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Spdloader 11-17-2006 09:14 PM

Fuel Gauge Prob
 
1987 Wrangler, 4.2L 5spd

Fuel tank is new, sending unit is original, and worked prior to tank
replacement.

Problem is, with switch on, gauge on dash reads full until tank is almost
completely empty, then gauge drops down to
1/4 mark.

I'm scratching my head over this one, but I'm guessing I've got it grounded
wrong somehow.

Any ideas?

I might add, there is no rust on this vehicle.

Spdloader



Red Jeep 11-17-2006 11:06 PM

Re: Fuel Gauge Prob
 

Check the ground from the battery negative to the body. The wire can
corrode inside the connector and look OK from the outside. Use a jumper
cable from the battery negative to something mounted to the body (horn,
starter solenoid).


"Spdloader" <askforit@nospam.triad.rr.com> wrote in
news:a0u7h.44349$39.11843@southeast.rr.com:

> I'm scratching my head over this one, but I'm guessing I've got it
> grounded wrong somehow.
>


Red Jeep 11-17-2006 11:06 PM

Re: Fuel Gauge Prob
 

Check the ground from the battery negative to the body. The wire can
corrode inside the connector and look OK from the outside. Use a jumper
cable from the battery negative to something mounted to the body (horn,
starter solenoid).


"Spdloader" <askforit@nospam.triad.rr.com> wrote in
news:a0u7h.44349$39.11843@southeast.rr.com:

> I'm scratching my head over this one, but I'm guessing I've got it
> grounded wrong somehow.
>


Red Jeep 11-17-2006 11:06 PM

Re: Fuel Gauge Prob
 

Check the ground from the battery negative to the body. The wire can
corrode inside the connector and look OK from the outside. Use a jumper
cable from the battery negative to something mounted to the body (horn,
starter solenoid).


"Spdloader" <askforit@nospam.triad.rr.com> wrote in
news:a0u7h.44349$39.11843@southeast.rr.com:

> I'm scratching my head over this one, but I'm guessing I've got it
> grounded wrong somehow.
>


Lee Ayrton 11-19-2006 08:03 AM

Re: Fuel Gauge Prob
 

Jumper from battery negative to starter relay? I can think of a _lot_ of
less hazardous places to put a jumper on.


On Sat, 18 Nov 2006, Red Jeep wrote:

> Check the ground from the battery negative to the body. The wire can
> corrode inside the connector and look OK from the outside. Use a jumper
> cable from the battery negative to something mounted to the body (horn,
> starter solenoid).
>
>
> "Spdloader" <askforit@nospam.triad.rr.com> wrote in
> news:a0u7h.44349$39.11843@southeast.rr.com:
>
>> I'm scratching my head over this one, but I'm guessing I've got it
>> grounded wrong somehow.
>>

>


--
"I defer to your plainly more vivid memories of topless women with
whips....r"
R. H. Draney recalls AFU in the Good Old Days.


Lee Ayrton 11-19-2006 08:03 AM

Re: Fuel Gauge Prob
 

Jumper from battery negative to starter relay? I can think of a _lot_ of
less hazardous places to put a jumper on.


On Sat, 18 Nov 2006, Red Jeep wrote:

> Check the ground from the battery negative to the body. The wire can
> corrode inside the connector and look OK from the outside. Use a jumper
> cable from the battery negative to something mounted to the body (horn,
> starter solenoid).
>
>
> "Spdloader" <askforit@nospam.triad.rr.com> wrote in
> news:a0u7h.44349$39.11843@southeast.rr.com:
>
>> I'm scratching my head over this one, but I'm guessing I've got it
>> grounded wrong somehow.
>>

>


--
"I defer to your plainly more vivid memories of topless women with
whips....r"
R. H. Draney recalls AFU in the Good Old Days.


Lee Ayrton 11-19-2006 08:03 AM

Re: Fuel Gauge Prob
 

Jumper from battery negative to starter relay? I can think of a _lot_ of
less hazardous places to put a jumper on.


