Fuel gauge help please...

Well, I assembled the speedo cluster and made sure that the fuel gauge was grounded (i even took the case down to bare metal). I followed the wiring diagram, but when I turn the key to the "on" position all I get is a buzzing noise from the gauge. Moved the float to see id it works and nothing. Any Ideas? I'm stumped on this on.

 

Not sure about the buzzing. Does the needle move off "E"?

If you don't already know, Stan (board member) has a very informative gauge troubleshooting site:
http://home.comcast.net/~sday77/binky/index.htm

HTH!
-Alan

 

no, the needle stays where it is.

 

Also, I refered to Stan's website and followed what he had on the gauge schematics. That's why I can't understand it doesn't work.

 

I always try to divide and conquer. I'd first test that the sending unit resistance changes as it's supposed to as the float goes up and down. Then I'd use a resistor (assortment available at Radieux Shaque) to sub for the sender, and see if the guage moves as I sub in different resistances. There should be a spec for the range of resistance that the sender must have, full to empty. The sending unit is a circuit, from the connection on the guage, through the body, back to the ground connection on the gauge.

 

BTW if you take the sender out of the tank and move the float, nothing will happen unless you also ground the sender to the body. May be obvious, but I thought I should mention.

 

I thought of that too, and I made sure it was. Could a buzzing mean a bad gauge?

 

OK, I just looked at it again and did the same thing with grounding everythig. The gauge is out of the dash but grounded. The gauge worked with no buzzing. Shut the key off and turn it back to "on" and the buzzing came back. The rear of the fuel gauge is warm, and it seems that I'm grounding out some circuit.??????

 

Might be a bad gauge from the sound of it. Is the temp gauge working OK? The fuel gauge acts as the CVR (constant voltage regulator) by pulsing on and off. This may be the "buzzing" you're hearing. Do you have another gauge to try? I'd check the following items as well:

• • Sender resistances (about 73 ohms empty, about 10 ohms full).
  • Battery voltage with engine off (about 12V) and on (about 14V).
  • 5V voltage checkpoint on the gauge strap (points "A" on the gauges on my site gauge diagram). With an analog meter you should see about 5V, with a digital you'll see a reading fluctuating up and down fairly rapidly. With the digital what you don't want to see is a steady voltage.

See if that helps pinpoint it. Let us know what you find!

Stan

 

Stan,
I followed what you have on your site before the whole gauge cluster installation and that's where I'm stumped. I'm not sure on how to check the temp gauge. Right now I have 12v going to the I post of the gauge and nothing on the other posts. Could I have fried the gauge if one or any of the posts were touching the case?

 

If the "I" post touched ground you should just blow a fuse somewhere. If the "S" post got grounded I think the gauge would go all the way up. If you left it that way long enough then you can do some damage. You can test the gauges by using a jumper and carefully touching the "S" of one or the other gauge to ground momentarily. That gauge should go to the "full" or "hot" side. If the fuel gauge is bad then the temp gauge will probably not work until the fuel gauge is fixed, so fix the fuel gauge first, then see if the temp gauge will work.

What I did to fry mine was to run the gauges without the fuel gauge being grounded so my problem was a bit different than yours. You might also look at this link for some good diagnostic test procedures to try:

http://www.monsterslayer.com/jeep/Gauges.htm

Stan

 

ok, I just took the face off the fuel gauge. as you look at it straight on, there is a metal band (fusable link?) on the left post that is broken. On the right where the needle is (E position) the coiled wire is cooked. How did this happen?

 

Back several years ago I would have said I was an expert, but once I got everything working some of the details escape me now. One point has already been mentioned, but I will elaborate. About the sending unit being grounded, if you have it out and grounded for testing and it works, put it back in and it does not work...Voila! Perhaps your tank is not well grounded! I had my tank rhino lined and it took me about a half hour of head scratching before I figured out that it was not grounded anymore. I ran a separate ground wire to one of the screws that hold the sending unit to the tank. I would recommend doing that in all cases, rather than relying on a painted or rusted tank to ground through the hold down strap or even the fuel line.

 

Probably too much voltage. On mine that was due to a poor ground, but could also be a bad alternator or generator putting out too much voltage, and I suppose if something had shorted just right that may have caused it. Those gauges are fairly fragile. At least that explains the non-functioning! Get a replacement gauge and that should take care of it. I got a NOS gauge from Willys Works in AZ, there may be some other sources too that some of the guys on the board can give you.

Stan

 

Stan,
I don't think it was too much voltage, because I had the voltmeter on it (showing about 12v) and I only got as far as turning the key to the "on" position. You mention a bad ground. I sanded down to bare metal the ground area on the case to make sure the fuel gauge was grounded. The more I look at it, I made the cardboard insulator out of the box the gauges came it. I may have tightened it down to the point where the nut penetrated the cardboard and grounded the post. I want to make sure of this before I waste another one. Could this have been the cause?

 

You should only see 12V on the "I" post, not the strap or "A" posts. There should only be a mounting insulator on the temp gauge, not the fuel gauge. If you had an insulator on that gauge then it was not grounded. If that one is not grounded it can't regulate the voltage and you'll get 12V where there should be about 5V and the gauge will fry.

Stan

 

A couple of things:

1. Wouldn't the fuel gauge be grounded by the ground contact-to-case on the rear of the gauge? (based off the information on your site)
2. If there wasn't an insulator on the fuel gauge, then shouldn't it "short" through the 'I' post?

 

> 1. Wouldn't the fuel gauge be grounded by the ground
> contact-to-case on the rear of the gauge? (based off the information
> on your site)

It should ground that way as long as the back of the gauge is touching the metal of the housing and where it's touching is clean.

> 2. If there wasn't an insulator on the fuel gauge, then shouldn't it
> "short" through the 'I' post?

Oh, I think I see what you mean. Yes, I guess there was an insulator on the other side of the thing to keep the nuts from grounding out. It's been a really long time since I've had that thing apart! But I think you're right. Insulator on one side and not the other of the fuel gauge. And yes, you do have to be careful that the gauge studs are centered in their respective holes in the housing so things don't short out.

I don't have that Jeep with me right now but I'll try to get out to the garage tonight and take a look at that speedo and gauge setup for you.

Stan