Switching from gas to diesel fuel tanks

[pat english]

I can only find threads on people switching from diesel to gas or switching from gas to a duramax..
I'm switching from 454 gas to the 6.2 diesel.My truck has 3 gas tanks.I'd like to delete the 2 side tanks and just use the one in the back.What would i need to do?I will probably buy a new tank for the rear anyways because it's been sitting with the cap off for over 20 years.
Are the tanks the same but with different sending units?Thanks,Pat

[kipps]

GM never equipped a truck with three tanks from the factory. The pickups got one or two of the side-saddle tanks, and the Blazers/Suburbans got the rear tanks. No pickup ever came with a rear tank.

Somebody obviously added the rear tank from a Blazer or Suburban at some point in the past. How did they plumb the fuel filler? Through the bed? Behind a tail-light?

If you intend to keep the rear tank, I'd suggest you pull measurements, and try to figure out which tank was used. There were two different sizes; 30-gallon and 40-gallon, IIRC. There shouldn't be anything fundamentally different about the sender between gas and diesel, as long as it has the correct size and number of ports. A diesel sender will need to accommodate a fuel return. Most gas sender units didn't bother with a return.

[pat english]

Originally Posted by kipps

GM never equipped a truck with three tanks from the factory. The pickups got one or two of the side-saddle tanks, and the Blazers/Suburbans got the rear tanks. No pickup ever came with a rear tank.

Somebody obviously added the rear tank from a Blazer or Suburban at some point in the past. How did they plumb the fuel filler? Through the bed? Behind a tail-light?

If you intend to keep the rear tank, I'd suggest you pull measurements, and try to figure out which tank was used. There were two different sizes; 30-gallon and 40-gallon, IIRC. There shouldn't be anything fundamentally different about the sender between gas and diesel, as long as it has the correct size and number of ports. A diesel sender will need to accommodate a fuel return. Most gas sender units didn't bother with a return.

Alrighty good to know.thanks for the tips.heres where they put the filler

(Sorry for the crummy pics.i have the truck close to the wall and was standing on the bumper)

[kipps]

Is this a dually truck?

[pat english]

Originally Posted by kipps

Is this a dually truck?

Yes.

[Dead Parrot]

Watch the fill tube size. IIRC, diesel nozzles are larger then the standard unleaded nozzle. If you have a fill tube from the leaded gas era, you might be OK.

Electrically, the senders are compatible. I have an 84 CUCV(military version of a K30) with the 6.2. Replaced the broken fuel gauge with a "Unleaded Fuel Only" gauge. Other then the wrong labeling, it works fine.

I would paint the filler cap green and put an obvious "Diesel Fuel Only" label as a best effort to prevent fueling mistakes.

Not sure what your plans are but you might want to make sure the RPM limitations on the 6.2 won't be a problem.

[pat english]

Originally Posted by Dead Parrot

Watch the fill tube size. IIRC, diesel nozzles are larger then the standard unleaded nozzle. If you have a fill tube from the leaded gas era, you might be OK.

Electrically, the senders are compatible. I have an 84 CUCV(military version of a K30) with the 6.2. Replaced the broken fuel gauge with a "Unleaded Fuel Only" gauge. Other then the wrong labeling, it works fine.

I would paint the filler cap green and put an obvious "Diesel Fuel Only" label as a best effort to prevent fueling mistakes.

Ok thanks.good to know.

[pat english]

Hey kipps,didnt the later 80s suburban tanks have the fuel return port on the sending unit?I pulled one of those tanks from my buds 72 a few years ago and thought it had the return.
(And I just scrapped the tank..now I could use it.i throw away alot of stuff then end out needing it years later..)

[kipps]

Almost any squarebody sender from 87-91 was designed for a return. Both the diesel and the TBI gas engines depended on a return. There were a few carbureted engines left after 1987 though, particularly big blocks.

The 6.2 was available in the Suburban and Blazer. I'd suggest just buying a new tank and sender for a '82-'83 diesel 'Burb/Blazer, and installing that. That way, everything is new and rust free, and it's as close to stock as it gets. The only thing that will be non-stock on your fuel system is the filler neck location, since GM never had a rear-mount filler on the pickups.

Before you install any new or used sender, definitely check the resistance with a multi-meter. There's no sense in completing the install, only to find out the sender was defective from the factory.

[kipps]

Also, before you buy a new tank, drop your old one and look it over good. Compare the measurements to see what tank to buy, and also look for any modifications that needed to be done to the tank to make it work. You'll likely need to make the same modifications to the new tank.

A blazer/suburban tank will have some conflicts with the shock mounts on the 1-ton trucks, since the c30 and k30 moved the shocks inboard of the frame. One option is to clearance the tank a little with a hammer. The other option is to move one of the shocks to the front of the axle, so that both shocks are forward of the axle, instead of one in front and one behind.

Also, it's possible some mods were done to the filler neck on the tank to increase clearance. It's better to know about any necessary mods before you buy tanks instead of afterward. That way, if you decide it's too involved to duplicate any modifications, you can still resort to plan B, and run the factory side-saddle tanks.

