That sounds like a connection issue. When the sender up and dies, it
doesn't fix itself. If it was 'stuck' then it might be like Bill
mentions. That still wouldn't call for a replacement, just an
adjustment.

Mike

Joe and Joann wrote:
>
> Aloha
> Well, an interesting thing happened. I had refueled yesterday and the
> guage still didn't move off empty. Today I was driving and the guage
> went up to full and has been working steadily since then. Thanks to all
> who replied. I am saving a copy of this thread so that when it comes
> back I will be ready.
>
> Meanwhile I will continue trying to track down a replacement at a
> reasonable price. The Mopar parts on line shows one sender for 1990, but
> it does't differentiate between the 20 and 15 gallon tank, nor FI or the
> carbed I6. So I don't have a lot of confidence in that one. Its price is
> $150 or so, at least better than the dealer.
>
> The problem could be a bad ground, but it seems rock solid now. I would
> think an intermittent ground would give more unsteady readings, but who
> knows. Maybe the float was somehow stuck on empty.
>
> By the way Mike, the tank is 51/2 inches below the rear cross member, so
> itis the smaller tank.
>
> Aloha from Maui and thanks Mike, Earle and Bill for the ideas

 

My opinion is that the highest probability is that the wire leading to
the sender is open. Next, that the sender (potentiometer) is open. I
would make a resistance measurement at the sender with the wire
disconnected. If you don't read a very high value (perhaps in the
MegOhm range) then don't condemn the sender, I would look for the open
wire from tank to gauge.

www.telstar-electronics.com

 

My opinion is that the highest probability is that the wire leading to
the sender is open. Next, that the sender (potentiometer) is open. I
would make a resistance measurement at the sender with the wire
disconnected. If you don't read a very high value (perhaps in the
MegOhm range) then don't condemn the sender, I would look for the open
wire from tank to gauge.

www.telstar-electronics.com

 

My opinion is that the highest probability is that the wire leading to
the sender is open. Next, that the sender (potentiometer) is open. I
would make a resistance measurement at the sender with the wire
disconnected. If you don't read a very high value (perhaps in the
MegOhm range) then don't condemn the sender, I would look for the open
wire from tank to gauge.

www.telstar-electronics.com

 

The fuel gauge meter movement is heavily damped and gets its signal
voltage intermittently by design, so an intermittent open ground
probably won't be noticeable unless it stays connected for several
seconds. The sender ground line in earlier CJ's runs from the sender to
a self-tapping screw driven into the frame cross member just forw'd of
the fuel tank, driver-left of center, I'm guessing that yours is the
same. You /might/ be able to see it if you pull the left rear wheel and
look into the space above the front part of the fuel tank, but you won't
be able to reach it with your hand. Hurm. There might also be a quick
disconnect for the hot side of the line where it comes out of the wiring
harness in the wheel house (again, driver-left side of the Jeep). It
might have gotten grotty inside and isn't conducting. Pull it apart,
clean or replace as needed, pack with silicone bulb grease when
reassembling to prevent further corrosion.

Mike: Does anything other than the fuel sender take its ground from the
frame? I think everything else grounds through the body sheet metal or
engine block. Perhaps the ground strap from the block to the frame is
missing or broken. On 1970s-80s CJ I-6s it was a #8AWG cable that
jumpered the left engine mount, dunno about other engines. Joe: It
can't hurt to add one (universal mesh straps are available in the
"Help!" sections in retail chain auto parts stores) if the frame ground
is missing then the only one the sender can get is to "steal" one
through the body mount bolts and random places where the frame hits the
body. It would be a good idea to eyeball the engine mounts anyway.
They're 16 years old and probably getting soft or broken.

