Fuel tank replacement, fuel pump

SD diesels were widely available in the US in the 1981-86 Datsun/Nissan 720 pickups, and in Canada through '87 in the D21 pickup.

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indogwetrust88
Posts: 12
Joined: 5 years ago

Fuel tank replacement, fuel pump

#1

Post by indogwetrust88 » 3 years ago

Hey everyone,

So I pulled the fuel tank off my 81 diesel datsun 720 to have it cleaned. It sat for a year before I bought it and there's a lot of crap in the the tank. I'm gonna take it to a place that'll chemical wash it tomorrow and get a quote.

I don't have hardly any money to spend on this though, so I'm considering buying a new tank set up if it's cheaper. If I get a new tank I thought I'd need to know what fuel pump to pair with it. But when I took the tank off I saw it didn't even have a fuel pump inside. What the duck is that about? Does this truck only have a lift pump to pull fuel to the engine?

I'm wondering if anyone on this forum has ever replaced their fuel tank/fuel delivery system and what all they had to do for it. Anybody got some advice for me?

Also, if I have the original fuel tank cleaned do I need to get it lined for protection?

Keep in mind, I'm doin this on a tight budget. Thanks.

waynosworld
Posts: 517
Joined: 7 years ago
Location: Vancouver Washington USA

Re: Fuel tank replacement, fuel pump

#2

Post by waynosworld » 3 years ago

If your tank doesn't have any holes in it I would find a small/short piece of heavy chain, put it in the tank and tilt the tank all directions knocking all flakes of rust and dirt loose from the inside of the tank, you could likely use a bunch of lead sinkers also, then empty them out of the tank, blow it out with air till nothing but air comes out of the holes.
Then buy the best quality tank liner you can buy and coat the inside of the tank, follow the directions, make sure you keep blowing air thru the pickup tube so it don't get sealed shut, set the tank on it's end, upside down, anything other than level as the lowest part of the tank is where the pickup tube is and the liner material will go/settle there and plug up the pickup tube.
This is what I would do unless you can find another tank that is good in the wrecking yard out of a 720.
We don't know where you are located so maybe there are no Datsun trucks like yours(kingcab-regular cab?) in the wrecking yards around you, also there is the question are the diesel tanks different than the gasser tanks, every tank I have cut in half to scrap looked exactly the same to me.
I know the voices are not real,
but they have some really good ideas.

indogwetrust88
Posts: 12
Joined: 5 years ago

Re: Fuel tank replacement, fuel pump

#3

Post by indogwetrust88 » 2 years ago

Thanks!

I'm cleaning it out with muriatic acid before coat it. That's what I was told to by a guy who's cleaned tanks for years here in town. (Knoxville, TN)

If cleaning it out doesn't fix the problem I was gonna move on to the fuel pump. The only pump I have is a lift pump. No in tank or external fuel pump other than that. Does that sound right? I'm a greenhorn.

Thanks again.

Nissan_Ranger
Posts: 264
Joined: 13 years ago
Location: Canada

Re: Fuel tank replacement, fuel pump

#4

Post by Nissan_Ranger » 2 years ago

indogwetrust88 wrote:Thanks!

The only pump I have is a lift pump. No in tank or external fuel pump other than that?
That is correct. The only pump involved with primary fuel transport is the lift pump on the injection pump body.

Cleaning that tank out with muriatic acid is a nasty job. You want to have a respirator to use and clothes that you can sacrifice if needed. The muriatic acid can eat through the good metal in minutes and must be neutralized with an alkaline wash (like sodium bicarbonate) after treatment. Be sure to have at least a couple of pounds of the sodium bicarbonate on hand to treat any spillage. Spilled acid that is diluted may not manifest itself immediately. Once the water in it evaporates, it will damage/injure any surface it is on except glass and some plastic. So be careful!

Alternatively, you could put several pounds of sharp edged crushed gravel into it and shake it around for a while. If there are gummy deposits, dump a can or two of carb cleaner in with the stone. This will dislodge the worst of the rust and dirt after which you can clean it out. Sticking a good sized in-line fuel filter in the fuel line will catch any residual loose dirt. I did this with my tank and never had a problem. The lining is needed if the tank has really bad spots that might leak.

Andy
The old 'six gun' was as popular as the cell phone in its time and just as annoying when it went off in the Theater.

indogwetrust88
Posts: 12
Joined: 5 years ago

Re: Fuel tank replacement, fuel pump

#5

Post by indogwetrust88 » 2 years ago

Okay, y'all.