On Sat, 18 Nov 2006, Red Jeep wrote:

> Check the ground from the battery negative to the body. The wire can
> corrode inside the connector and look OK from the outside. Use a jumper
> cable from the battery negative to something mounted to the body (horn,
> starter solenoid).
>
>
> "Spdloader" <askforit@nospam.triad.rr.com> wrote in
> news:a0u7h.44349$39.11843@southeast.rr.com:
>
>> I'm scratching my head over this one, but I'm guessing I've got it
>> grounded wrong somehow.
>>

>


--
"I defer to your plainly more vivid memories of topless women with
whips....r"
R. H. Draney recalls AFU in the Good Old Days.


DougW 11-19-2006 11:12 AM

Re: Fuel Gauge Prob
 
Lee Ayrton wrote:
> Jumper from battery negative to starter relay? I can think of a
> _lot_ of less hazardous places to put a jumper on.


Especially since the wires on a starter relay/solonoid are hot.
http://www.prestolite.com/pgs_training/training_4.php

The test for rotted motor strap is battery ground (or frame) to
the engine block side of the motor mount or somewhere out of the
fan and belts.

> On Sat, 18 Nov 2006, Red Jeep wrote:
>
>> Check the ground from the battery negative to the body. The wire can
>> corrode inside the connector and look OK from the outside. Use a
>> jumper cable from the battery negative to something mounted to the
>> body (horn, starter solenoid).
>>
>>
>> "Spdloader" wrote :
>>
>>> I'm scratching my head over this one, but I'm guessing I've got it
>>> grounded wrong somehow.





DougW 11-19-2006 11:12 AM

Re: Fuel Gauge Prob
 
Lee Ayrton wrote:
> Jumper from battery negative to starter relay? I can think of a
> _lot_ of less hazardous places to put a jumper on.


Especially since the wires on a starter relay/solonoid are hot.
http://www.prestolite.com/pgs_training/training_4.php

The test for rotted motor strap is battery ground (or frame) to
the engine block side of the motor mount or somewhere out of the
fan and belts.

> On Sat, 18 Nov 2006, Red Jeep wrote:
>
>> Check the ground from the battery negative to the body. The wire can
>> corrode inside the connector and look OK from the outside. Use a
>> jumper cable from the battery negative to something mounted to the
>> body (horn, starter solenoid).
>>
>>
>> "Spdloader" wrote :
>>
>>> I'm scratching my head over this one, but I'm guessing I've got it
>>> grounded wrong somehow.





DougW 11-19-2006 11:12 AM

Re: Fuel Gauge Prob
 
Lee Ayrton wrote:
> Jumper from battery negative to starter relay? I can think of a
> _lot_ of less hazardous places to put a jumper on.


Especially since the wires on a starter relay/solonoid are hot.
http://www.prestolite.com/pgs_training/training_4.php

The test for rotted motor strap is battery ground (or frame) to
the engine block side of the motor mount or somewhere out of the
fan and belts.

> On Sat, 18 Nov 2006, Red Jeep wrote:
>
>> Check the ground from the battery negative to the body. The wire can
>> corrode inside the connector and look OK from the outside. Use a
>> jumper cable from the battery negative to something mounted to the
>> body (horn, starter solenoid).
>>
>>
>> "Spdloader" wrote :
>>
>>> I'm scratching my head over this one, but I'm guessing I've got it
>>> grounded wrong somehow.





Mike Romain 11-19-2006 11:18 AM

Re: Fuel Gauge Prob
 
Here is a good site on how the older gauges work. It is for CJ's, but I
believe the early YJ 4.2 was the same.

http://web.archive.org/web/200605230...eep/Gauges.htm

This is a Bill ------ link, the original seems to have gone.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

Spdloader wrote:
>
> 1987 Wrangler, 4.2L 5spd
>
> Fuel tank is new, sending unit is original, and worked prior to tank
> replacement.
>
> Problem is, with switch on, gauge on dash reads full until tank is almost
> completely empty, then gauge drops down to
> 1/4 mark.
>
> I'm scratching my head over this one, but I'm guessing I've got it grounded
> wrong somehow.
>
> Any ideas?
>
> I might add, there is no rust on this vehicle.
>
> Spdloader


Mike Romain 11-19-2006 11:18 AM

Re: Fuel Gauge Prob
 
Here is a good site on how the older gauges work. It is for CJ's, but I
believe the early YJ 4.2 was the same.

http://web.archive.org/web/200605230...eep/Gauges.htm

This is a Bill ------ link, the original seems to have gone.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

