In Tank Fuel Pump - 1992 Cherokee

The thing does a have fuel-injection, whether that has any bearing on my question or not.

I have good reason to NOT want to put another fuel pump inside the tank; the reason being I need the vehicle to be able to run off of a portable gas-can/tank and not be sitting around with a tank full of old gas.

As I see it, fuel pressure is fuel pressure, whether the pump is in the tank or in the back seat, right ?

Has anyone else replaced a dead in-tank fuel pump with one not in the tank ?

Thanks.

You have given me something to chew on there.

I will look into figuring out which connection in the in tank pump actually is power to the pump and tie into that to power my not-in-the-tank pump; if the computer wants to do silly things, it will think the in tank pump is doing them when all it is doing is going along for the ride.

Ever think about why everything on a vehicle is included in various assemblies ?

The pump is not in the tank because that is a better place for it to be; the pump is in the tank so that some little satellite non-union factory somewhere in Kentucky, working these tobacco strippers for minimum wage, can assemble the tank, including pump and whatever else, and send it to the auto manufacturer ready for plug-and-play.

Same as for the steering columns; dimmer switches THAT BELONG ON THE FLOOR, wiper switches, head-light switches, even the radio, are contained within the column assembly.

Contrary to what was very illegal a few years ago, steering wheels are not mechanically connected to the vehicle in any way; the steering wheel could be mounted back there in the boat trailer and plugged in with a pigtail.

All this so minimum wage non-union little factories can assemble this stuff and send the assembled units to the auto manufacturer, sidestepping any union wages. 

it would be cheeper to convert to lp !

Sounds as if the vehicle does not see a lot of usage. Simplest solution is to run non ethanol gasoline in the tank which has a much longer storage life than the alcohol based crap we are blessed with at the retail pumps.

There is more to it than just maintaining fuel pressure in the system Chrysler used. Albeit simple overall, the original system worked quite well. IIRC the fuel tank pump does operate full time after the crank sensor establishes engine rotation, but the fuel pump's rpm's are varied/modulated by the engine ECM to maintain fuel pressure(s) dependent upon engine load. Again, IIRC, high engine power requirements spec was 62psi, idle was about 26psi and after a 20 minute or so leakdown with the engine shut down, 22psi measured on the fuel rail. Very reliable system overall.

I had a couple XJ Cherokee  vehicles with the 4.0ltr engine and ran both over 350K on the clocks before the rear spring perches and floors rotted out rendering both unsafe to drive.

Thanks for all this information.

I guess my best bet for this vehicle is to put a sump-drain on the bottom of the tank with a down-hill line and cut-off near the trailer hitch and just drain the thing when I am not using it.

Another idea you put in my head = almost everything on the place is diesel --- I wish it all was diesel, even the Stihl chainsaws and the weedeater.

Having diesel to pour in something is never a problem.

Non-ethanol gas is a different matter.

I only ever use non-ethanol for all the small engines around here.

The nearest actual stand-alone non-ethanol pump is way over in the next town; and, being at one of those modern computer-controlled convenience stores, not the handiest place to fill up a few jugs.

I am always scraping the bottom of the barrel for non-ethanol gas.

The solution you have provided = put the drain on the Cherokee tank, handy back there near the trailer hitch.

In the busiest part of the day, when nobody notices such things, slide down there to the non-ethanol pump and fill her to the brim.

Then, when I need a gallon or so, get it from the Cherokee.

Of course, this only works after I buy/install a new fuel-pump.

I don't understand --- why not ?

I would assume that would be exactly what you wanted to drain out.

Right you are.

Your advice put the gears in my head to turning and I will now put TWO drains in the tank; one a bit higher for drawing off mower gas and the other in dead bottom to drain off water accumulation.

As for condensation in tanks, I grew up in an old time full service filling station and I know all about it raining inside gas tanks.

I have seen and heard it all --- and still see and hear it.

Old Farmer Brown will have an old grain truck sitting back in the fence-row; been sitting there since last grain season.

It had maybe two quarts of gas in a huge steel step-tank when he parked it.

He will come to the filling station and get a couple five-gallon cans of gas and go dump it in, thoroughly stirring up all that water and sludge that has been sitting there fermenting all year.

