Temp and fuel level gauges reading very low

[Jfryjfry]

This is a recent build and I’ll give the problem, the layout, and what Ive checked.

Our temp gauge and fuel gauge barely move. Fuel to just a hair over E (with 1/2 tank) and temp gauge to almost the first mark (120).

The tank is a wild horses Sherman tank with their pump. I put a plug on it just in front of the tank with the three wires (ground sender pump hot). until a week ago it was dry. Finally got the fitech unit in and am using the tank now so I put 10 gallons in.

The temp sending unit is in the back of the motor where it isn’t as hot as if it were in the front so I chalked it up to just being colder and maybe a bad unit.

The ivr is a new electronic unit probably from toms

The oil pressure gauge seems to work. It climbs very slowly but gets up to about 70psi.

But now seeing that the fuel gauge acts the same as the water temp, I wonder if they are related.

I grounded the signal wire at the tank and the gauge climbed pretty quick to F before I shut it off.

The sending unit seems to be reading 40 ohms (with half a tank, so I think it is correct).

I am getting about 5v on the wire to the tank sending unit.

The grounding, volt reading and the ohms were done at the plug at the tank.


Thoughts??

 

[DirtDonk]

The ivr is a new electronic unit probably from toms

Always a good idea to check output voltage on any of these. But it sounds from your testing that it's set properly. Normally you expect 5 to 6 volts if I remember.

The oil pressure gauge seems to work. It climbs very slowly but gets up to about 70psi.

That's almost too bad! If it was also low, at least you could narrow your hunt down a bit. But hey, it's never quite that easy is it?
But to get all our ducks in a row, just how slow does it rise to the top? Take less than 10 seconds? Should be fine.
Longer than that and there might be a problem.

But now seeing that the fuel gauge acts the same as the water temp, I wonder if they are related.

Could be, but not from the power source/IVR at least. Just as likely they are unrelated.
Is this all stock wiring, or has the Bronco been re-wired?

I grounded the signal wire at the tank and the gauge climbed pretty quick to F before I shut it off.

The sending unit seems to be reading 40 ohms (with half a tank, so I think it is correct).

My first thought would have been that your sender was not playing nice with the gauge. But at 40ohms, it sounds close. I know there are charts hereabouts that show what reading you should get at different levels. Maybe you can find one of those and verify.
Never hurts to verify...

But what about a dash switch for dual tanks? Are you using, or did yours originally have duals? If there is a switch, I would temporarily bypass it to see if it's effecting the reading.
Happens a LOT with these old switches.

I am getting about 5v on the wire to the tank sending unit.

Check the oil voltage for the oil sending unit wire too, just to be sure.
You said you grounded it and it went to full, correct? If not go ahead and do that sender as well.

Paul

 

[B RON CO]

Hi, make sure the tank sender is grounded. Make sure you have a temp sender for a gauge, not a light, and do not use teflon tape on the temp sender, teflon tape could interfere with the ground. Good luck

 

[68Broncoz]

I used this https://www.amazon.com/gp/product/B002IABL6C/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1 and was able to swing my temp and oil pressure back and forth to ensure it worked. Someone posted the resistance values for the senders and gauges and I used those to see if my gauges were close to accurate and would actually move correcly.

Chris

 

[Jfryjfry]

thanks Chris -
I decided to order one to have as a tool to check this kind of thing. I got busy today but will run some of Paul's checks as well.