fuel guage sending unit question

[brian]

On my 89 mj 4x4 I have tried several times to get my fuel sending unit to operate but it seems every time I put the darn unit back into the gas tank the float gets stuck. I've tried bending the arm a little(the arm on the float..not mine) but the guage says the float is always stuck in the empty position. Once in a while when the tank gets filled up it will jump up to read full but then it ends up stuck on empty later. The sending unit works fine when I test it outside of the tank.

I stuck my arm waaayyy down inside the tank to get an idea of what might be causing the problem and discovered what feels like many ridges and flanges sticking up from the bottom of the tank. I can't imagine what they could be good for. I can see how they might interfere with the float.

 

Some of you must have figured this out in the past.???? :dunno:

thanks in advance

PS Correy--did my private message ever get to you?

[Pete M]

bump for ya

[jeepdoggydogB]

I have a 1991 so the electronics on mine are different, but when I bought a new tank I noticed that there was a "baffle" that was positioned in such a way that it surrounded the float when the sending unit is inserted. I was told that this baffle keeps the needle from jumping when the gas in the tank shifts during turns. I wonder if your float is getting stuck on the baffle?

[brian]

Thanks Pete for the bump...whatever that means

[brian]

Thanks jeepdoggie

I'm pretty sure that what you described is the problem. But how in the heck do I fix it? Like I said I've tried bending the arm just a bit in different directions hoping it would clear the obstruction but no luck. :wall:

[jeepdoggydogB]

Thanks jeepdoggie

I'm pretty sure that what you described is the problem. But how in the heck do I fix it? Like I said I've tried bending the arm just a bit in different directions hoping it would clear the obstruction but no luck. :wall:

I don't think you can bend the baffle easily, and bending the float is difficult because you can't see in the tank to determine which way to bend. Is your tank dented at all? You might need a new tank, but now that the float is bent you might not be able to get it line up in a new tank. I hate to say this but if it where me I would get a new tank and a junk yard sender unit. I got my new tank on ebay for $100 shipped four years ago and what I am seeing on ebay now they are now pricier. Don't forget to pickup a new fuel pump and strainer as the JY ones usually aren't any good.

[Pete M]

Thanks Pete for the bump...whatever that means

 

"bump": internet slang for bumping a topic back up to the top of the forum. :typing:

[brian]

Surely you jest doggy

why would I go get a new tank when I can knock myself out dinking around with the one I have.?

Seriously You may be right.

I didn't try bending the baffel.It was all I could do to get my arm down in there to feel around. Damn near didn't get it back out!

Now that I think about it... The sending unit/pump I'm dealing with now is one I picked up at the wrecking yard to replace the original which didn't work when I bought the rig. I even compared the float arm on both to see if one was bent differently than the other.nope.

The bent tank idea is good but.. no dent.

The info above suggesting the baffels are to keep the float from bouncing around sounds about right.

[Wildman]

You have the '89, and the tank should have a "Fuel Reservoir" in the bottom of the tank to keep the pump from starving for fuel, there are no baffles inside the gas tank, from '87- '90 that I know of.

 

The pump sits inside the reservoir, and there is a "Cup" that the fuel return sits in.

 

It is possible to install the sender unit, and catch the float arm on the side of the reservoir.

 

If you bend the float arm in the wrong direction, you'll be reading fuel level completely off, so you need to be careful of that.

 

Seen how you 'picked one up at the junk yard'........you didn't by chance get a sending unit from a Cherokee.......did you :dunno:

[brian]

thanks wildman

good ideas. I wouldn't know a baffel from a reservoir. But if I recall when my arm was inside the tank, the only metalflanges or whatever were on the bottom. Sounds like the reservoir.

I 'm pretty sure I got the unit from a comanche.it was quite a while back so I'm not positive but It is exactly like the one I took out.

I've only tweaked the float arm so as not to get too far off from what it should be. I realize too much bending would cause a faulty readout.

 

I'm tired of taking it out and putting it back in. :headpop:

[Wildman]

OK.........just want to make sure the sending unit your working with from the JY was the same.

 

Others have tried to make a XJ sending unit work, and......... :no:

 

It's a complete 180* backwards to the MJ's sending unit.

 

 

 

I'm tired of taking it out and putting it back in.

 

 

Yea, but each time you do that, I'm sure your getting quicker :D

[Geonovast]

I'm tired of taking it out and putting it back in.

 

 

Yea, but each time you do that, I'm sure your getting quicker :D

 

Too... many... comments...

[lostissues]

aren't there 2 different size float arms on Comanche senders? if that is the case you may have grabbed a long armed one and it is hitting the edge of the reservoir in the tank designed to use the short arm one. Just a thought.

[brian]

aren't there 2 different size float arms on Comanche senders? if that is the case you may have grabbed a long armed one and it is hitting the edge of the reservoir in the tank designed to use the short arm one. Just a thought.

