" hard rubber fuel pump access cover in the floor pan under the back seat to provide easy access to the pump assembly. You can clean the pickup, change the pump, check the sending unit, check the electrical, etc all without removing the tank.
Now they do it. The third time I had to get get in my tank (86 Astrovan) instead of dropping it I just cut a whole through the floor and wondered why it wasn't already there. Ever notice you always seem to need to drop the tank just after a fill up?
 
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Old 08-08-10, 03:43 PM
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Next truck I buy, I am tempted to cut a hole in the bed over the fuel pump and then put a piece of plywood in the bed. That should be much easier than dropping the gas tank which I have done before and it wasn't fun.
 
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Old 08-08-10, 04:22 PM
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Many MFR's have been doing that for years. As for a Truck..."Sportsfan".....The tanks are engineered to fit in specific places, and never in a "Crumple Zone". You would likely hit a framing rail, or other structural Box rail, sacrificing the integrity of the Bed...DONT DO IT.
 
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Old 08-08-10, 05:29 PM
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I have found it much easier to raise and safely block the bed of a pick-up to replace a fuel pump.
 
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Old 08-08-10, 08:19 PM
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Originally Posted by GregH View Post
I have found it much easier to raise and safely block the bed of a pick-up to replace a fuel pump.
We have an older guy at the shop who zips around on a creeper, and a double post lift that folds under the car from the sides.

Unbolt the bed, toss the legs of the lift under it and raise the bed. After a friendly bet with the guys in the shop, the entire replacement was complete in 7 minutes and 23 seconds. Fastest 50 bucks I have ever managed to lose.
 
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Old 08-09-10, 04:05 AM
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The fix for a stock engine mounted lift pump on Cummins diesels is to retro one into the tank. No thanks. Pump pressure is too critical for the injector pump to have them put in a pump that will only put out 10psi when the minimum needed is 10 psi. Hit the throttle and it drops to 5 psi, slowly frying the injector pump. 70% of the diesel fuel pumped is returned to the tank. It is used for lubrication and cooling only. I have opted to remove the stock pump which is minimally effective anyway and go with a frame mounted racing pump that puts out 15 psi, keeping it around 11-12 at wot. They recommend, however, the pump location be as level to the top of the tank as possible, so it has to be mounted near the tank on the frame.
 
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Old 08-10-10, 06:49 PM
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Originally Posted by mickblock View Post
Also many manufacturers (specifically the one I work for I might add) are making a 10" hard rubber fuel pump access cover in the floor pan under the back seat to provide easy access to the pump assembly. You can clean the pickup, change the pump, check the sending unit, check the electrical, etc all without removing the tank.
All vehicles should have had that, from the get go, IMO.
 
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Old 08-10-10, 06:52 PM
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Originally Posted by ray2047 View Post
Now they do it. The third time I had to get get in my tank (86 Astrovan) instead of dropping it I just cut a whole through the floor and wondered why it wasn't already there. Ever notice you always seem to need to drop the tank just after a fill up?
Weren't you afraid of sparks, when cutting the hole? Or did you butcher out some hole say with tin snips?
 
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Old 08-10-10, 06:55 PM
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Originally Posted by GregH View Post
I have found it much easier to raise and safely block the bed of a pick-up to replace a fuel pump.
And I guess some truck mfgers have it that removing the entire cab to work on the engine must be the best way to do the engine work. (I'm serious, not sarcastic.)
 
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Old 08-20-10, 05:58 PM
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fuel pump

Can you say FoMoCo boys and girls?
 
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Old 08-20-10, 06:53 PM
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Bill,

Something tells me you're going to appreciate this.

Best Regards
Sam

Fuel pump - Wikipedia, the free encyclopedia
 
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Old 08-21-10, 01:29 PM
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Originally Posted by retired wrench View Post
Can you say FoMoCo boys and girls?
In your opinion, does that hasten the ability to quickly do more engine work, from all angles, or is this an elephant of an extra labor expense, to pull the cab?
 
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