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CUCV M1009: Is it 3 OR 4 Outlets for Fuel Tank Sending Unit??

ezgn

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Lake Elsinore Ca.
Ok, I'm trying to figure out what I will need


Thanks for the video ADF [thumbzup] [thumbzup]

From what he is saying, or at least from what I understand, my gauge may not be getting any connection to the "signal" wire from the sending unit. As it shows way past full, around the 3 o'clock position just as he states. He stated something about "shorting" the gauge and if it was good, it would go back to empty. I'm not sure what he means by this... my guess is he means grounding the signal wire? Or grounding the "electrical stud" on the back of gauge that the signal wire connects to? If I can test the gauge in this manner, it would at least tell me if the gauge is working.

Also he shows a resistor on his fuel gauge connecting two of the "electrical studs" that connect to the printed circuit board. Is the CUCV fuel gauge supposed to have this resistor?? Because the last time I had the instrument panel apart, I don't remember seeing one. But my memory and recall is not good.

IF I can test the gauge and see that it is Able to work, thereby eliminating it as the cause. Then the next issues could be the signal wire and/or the printed circuit panel for the instrument cluster.

If I pull the instrument panel again, I was considering going ahead and replacing the printed circuit board since it is 40 years old. Eliminate future issues hopefully. And get one while LMC still sells them. From my searching, I am fairly certain that the correct one is LMC part # 38-8036
I'll also get some new retaining clips that connect to the gauge and panel also. I think only the fuel gauge has those clips, so should only need 3.


Was looking at the gauges on LMC also, if I end up needing to replace it. Pretty sure it's # 36-1966

Why is it that the Diesel gauge is the Only one that has "circles" for empty/half/full, instead of just "E - F" ?? Do they think people using diesels can't read??
Would get one of the others that have E to F as they appear to mount the same, but they probably wouldn't read right or something. But hopefully I won't need a gauge to start with.

In any case, I'm going to try to test the gauge first. If I could get it to "read correctly" with the right wires being grounded or not, then that would at least tell me the gauge is working. So guess my next step is to figure out how to ground the signal wire... to bad I already reinstalled the tank.... and I just got my side step and the skid plate re-installed today. If I have to get to the sending unit signal wire, I'll have to pull all that back down again.... ☹
https://www.classicindustries.com/product/1986/chevrolet/truck/parts/25053623.html
 

jplace1011

Well-known member
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Location
Santa Ana, CA
If you do tear into your dash you may want to consider replacing the bulb holders, they aren't very expensive and will eliminate any faulty ones you may have. Also here is a entertaining video about your dash lights.
I haven’t been on for about a month. Look how this Topic has grown. Wow!

You guys are having a good old time with the Fuel Gauge. What a mess huh?

I’m stating the obvious, but if you take your dash apart again, make sure that Big Main Plug clicks back in on Both sides. It can make a huge difference.


Sent from my iPhone using Tapatalk
 

ehuppert

Active member
279
138
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Location
Upstate NY
Been dealing with some gauge issues myself! (Had previously installed civy gauges and re-pinned connector) Gauges would work, then not work, to include fuel gauge. Only a plow truck for the property at the moment so wasn't a big deal....

Had pulled the steering column to replace the wiper switch (PITA) and decided to look into the gauge issues. Turns out the cluster plug had a broken clip and was rotating out of the cluster. Which then was breaking the traces loose from the backing. (Carefully glued traces down)

The plug was used for 73-90 square body's and some Fords. Found allot of used ones with pigtails for sale, but wasn't interested in buying a 30+ year old plastic plug!!!!

Morale of the story: Turns out Ron Francis Wiring sells a new plug.


Got through summit as needed some other stuff. Re-pinning is easy and plug is now secure. Now have an issue with temp gauge and will end up replacing the printed circuit board as mine is pretty beat up....
 

adf5565

Well-known member
Steel Soldiers Supporter
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Location
Tioga, PA
If you do tear into your dash you may want to consider replacing the bulb holders, they aren't very expensive and will eliminate any faulty ones you may have. Also here is a entertaining video about your dash lights.
On this note do you know if they’re 5/8” or 1/2” sockets? Or are both present for different indicators? No big deal if you don’t know, I’ll be able to tell when I pull the cluster back out.849150B7-15BA-4463-8841-47DB098E3261.jpeg
 

Commander5993

Active member
Steel Soldiers Supporter
Hey all, been going to post an update since feb 1st when I got this job done. Seems like never enough hours in the day. Also the day I finished this it was still early in the day, so I went ahead and pulled the rear tire and hub to find out what the "little leak" was around the drum/backplate... well that quickly turned into its own thread... here's link if anyone wants to see that mess. Waiting on parts at the moment.

