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CUCV Fuel gauge issues and fixes

Barrman

Well-known member
5,266
1,782
113
Location
Giddings, Texas
I have owned one of my M1009's almost 3 years now. I think the fuel gauge has worked correctly about 2 weeks of that time. When I first got it, the needle pointed waaay past F and never moved. The previous owner said it had worked sometimes. I followed what the manual said:

29. FUEL GAGE INACCURATE​
Step 1. Check 20 amp ignition fuse.Replace if burned out.trace circuit. (See wiring diagram F-4 or
DO NOT leave keyin “RUN” position for more than 2 minutes. Failure tomay result in damage to glow plugs.
Step 2. Disconnect fuel tank sending unit ground from frame. Turn key to “RUN” position.If fuel gage reads “F“ (Full), perform step 3.If fuel gage does not read “F” (Full), replace fuel gage. (See paragraph 4-7)​
2-70Table 2-4. Electrical TroubleshootingTM 9-2320-289-20(Con’t)MALFUNCTIONTEST OR INSPECTIONCORRECTIVE ACTION​
Step 3. Disconnect pink fuel tank sending unit lead and touch lead to any ground.If fuel gage reads “E“ (Empty), replace fuel tank sending unit,paragraph 3-11 or 3-12)If fuel gage does not read “E” (Empty), replace fuel gage.​
paragraph 4-7)

I found the pink wire to the back was cut above the rear axle. I spliced it together and had a working fuel gauge. A few weeks later I took the truck on a 600 mile road trip. The gauge worked perfect. I stopped to top off the tank and when I started back up, it only went to just below 1/2 tank. I lived with it working just fine but on half scale the rest of the trip. When I got home I did the manual steps.

It went full scale when I grounded the pink wire at the tank, so it had to be the sender unit. About that time my wife totalled our family Suburban and began driving the M1009 as her daily driver. She would call me ever so often and say she hit a big bump, speed bump, pot hole, curb and the fuel gauge would go up to 3/4 of a tank or full or whatever. I even had it happen a few times with me on a dirt road. It would work fine until the truck was turned off. Then it would be back to 1/2 tank as full.

I got a new LMC sender and ran into all kinds of rusted fasteners while trying to take the tank out a month or so ago. Here is a thread about that:
http://www.steelsoldiers.com/showth...-and-dropping-a-fuel-tank&highlight=fuel+tank

Once I got another LMC box with new fuel tank straps and an afternoon to work on it when the fuel level was low. I went to changing out the sender. I did hook up the new one and moved the arm while Colton looked at what the gauge read before I dropped the tank. Full arm up and just shy of 3/4 tank on the gauge. Full arm down and spot on E at the gauge. Hmm, LMC sent me a bad sender. Before I called them to complain, I looked up what Ohms the sender should have. Autometer seems to have the best chart for all fuel senders:

http://www.egauges.com/ATM_Tips.asp?TipPage=fuel_level_gauge.htm

A fast check showed my new sender was 0-92 Ohms. Close enough to the 0-90 it was supposed to be. I dropped the tank, replaced all the rubber parts back there and put in the new sender. Empty really was E on the gauge. I topped it off and it read just shy of 1/2 tank. AARRRRGH! I drove it for a week because I was out of work time that day and I wanted to make sure nothing leaked before I put the skid plate back on the truck. At least I knew the tank was secure with new straps, the lines were fresh and the sender for sure was not the problem.

I did the checks the manual list again and again, the guage passed just fine by doing exactly what the manual says it should do. I traced the pink wire all the way under the truck again and only my splice for a few years ago was there. I was going to cut it out and do it again until I thought about it. 90 Ohms is full tank. If my connection was bad, the error would be to the full side of the gauge which was what I wan't getting.

I checked the fuse and all good. It had to be the gauge, the big plug on the back of the gauge panel or the plug ins at the gauge itself. I have had the little flexible tabs on the back of the gauge panel break off in the past and now don't undo that plug unless I have to. So, I pulled the dash pad, undid all 4 battery terminals, pulled the gauge bezel, pulled the gauge clear cover and the gauge metel bezel off with the panel still in the truck. I plugged the batteries back in and placed my 3 spare fuel gauges in the passenger seat. I pulled the fuel gauge out, cleaned the contacts in the panel and on the back of the gauge. Then put it back in. No change when I turned the key on.

I went to pull it out with the key still on and about 1/4 inch of pulling had the gauge needle sweeping toward full. I pushed it back in and the needle went down. I pulled it out and cleaned everything again with more vigor and a points file. Back in and the gauge worked like it was supposed to. I turned the key off and moved the needle way down past E. Key on and it went to where the fuel level should be for a tank with 130 miles and a parade on it the day before. I turned the key off and pushed the needle way past F. Key back on and it went to the same proper spot again. Hmm, all this time I have refrained from beating on the dash, kicking the dash or any of that stuff because I was convinced the sender was the problem. Because that is what the manual said it was. Now I find out is was in front of me all the time and a good whack probably would have made it work.

I kept spinning the needle and turning the key on just to make sure it really did work. Colton was sanding on RED and kept hearing the glow plug relay clicking everytime he was changing out DA sand paper. He finally came over to see what I was doing. All he had to say was that his fuel gauge works just fine. Kids. Anyway, I cleaned all the dust out of the gauge panel, put everything back together after I remembered to un hook the batteries again. I even got the gauge plastic bezel and dash pad on without breaking off another heater fan switch tip which is something I do about every 4 dash pulls. It worked when I fired the truck up so I could put the skid gaurd back on the fuel tank. It worked last night when I drove it to Scouts too. I will top it off later in the week and see where my new FULL is.

"Clean every contact" Just keeps coming up as something to do before you buy parts on a CUCV.I spent over $100 to fix a dirty connection is what this thread boils down to. Yes, I do have a new sender, new fuel tank straps and new hoses back there. Which is something nice for the next 10 years. But I would rather of had the free fix it turned out to be.




 

Barrman

Well-known member
5,266
1,782
113
Location
Giddings, Texas
I topped the truck off this morning and it actually still works. With the LMC sender, totally topped off and no room for any more fuel in the tank the gauge exactly covers up the hash at F. I have never had a square body Chevy where F actually meant full. They always go past full and need 100 miles of driving to actually point at full. It is going to take some getting used to. Especially, when I figure in that E actually means empty with this set up.

Wanted to post an update for future reference.
 

rivcrazy2000

New member
43
0
0
Location
Anchorage, AK
Mine does this, I pulled the gauge out to clean it a couple months ago and replace the bulbs behind it since they were burned out. I put it back in and the needle still sweeps just 1/2 tank is as high as it reads and it will go way further down past empty. It sounds like this is what yours would do? I will try this when I get some spare time, I was going to just buy a new gauge since I thought I got water in it or something when I cleaned it but if it sounds similar to your problem I will try the contacts first.
 
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