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Topic Review (Newest First)
02-06-2011 12:45 PM
sqzbox One other thing I noticed after re-reading the thread post #8 is the electric pump being under the drivers seat on the frame rail is not the correct location for it. It should be mounted as close to the fuel tank as possible to PUSH the fuel to the carb, not pull it from the tank. Being mounted under the drivers area must be annoying having to listen to the buzzing all the time.
02-06-2011 12:35 PM
bigdog7373
Quote:
Originally Posted by DanielC
I think a lot of people are too quick to abandon mechanical pumps.
A mechanical pump pumps more gas as the RPMs go up, a good thing.
A mechanical pump uses the cam motion not to pump gas, but to draw the gas into the pump, under the diaphragm, and it is the spring in the mechanical pump that pushes the gas to the carburettor needle seat. The pressure on the needle, from the float balances against the spring in the mechanical pump, and it all balances out. The spring only delivers gas into the carb when it is actually needed. On a factory system, the fuel pump cannot over-pressurize the needle and seat.
Your fuel level stays where it should be.
I agree with you completely. I went to an electric pump a few months ago and just switched back to mechanical last week. The electric pump is noisy, and i hate having to let it prime before you start the engine. Mech is also more reliable. The electric pump left me stranded in a parking lot so that was enough of that.
02-06-2011 10:35 AM
eloc431962
Quote:
Originally Posted by sqzbox
The OP said the PO installed it before he bought it.

Oh so it's been doing this since he got it.



Cole
02-06-2011 10:32 AM
dion I checked the charcoal canister and everything looks to be in good working order, except the in line filter. It looks to be ten years old. I'll swap it out. I am leaning towards pressure though judging from the amount of gas consumption. This is a stock 360 and is only getting a couple of gallons better MPG than my 72 Chevy with a speed demon carb, vic jr intake, 550 lift cam, 3000 stall, racing gears did. Thanks for the input guys.
02-05-2011 10:54 AM
DanielC I think a lot of people are too quick to abandon mechanical pumps.
A mechanical pump pumps more gas as the RPMs go up, a good thing.
A mechanical pump uses the cam motion not to pump gas, but to draw the gas into the pump, under the diaphragm, and it is the spring in the mechanical pump that pushes the gas to the carburettor needle seat. The pressure on the needle, from the float balances against the spring in the mechanical pump, and it all balances out. The spring only delivers gas into the carb when it is actually needed. On a factory system, the fuel pump cannot over-pressurize the needle and seat.
Your fuel level stays where it should be.
02-05-2011 10:20 AM
sqzbox
Quote:
Originally Posted by dion
There's one line from the tank to the pump and to the carb..
Answers that Q. Oops, forgot about tank to canister, sorry.
02-05-2011 10:16 AM
sqzbox
Quote:
Originally Posted by eloc431962
When exactly did it start doing this before the new pump or after ?
And what engine is in the jeep and what carb is on the engine ?


Cole
The OP said the PO installed it before he bought it.

Dion, someday's it's Bad and someday's it's good could be the difference between a windy day or, cold weather when it could handle the extra fuel.
Depending on what elec. pump was installed (some are rated at 51/2- 7 lbs.) you can get away with it. Some are rated higher and you can't without a regulator. A good regulator that will work as far as engine demand/performance/mileage, is a vacuum controlled fuel pressure regulator.
It cost's a little more but will work good across the board. When the engine vacuum is high like at idle or cruise it will miser pressure and when the vacuum is low like accelerating or wide open throttle it will allow more pressure according to engine demand. If you find that pressure is the problem, this is one option you can look at but first, you need to check it out and make sure that no damage has been done to the power valve/floats/inlet valves.
02-05-2011 10:13 AM
LATECH I would check the evaporative system out. It seems I remember the canisters were noted for getting fule backed up into them from the tank.Seems to happen more so on a full tank than less on a half tank or less?
There is a check valve in the tank fitting for the evap system that sticks and raw fuel gets in there get sucked up into the canister . Do you even have the evap hooked up properly?If the hoses are just swinging in the breeze that could do it also.
02-05-2011 10:08 AM
001mustang
Quote:
Originally Posted by dion
It smells like raw gas. There's one line from the tank to the pump and to the carb. The pump is mounted on the frame under the driver side door. Could very well be pressure, that would make sense. It's been this way since I bought it about three weeks ago. 360 engine. It passed smog at the beginning of Jan so I don't get why this is happening now. The weird thing is that it doesn't do it all the time. There's some days when I'll drive all the way to work and won't smell any gas and then other days where you just can't breathe.
let it idle.
pull a plug.
is plug black then its rich.
if rich the new pump may be overpowering carb as others said.
verify there are no loose vent lines or leaks.
02-05-2011 10:06 AM
johnsongrass1 Your saying your not using the stock mech pump any longer right? If this is right, the the open nipple on the mech pump doesn't make any difference as long as there isn't an attached line from the tank to the pump.

Do you have any open nipples on the top of the tank? Like where the stock pump might have plugged into?
02-05-2011 09:37 AM
eloc431962 What carb ? If the carb has a blown power-valve it will do this also. JMO


Cole
02-05-2011 09:31 AM
dion It smells like raw gas. There's one line from the tank to the pump and to the carb. The pump is mounted on the frame under the driver side door. Could very well be pressure, that would make sense. It's been this way since I bought it about three weeks ago. 360 engine. It passed smog at the beginning of Jan so I don't get why this is happening now. The weird thing is that it doesn't do it all the time. There's some days when I'll drive all the way to work and won't smell any gas and then other days where you just can't breathe.
02-05-2011 06:56 AM
eloc431962 When exactly did it start doing this before the new pump or after ?
And what engine is in the jeep and what carb is on the engine ?


Cole
02-05-2011 06:21 AM
bigdog7373 Yep, fuel pressure is way to high, as expected with an electric pump. I had the same problem. Fuel pressure regulator solved the problems.
02-05-2011 05:22 AM
sqzbox Sounds like you need to check the fuel pressure. You may need a fuel pressure regulator if it's pumping more pressure than needed to the carb.
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