Spdloader wrote:
>
> 1987 Wrangler, 4.2L 5spd
>
> Fuel tank is new, sending unit is original, and worked prior to tank
> replacement.
>
> Problem is, with switch on, gauge on dash reads full until tank is almost
> completely empty, then gauge drops down to
> 1/4 mark.
>
> I'm scratching my head over this one, but I'm guessing I've got it grounded
> wrong somehow.
>
> Any ideas?
>
> I might add, there is no rust on this vehicle.
>
> Spdloader


Mike Romain 11-19-2006 11:18 AM

Re: Fuel Gauge Prob
 
Here is a good site on how the older gauges work. It is for CJ's, but I
believe the early YJ 4.2 was the same.

http://web.archive.org/web/200605230...eep/Gauges.htm

This is a Bill ------ link, the original seems to have gone.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

Spdloader wrote:
>
> 1987 Wrangler, 4.2L 5spd
>
> Fuel tank is new, sending unit is original, and worked prior to tank
> replacement.
>
> Problem is, with switch on, gauge on dash reads full until tank is almost
> completely empty, then gauge drops down to
> 1/4 mark.
>
> I'm scratching my head over this one, but I'm guessing I've got it grounded
> wrong somehow.
>
> Any ideas?
>
> I might add, there is no rust on this vehicle.
>
> Spdloader


Lee Ayrton 11-19-2006 12:34 PM

Re: Fuel Gauge Prob
 

I'm guessing that "Red Jeep" meant to attach the clip to the relay _frame_
so he could get to a body ground, but as you know that's far too close to
high-amperage connections for comfort.

On Sun, 19 Nov 2006, DougW wrote:
>
> Especially since the wires on a starter relay/solonoid are hot.
> http://www.prestolite.com/pgs_training/training_4.php
>
> The test for rotted motor strap is battery ground (or frame) to
> the engine block side of the motor mount or somewhere out of the
> fan and belts.


> Lee Ayrton wrote:


>> Jumper from battery negative to starter relay? I can think of a
>> _lot_ of less hazardous places to put a jumper on.

>
>> On Sat, 18 Nov 2006, Red Jeep wrote:
>>
>>> Check the ground from the battery negative to the body. The wire can
>>> corrode inside the connector and look OK from the outside. Use a
>>> jumper cable from the battery negative to something mounted to the
>>> body (horn, starter solenoid).
>>>
>>>
>>> "Spdloader" wrote :
>>>
>>>> I'm scratching my head over this one, but I'm guessing I've got it
>>>> grounded wrong somehow.

>
>
>
>


--
"I defer to your plainly more vivid memories of topless women with
whips....r"
R. H. Draney recalls AFU in the Good Old Days.


Lee Ayrton 11-19-2006 12:34 PM

Re: Fuel Gauge Prob
 

I'm guessing that "Red Jeep" meant to attach the clip to the relay _frame_
so he could get to a body ground, but as you know that's far too close to
high-amperage connections for comfort.

On Sun, 19 Nov 2006, DougW wrote:
>
> Especially since the wires on a starter relay/solonoid are hot.
> http://www.prestolite.com/pgs_training/training_4.php
>
> The test for rotted motor strap is battery ground (or frame) to
> the engine block side of the motor mount or somewhere out of the
> fan and belts.


> Lee Ayrton wrote:


>> Jumper from battery negative to starter relay? I can think of a
>> _lot_ of less hazardous places to put a jumper on.

>
>> On Sat, 18 Nov 2006, Red Jeep wrote:
>>
>>> Check the ground from the battery negative to the body. The wire can
>>> corrode inside the connector and look OK from the outside. Use a
>>> jumper cable from the battery negative to something mounted to the
>>> body (horn, starter solenoid).
>>>
>>>
>>> "Spdloader" wrote :
>>>
>>>> I'm scratching my head over this one, but I'm guessing I've got it
>>>> grounded wrong somehow.

>
>
>
>


--
"I defer to your plainly more vivid memories of topless women with
whips....r"
R. H. Draney recalls AFU in the Good Old Days.


Lee Ayrton 11-19-2006 12:34 PM

Re: Fuel Gauge Prob
 

I'm guessing that "Red Jeep" meant to attach the clip to the relay _frame_
so he could get to a body ground, but as you know that's far too close to
high-amperage connections for comfort.

