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I have a ford f-250 1991 with a 7.3 diesel.

I changed the rusted 19 gallon center tank with one from a salvage yard. The replacement tank came out of a regular gas truck. It looked identical in every dimension and aspect to the original tank I replaced.

It had a submerged pump in it but my truck did not have a submerged pump, so I put the fuel quantity sending float unit in that was in my truck to begin with.

My issue is now when I burn 7 gallons out of the 19 gallon tank from being full- it stops running due to no fuel siphoning from the tank for the engine driven lift pump to pull to the injector pump.

This is very annoying I have to fill up every other day otherwise it will stall and leave me stranded. I have the bed box off now and I look inside the tank and note that the pickup on my sending unit goes to the bottom of the tank. I see no reason why this is happening other than there is not enough head pressure at 12 gallons to keep the fuel delivery line primed.

Does anyone have any thoughts or ideas. I am thinking about purchasing a Submerged pump and quantity float assembly that was intended for the tank but I wondering-since these are for gas models-not diesel if there will be any issues.
 

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At the end of the pickup tube is the Cone of Failure, the plastic cone gets old, brittle, cracks, then falls off. VERY common problem. Only thing that gives me pause here though is that usually means you can use up the first 3/4 of a tank of fuel before it starts sucking air. You're not even getting to 1/2 a tank the way you're describing it.

So two other things to look at, look very carefully at the pickup tube itself for corrosion and/or rust pin holes.

See if the rubber check valve is still on the end of the return tube, if it's not you might be sucking air into your system when you shut down, but it won't when there's enough fuel in the tank to keep the end of the return submerged.

I think I have a picture, I'll post it in a minute if I can find it.
 

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Here it is, you can see that my Cone of Failure had failed and that's the rubber check valve on the end of the return that looks like a pencil eraser:

 

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I wonder if your problem might be venting. "Gas" tanks have to maintain a sealed system so you don't vent vapors into the atmosphere. I'm not 100% positive, but I think the gas and diesel tanks are different in that regard, and as such, you may be creating a vacum, losing the ability to pull fuel.

Take the fill cap off and see what happens.


Sent from AutoGuide.com App
 

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That's a good point, since the gas tank's original sending unit had lines that 'vented' into the charcoal canister the tank itself more than likely doesn't have the open air vent on the top of the tank that the diesel has.
 

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I wonder if your problem might be venting. "Gas" tanks have to maintain a sealed system so you don't vent vapors into the atmosphere. I'm not 100% positive, but I think the gas and diesel tanks are different in that regard, and as such, you may be creating a vacum, losing the ability to pull fuel.
Take the fill cap off and see what happens.
Sent from AutoGuide.com App
Just what I was thinking, plus did he plumb in a drainback line?
 

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He said he put in his origional diesel sender. Venting is very pluasible issue I have had this issue on a few tanks befor, more from gensets but a tank is a tank.
 

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Understood, key words were, "did he plumb it in?".
I'm not 100% positive, but I think the gas and diesel tanks are different in that regard, and as such, you may be creating a vacum, losing the ability to pull fuel.
Yep, the salesman warned me with my (fairly) new gas 1/2 ton if I don't go past tight with the cap until it clicks the engine warning light can/will come on. On my '91 diesel both caps are vented one way.
 

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Read this with much interest as it describes my problem to a T. I was able to purchase the part mentioned at the Ford dealer. Am anxious to install it. Does it require a hose clamp to keep it on or does it just slip on? Any other things I should be aware of?
 
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