I'm wondering if the weight of the full tank has shifted something just
enough to restore the ground. But I'd drop the tank and check the wires
before ponying up a wad of cash for a new sender. Beware of two things,
though: If your `90 is like the earlier CJ tanks you can't can't remove
the sender from the tank for inspection without replacing the lock ring
and gasket (it _will_ leak), and the threaded stud welded to the strap
that crosses the top of the tank from fore to aft will probably twist
off when you turn the nut (the center nut at the rear cross member.)
You'll either need a replacement strap or weld another stud onto the
strap. If you're not especially handy with tools or unlucky, expect to
spend the whole day at it.


Joe and Joann wrote:
> Aloha
> Well, an interesting thing happened. I had refueled yesterday and the
> guage still didn't move off empty. Today I was driving and the guage
> went up to full and has been working steadily since then. Thanks to all
> who replied. I am saving a copy of this thread so that when it comes
> back I will be ready.
>
> Meanwhile I will continue trying to track down a replacement at a
> reasonable price. The Mopar parts on line shows one sender for 1990, but
> it does't differentiate between the 20 and 15 gallon tank, nor FI or the
> carbed I6. So I don't have a lot of confidence in that one. Its price is
> $150 or so, at least better than the dealer.
>
>
> The problem could be a bad ground, but it seems rock solid now. I would
> think an intermittent ground would give more unsteady readings, but who
> knows. Maybe the float was somehow stuck on empty.
>
> By the way Mike, the tank is 51/2 inches below the rear cross member, so
> itis the smaller tank.
>
> Aloha from Maui and thanks Mike, Earle and Bill for the ideas

 

The fuel gauge meter movement is heavily damped and gets its signal
voltage intermittently by design, so an intermittent open ground
probably won't be noticeable unless it stays connected for several
seconds. The sender ground line in earlier CJ's runs from the sender to
a self-tapping screw driven into the frame cross member just forw'd of
the fuel tank, driver-left of center, I'm guessing that yours is the
same. You /might/ be able to see it if you pull the left rear wheel and
look into the space above the front part of the fuel tank, but you won't
be able to reach it with your hand. Hurm. There might also be a quick
disconnect for the hot side of the line where it comes out of the wiring
harness in the wheel house (again, driver-left side of the Jeep). It
might have gotten grotty inside and isn't conducting. Pull it apart,
clean or replace as needed, pack with silicone bulb grease when
reassembling to prevent further corrosion.

Mike: Does anything other than the fuel sender take its ground from the
frame? I think everything else grounds through the body sheet metal or
engine block. Perhaps the ground strap from the block to the frame is
missing or broken. On 1970s-80s CJ I-6s it was a #8AWG cable that
jumpered the left engine mount, dunno about other engines. Joe: It
can't hurt to add one (universal mesh straps are available in the
"Help!" sections in retail chain auto parts stores) if the frame ground
is missing then the only one the sender can get is to "steal" one
through the body mount bolts and random places where the frame hits the
body. It would be a good idea to eyeball the engine mounts anyway.
They're 16 years old and probably getting soft or broken.

I'm wondering if the weight of the full tank has shifted something just
enough to restore the ground. But I'd drop the tank and check the wires
before ponying up a wad of cash for a new sender. Beware of two things,
though: If your `90 is like the earlier CJ tanks you can't can't remove
the sender from the tank for inspection without replacing the lock ring
and gasket (it _will_ leak), and the threaded stud welded to the strap
that crosses the top of the tank from fore to aft will probably twist
off when you turn the nut (the center nut at the rear cross member.)
You'll either need a replacement strap or weld another stud onto the
strap. If you're not especially handy with tools or unlucky, expect to
spend the whole day at it.