[pat english]

Originally Posted by kipps

Also, before you buy a new tank, drop your old one and look it over good. Compare the measurements to see what tank to buy, and also look for any modifications that needed to be done to the tank to make it work. You'll likely need to make the same modifications to the new tank.

A blazer/suburban tank will have some conflicts with the shock mounts on the 1-ton trucks, since the c30 and k30 moved the shocks inboard of the frame. One option is to clearance the tank a little with a hammer. The other option is to move one of the shocks to the front of the axle, so that both shocks are forward of the axle, instead of one in front and one behind.

Also, it's possible some mods were done to the filler neck on the tank to increase clearance. It's better to know about any necessary mods before you buy tanks instead of afterward. That way, if you decide it's too involved to duplicate any modifications, you can still resort to plan B, and run the factory side-saddle tanks.

Looks like my rear tank is a homemade job.
Can I just run 1 saddle tank for now?just trying to get it running cheap as possible for now.

(Pics upside down)

[kipps]

If you don't have any fabrication skills, the single side-saddle tank will definitely be the cheapest. Since that tank was homebuilt, there's no guarantee that a factory suburban tank will match up with the filler neck.

Again, you'd want to buy a 20-gallon tank and sender for a '82-'83 diesel pickup. Your existing filler neck should work on the new tank, unless it's a choked down size for unleaded gas. If it is, you'll need to find the larger filler neck, in order to fit a diesel nozzle into the opening. Buy the tank and sender from RockAuto or somewhere similar. If you need a filler neck, Ebay or LMCtruck are good options.

[pat english]

Originally Posted by kipps

If you don't have any fabrication skills, the single side-saddle tank will definitely be the cheapest. Since that tank was homebuilt, there's no guarantee that a factory suburban tank will match up with the filler neck.

Again, you'd want to buy a 20-gallon tank and sender for a '82-'83 diesel pickup. Your existing filler neck should work on the new tank, unless it's a choked down size for unleaded gas. If it is, you'll need to find the larger filler neck, in order to fit a diesel nozzle into the opening. Buy the tank and sender from RockAuto or somewhere similar. If you need a filler neck, Ebay or LMCtruck are good options.

I do fab work on classics for a living, but I prefer factory stuff on my own vehicles.ill fill in that hole in the bed at some point.when I remove all the tanks.
Thanks for the advice.

[kipps]

Originally Posted by pat english

I do fab work on classics for a living, but I prefer factory stuff on my own vehicles.ill fill in that hole in the bed at some point.when I remove all the tanks.
Thanks for the advice.

That changes things a bit. Yes, still the cheapest option for now, is just bolt up a side-saddle tank and run it. Later on, the rear suburban tank could be pursued, but it might take some more fab work to get the filler neck positioned correctly to work with a stock GM tank.

[pat english]

Originally Posted by kipps

That changes things a bit. Yes, still the cheapest option for now, is just bolt up a side-saddle tank and run it. Later on, the rear suburban tank could be pursued, but it might take some more fab work to get the filler neck positioned correctly to work with a stock GM tank.

Yeah for now I'll do that.maybe do a custom tank in the future.i like the body and interior to be stock,but I do like them lowered too.im just focusing on getting it running for now because with most of my projects in the past I start with the cool stuff,then rarely get them running and sell everything off..so I'm trying to do it differently on this one.i want to post a build thread,but those have cursed my projects in the past too for some reason.if I do a build thread on something I always sell it.
Anyways, thanks for the help.

[Ziegelsteinfaust]

Pat, depending on how you want the project to sit. A 25 gallon blazer tank maybe better then a deeper suburban what are they 40 gallon?

The brackets to pull the tank up against are easy to do, and weld in. You just have to pull the bed to make it easy.

Personally I would do everything to make a 40 gallon fit since even a diesel will be a bit thirsty in the dually. Such as if your going to drop it heavily. I would raise the bed floor to raise the tank up too. With that being said I would make sure the bumper is tucked up too. At a 5/7 drop, and even more so at a 6/8. You can get high centered in those long trucks, and or drag the rear of the truck up steeper driveways.

[pat english]

Originally Posted by Ziegelsteinfaust

Pat, depending on how you want the project to sit. A 25 gallon blazer tank maybe better then a deeper suburban what are they 40 gallon?

The brackets to pull the tank up against are easy to do, and weld in. You just have to pull the bed to make it easy.

Personally I would do everything to make a 40 gallon fit since even a diesel will be a bit thirsty in the dually. Such as if your going to drop it heavily. I would raise the bed floor to raise the tank up too. With that being said I would make sure the bumper is tucked up too. At a 5/7 drop, and even more so at a 6/8. You can get high centered in those long trucks, and or drag the rear of the truck up steeper driveways.

I think the burb tanks are 40 gallons.they are pretty big

Are you talking about a blazer tank from a first or second gen?

Now I got some stuff to think about...I can't really take the bed off right now anyways.i got my buds trucking the garage right now.