Fuel Gage ?

Fuel Gage ?

Bunky67

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SW Michigan
Vehicle(s)
1977 CJ5 304 V8 3 speed Trans Fiberglass front end,
The fuel Gauge in my Jeep is not working I just put a new sending unit in when I installed the new tank, (I got the Jeep with a bad tank and the Sending unit was rotted gone), The wire to the gauges had the plastic melted off, So I replaced that with a new wire, After doing a couple of test on the gauge, I have no power, or pulsing of the test light on the terminal going to the sending unit,

Should I figure that the gauge is just bad, is it possible it shorted out causing the wire to get hot and melt ???

Also where should I get a new gauge ?? are the new replacements decent units ??
 
http://street2mud.com/webfiles/Basic%20Troubleshooting%20for%20CJ%20gauges.pdf

This is Jeep Guru John Strenks layout of how to work on that system, there is an array of stuff on the net regarding it.
It can be purchased at 4WD Hardware and 4WPW as a fuel/temp gauge combo. Some guys don't think a lot of them, and install a mechanical system, or something else. If it installed correctly and if you have a fair idea how it works, it is fine. It sounds like your setup is fried, which is easy to do.
 
OK well I'm looking at some replacement gauges, but some say they need to be changed together, is there a reason for this or is this just certain brand gauges ??
 
Do they mean the sender and gauge?

For the gauge you need 12v or key on power and a good ground.

Then the sender wire and the sender itself needs to be grounded.

To test the gauge, remove the sender wire and ground it; or just jumper the back of the gauge to ground. This should peg the gauge if it is operable.

Gotta have power and ground to it first though.

Not sure what you meant by pulsing test light?
 
Made in usa fuel sender for jeep cj and other jeeps

OK well I'm looking at some replacement gauges, but some say they need to be changed together, is there a reason for this or is this just certain brand gauges ??


As said above John's Strenks write ups on gauges are the best. Since you said the power was not pulsing sounds like you have read Johns write ups on trouble shooting jeep cj gauges.

The Fuel Gauge is part of the speedo. It has two bimetal springs adn wire wraped heater coils. One is the voltage adjust for the fuel gauge and the temp gauge. The heat coil wire heats the bimetal spring and it opens a contact and drops the 12V apply voltage.... Cools off and closes the points/contact again and starts the heat cycle. This contact/point is what you tested for looking for the pluse output of the bimetal/contact piece. The second bimetal deflects the pointer in the gauge and his heated by the lower pulse voltage of the first bimetal. Just got done doing this myself and calibrating the gauge and sender together..... yes they can be calibrated.

The CJ fuel sender and Guage are NON LINEAR meaning the F to E has a range 10-70 ohms but half full is not half way on OHMs. Linear half way would be (70-10)/2 +10 or 40 ohms. But the CJ is non linear and half way is 22 ohms if memeory serves me right...

So we need the gauge and sender to match.... Very hard to get a CJ sender the Crown ones fail pretty quick and the new more current senders and gauges are linear often.... So then looking at mtd hardware, height, floats.... its a bit of mess...

I and bud are cking a USA maker of the CJ Senders and could be good solution for many of us jeepers. more later on this...

MADE IN USA FUEL SENDER FOR JEEPS

MTS Company
MTSCompany.com
800-522-1622 M-Friday central time
CJ-su-1 is their part # for CJ its $29.95 and $5.3 shipping
one year warranty... but has platic float...
includes the filter on pick up, new mtd gasket, new lock ring
making these for the past 23 years they told me
MANY jeepers do not know aobut them....
Can also buy this sender from Quadratec

So.....
I suggest test your fuel & temp cluster with the point to point tests. IF bad the fuel gauge can be swaped with any 76-86 CJ speedo fuel gauge all the same. Run thru a point to point test before buying fuel gauge. Many I just tried to buy failed the point to point testing even tho owner said it was a good speedo or fuel gauge. The output of fuel sender can also be tested with a mutlmeter resistance. Tank full will be 10 ohms or close..... Empty Tank, carry some gas in can, then measure emplty will be close to 73ohms. Senders like to loose ground via the little ground wire......... major fault location with jeep fuel indication. Also if you change the sender swap over the brass float they are better. Keep the extra floats that are brass and not leaking if come acrosss one.

that should get you fixed up...
 
Ok well today I got the new gauge ( rugged Ridge) and the gauge went up to 1/4 tank so I drove to the gas station and put $5 in the tank and it was full to the filler neck, and the gauge still read 1/4 tank, so I went back home and only had a regular ohm meter not a DOM and it read approximately Zero Ohms, so I went an unhooked the pink wire from the gauge and shorted it and the gauge went to "F" So I gather from this that the new sending unit I installed with the new tank is off ?

