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

[adf5565]

It’ll be hard to find a new filler hose that fits the cucv neck as I’m not sure they make them. Hopefully you can reuse yours, or find a gently used one online (I think hillbilly wizard had some). Or switch to the civy neck and hose.

And with the tank strap rivets, I just drilled them out and replaced with 1/4-20 bolts or something similar. As long as you have the insulators in there it’ll be fine.

 

[Commander5993]

It’ll be hard to find a new filler hose that fits the cucv neck as I’m not sure they make them. Hopefully you can reuse yours, or find a gently used one online (I think hillbilly wizard had some). Or switch to the civy neck and hose.

And with the tank strap rivets, I just drilled them out and replaced with 1/4-20 bolts or something similar. As long as you have the insulators in there it’ll be fine.

Yeah after I got the hoses cleaned up, I think they are reusable. I think it was the stripped out clamp that I found later that was allowing it to leak. I wouldn't mind switching to a civy fuel neck and hose, but I'll have to let that go for now.

I got the rivets drilled out and 1/4" - 20 short bolts should work. I got some grade 8 bolts and nylon lock nuts, or I could use regular nuts with some Loctite.

 

[87cr250r]

Either would be acceptable.

 

[Commander5993]

got new sending unit. is this black wire on the sending unit for a water in fuel sensor? if so is the cucv supposed to have this sensor in the tank? As I thought it was in the fuel filter housing. if it's not needed, should I cut it off? zip tie it up?





pulled old unit, looks completely different. guessing either old style, or for gas engine. I think someone pulled this tank from civy truck, and just stuck whole thing on this truck.

Looked inside old tank, I should have pulled all this first as I probably wouldn't have bought new tank. Only reason I didn't, I was trying to minimize how long the truck would be down. But old tank looks pretty clean inside. Anyway, got the new tank already. guess I can keep the old one as a back up or something.

 

[Commander5993]

well now the 2nd strap won't reach. 1st one fit fine on small end of tank. Bo⁰th these straps are the same length, and are the ST01 which I read on other threads was the right part number. also what was listed by summit as being the straps for this Tann. I have beat the lip of the tank in about as far as it will go and I'm still an inch short from going back through the hole of the bracket.

 

[Commander5993]

now I flipped the straps and the big end of the tank fit now... but now the small end of the tank won't reach

 

[Commander5993]

if you can't fix it, you just need a bigger hammer

 

[Commander5993]

my luck the tank will leak now

 

[ezgn]

got new sending unit. is this black wire on the sending unit for a water in fuel sensor? if so is the cucv supposed to have this sensor in the tank? As I thought it was in the fuel filter housing. if it's not needed, should I cut it off? zip tie it up?

View attachment 889151

View attachment 889152

pulled old unit, looks completely different. guessing either old style, or for gas engine. I think someone pulled this tank from civy truck, and just stuck whole thing on this truck.

Looked inside old tank, I should have pulled all this first as I probably wouldn't have bought new tank. Only reason I didn't, I was trying to minimize how long the truck would be down. But old tank looks pretty clean inside. Anyway, got the new tank already. guess I can keep the old one as a back up or something.

View attachment 889153

Don't need it, leave it or cut it out. must be for a different application with an inside fuel pump.

 

[Commander5993]

Don't need it, leave it or cut it out. must be for a different application with an inside fuel pump.

i ended up zip tying it up under the bottom side of the sending unit out of the way.

 

[Commander5993]

well... working on truck today, went to change my fuel hoses preparing to begin reinstall..... and here's "something" i ran into...

We all know there are 3 ports on civy fuel sending unit, instead of the 4 ports on the military sending units, one of which is capped off as it was only used to run external equipment like a generator or etc.

So on this 3 port civy sending unit I thought that these ports were:
1 - 3/8" Draw to fuel lift pump
2 - 5/16" Return line from engine
3 - 1/4" Tank Vent



However on this truck they only have TWO lines going to engine. The 3/8" and the 1/4".

The 5/16" (center port in sending unit) is the line that was Capped Off.... which before, when tank was still in the way, I thought this line was the "4th line" that had been disconnected and wasn't being used since someone had already switched this from the original military 4 port to a civy 3 port fuel sending unit.