I some more questions but first of all, thanks for all the help so far!

I pulled and cleaned the tank with muriatic acid like I had mentioned in the prior posts. It was a giant pain and I do NOT recommend this to anyone. Muriatic acid is toxic stuff and there's not really any easy way to dispose of it when you're finished. You'll have to bottle it up and transport it to facility that can properly dispose of it. Plus, this process took me several days, as I was trying to make sure I got everything out of the tank.

Anyway, I did all that and I'm pretty sure I didn't even get all the debris/rust out. This is most likely because the inner top of the fuel tank is inaccessible from any available entry point. (I'm almost certain you would have to cut the tank open to be completely sure it's clean). At the end of all this the truck ran good for a day or two. But now it's loosing power and I'm pretty sure it's because some debris that remained on the tank's ceiling is clogging up the fuel delivery.

So here's what I'm thinking about trying:

I'm want to make a new fuel tank out of a diesel grade plastic fuel can that you can buy at most tractor supply shops. (I would just buy a new tank, but they're way too expensive for me right now. Then I'm gonna go to the local junk yard, pull a fuel tank off a car with same size fuel line fittings as a 1981 diesel 720, cut the tank open to pull out those fittings, and epoxy them into the plastic gas can. The end result will ride in the bed of the truck.

Does anyone know the fuel line fitting sizes on the diesel 720 (1981)? It'd save me the time of pulling off my tank to measure them. Also, if there is a better way to do this I will gladly take advice! I just don't have hardly any money, so please keep that in mind.

Best regards,
M.

waynosworld
Posts: 517
Joined: 7 years ago
Location: Vancouver Washington USA

Re: Fuel tank replacement, fuel pump

#6

Post by waynosworld » 2 years ago

indogwetrust88 wrote:Okay, y'all.

I some more questions but first of all, thanks for all the help so far!

I pulled and cleaned the tank with muriatic acid like I had mentioned in the prior posts. It was a giant pain and I do NOT recommend this to anyone. Muriatic acid is toxic stuff and there's not really any easy way to dispose of it when you're finished. You'll have to bottle it up and transport it to facility that can properly dispose of it. Plus, this process took me several days, as I was trying to make sure I got everything out of the tank.

Anyway, I did all that and I'm pretty sure I didn't even get all the debris/rust out. This is most likely because the inner top of the fuel tank is inaccessible from any available entry point. (I'm almost certain you would have to cut the tank open to be completely sure it's clean). At the end of all this the truck ran good for a day or two. But now it's loosing power and I'm pretty sure it's because some debris that remained on the tank's ceiling is clogging up the fuel delivery.

So here's what I'm thinking about trying:

I'm want to make a new fuel tank out of a diesel grade plastic fuel can that you can buy at most tractor supply shops. (I would just buy a new tank, but they're way too expensive for me right now. Then I'm gonna go to the local junk yard, pull a fuel tank off a car with same size fuel line fittings as a 1981 diesel 720, cut the tank open to pull out those fittings, and epoxy them into the plastic gas can. The end result will ride in the bed of the truck.

Does anyone know the fuel line fitting sizes on the diesel 720 (1981)? It'd save me the time of pulling off my tank to measure them. Also, if there is a better way to do this I will gladly take advice! I just don't have hardly any money, so please keep that in mind.

Best regards,
M.
You do not need to buy a tank with the same size fittings, you just need the pick up, the return, and a vent.
As I said the first post, put a small piece of heavy small chain or a whole bunch of lead sinkers in the tank and shake it around for a while, this knocks all the looser stuff off the inside of the tank, then empty it out and rinse it and let it dry, then tape all the holes shut, then buy the best quality tank liner you can buy and coat the inside of the tank, then take out the drain plug and empty the tank of all extra sealer, put the drain plug back in and set the tank on its end, blow air thru the pick up tube frequently to keep it clear several times over several hours, you might even use a broken speedo cable in the pick up tube, stick in in till it hits the bottom of the tank and spin it.
Once dry you are good to go, fill it and enjoy driving it.
I have fixed pressurized tanks with pin holes in them, it is the best and cheapest avenue in your case, new tanks are expensive, having them dipped is expensive, having someone else fix them is expensive.
I know the voices are not real,
but they have some really good ideas.

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