On Sun, 19 Nov 2006, DougW wrote:
>
> Especially since the wires on a starter relay/solonoid are hot.
> http://www.prestolite.com/pgs_training/training_4.php
>
> The test for rotted motor strap is battery ground (or frame) to
> the engine block side of the motor mount or somewhere out of the
> fan and belts.


> Lee Ayrton wrote:


>> Jumper from battery negative to starter relay? I can think of a
>> _lot_ of less hazardous places to put a jumper on.

>
>> On Sat, 18 Nov 2006, Red Jeep wrote:
>>
>>> Check the ground from the battery negative to the body. The wire can
>>> corrode inside the connector and look OK from the outside. Use a
>>> jumper cable from the battery negative to something mounted to the
>>> body (horn, starter solenoid).
>>>
>>>
>>> "Spdloader" wrote :
>>>
>>>> I'm scratching my head over this one, but I'm guessing I've got it
>>>> grounded wrong somehow.

>
>
>
>


--
"I defer to your plainly more vivid memories of topless women with
whips....r"
R. H. Draney recalls AFU in the Good Old Days.


Lee Ayrton 11-19-2006 02:10 PM

Re: Fuel Gauge Prob
 

My SWAG is that the sender worked fine until you disturbed it and now it
is bust, but that's just my SWAG. As you saw when you pulled it out it is
just a length of fine wire wrapped around a bit of card. The fuel gauge
circuit goes something like this:

[ Gauge ] Sender
B+ >---------[ Voltage ]----[gauge]---/\/\/\/\
[Regulator] ^
|----------> Ground

For yours, the higher the voltage seen by the gauge the higher the needle
indicates. If the ground is faulty or completely open the gauge won't see
any voltage and will just sit. You can check the ground straps from
engine to body and engine to frame (the fuel sender gets its ground from
the frame, not the body) but I'm guessing that if you haven't seen other
electrical problems then chasing the ground won't yield anything useful.

I think that you're going to have to drop the tank again. You'll need to
do that anyway if you want to check the ground connection.

Troubleshooting guide:

http://www.off-road.com/jeep/tech/electrical/gauges/



On Sat, 18 Nov 2006, Spdloader wrote:

> 1987 Wrangler, 4.2L 5spd
>
> Fuel tank is new, sending unit is original, and worked prior to tank
> replacement.
>
> Problem is, with switch on, gauge on dash reads full until tank is almost
> completely empty, then gauge drops down to
> 1/4 mark.
>
> I'm scratching my head over this one, but I'm guessing I've got it grounded
> wrong somehow.
>
> Any ideas?
>
> I might add, there is no rust on this vehicle.
>
> Spdloader
>
>
>


--
"I defer to your plainly more vivid memories of topless women with
whips....r"
R. H. Draney recalls AFU in the Good Old Days.


Lee Ayrton 11-19-2006 02:10 PM

Re: Fuel Gauge Prob
 

My SWAG is that the sender worked fine until you disturbed it and now it
is bust, but that's just my SWAG. As you saw when you pulled it out it is
just a length of fine wire wrapped around a bit of card. The fuel gauge
circuit goes something like this:

[ Gauge ] Sender
B+ >---------[ Voltage ]----[gauge]---/\/\/\/\
[Regulator] ^
|----------> Ground

For yours, the higher the voltage seen by the gauge the higher the needle
indicates. If the ground is faulty or completely open the gauge won't see
any voltage and will just sit. You can check the ground straps from
engine to body and engine to frame (the fuel sender gets its ground from
the frame, not the body) but I'm guessing that if you haven't seen other
electrical problems then chasing the ground won't yield anything useful.

I think that you're going to have to drop the tank again. You'll need to
do that anyway if you want to check the ground connection.

Troubleshooting guide:

http://www.off-road.com/jeep/tech/electrical/gauges/



On Sat, 18 Nov 2006, Spdloader wrote:

> 1987 Wrangler, 4.2L 5spd
>
> Fuel tank is new, sending unit is original, and worked prior to tank
> replacement.
>
> Problem is, with switch on, gauge on dash reads full until tank is almost
> completely empty, then gauge drops down to
> 1/4 mark.
>
> I'm scratching my head over this one, but I'm guessing I've got it grounded
> wrong somehow.
>
> Any ideas?
>
> I might add, there is no rust on this vehicle.
>
> Spdloader
>
>
>


--
"I defer to your plainly more vivid memories of topless women with
whips....r"
R. H. Draney recalls AFU in the Good Old Days.