In any case, I did finally fix my fuel gauge problem. I ended up ordering a new flexiable circuit panel for the instrument cluster, as well as all new bulb holders, and a new fuel gauge. However, I ended up not needing the fuel gauge, so I'm planning on returning that. I was intending to get the truck out and drive it first before I returned it, but truck will be sitting in barn for at least another week.

But to my fuel gauge problem, I did run into some issues that I'll get too.

I tried to test the gauge by pulling the signal wire from the sending unit on the tank, without pulling the tank back down. I had just enough room between the bed and the truck cab to see and try to reach in there and work. I ended up using a long screw driver & prybar, and one of those 4 prong long flexiable push button grapeling tools, usually used for picking up small parts thats not magnetic. Anyway, got the wire off, got under the truck and pulled it back through the frame. Used a set of vise grips and a tiny screw driver to ground the wire to the truck frame. Turned on ignition, but the gauge did not move. Still sat at the 3'oclock position, instead of returning to empty as it should have. Anyway, I decided it must be the circuit panel and/or the fuel gauge, so I ended up ordering both as well as all new light bulb holders and the 3 clips that attack the fuel gauge to the ciruit panel.

After getting my parts in, I pulled the dash apart... again... and pulled the instrument cluster. As you can see, the circuit panel contacts are clean, but the internal wiring is pretty green, much more so than I remember from the last time I had this apart. So it was corroding internally and that is what caused my problems.

When I took the cluster apart, I found that my fuel gauge was a replacment unit. It had a date code of 2008. I also found that it does not use the "cermaic" resistors. Instead its just a peice of plastic that acts as a spacer where the oriringal resister would have been.

2.jpg

4.jpg I



I looked at the new gauge that I had just gotten, and it looks identical but had a date code of 2021.

6.jpg


Another interesting thing I found was that these guages read around 67 to 68ohms, instead of the 90 ohms that I have read elsewhere concerning the original fuel gauges.

20230131_155259.jpg



So with this being a new-er gauge, I figured I first would try just replaceing the circuit panel. Here are the new and old compared. You can see how the old panel circuits were getting pretty green.

7.jpg


If anyone is interested, these are the leds that I replaced the old bulbs with back a year ago. They have worked perfectly, and are a Great Improvement over the stock bulbs. I replaced All the bulbs in the instrument cluster with these. I did not replace the glow plug "wait light" and the light next to it (can't remember what it is right now) as those are different bulbs. But those are bright enough anyway.

9.jpg


In any case, when I got the base back together and plugged into the main harness, turned on the ignition and... the fuel gauge went straight to empty! :clinto: Which is what it should have done since I still had the signal wire grounded to the frame.

BUT... after a few minuets I started thinking that something didn't look right. So I went back and turned on the ignition again, only to realize that MOST of my dash lights were Not working... only had the 4x4 light (as the truck was in 4-wheel drive as we had a big snow here and I had driven it to town the day before) the "seatbelt" light, and Only the Left Turnsignal light worked, the right one didn't do anything and everything else was out including the normal background dash lights. So great now what...

10.jpg

For the next hour or so, I was going back and forth trying to figure out what happened. As all my lights was working fine before I had pulled the cluster out, just not the fuel gauge. Now the fuel gauge works and most of my lights don't :doh:

So I started thinking the main plug wasn't making contact, or that it was "misaligned" with the new circuit panel or.... After going through the plug and not seeing any reason that it wouldn't make contact, and seeing marks on the copper contacts on the new circuit planel from the plug contacts (as I had plugged and unplugged it multiple times at this point) I finally took the cluster back out, removed the new circuit panel, and reinstalled the old one. But even then it still had the same problem, most of the lights were still out.

