# ? about gas tanks & sending units



## danmc (Jan 8, 2004)

Hello all,
I have an 89 F250, 5.8L. Can someone give me some advice/insight on a few problems I am having? My front tank is leaking right in the front at the seam where the two halves join. I was thinking of trying to patch it but I went to gastanks.com and found a replacement tank for $95. So I think I'll go that route. My problem right now though is I am not getting any fuel to the engine - I'm thinking there's a clog somewhere. Am I correct in guessing I have a sending unit for each tank? Is it possible to change to one large rear tank instead of having two 19 gallon tanks (thinking I'll have half as many potential issues with one tank/sending unit instead of two of each). Also, my fuel gauges aren't working properly - the gauge for the front tank doesn't read anything and when I switch to the rear tank it reads extreme full when the tank is full and reads empty when I have half a tank. Is this more of a wiring issue or sending unit issue? Any help is greatly appreciated!

Thanks,
Dan


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## maintenanceman (Jan 18, 2003)

Here are some suggestions. First switching to just one tank is a pain. i did it on my 91 ford. the main problem is the fuel lines. Mine were plastic and i had to modify them to remove the second line. The sending unit and gages are all in one unit. the unit also contains a shut off valve for the fuel lines to direct excess fuel back to the correct tanks. thus the reason why i needed to modify the fuel line. Your lack of fuel is likely due to your fuel filter being clogged as a leaky tank is usually due to rust and all the rust in the tank has probably plugged your fuel filter. Your gage problem could be in the wiring under the truck but sounds like the tank selector switch is worn out. hope this helps.


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## b2driver (Jul 22, 2004)

Have to agree with maintenance man. I'll add that it sounds as if you have multiple issues. Wiring problems and a clogged filter would be my guess, although bad pumps are a possiblity. I've had to change out two in the same truck before. If there are other gauges that aren't working properly though, such as the temp or oil pressure, it would indicate that your instrument voltage regulator on the back of your instrument cluster is failing. It affects all the readings of all the gauges.


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## 85F150 (Mar 13, 2003)

there is a sending unit/pump in each tank then a high pressure pump on the frame rail. take the gas caps off the tank, opne the little flapper where you stick the nozzle in and have someone turn the key on, listen for the pump to come on, on whichever tank you have selected from the switch. if one works and the other doesn't (when checking both tanks) then you know which tank has a bad fuel pump/sender or the ground/wiring could have issues at the plug in. 

if neither tank pumps make any sounds go under hood to the relay mounting and have some one do the key on again and listen for it to click or make noise, if it doesn't wiggle the wires or check to make sure the wires are getting powerlike how a normal relay should, (key on power, power all the time, gorund, then a wire with no power which the relay would send power down when turned on) if the relay is getting proper power and stilll isn't working replace it. if relay is getting power trace bback through the harnes to find the bad wire(s)

back to the tank though, you can check the plug in at the tank with a test light, have some one do the key on again and at least one wire should light up which will at least tell you, you are getting power to tanks.

good luck, need any more help, please post


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## b2driver (Jul 22, 2004)

I thought it was just a high pressure pump in each tank. I was under the impression that they stopped using the low pressure in tank pumps and high pressure rail pumps in the late 80's.


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## 85F150 (Mar 13, 2003)

sometimes they had both and sometimes not, it just depends on which way the wind blows, i have an 88 with that setup and an 87. My dads 91 van is also that way


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## ace911emt (Nov 27, 2004)

The first thing I would check would be the grounds because both a pump issue (low voltage) and gage issue(Low voltage) Leak issue, rust = non conductive, check the grounds..


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## MickiRig1 (Dec 5, 2003)

I have the same truck and the same issues in the past.
Try switching to the tank that's not sending fuel,climb under and have someone turn on the key,with your ear the the tank see if you can hear the pump running. If it is, find the tanking switching canister. It's black and both tanks feed into it to the rear and one line out to the front and a return line into it.
If the pump in the tank is running try LIGHTLY tapping the canister with a hammer. If you hear the high pressure pump sound change then it's probable the canaster's not switching the tank.
You should hear both tanks with the low pressure pump running when the switch is switched to that tank.
You turn on the key and should hear--> Click/Click VERT <--That's the pressure regulator bleeding pressure.
There are places that will rebuild the sensor plate,they replace the pipes in and the circuit board / sender. Make sure you replace the fuel line clips, never ever reuse them. Check the pressure reg by taking the vacuum line off when it's running, the engine will rev up if it's working, it will do the VERT sound at key on if that tank is giveing enough to have the right pressure.


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