Fuel Sending Unit questions

[Print Dad 58]

Hello All,

Started having troubles with the gas gauge on our 70 Mach.

 

Little history - All factory gauges are working BUT issues with the gas gauge.

Sending Unit and Tank were purchased about 3 years ago from MU.

 

Lately, when the needle reads 1/4 - - if I fill the tank she only takes 9 gallons and the needle reads full.

 

I was thinking a leaky FLOAT but then got to thinking if the float was filled she would not read FULL on the gauge.

 

Because it is getting close to end of the season I do not want to loose time by pulling things apart and then ordering parts - I would like to order parts before I pull things apart that way I loose no nights of cruising.

 

I should mention - - I STINK at elctrical - -have a few meters BUT don't know how to read them.

 

So do you people think it is the sending unit or something else like in the gauage itself. I have NOT swapped the voltage reg on the instrument cluster.

 

This issue seems to have started recently.

 

Also - if it is the sending unit - is there a better unit available than the one from MU with the plastic float? I would rather spend a little more and get something that will last longer.

 

Thanks as always - - Print DAd

[rangerdoc 22]

Unplug your sending unit at the tank and then ground out the wire to the frame or something else back there. Have someone look at the gas gauge while you do this. If your gas gauge goes to full then your sending unit is bad. Don't keep it grounded too long or you can damage a good gauge. Don't forget to turn the key to give power to the gauge.

 

It is possible to get a bad unit, I had to use 2 as the first one didn't register properly. I like the plastic as I don't have to worry about it corroding.

[Print Dad 58]

Hello rangerdoc,

The gauge will read full when I put in 9 gallons from the 1/4 reading.

I had not long ago grounded the wire on the sending unit and it does go to full.

 

So it does sound like the sending unit - BUT I sure hope I can buy one that

lasts longer then 3 years. Not to sure if plastic or brass float is better. All I know is the original brass lasted 40 years and the new one sure didn't make it

long.

 

Thanks for your input

 

Print Dad

[Mike65 476]

I would tend to say it is a bad sending unit. I think if the IVR was bad it would affect all the gages.

[LoneWolf2U 136]

Sadly most repo parts are far from being anything near as good as orginial parts.

Once you remove the sending unit from the tank, Hook the wire back on and attach a ground strap to it.

With the key on, test the sending unit by letting the float hang. It should read E on the guage. Move the float thru the levels while watching the guage to see if it is accurate as 1/4-1/2-3/4-full as you move the float level upward.

My guess would be that the sending unit has a missreading spot in it, Like my new float has. In a 22 gal tank with 5 gals in it reads 1/4.

Place 10 gals in it and it reads 1/3, 15 gals reads between 1/2 and 3/4.

But a full tank reads full.

[Print Dad 58]

Hello All,

Figured I post a little more info as a follow up.

I was curious so last night I crawled under the car and grounded the

wire from the sending unit and the gauge goes to FULL.

 

When I filled the tank last evening - -it would only read a little less than 1/2.

 

My guess is the float has a hole - -BUT - -I am going to purchase a new sending

unit and an extra FLOAT - -maybe I can use the SU in the tank as a back-up.

 

Mach1Rider - -I will try moving the float thru the various positions when I pull it and that should tell me a lot more as well.

 

The good thing - is when I replaced the tank and SU a few years ago, I purchased a tank with the drain - so I can swap out the SU on a rainy day

in the garage.

 

Now the only dillema is where to get a GOOD sending unit and not some import stuff that will not last.

 

ANyone know of a GOOD sending unit????

 

THANKS to ALL - -I appreciate the help, tips and ideas

 

Print DAD