After going through everything I could think of... I finally pulled ALL of the "new" bulb holders and reinstalled my old ones and BAM it all lit up.

11.jpg

So I got to looking closly at these "new" bulb holders and found that the electrical contacts were flat against the plastic base. There was Zero "spring tension" to push the contact into the circuit board. So I went through and bent ALL of the contacts forward, then reinstalled them, and then they worked fine.

Hard to see, but going from left to right, the first photo on the left shows the flat contact in the new bulb holders. The next two photos show how I bent the contacts up/forward.

bulb holders.png

Just ridiculous to pay $26 for new bulb holders, only to have to fix them. I had done the exact same thing with my old bulb holders before, which I should have just kept and sent all of these back, but some of my old holders were broke and needed replaced.

**BTW anyone who is going to order bulb and/or bulb holder replacements... there are 14 bulbs in the instrument cluster... somehow I only managed to count 13 and that was how many holders I ordered, so I still ended up using one of my old one's.

In any case, the next morning I was able to finish putting the dash back together. And I fished my fuel signal wire back up through the frame to the top of the tank. Took a bit, but finally got it pressed and locked back down onto the electrical stud on the sending unit. Turned the igntion and the gauge went to just above the full mark. Which is just fine for me, as I had just filled the tank again when I had went to town.

15.jpg


🔴🔴 By the way that reminds me. Here's something for you experts on here. You know how I mentioned earlier in this thread, that after I had dropped the old fuel tank and when I looked inside, it only appeared to be half full, even though I had just "topped it off" just before I started this project (as I wasn't planning on doing this project when I filled the tank).
Well, after I got the new tank installed, and was waiting for the circuit panel and other parts to arrive. We had a big snow and I drove this truck to town, which is only an 8 mile drive one way. While I was there, I figured I would try to "top off" the tank again just to see how much it would take. Well, it took 12 GALLONS. So I am figuring, with what little I had driven the truck since I had last "topped off" the tank, I am estimating the tank was Only Holding about 10 gallon of fuel previously, even though it was "full" and visible in the fuel neck.
But how is this possible? What would stop the tank from taking more fuel with fuel visibly in the fuel neck, when the tank was only approx half full??

With the new tank installed, and adding 12 gallons of fuel to what I already had, it should be holding the full 20 gallons now. But I had no idea that I was only getting a "half a tank" before. Since the fuel gauge didnt' work, I just got used to topping the tank off until I could see the fuel in the fuel neck *Assuming* at that point I had a "full tank". Just glad I didn't take any long trips recently, or I would have thought I was getting really horrible fuel mileage :lol:

Anyway, thats Hopefully the end of my escapades to fix my fuel gauge, and the other issues I found along the way. Just wanted to do this update to post my end results. I hate reading through an entire thread, only to be left hanging at the end to never find out the "end of the story"

Thanks for the help All! [thumbzup] [thumbzup]

......Now on to fixing my rear hubs, bearings, brakes and etc.... but thats in the new thread.


P.S. Excuse my poor spelling, which usually is where I reverse the order of some letters in a word. I don't know why but my spell check stopped working. Have tried selecting both "enhanced spell check" and "basic spell check", but neither one works.
 
Last edited:

adf5565

Well-known member
Steel Soldiers Supporter
316
579
93
Location
Tioga, PA
Hey all, been going to post an update since feb 1st when I got this job done. Seems like never enough hours in the day. Also the day I finished this it was still early in the day, so I went ahead and pulled the rear tire and hub to find out what the "little leak" was around the drum/backplate... well that quickly turned into its own thread... here's link if anyone wants to see that mess. Waiting on parts at the moment.

In any case, I did finally fix my fuel gauge problem. I ended up ordering a new flexiable circuit panel for the instrument cluster, as well as all new bulb holders, and a new fuel gauge. However, I ended up not needing the fuel gauge, so I'm planning on returning that. I was intending to get the truck out and drive it first before I returned it, but truck will be sitting in barn for at least another week.

But to my fuel gauge problem, I did run into some issues that I'll get too.