Or is there another possible cause ?
 
Are you certain all your grounds are up to snuff?

Fuel Gauge can take more than a few minutes to show a true tank reading. If you started adjusting float linkage without considering this, you may have caused a problem for yourself.

You did check the float linkage, right?



I and bud are cking a USA maker of the CJ Senders and could be good solution for many of us jeepers. more later on this...

MADE IN USA FUEL SENDER FOR JEEPS

MTS Company
MTSCompany.com
MNCJ7, nice find. :notworthy: Have you dealt with these folks before?
 
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Should be in the 10 -12 ohm range when full. Just test it across the two sender terminals.

I actually just installed a new fuel cell and sender and was getting readings like you are describing. Tested the sender and its perfect.

My gauge does do a full sweep when I ground the sender wire, but there must be enough resistance in the wire due to age that it reads 1/2 full even when the tank is full.

Grab a jumper wire and jumper from the sender to gauge; or test the resistance of the sender wire with it unhooked from everything.
 
Ok well today I got the new gauge ( rugged Ridge) and the gauge went up to 1/4 tank so I drove to the gas station and put $5 in the tank and it was full to the filler neck, and the gauge still read 1/4 tank, so I went back home and only had a regular ohm meter not a DOM and it read approximately Zero Ohms, so I went an unhooked the pink wire from the gauge and shorted it and the gauge went to "F" So I gather from this that the new sending unit I installed with the new tank is off ?

Or is there another possible cause ?


You are getting closer.... but need to look at the sender as one item and the fuel/temp cluster pieces as a second item.

First do a point to point on the fuel/temp gauges and verify they match what John S write up tell you..... they need to match... Verifty each of the 3 coils are there via resistance. There are like 6 tests for the fuel/temp gauge alone. If you do not understand a pc of his write up... ask... I can most likely work you thru it, the testing.

The next part of the fuel/temp gauge testing is make some resitance jumpers... We use the jumpers to FAKE resistance for the fuel gauge for empty/full/half full and then we can verify the gauge reads with resistance. I just make up these jumpers..... Radio Shack has pre made jumper with wire and allegator clips already made up or you can buy climps and use your own wire.... I used 10 ohm resisters and 68 ohm resistors..... Jumper with 10 ohm resistor is full, 2x 10 ohm resistors in series (wire/res/res/wire) will be 20 ohms close to 22 ohm half full, and the 68 ohm resistor is close to full AND I made a 68 ohm & 10 ohm resistor to make a 78 ohm jumper and that should be complete full or over full.

I used these jumpers to FAKE OUT the fuel gauge so it would read and should match empty/half/full with these jumpers. I soldered every resistor, wire, allegator clip and covered with heat shrink.... Or used the premade jumpers cut the wire and solder in resistors, cover with heat shrinnk. I used sharpe to mark reistance value on jumper and added a paper lable with scotch tape. Measure each resistance jumper with your multi meter to verify resistance and your work and connections. Let your CJ buds know you have the jumpers if they need to trouble shoot fuel gauge sender.

At this point we have ck the fuel/temp gauge and made them read correctly with resistance jumpers and did point to point resitance measurements with multimeter. Digital Multi Meter or Analoge Meter does not meter.

Now lets look at the fuel sender...
the part in the gas tank and the one that can take a half a day to change out.... Replacements are CHEAP AND FAIL many posted have after market CJ Fuel Senders that fail in wks or failed as new.. That is why i posted the MADE IN USA SENDER........THIS IS A BIG BIG BIG DEAL..... I have not seen the product in my hand or ordered on yet... but have read from folks that have a apprears to be a VERY GOOD CJ SENDER.

About the best we can do for fuel sender is measure resistance at empty/half full/full. So I hope you measured your fuel sender when your tank was lower by 5 gal or 2/3 full. That would be your first measurement. Now you are full/over flowing.... that is your second resistance measruement. I could not siphon out of my CJ Tank, some block, not sure if yours is same way or not. Empty would be the next usefull measuremnt. Put in 7 gal back in and will be close to half way full and would be the next usefull resistance measurement..

that is what needs to be done to trouble shoot your fuel gauge.



If the fuel gauge or sender do not match the 10/22/70 ohm readings full/half/empty then the faulty pc needs to be corrected. If both halves work but the reading does not work.... we look at the grounds or wires.
 
MNCJ7, nice find. :notworthy: Have you dealt with these folks before?