Now looking at these, with tank out of the way, there is no 4th line anywhere. There is not even 3 actual lines.

So what is the the center 5/16" port on fuel sending unit supposed to be? And how can it just be capped off?? Maybe I'm completely off here, and this is how it's supposed to be. But from the info I had read on here before, I don't think 1 of these 3 ports should be capped off should they?? If that is the case, does that mean the original 4 port sending unit actually had Two lines capped off??


->EDIT: I've quit for today, because I don't want to reconnect this the way it was only to find out its wrong and I have to pull the tank down again. I did get a few other odds and ends done though, so once I figure this out everything should be ready to reinstall.

In pic below I'm pointing to the 5/16" line that would connect to the "center" port on the fuel sending unit. In the next two pics is that same line showing where it is capped off on the other side of the frame. And the two hardlines going to the engine. Any thoughts??

 

[adf5565]

well... working on truck today, went to change my fuel hoses preparing to begin reinstall..... and here's "something" i ran into...

We all know there are 3 ports on civy fuel sending unit, instead of the 4 ports on the military sending unitals, one of which is capped off.

so on this 3 port civy sending unit I thought that these ports were:
1 - 3/8" Draw to fuel lift pump
2 - 5/16" Return line from engine
3 - 1/4" Tank Vent

View attachment 889284

However on this truck they only have TWO lines going to engine. The 3/8" and the 1/4".

The 5/16" (center port in sending unit) is the line that was Capped Off.... which before, when tank was still in the way, I thought this line had been disconnected and wasn't being used since someone had already switched this from the original 4 port to a civy 3 port fuel sending unit.

now looking at these, with tank out of the way, there is no 4th line anywhere.

So what is the the center 5/16" port on fuel sending unit supposed to be? And how can it just be capped off?? Maybe im completely off here, and this is how it's supposed to be. But from the info I had read on here before, I don't think 1 of these 3 ports should be capped off should they??

View attachment 889286

View attachment 889287


View attachment 889290

Can’t answer the why question but mine was the same way so no worries there.

 

[Commander5993]

Got the tank back on and everything installed, including the new ground wire, reconnected the original sending unit "signal" wire, and installed the new sending unit hoses to the hard lines
I had to make a new ground wire as the connector on the old one broke off when I was removing the tank. So I made a new one out of 10 awg wire and soldered on a appropriate connector to the sending unit, and a copper lug where it goes to the frame. Used marine shrink tubing for both ends. Fit good and solid on both ends when installed.




After getting the tank, filler, filler hose and vent hoses all installed. I tried the key in the truck and turned it to the "on" position.... the guage didn't move . Still showed way past full. I was expecting it to go back to empty at this point, since the tank was empty.

Then I figured well maybe if I put some fuel in it, that will move the float on the sending unit and then maybe trigger the gauge. So I got my fuel pump that I made back some months ago for my gas cans, it uses an low psi (3 to 7psi?) vehicle fuel pump that was rated for gasoline or diesel. And I setup hoses and battery clamps for power, and an on/off switch. Its great for filling lawn mowers or our small tractor, instead of holding a gas can with fuel always leaking around the base of the nozzle... no matter what replacement nozzles I've tried. I only have one "regular" gas can that doesn't leak this way, and it cost like $50 back last spring. But I use this "pump" can for most things now.



When I made this "pump can", I also knew I could use it to empty a fuel tank if I ever needed to. Figured I'd post about this as maybe it can give someone an idea in the future for whatever they are working on. So I disconnected the hose that normally connects the pump to the gas can, added an inline fuel filter, a length of hose, and a double ended barb fitting on the end just for a weight to hold it at the bottom of the old fuel tank. I first ran diesel through it into a bucket to flush any gasoline out of the pump and line. Then put the "output" hose into the truck.





It isn't the fastest setup for transfering fuel from a larger tank, but it works steadily and on its own.

As a side note, when I began to pull fuel out of the old tank, I took my light and looked inside. And as far as the "total volume" of the tank, it looked like it was only half full. However the last time I drove this truck to town just before the starter died, I filled the truck up until I could see fuel in the fuel neck. I know that a "full tank" isn't actually going to fill the tank to the brim for vent and to make room for the float. But I would have figured it would be more than "half full". But what do I know

After a while the pump emptied the old tank completely, as I had the tank sitting on a slant with this end pointing downward.

In any case, after it was done and the old tank was empty, I once again turned on ignition to look at the fuel gauge.... still nothing. I started the truck for 10 seconds or so, didn't want to run it in the barn as it was closed up, but the gauge still didn't move at all. Needle still sitting in the same place it was before I started all this. And the thing is, before starting this job, as the tank fuel level dropped the gauge ALSO moved to show "less fuel"... just not to the actual level.

Now it apparently doesn't do anything. Even if there was an issue in the signal wire going from the fuel sending unit... like if it was broke somewhere now... wouldn't the fuel gauge just drop to Empty???




So... after $250, waiting on parts with the wrong part "mix-ups" etc, and the work to get this all in... I guess I at least got a clean fuel strainer

My only guess at this point is the actual gauge and/or the flexible "circuit board" on the instrument panel is bad. Even though when I took the instrument cluster out a few months ago, everything looked good and clean. So still just a guess.

Can anyone think of any other possibilities besides just a bad gauge / circuit panel?? Is there anything else left?

 

[Commander5993]

Can’t answer the why question but mine was the same way so no worries there.

Thanks for reply, I hooked mine back up that way as there is no 3rd fuel hard line on the truck. So I'm not sure what everyone else seems to refer to there originally being 3 lines + 1 capped off. Truck ran before hooked up this way, should run again the same. I just dont know how the tank is vented, as the cap doesn't appear to be a vented fuel cap.

 

[Commander5993]

The other thing I can think of besides the fuel gauge and circuit panel is that this new fuel sending unit is bad

I should have tested it before install, as just because parts are new doesn't mean they work.

 

[adf5565]

The other thing I can think of besides the fuel gauge and circuit panel is that this new fuel sending unit is bad

I should have tested it before install, as just because parts are new doesn't mean they work.

Try this. Shows the condition you have and how to troubleshoot.

 

[ezgn]

The other thing I can think of besides the fuel gauge and circuit panel is that this new fuel sending unit is bad

I should have tested it before install, as just because parts are new doesn't mean they work.

This is general good information that may come in handy.https://www.steelsoldiers.com/threads/cucv-instrument-cluster-decoded.46054/

 

[Commander5993]

Ok, I'm trying to figure out what I will need

Try this. Shows the condition you have and how to troubleshoot.

Thanks for the video ADF

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.

1981-89 Printed Circuits and Retaining Clip

Shop from thousands of parts and accessories to help you restore, maintain, and customize your Chevrolet, GMC, Dodge or Ford truck or SUV. Keep 'em on the road with the right part, right price, right now.

www.lmctruck.com

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

Fuel Gauge

Shop from thousands of parts and accessories to help you restore, maintain, and customize your Chevrolet, GMC, Dodge or Ford truck or SUV. Keep 'em on the road with the right part, right price, right now.

www.lmctruck.com

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....

 

[Commander5993]

This is general good information that may come in handy.https://www.steelsoldiers.com/threads/cucv-instrument-cluster-decoded.46054/

Thanks EZGN I was just going to look up to see if I could find some diagrams/photos of the circuit panel and wiring.

 

[ezgn]

Ok, I'm trying to figure out what I will need


Thanks for the video ADF

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.

1981-89 Printed Circuits and Retaining Clip

Shop from thousands of parts and accessories to help you restore, maintain, and customize your Chevrolet, GMC, Dodge or Ford truck or SUV. Keep 'em on the road with the right part, right price, right now.

www.lmctruck.com

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

Fuel Gauge

Shop from thousands of parts and accessories to help you restore, maintain, and customize your Chevrolet, GMC, Dodge or Ford truck or SUV. Keep 'em on the road with the right part, right price, right now.

www.lmctruck.com

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....

I think checking the resistor on the fuel gauge might be the least invasive chance of solving your issue.