I tried to test the gauge by pulling the signal wire from the sending unit on the tank, without pulling the tank back down. I had just enough room between the bed and the truck cab to see and try to reach in there and work. I ended up using a long screw driver & prybar, and one of those 4 prong long flexiable push button grapeling tools, usually used for picking up small parts thats not magnetic. Anyway, got the wire off, got under the truck and pulled it back through the frame. Used a set of vise grips and a tiny screw driver to ground the wire to the truck frame. Turned on ignition, but the gauge did not move. Still sat at the 3'oclock position, instead of returning to empty as it should have. Anyway, I decided it must be the circuit panel and/or the fuel gauge, so I ended up ordering both as well as all new light bulb holders and the 3 clips that attack the fuel gauge to the ciruit panel.

After getting my parts in, I pulled the dash apart... again... and pulled the instrument cluster. As you can see, the circuit panel contacts are clean, but the internal wiring is pretty green, much more so than I remember from the last time I had this apart. So it was corroding internally and that is what caused my problems.

View attachment 890365

When I took the cluster apart, I found that my fuel gauge was a replacment unit. It had a date code of 2008. I also found that it does not use the "cermaic" resistors. Instead its just a peice of plastic that acts as a spacer where the oriringal resister would have been.

View attachment 890366

View attachment 890367 I



I looked at the new gauge that I had just gotten, and it looks identical but had a date code of 2021.

View attachment 890368


So I figured I would try just replaceing the circuit panel first. Here are the new and old compared.

View attachment 890369


If anyone is interested, these are the leds that I replaced the old bulbs with back a year ago. They have worked perfectly, and are a Great Improvement over the stock bulbs. I replaced All the bulbs in the instrument cluster with these. I did not replace the glow plug "wait light" and the light next to it (can't remember what it is right now) as those are different bulbs. But those are bright enough anyway.

View attachment 890370


In any case, when I got the base back together and plugged into the main harness, turned on the ignition and... the fuel gauge went straight to empty! Which is what it should have done since I still had the signal wire grounded to the frame.

BUT... after a few minuets I started thinking that something didn't look right. So I went back and turned on the ignition again, only to realize that MOST of my dash lights were Not working... only had 4x4 light (as the truck was in 4-wheel drive as we had a big snow here and I had driven it to town the day before) and the "seatbelt" light, and Only the Left Turnsignal light worked, the right one didn't do anything. So I thought great now what...

View attachment 890372

For the next hour or so, I was going back and forth trying to figure out what happened. As all my lights was working before I had pulled the cluster out, just not the fuel gauge. Now the fuel gauge works and most of my lights don't.

So I started thinking the main plug wasn't making contact, or that it was "misaligned" with the new circuit panel. After going through the plug and not seeing any reason that it wouldn't make contact, and seeing marks on the copper contacts on the new circuit planel from the plug contacts (as I had plugged and unplugged it multiple times at this point) I finally took the cluster back out, removed the new circuit panel, and reinstalled the old one. But even then it still had the same problem, most of the lights were still out.

After going through everything I could think of... I finally pulled ALL of the "new" bulb holders and reinstalled my old ones and BAM it all lit up.

View attachment 890373

So I got to looking closly at these "new" bulb holders and found that the electrical contacts were flat against the plastic base. There was Zero "spring tension" to push the contact into the circuit board. So I went through and bent ALL of the contacts forward, then reinstalled all of them, and then they worked fine.

Hard to see, but the first photo on the left shows the flat contact in the new bulb holders. Photos 2 and 3 going to the right show how I bent the contacts "up".

View attachment 890374

Just ridiculous to pay $26 for new bulb holders, only to have to fix them. I had done the exact same thing with my old bulb holders before, which I should have just kept and sent all of these back, but some of my old holders were broke and needed replaced.

**BTW anyone who is going to order bulb and/or bulb holder replacements... there are 14 bulbs in the instrument cluster... somehow I only managed to count 13 and that was how many holders I ordered, so I still ended up using one of my old one's.

In any case, the next morning I was able to finish putting the dash back together. And I fished my fuel signal wire back up through the frame to the top of the tank. Took a bit, but finally got it pressed and locked back down on the electrical stud on the sending unit. Turned the igntion and the gauge went to just above the full mark. Which is just fine for me, as I had just filled the tank when I had went to town.

