Fuel System Issue

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Vietnam Mutt
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Fuel System Issue

Unread post by Vietnam Mutt » March 19th, 2018, 12:15 am

Hi Everyone,

I have a very strange issue by the general fuel system.
My fuel gauge shows from beginning on not the correct amount of fuel in the tank. Now I had the time to check the system.
I have bought a new sender unit for the M151A2 and measure the ohm for empty = 0 ohm and for full = ~ 31-33 ohm. The sender unit shows correct if I test it with the ohm meter.
I have replaced the cable to the fuel gauge and check if the sender unit sends the correct ohm to the gauge. It's match. The gauge is 24V and ~ 30 ohm and is the match for the general system. Additional I add one more ground cable to the send unit to the chassis. Everything works well.
Now my problem is as soon I put in the sender unit into the tank (full) is shows me only 2/4 full = ~ 12 ohm output only. I read before to bend the arm for adjustments but the maximum I get with this adjustment is 16 ohm. Means still not show full but visual the tank is full.
I also try with different swimmer because I think maybe the brass swimmer is to heavy and get not enough uplift. Unfavorable I lost it in the tank. :-)

Did anyone has the same issue that you check everything and is ok until you place the sender unit into the tank?

Thanks in advance for your comments and ideas.
Kind Regards,
Vietnam Mutt

1975 M151A2

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muttguru
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Re: Fuel System Issue

Unread post by muttguru » March 19th, 2018, 11:43 am

Have you installed the sender in the correct position? In theory, there are several positions the sender can be fitted, but only one is correct. If the sender is installed in the wrong position, the movement of the operating arm will be restricted and you will not have the correct reading.

Have a look at TM9-2320-218-20-1-1 Section 5-63 page 5-167 for correct installation.
ken
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Note for 2023..... Ken..."Less Stress - More Exercise!"

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rickf
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Re: Fuel System Issue

Unread post by rickf » March 19th, 2018, 2:18 pm

It sounds like you have very thoroughly checked out all of the electrical problems that would normally happen and it definitely sounds like the float is not coming all the way to the top. Either it is hitting something OR, it is already bent too far and it is hitting the top of the tank too early. Try bending the arm down a little, this will cause the electrical sweep to rise up more.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
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halftracknut
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Re: Fuel System Issue

Unread post by halftracknut » March 19th, 2018, 6:17 pm

I had one do that and it was the float half full of gas....shake it and you should be able to hear it..could be ground is poor..
slowest mutt east of the missippi..

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Re: Fuel System Issue

Unread post by Vietnam Mutt » March 19th, 2018, 7:54 pm

Hi All,

thanks for all your reply.
a. I have checked the position twice and I follow the manual and also the picture from Ken what he has uploaded times ago. The position of the sender unit is correct.
b. The I have made a additional ground cable already and it's work fine
c. If I shake the Mutt the need in the gauge move up and down but I hear not a sound that something will be hit in the tank from the float arm.
d. I bend the float arm and measure with the ohm meter but the maximum I can get after install back into the fuel tank is 18 ohm. If I bend more the ohm will go down again. I spend two days on bending the floating arm and measure the ohm. If I got the 18 ohm I plug in the sensor cable to cross check with the gauge and the gauge shows me the correct amount of fuel follow the 18 ohm.

May I open the fuel tank complete to check everything from the inside to see if it stacks or touch something. Really is strange to me. Hummm......
Kind Regards,
Vietnam Mutt

1975 M151A2

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rickf
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Re: Fuel System Issue

Unread post by rickf » March 19th, 2018, 8:50 pm

I would drive it around until it is almost empty or siphon the gas into cans and then look in there with a small inspection mirror so you can see exactly what is going on with the float. You should be able to see it from the fill hole with a mirror. You might even be able to sneak in a piece if stiff wire to move it up and down while watching the mirror and have someone tell you what the gauge or meter is reading.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

Vietnam Mutt
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Re: Fuel System Issue

Unread post by Vietnam Mutt » March 19th, 2018, 9:19 pm

Hi Rickf,

thanks for your suggestions. I will check it out on this weekend.
If I have news I will update it.
Kind Regards,
Vietnam Mutt

1975 M151A2

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Horst
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Re: Fuel System Issue

Unread post by Horst » March 20th, 2018, 4:28 am

let me know what you will find. I have the same issue.
Horst

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Vietnam Mutt
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Re: Fuel System Issue

Unread post by Vietnam Mutt » March 21st, 2018, 7:50 pm

Hi,

forgot one point in the check list.
I have checked the voltage of the gauge and it was 3.5V. Means the fuel gauge have the correct voltage to the sender unit.
Kind Regards,
Vietnam Mutt

1975 M151A2

Vietnam Mutt
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Re: Fuel System Issue

Unread post by Vietnam Mutt » March 21st, 2018, 11:37 pm

Hi All,

I have researched more and find a very interesting post from 2005 from Louie in the G503 forum called " Is your fuel gauge needle fluctuating?".
He describe nearly the same issue I have and it's say that more ground must be add to the floating arm & floating measure unit by connecting a thin wire to the grounded fuel tank body.
Unfavorable I can't see the images he posted how he did it.
I will check if I find a wire like he describe and test it if I find nothing more out after I open the fuel tank on the weekend.
Maybe is one think more for make it working. :-)
Kind Regards,
Vietnam Mutt

1975 M151A2

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Re: Fuel System Issue

Unread post by rickf » March 22nd, 2018, 10:40 am

Basically what he was saying was that the ground from the tank to the body was not good so he added a ground from the sender to the battery. I think you said you already did that earlier.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

Vietnam Mutt
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Re: Fuel System Issue

Unread post by Vietnam Mutt » March 22nd, 2018, 7:58 pm

Hi Rickf,

yes I did an additional ground cable from the sender unit to the body.
I understood him like he have additional make a thin wire who works as second ground cable from the floating arm & floating measure unit from inside the tank to the ground cable of the body.
Kind Regards,
Vietnam Mutt

1975 M151A2

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Re: Fuel System Issue

Unread post by rickf » March 23rd, 2018, 9:29 pm

I guess that would not hurt but from the readings you have given I don't think it will make any difference. That stuff is all usually soldered together at the factory. The Chinese sending units have been an issue for not working at all, not working for long or not working well when they do work. Even the originals did not work all that well, I think the way the military looked at it was that yo have a huge hole there, if the gauge says it is low then open the cap and look in and see. A lot of people just have a paint stirrer that they keep next to the seat and it is marked off with a marker as to how much gas is at each line. Can't get any more accurate than that, no electrical gremlins either. :lol:
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

Mark
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Re: Fuel System Issue

Unread post by Mark » March 23rd, 2018, 9:42 pm

Ya, I used to carry a lath in the mutt, as my fuel gauge, that also applied to a lot of the construction equipment in my other life, never tried a match in the tank opening though, I wasn't smart enough to make it work without damage to equipment.LOL
mark


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raymond
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Re: Fuel System Issue

Unread post by raymond » March 25th, 2018, 12:32 pm

If you insist on relying solely on your fuel gauge you should:

A) Wear comfortable walking shoes.
B) Carry a cell phone.
C) Keep your AAA or other automobile club membership current.
Raymond


"On the day when crime puts on the apparel of innocence, through a curious reversal peculiar to our age, it is innocence that is called on to justify itself." Albert Camus

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