Once the thing starts, it will go about a hundred feet and die, never to start again.

Along comes his brother-in-law, born with a wrench in his hand, and checks things out.

"Where did you get this gas"

"Down there at BuckSkin's filling station"

"Well, he sold you some bad gas -- this is full of water"

Our "stick" was longer than the entire building.

It resided in a long horizontal pipe about head high.

Every night at a certain time, somebody would go from pump to pump with a clip-board and flashlight and record that string of numbers that was akin to reading an electric meter, except the numbers were tiny and there were a lot more of them.

Then, we would make the rounds from tank to tank, two of us, if two of us were there, one carrying and handling that long stick and the other lifting away the metal cover-plates and then removing those double-latched metal lids that exposed the pipe coming from the tank.

We always had this tiny jar of blue paste that we would stick our finger in and smear a streak on the bottom couple inches of the stick; if there were moisture present, the paste would turn pink.

As the long stick came back up out of the ground, the flashlight holder would make note of the fuel level - in inches.

We had this chart on the wall by the phone that converted the inches to gallons, a column for each size tank.

The refinery took this water business serious.

If you found water, first, before calling anyone, you made a longer smear of paste and measured how many inches of water.

They had a special truck they would send that could suck from the bottom of the tank.

It was very rare, even in heinously humid Kentucky, where you can cut the air with a knife and we would feel weird if our clothes were not stuck to us, to ever find water; but, way every once in a while, we did.

It is a wonder our stick survived; as, my father was forever finding uses for it at the farm and at the house; and, other people were forever borrowing it for like uses as well.

When I hauled crude oil, we didn't have a stick.

We had this long metal tape on a reel with a very heavy plumb-bob of a thing on the end.

You lowered the weight down into the tank until you felt it touch bottom.

If you wanted to live, you never got on top of a tank; as, crude oil is more salt water than oil and the tops of the tanks will rust away from the inside out; they may look solid as rock and be thin as tissue. 

That thing was no more than an inch square, yet terribly long, and WOOD.

It got used and abused for generations and never did break.

Where are you going to find any clear knot-free wood today that is long enough to saw out such a stick that isn't going to break the first time you use it ?

This "sustainable yield" crap of today, it won't even make a decent yard-stick.

Yep, modern Veeder-Roots have sensors for that moisture, and not far from the dump zone is a long plastic tube that the dipstick is stored in.  I have a piece of broken dipstick out in my shed... works great for measuring overhead clearance... before I smack something tall into the pole barn roof

The '92 XJ's injection system is constant flow, rail-regulator with bypass return to tank.  The pump IS cooled by fuel, and it'll survive a little water, but it's very hard on the pump to do so.  There's an inlet sock on the pump, pickup sits in the bottom as expected.

You don't need to 'drop' the tank to change the pump-  You can flip up and remove the lower seat bottom, eyeball the location of the tank top, and chain-drill the floor pan with a depth stop, lift the piece out, and remove the tank plumbing and lid right there.  As many have said, they will run for a LONG time, and they weren't assembled that way for production efficiency, they were done so because the LUBRICATION of the pump bushings is also accomplished by being in fuel.  Water is hard on it, because the bronze bushing material becomes a bit incompatible with the armature steel in water... the wear occurs, and they start to get noisy and drag, which doesn't affect pressure much at idle or light load, but when you ask it to work, the pump's internal drag starts limiting the pressure available at the rail.  The rail regulator is normally bypassing, eventually flow becomes so weak, that the regulator is fully closed off (no bypass) and any sag in electrical load now reduces fuel pressure, which causes injectors to either not fire, or not fire and reseat properly.

Another way to resolve the problem here, is disconnect the fuel filler, and pipe it into a small under-floor can (an old fire extinguisher, or a piece of pipe with a cap) filled with mineral spirits and lacquer thinner.  Move the 'real' filler to someplace hidden...

The 11-48... long action... excellent machine.  Mine has a very long barrel, full choke, fires long magnums, and will knock down a goose at a LONG LONG way.  Don't use it for shooting clays unless you're on 'cleanup', because it's pattern stays tight for a whole lot further than an average over-under clays gun.