View attachment 890375


🔴🔴 By the way that reminds me. Here's something for you experts on here. You know how I mentioned earlier in this thread, that after I had dropped the old fuel tank and when I looked inside it only appeared to be half full, even though I had just "topped it off" just before I started this project (as I wasn't planning on doing this project when I filled the tank).
Well, after I got the new tank installed, and was waiting for the circuit panel and other parts to arrive. We had a big snow and I drove this truck to town, which is only an 8 mile drive one way. While I was there, I figured I would try to "top off" the tank again just to see how much it would take. Well, it took 12 GALLONS. So I am figuring, with what little I had driven the truck since I had last "topped off" the tank, I am estimating the tank was Only Holding about 10 gallon of fuel previously, even though it was "full" and visible in the fuel neck.
But how is this possible? What would stop the tank from taking more fuel with fuel visibly in the fuel neck, when the tank was only approx half full??

Now with the new tank installed, and adding 12 gallons of fuel to what I already had, it should be holding the full 20 gallons now. But I had no idea that I was only getting a "half a tank" before. Since the fuel gauge didnt' work, I just got used to topping the tank off until I could see the fuel in the fuel neck *Assuming* at that point I had a "full tank". Just glad I didn't take any long trips recently, or I would have thought I was getting really horrible fuel mileage :lol:

Anyway, thats Hopefully the end of my escapades to fix my fuel gauge, and the other issues I found along the way. Just wanted to post this update to post my end results. I hate reading all through a thread and then never find out the "end of the story"

Thanks for the help All! [thumbzup] [thumbzup]

......Now on to fixing my rear hubs, bearings, brakes and etc.... but thats in the new thread.


P.S. Excuse my poor spelling, which usually is where I reverse the order of some letters in a word. I don't know why but my spell check stopped working. Have tried selecting both "enhanced spell check" and "basic spell check", but neither one works.
Nice work! Was the circuit panel you purchased the one from LMC? Or did you get that somewhere else?

And with regards to the tank filling, I can’t say for sure but in my experience I’ve had a couple times when I was at the pump I either didn’t have the nozzle angled right in the filler or the flow was too high so a little fuel came back out which initially gave me the impression the tank was full. But then I just slowed down the filling and moved the nozzle and it took a lot more.
 

Commander5993

Active member
Steel Soldiers Supporter
Nice work! Was the circuit panel you purchased the one from LMC? Or did you get that somewhere else?

And with regards to the tank filling, I can’t say for sure but in my experience I’ve had a couple times when I was at the pump I either didn’t have the nozzle angled right in the filler or the flow was too high so a little fuel came back out which initially gave me the impression the tank was full. But then I just slowed down the filling and moved the nozzle and it took a lot more.
I ended up ordering everything from Classic Industries, mostly because they had the bulb holders and a couple other small items that I couldn't find on LMC.

And yeah, I have filled a tank a bit to fast before and had the pump kick off. I always just waited for the foam to go down, and start filling it slower. But I always filled it up to where fuel stayed in the fuel neck before I quit. So I don't know. Just a weird issue I guess.
 

Commander5993

Active member
Steel Soldiers Supporter
hey guys, question: are the temp light and low coolant light (below speedometer) supposed to come on when you first turn on key??

just had to pull instrument cluster again as I didn't get my speedometer cable plugged fully in, and tested my dash lights before closing her backup, and those two lights are not coming on. I can't remember if they are supposed to or not. checked bulbs sockets, repeated them several times, pulled main harness and reinstalled it. still nothing.
 

Commander5993

Active member
Steel Soldiers Supporter
switched those two bulbs/sockets with two others, bulbs were fine as they worked in other spots. temp and low coolant lights still don't light up.

TM said low coolant light is supposed to come on when key is first turned on, doest say about temp light.

checked wires on both new sensors, solid connections. I even unplugged low coolant wire, light still didn't come on
 

Commander5993

Active member
Steel Soldiers Supporter
screw it, I'm putting it back together, i have too much other work to keep fooling with this. need truck tomorrow.

I always keep check on fluids anyway, have a small antifreeze leak that i cant locate thus far. going to try some uv dye and see..

have no way to know if temp light works, if she overheats, guess I'll just have to hope I catch it before damage is done.
 
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