Thanks Bondo,

No i have not ordered or used one of their senders. Mentioned above I needed to get one and ck it out yet a bud will be doing the same. If a member has used them for the CJ please post and let me know.

Looks to be a great solution for the CJ from my reading......
A GREAT CJ SENDER SOLUTION
 
Thanks for the info I am battling the gauge and sender too. I have a 20 gallon tank...mts is a good find! But they only make it in 15 or 21 gallons, plan to call them first thing in the morning...

Do you think I can shorten the 21 to work?
 
Thanks Guy's


The sending unit I installed is a Dorman, I assumed it was USA made, if not maybe I should switch it out,

I think maybe this weekend I will invest in some resistors and check this out more thoroughly, I didn't check the ohms at the tank either I just checked them at the gauge by removing the sending unit wire, and then grounding the gauge there to peg the gauge, It also could be a Grounding issue the previous owner had the battery installed in the rear by the tailgate and I moved it back where it belongs, I will check it out this weekend

Thanks again
 
I just ordered the fuel sender and hoses from MTS Company - VERY good customer service, and VERY knowledgeable of our Jeeps.

They make the sender in house in Iowa, I would call Mike at MTS with any problem you are having he will be able to solve it.

Shad
 
From what I've read on the subject, the fuel guage is grounded through the speedometer housing and is very often the reason that the guages fail.. it's also been said that if the guage cluster isn't properly grounded BEFORE you apply power, it will ruin the fuel guage, not too sure how true that last part is though.. I'll be watching this thread, I'm getting tired of running out of gas myself...
 
OK well I think I have narrowed down the gauge as the problem, today I bought a 10ohm resistor, and soldered in between to alligator clips and grounded one end and put the other end on where the Pink wire goes to the sender and it only reads 1/4 tank so I contacted the seller and omix-ada so we will see what happens next,
 
Sounds like youre getting there.

You confirmed that the ground is good?

The other guy wasn't kidding about the grounds on the fuel and temp gauge. They are often faulty and this would cause you to have a lower fuel reading than you should.
 
I will double check the grounds on the gauges, but I'm pretty sure they are good, but never hurts to double check
 
I will double check the grounds on the gauges, but I'm pretty sure they are good, but never hurts to double check


When you do the point to point testing for the fuel/temp gauge.... you are testing for gounds.

The fuel gauge and temp gauge mount to the speedo.... and get their ground from the speedo mounting studs, and that ground is from the dash.... The DASH is one of the CJ items that can use a aux ground. The fuel sender gets and needs ground from a small wire that is groounded by the gas tank..... so the sender acts like a vairable resistor that uses the supplied ground wire.......... The fuel sender uses variable resistance and sends it to the measurement half of the fuel gauge... The second half of the fuel gauge is the "points" part of the fuel sender that uses a bimetal and coil heater to open/close points to supply a lower than "12V DC" to the second half of fuel gauge/reading half and the temp gauge.

Volt gauge and Oil gauge work on their own and not related to fuel/temp.

NOTE.
If you remove, clean, change the fuel or temp gauge make sure they are centered and installed right.... Both fuel/temp gauge can be shorted out to the speedo body on the Pink or Red studs on the back of fuel gauge for example. Crooked installs of the fuel or temp will cause shorts and possible failure of these gauges.... Crooked install will also keep them from working.... so install them carefull the first time while working with them on the bench..... SO the temp/fuel need to be goundeed to the speedo but the I/O studs on the back cannot be grounded out by mistake to the speedo..... It does happen .... happened to me a few wks ago and need to tear down speedo again. The fuel gauge was crooked a bit. FYI.
 
Any feed back on the best new gauge? The shop working on my Jeep said they test the gauge and it shot.
 
Any feed back on the best new gauge? The shop working on my Jeep said they test the gauge and it shot.

Any brand gauge should suffice, IF it is installed correctly with proper grounds throughout the circuit first and every time voltage is applied.

A few seconds on a bumpy road can cause a loss of ground in a thirty year old Jeep. This equals something getting burned out. Run dedicated ground wires.

I've had much luck with the hated "china" brands with both my own and others' CJ's by verifying the wiring was up to snuff (and installing a dedicated ground to the cluster). I've seen senders get burned out, by just hoping the dash had enough ground. Add dedicated grounds.

Checking for continuity to ground isn't enough, you want low resistance as well.

The Strenk write-up pushes checking the wiring, and proper grounds for a reason. The OEM Stewart-Warner gauges had the same weaknesses. The design stinks.

A near exact (read import here) copy of a stinky design gives you a stinky gauge.

The design of the circuit is poor, not so much the materials or construction used in the components.
 

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