 

Now that's a possibility! I have the one I took out when I bought the truck and it looks identical to the one I'm fiddling with now. But...maybe they both are the wrong arm length.

Anyone have a camera that will fit down the fuel fill hole so I can see whats going on in there? :hmm:

[Geonovast]

Drop the tank.

 

Now only will you not have to do all this crap under the truck, but you won't mind having to take it out and put it back in.

 

Also, you can pop the vapor ports out, shine a flashlight in one, and see what's going on through the other.

 

I know it's possible to do a fuel pump with the tank in the truck... I've done it both ways. I will never do another pump with the tank in the truck. It is 1000x easier sitting on the tailgate.

[brian]

Drop the tank.

 

Now only will you not have to do all this crap under the truck, but you won't mind having to take it out and put it back in.

 

Also, you can pop the vapor ports out, shine a flashlight in one, and see what's going on through the other.

 

I know it's possible to do a fuel pump with the tank in the truck... I've done it both ways. I will never do another pump with the tank in the truck. It is 1000x easier sitting on the tailgate.

 

Vapor ports?? flashlight...hmmm. I would like to see in there .Is that really possible? There you go confusing me with common sense again

[Geonovast]

There are two ports on the top of the tank with vacuum lines running from them, to a T above the tank, and a main line that IIRC, runs up to the charcoal canister.

 

You can pop those out with the tank out of the truck, and gives you two roughly 1 1/4" holes to peer through. Look through one, shine through the other.

 

[brian]

you young whippersnappers! with your logic and energy. Makes me tired just listening to ya.How the heck do you know so much about comanches? Did you disect one in high school biology or somethin'

[Geonovast]

Almost everything I know, I learned from people on here.

[Wildman]

On the float arms............I just measured them for another member here......

 

one is 2-1/2" and the other is 5-1/2", so there very noticeable in difference.

 

The jury is still out which one fits the swb tank, we were thinking that the 5-1/2" fit the 18 gallon tank, but we're called on that, and no time to pull one apart to double check.

 

For seeing inside your tank, you should buy one of these, then we can all barrow it from you when we need it :D

 

http://cgi.ebay.com/Milwaukee-2310-21-C ... 255a935058

[brian]

On the float arms............I just measured them for another member here......

 

one is 2-1/2" and the other is 5-1/2", so there very noticeable in difference.

 

The jury is still out which one fits the swb tank, we were thinking that the 5-1/2" fit the 18 gallon tank, but we're called on that, and no time to pull one apart to double check.

 

For seeing inside your tank, you should buy one of these, then we can all barrow it from you when we need it :D

 

http://cgi.ebay.com/Milwaukee-2310-21-C ... 255a935058

 

Both of mine are the 51/2 "

If there is on 3" shorter and That's what should be in my '89 swb then I can see why I'm having problems!!

I'll order that thing from ebay right away.

[Wildman]

At one time we were thinking that the 2-1/2" float arm was for the LWB (23.5 gallon) tank, and the 5-1/2" float arm was for the SWB (18 gallon) tank, them someone said that was wrong :dunno:

 

It make sense that the longer arm would have a greater radius sweep, making up for less volume, and I still think that.........but until I get time to pull a sending unit out of a LWB tank I have pulled.........like I said, the jury is still out on that...........but, I think you have the correct one :roll:

 

You might be just snagging it on the reservoir pan while your installing the sending unit, and once you get that 'Inspection camera' down in there, you'll find out for sure ;)

[brian]

That theory on long arm = greater radius sweep in shallow tank = more accurate read out at dashboard was once presented by Albert Einstein in a lecture years ago... but when rebuffed by his peers, he moved on to his now famous theory on relativity.

The trouble with his theory on relativity is that even if a man could travel at or faster than the speed of light..his hat would keep blowing off! :smart:

 

seriously..that was some pretty smart thinking on the float arm .i think you are right :thumbsup:

[Wildman]

That theory on long arm = greater radius sweep in shallow tank = more accurate read out at dashboard was once presented by Albert Einstein in a lecture years ago... but when rebuffed by his peers, he moved on to his now famous theory on relativity.

The trouble with his theory on relativity is that even if a man could travel at or faster than the speed of light..his hat would keep blowing off! :smart:

 

seriously..that was some pretty smart thinking on the float arm .i think you are right :thumbsup:

 

 

:dunno: I think I missed that lecture by Al :hmm:

 

You would think someone would come up with a hat strap to solve that problem with the hat blowing off after all these year :dunno:

 

My problem is.........what I thought was right, someone changed my mind, either proven right or wrong.......and with the 20 other things I have to remember everyday, they get crossed with each other..........and I get things mixed up :nuts:

 

I'll see if I can pull that tank apart this weekend, and prove my theory :D

[brian]

I'll be waiting to hear if you are right about the float arm. I'm betting on you. :banana: