Fixed; Another Fuel gauge thread

[carter262]

Vehicle 1987 M1008

Problem:
My gauge will only go to 3/8 when I will it up until I can't get any more in there. I just want another opinion before I order a new fuel gauge.

What I have tested and done:
TM test preformed.
Step 1 fuse is good. Contacts are good and have been cleaned.
Step 2 Disconnect ground to sending unit. Nothing changed. The gauge did not go to full or empty.
Step 3 Disconnect pink wire to sending unit and ground it. Went to "E" when grounded and went to Full when not grounded or attached to anything.

Tested the pink wire from sending unit to fuse box. It zeroed out with the ohm meter. So the pink wire is good.
Ran a ground wire from the ground on the battery to the sender unit (tested both at where the frame and directly on the sender unit). NO change.

Work I have already done trying to fix this issue:
Fuel gauge has been removed that post on the back were cleaned. The sockets that the fuel gauge plugs into have been cleaned. The sending unit has already been replaced with a new one. The ending unit was also check with an ohm meter prior to installing and it check out.

So I have narrowed it down? Is there anything that I have missed and need to check?

I don't understand my result with Step 2. I feel that there should of been some kind of reaction from the fuel gauge.

 

[cruzer747]

check with a DVM to see if your tank and frame are grounded together... tank is probably getting ground through strap or whatever and is redundant in addition to ground wire. Sounds like sending unit for sure shout though.

 

[carter262]

check with a DVM to see if your tank and frame are grounded together... tank is probably getting ground through strap or whatever and is redundant in addition to ground wire. Sounds like sending unit for sure shout though.

Thanks for the reply.

What is "a DVM"?

The sending unit is brand new. I know you can get a bad one new but we tested it before installing it and the Ohms zeroed at empty and were around 90 at full. So hwy do you believe that the sending unit is bad?

 

[cruzer747]

Thanks for the reply.

What is "a DVM"?

The sending unit is brand new. I know you can get a bad one new but we tested it before installing it and the Ohms zeroed at empty and were around 90 at full. So hwy do you believe that the sending unit is bad?

digital volt meter.

since your gauge goes to e when given ground and full when "open" it appears to work but I guess it could be out of whack still. Take a meter and measure what you are getting from the sending unit now when full. if ~ 90 ohms adn it is making good connection to the wire but the gauge is only going up a little then it could be the gauge I suppose.

I would do a redundant test and get a 100 ohm resistor

(common and easy to find if you have any scrap electronics https://somanytech.com/100-ohm-resistor-color-code/)

and connect it from wire to ground and see what the fuel gauge reports. Should go to full, if not then it may be the gauge. Could also just be a bad connection on the sending wire side of things.

 

[carter262]

I pulled the dash apart the other day. I checked everything, cleaned all the contacts since I was in there, and put in s different fuel gauge. Now everything works.

Well that is one thing off the to do list. Thanks for the help.