Joe and Joann wrote:
> Aloha
> Well, an interesting thing happened. I had refueled yesterday and the
> guage still didn't move off empty. Today I was driving and the guage
> went up to full and has been working steadily since then. Thanks to all
> who replied. I am saving a copy of this thread so that when it comes
> back I will be ready.
>
> Meanwhile I will continue trying to track down a replacement at a
> reasonable price. The Mopar parts on line shows one sender for 1990, but
> it does't differentiate between the 20 and 15 gallon tank, nor FI or the
> carbed I6. So I don't have a lot of confidence in that one. Its price is
> $150 or so, at least better than the dealer.
>
>
> The problem could be a bad ground, but it seems rock solid now. I would
> think an intermittent ground would give more unsteady readings, but who
> knows. Maybe the float was somehow stuck on empty.
>
> By the way Mike, the tank is 51/2 inches below the rear cross member, so
> itis the smaller tank.
>
> Aloha from Maui and thanks Mike, Earle and Bill for the ideas

 

The fuel gauge meter movement is heavily damped and gets its signal
voltage intermittently by design, so an intermittent open ground
probably won't be noticeable unless it stays connected for several
seconds. The sender ground line in earlier CJ's runs from the sender to
a self-tapping screw driven into the frame cross member just forw'd of
the fuel tank, driver-left of center, I'm guessing that yours is the
same. You /might/ be able to see it if you pull the left rear wheel and
look into the space above the front part of the fuel tank, but you won't
be able to reach it with your hand. Hurm. There might also be a quick
disconnect for the hot side of the line where it comes out of the wiring
harness in the wheel house (again, driver-left side of the Jeep). It
might have gotten grotty inside and isn't conducting. Pull it apart,
clean or replace as needed, pack with silicone bulb grease when
reassembling to prevent further corrosion.

Mike: Does anything other than the fuel sender take its ground from the
frame? I think everything else grounds through the body sheet metal or
engine block. Perhaps the ground strap from the block to the frame is
missing or broken. On 1970s-80s CJ I-6s it was a #8AWG cable that
jumpered the left engine mount, dunno about other engines. Joe: It
can't hurt to add one (universal mesh straps are available in the
"Help!" sections in retail chain auto parts stores) if the frame ground
is missing then the only one the sender can get is to "steal" one
through the body mount bolts and random places where the frame hits the
body. It would be a good idea to eyeball the engine mounts anyway.
They're 16 years old and probably getting soft or broken.

I'm wondering if the weight of the full tank has shifted something just
enough to restore the ground. But I'd drop the tank and check the wires
before ponying up a wad of cash for a new sender. Beware of two things,
though: If your `90 is like the earlier CJ tanks you can't can't remove
the sender from the tank for inspection without replacing the lock ring
and gasket (it _will_ leak), and the threaded stud welded to the strap
that crosses the top of the tank from fore to aft will probably twist
off when you turn the nut (the center nut at the rear cross member.)
You'll either need a replacement strap or weld another stud onto the
strap. If you're not especially handy with tools or unlucky, expect to
spend the whole day at it.


Joe and Joann wrote:
> Aloha
> Well, an interesting thing happened. I had refueled yesterday and the
> guage still didn't move off empty. Today I was driving and the guage
> went up to full and has been working steadily since then. Thanks to all
> who replied. I am saving a copy of this thread so that when it comes
> back I will be ready.
>
> Meanwhile I will continue trying to track down a replacement at a
> reasonable price. The Mopar parts on line shows one sender for 1990, but
> it does't differentiate between the 20 and 15 gallon tank, nor FI or the
> carbed I6. So I don't have a lot of confidence in that one. Its price is
> $150 or so, at least better than the dealer.
>
>
> The problem could be a bad ground, but it seems rock solid now. I would
> think an intermittent ground would give more unsteady readings, but who
> knows. Maybe the float was somehow stuck on empty.
>
> By the way Mike, the tank is 51/2 inches below the rear cross member, so
> itis the smaller tank.
>
> Aloha from Maui and thanks Mike, Earle and Bill for the ideas

 

Ah, well, that's some useful info you're providing there, Perfesser.
Nice of you to take the time to share your guess^W opinion.

If Joe finds that his sender is reading even a decade north of 100 ohms,
let alone anywhere within sight of "the MegOhm range", the part is
farked. A definitive answer wasn't forthcoming on Google, but his YJ
fuel gauge wants one of these three sets of ranges:

Empty Full
73 Ohms 8-12 Ohms (`76-`86 standard, perhaps YJ*)
0 Ohms 88-90 Ohms (`89 YJ, perhaps others)

According to this** the FSM for the `91 YJ specs:
105 Ohms 5 Ohms.


The gentle reader will note the reversed ranges. Mixing senders across
models but will result in reversed gauge readings, as those who
swapped their ugly YJ dashes for manly CJ dashes found.

* <URL:http://www.bc4x4.com/faqs/yj.cfm?cat=10&faqid=102>
** <URL:http://jeepsunlimited.com/forums/showthread.php?t=145677>



Professor wrote:
> My opinion is that the highest probability is that the wire leading to
> the sender is open. Next, that the sender (potentiometer) is open. I
> would make a resistance measurement at the sender with the wire
> disconnected. If you don't read a very high value (perhaps in the
> MegOhm range) then don't condemn the sender, I would look for the open
> wire from tank to gauge.
>
> www.telstar-electronics.com
>

 

Ah, well, that's some useful info you're providing there, Perfesser.
Nice of you to take the time to share your guess^W opinion.

If Joe finds that his sender is reading even a decade north of 100 ohms,
let alone anywhere within sight of "the MegOhm range", the part is
farked. A definitive answer wasn't forthcoming on Google, but his YJ
fuel gauge wants one of these three sets of ranges:

Empty Full
73 Ohms 8-12 Ohms (`76-`86 standard, perhaps YJ*)
0 Ohms 88-90 Ohms (`89 YJ, perhaps others)

According to this** the FSM for the `91 YJ specs:
105 Ohms 5 Ohms.


The gentle reader will note the reversed ranges. Mixing senders across
models but will result in reversed gauge readings, as those who
swapped their ugly YJ dashes for manly CJ dashes found.

* <URL:http://www.bc4x4.com/faqs/yj.cfm?cat=10&faqid=102>
** <URL:http://jeepsunlimited.com/forums/showthread.php?t=145677>



Professor wrote:
> My opinion is that the highest probability is that the wire leading to
> the sender is open. Next, that the sender (potentiometer) is open. I
> would make a resistance measurement at the sender with the wire
> disconnected. If you don't read a very high value (perhaps in the
> MegOhm range) then don't condemn the sender, I would look for the open
> wire from tank to gauge.
>
> www.telstar-electronics.com
>

 

Ah, well, that's some useful info you're providing there, Perfesser.
Nice of you to take the time to share your guess^W opinion.

If Joe finds that his sender is reading even a decade north of 100 ohms,
let alone anywhere within sight of "the MegOhm range", the part is
farked. A definitive answer wasn't forthcoming on Google, but his YJ
fuel gauge wants one of these three sets of ranges:

Empty Full
73 Ohms 8-12 Ohms (`76-`86 standard, perhaps YJ*)
0 Ohms 88-90 Ohms (`89 YJ, perhaps others)

According to this** the FSM for the `91 YJ specs:
105 Ohms 5 Ohms.


The gentle reader will note the reversed ranges. Mixing senders across
models but will result in reversed gauge readings, as those who
swapped their ugly YJ dashes for manly CJ dashes found.

* <URL:http://www.bc4x4.com/faqs/yj.cfm?cat=10&faqid=102>
** <URL:http://jeepsunlimited.com/forums/showthread.php?t=145677>



Professor wrote:
> My opinion is that the highest probability is that the wire leading to
> the sender is open. Next, that the sender (potentiometer) is open. I
> would make a resistance measurement at the sender with the wire
> disconnected. If you don't read a very high value (perhaps in the
> MegOhm range) then don't condemn the sender, I would look for the open
> wire from tank to gauge.
>
> www.telstar-electronics.com
>