Lee Ayrton 11-19-2006 02:10 PM

Re: Fuel Gauge Prob
 

My SWAG is that the sender worked fine until you disturbed it and now it
is bust, but that's just my SWAG. As you saw when you pulled it out it is
just a length of fine wire wrapped around a bit of card. The fuel gauge
circuit goes something like this:

[ Gauge ] Sender
B+ >---------[ Voltage ]----[gauge]---/\/\/\/\
[Regulator] ^
|----------> Ground

For yours, the higher the voltage seen by the gauge the higher the needle
indicates. If the ground is faulty or completely open the gauge won't see
any voltage and will just sit. You can check the ground straps from
engine to body and engine to frame (the fuel sender gets its ground from
the frame, not the body) but I'm guessing that if you haven't seen other
electrical problems then chasing the ground won't yield anything useful.

I think that you're going to have to drop the tank again. You'll need to
do that anyway if you want to check the ground connection.

Troubleshooting guide:

http://www.off-road.com/jeep/tech/electrical/gauges/



On Sat, 18 Nov 2006, Spdloader wrote:

> 1987 Wrangler, 4.2L 5spd
>
> Fuel tank is new, sending unit is original, and worked prior to tank
> replacement.
>
> Problem is, with switch on, gauge on dash reads full until tank is almost
> completely empty, then gauge drops down to
> 1/4 mark.
>
> I'm scratching my head over this one, but I'm guessing I've got it grounded
> wrong somehow.
>
> Any ideas?
>
> I might add, there is no rust on this vehicle.
>
> Spdloader
>
>
>


--
"I defer to your plainly more vivid memories of topless women with
whips....r"
R. H. Draney recalls AFU in the Good Old Days.


Spdloader 11-19-2006 09:35 PM

Re: Fuel Gauge Prob
 
Thanks to everyone!
I'll update when I've time to try some of the ideas.

Spdloader




"Spdloader" <askforit@nospam.triad.rr.com> wrote in message
news:a0u7h.44349$39.11843@southeast.rr.com...
> 1987 Wrangler, 4.2L 5spd
>
> Fuel tank is new, sending unit is original, and worked prior to tank
> replacement.
>
> Problem is, with switch on, gauge on dash reads full until tank is almost
> completely empty, then gauge drops down to
> 1/4 mark.
>
> I'm scratching my head over this one, but I'm guessing I've got it
> grounded wrong somehow.
>
> Any ideas?
>
> I might add, there is no rust on this vehicle.
>
> Spdloader
>




Spdloader 11-19-2006 09:35 PM

Re: Fuel Gauge Prob
 
Thanks to everyone!
I'll update when I've time to try some of the ideas.

Spdloader




"Spdloader" <askforit@nospam.triad.rr.com> wrote in message
news:a0u7h.44349$39.11843@southeast.rr.com...
> 1987 Wrangler, 4.2L 5spd
>
> Fuel tank is new, sending unit is original, and worked prior to tank
> replacement.
>
> Problem is, with switch on, gauge on dash reads full until tank is almost
> completely empty, then gauge drops down to
> 1/4 mark.
>
> I'm scratching my head over this one, but I'm guessing I've got it
> grounded wrong somehow.
>
> Any ideas?
>
> I might add, there is no rust on this vehicle.
>
> Spdloader
>




Spdloader 11-19-2006 09:35 PM

Re: Fuel Gauge Prob
 
Thanks to everyone!
I'll update when I've time to try some of the ideas.

Spdloader




"Spdloader" <askforit@nospam.triad.rr.com> wrote in message
news:a0u7h.44349$39.11843@southeast.rr.com...
> 1987 Wrangler, 4.2L 5spd
>
> Fuel tank is new, sending unit is original, and worked prior to tank
> replacement.
>
> Problem is, with switch on, gauge on dash reads full until tank is almost
> completely empty, then gauge drops down to
> 1/4 mark.
>
> I'm scratching my head over this one, but I'm guessing I've got it
> grounded wrong somehow.
>
> Any ideas?
>
> I might add, there is no rust on this vehicle.
>
> Spdloader
>





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