Fuel gauge help please

[picurn]

Old subject but I'm new to the forum world. I have a 78 CJ5 AMC 258 i6 / 4.2l , i just replaced to metal fuel tank with a this..MTS 0051XLASSY Polyethylene 20 Gallon Fuel Tank with Complete Installation Kit for 78-86 Jeep® CJ5 & CJ7 from quadratec. Along with that i also replaced the dash and all the gauges, including the speedo cluster, also from quadratec. So all is hooked up and the fuel gauge is pinned on full. I have read a lot about this and here is what I have checked and the results. All grounds are good, body, block, frame, and dash were checked with test light. So i checked ohms next. I put 4 gallons of gas in the tank and apparently that's not enough to feed to pump very long before the engine stops, (don't ask how I figured that out . So I know that the tank is "Empty". Now for the ohms results...

Sending unit at the tank-
Empty- 83
Full - 10.3

Sending unit wire at the gauge-
Empty 83

Fuel gauge-
A to I- 2
A to S-23
S to I- 25
A to speedo housing- 46
I to speedo housing- 47
S to speedo housing- 70

Temp gauge-
A to S- 23

So from what I have read all these numbers sound like they are good? The only one I think is out of range is the A to I on the fuel gauge, should be less than 0.

So i hooked everything back up and the fuel is still on F. Any ideas and help is greatly appreciated. Thanks in advance guys.

 

[Lumpy Grits]

WELCOME!
4 gal of gas is plenty to feed the engine.
Are you sure the gas tank float is touching the top of the tank, when the tank is full?
LG

 

[picurn]

WELCOME!
4 gal of gas is plenty to feed the engine.
Are you sure the gas tank float is touching the top of the tank, when the tank is full?
LG

I just put in a DUI and replaced the fuel pump for an electric one. I put 4ish gallons of gas in the tank and started it to set the timing and check for leaks. All was good, went to take it for a test drive and it stalled at the end of the drive way. It would not start after that. I pulled the fuel line off at the regulator and cranked it over, no gas cane out if the line. I then dropped them tank and took the fuel line off he tank and placed it in a small gas can, turns the key and gas cane out of the hose at the regulator. Attached the line back to the tank and after what was in the line was pumped out, nothing. I then pulled the sending unit out and measured it approx 13in long, measures the tank, approx 13.5in deep, so you take 4 gallons and spread that out in a 20 gallon tank and my conclusion is, that's not enough in this tank. Things that make you go hmmm..., anyway on to the gauges. Thanks

 

[Lumpy Grits]

Why are you running a ele fuel pump? The OEM mechanical is fine, still run mine after 31+ yrs.
How close is the ele. pump to the tank(closer the better)? Ele pumps are 'pushers' not 'suckers, like the mech type are.
If you can't pump gas with 4 gals in the tank. The tank's pickup tube is set to far above the tanks bottom. 4 gal is 1/5 of your tanks capacity.
LG

 

[picurn]

I am getting ready to convert to fuel injection so I installed an electric pump. I mounted it right in front of the tank at tank level. I put more fuel in the tank and runs great, just no gas gauge now

 

[Lumpy Grits]

OK-makes sense now.
What did you GND the sender to?
LG

 

[picurn]

Sender to frame. Drilled a new hole and used a grinder to get rid of dirt and any rust. Frame has a good ground

 

[Lumpy Grits]

Is the sender matched/calibrated to the gauge?
LG

 

[picurn]

I have no idea. :-/ how do I find that out?

 

[Lumpy Grits]

Call the folks that made the gauge and sending unit.
LG

 

[picurn]

Is it possible it's reading the empty tank as full because of that?

 

[Lumpy Grits]

Float type senders work the same. Highest res when tank is empty.
But the gauge and sender need to be 'matched' to each other for accurate readings.
LG

 

[picurn]

The sending unit and gauge seem to be matched according the numbers on the companies websites. I wonder if o just have a bad gauge. Frustrating

 

[Lumpy Grits]

Could be a mis-match, bad gauge or sender.
LG