Fuel tank pickup/sender wiring?

[ny.wolcott]

I have a 1989 F350 7.3 diesel P/U with dual fuel tanks.

When on the rear tank the gauge always reads full.

When on the front tank the gauge reads full until the last 5 gallons or so, and then falls quickly.

Anyone have an idea what might cause this? Could there be an "open" in the wiring to the rear tank sending unit that causes the rear guage to always read full and a voltage variation to the front guage that could result in this?

Thanks in advance.

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[swuchase1]

I have the same problem with my 88 f-250 and the battery light is on. i think its a ground short??? do you see any change when you step on the brake? if/when i figure it out i will get back to you.

 

[ny.wolcott]

There are no other symptoms in my case. Brake light is off and nothing weird when brakes applied.

Yours does sound like a grounding problem somewhere.

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[allczns]

me too...

...both gauges are pegged past full until the last few gallons, then dive to empty. I drive by the odometer.
No answers, only questions...
cheers,

 

[Nicp]

I have same thing wrong with my 88 ford i posted a therd and basically came to the conclusion it my sending units you can check both them and i had buddy who had wholes in his floats to so there to place i would look first

 

[w4dsb]

my front one is always empty even with fuel running out the neck! I suspect my float has crapped out

 

[lpennock]

my front one is always empty even with fuel running out the neck! I suspect my float has crapped out

Your float is probally shot. Depending on the style of float you need you can just buy a replacement. My 92 was able to use the float from a old Bronco and it was a direct replacement. The float can be bought for about $5 from bronco graveyard so that you don't need to buy a complete sending unit

http://broncograveyard.com/bronco/i-10224-brass-sending-unit-float-66-77.html

 

[FORDMAN41291]

is there anyway to get my Gas Gauge needle to quit FLOATING!!!? I mean its worse than that POS Chevrolet thats sitting in my back yard. sometimes is floats really bad and other times it doesnt. it usually get bad when im betweem a half and 1/4 tank of gas. when i park on a hil or something the gauge goes back to normal after the float drained out for a while or so......

 

[I-HFreak]

so the floats can be replaced on a 1986 IDI? with dual tanks both dont work and exactly the same

 

[lpennock]

so the floats can be replaced on a 1986 IDI? with dual tanks both dont work and exactly the same

Most likely they can. The hard part is usually finding a new float piece. You won't know for sure until you drop the tank.

 

[gatorman21218]

my front one is always empty even with fuel running out the neck! I suspect my float has crapped out

X2

 

[FORDMAN41291]

I know I might just either need a new float or sending unit in my 94 F150 300 I6... anyone have one they could throw my way??

 

[lotzagoodstuff]

Floats should be available (changed both of mine, albeit its newer), not really that hard to change on a saddle tank as you should be able to sneak it out if you are patient. Rear tanks are definitely harder, you have to drop the tank in most cases. Have a look at the pickup tube while you have the sending unit out.

 

[FORDMAN41291]

what i dont understand is why Ford didnt put a pump in the tank itself but had a manual lift pump???

 

[lpennock]

what i dont understand is why Ford didnt put a pump in the tank itself but had a manual lift pump???

Actually consider that a good thing. When the stock lift pump goes out it is pretty easy to replace. If you have a in tank pump you have to drop the tank to change it. With the stock IDI pump you can always bypass it and put an inline electric pump without much effort. I need a better lift pump on my Cummins and I need to rip the in tank pump out make a adapter to pickup the fuel and then add a hi performance inline lift pump. All because the stock lift pump can't keep up under hard acceleration. Also have you looked at the replacement cost on a intank pump compared to what the IDI pump costs?