fuel tank rusted

[bleucrew6.2]

I have a 1989 3500 4x4 crewcab that looks like it needs a new drivers side fuel tank. Seems the plastic gravel guard has been collecting mud for years, and this has led to some incredible rust- on the tank, straps, gravel guard supports, etc. Has anyone tried polyethelene replacement tanks? should I still use the gravel guard pans? I do not go four wheeling in this truck, however I do spend some time in West Virginnia on dirt roads. If I replace the tank with a steel unit, can I coat it with something (rhino liner?) so I can eliminate the gravel guard? Can the tank be removed/replaced without removing the bed?
Thanks for the help!

[PFahlberg]

Pickups used to have steel tanks and steel pans, result was rusted out tanks.

Then steel tanks and plastic guards. Still rusted out tanks.

Then plastic tanks and steel guards. Now rusty guards, but no leaks.

[bleucrew6.2]

PF,
Thanks for the short history on these fuel tanks and their shortcomings. What I was really looking for was some advice on how to approach this issue, and what choices I have based on other peoples experience with this problem. I believe that is what this forum is all about. I find your response disappointing.

bleucrew6.2

[Yukon6.2]

Hi bleucrew
You idea of a steel tank witf rhino lining sounds like the ticket to eliminating the rust issue from the outside.Probly the fix i will do if i ever have the problem on my diesel.We don't have any dealers for a spray on system here,but i have seen do it yourself kits.
I have had a few leaks on other GM's over the years,my mud toy has the bottom rusted out,tow truck has one tank with a hole in it,my high school project truck has one tank with a hole in it.
All of these tanks i fixed temperaraly,i used Seal All on all of these tanks.The mud toy was the worst bottom corner looked like window screen.
My highschool truck still holds gas in the fixed tank,fixed that one over 20 yrs ago,amazing stuff SealAll.Sometimes my temporay,seems like permanent.
Don't lose faith in this site,when i got my diesel i didn't know a thing about GM diesels.Then i found this site.3 yrs later i would go anywhere with my diesel knowing that i can fix anything on it to get home,or what to repace to get home. There is an amazing amount of info in the forums and an awsome group of people willing to help those with GM diesels.
Keep reading
And Good luck

[john8662]

When I first bought my '86 I had a fuel leak, which wasn't the tank, but I pulled the plastic shields to look anyways.

Same thing, full of mud/dirt that was rusting the bottom of the tank away.

So, I removed both covers, cleaned and primed with metal primer and re-assembled.

I can see how it'll rust right through from the outside.

I like the comment about undercoater, I shoulda done that while I had the covers off.

But, now that I know these things hold dirt, when washing the truck I always take the spray nozzle and direct it into the plastic cover and wash loose dirt out of there. I figure if I do that it'll be longer before it really collects again to where I'll have to pull the cover. Plus now I ain't going down any dirt or cleache roads in that truck, so that's a plus.

J

[bleucrew6.2]

I had a good hard look at the problem/job this past Saturday. Removed one of the tank supports to try and reach the sending unit, and found that even with the tank sagging a bit I could barely touch the fuel lines at the unit. I think I need to remove the bed for this job, unless someone has a better idea to share. Because it looks like the bed is coming off, I'm planning to replace both tanks. I'm looking hard at the poly tanks that a company called MTS (mtscompany.com) sells. Any thoughts?

[john8662]

If you've got a helper, Just remove the bed.

I did this on my '82 and my '86. In both cases to replace ALL the fuel lines.

[Warren96]

The fuel tank on mine has flexible lines that allow you to lower it enough so that you can unhook the fuel lines and gauge wires, dose'nt yours?

[bleucrew6.2]

Warren,
When I let the tank down about three inches, I could reach over the frame rail and just barely touch the sending unit. I have no idea how much slack is in the rubber fuel lines attached to the sending unit, and am afraid of bending or damaging the metal lines. I'm thinking that taking off the bed will give me all kinds of access, and also allow me to inspect/replace the fuel lines.
I plan on keeping this truck for a good long while, and want to eliminate any possibility of fuel leaks in the future. Thats why I'm looking into polyethelene replacement tanks.

[Robyn]

HI
Drop the tank as far as it will go and then snake a hand in there with some long handled cutters and cut the lines.
Or as I did, a box cutter (sharp) tapped to a broom stick and go right down in there and cut the hoses. The sending wire is usually long enough.

There are two wires, sender and the ground, be sure to get the gound back on or the thing won,t work right. If you need you can make the wires longer too.

Replace the fuel hoses with much longer ones and wrap them with that opaque wire wrap coil to protect them and let them lay on the tank top.
The hoses need to lay in a nice long loop. Too short and they will kink and not work. A nice loop from the frame out and across the tank and then back around to the tank fittings. I think my hoses ended up being about 2ft long

I did my dually a couple years ago. Mine has goose neck hitch platform in the bed that was reeeeeeeeeeeeeeeeeeeealy put on making bed removal way to much work.

Just use longer hoses and the jobs a snap.
With the new tank supported as close as you can get it and still reach the steel lines that cross the frame you can do a nice clean job and not have any problems.

The tanks are originally installed before the bed or cab are on so the hoses are easy for the assembler to get at so they use very short connector lines.

Plastic tanks wouild be nice but use a guard.

A factory steel tank is ok too, just rhino it first on the bottom and the sides.

Hope this helps

Robyn

[bleucrew6.2]

Thank you Robin!
Always a pleasure hearing from you! And thank you to all the rest for your insight and suggestions.

Bleu

[wthif]

Thought I would bring up an old post.

bleucrew6.2,

How did you end up replacing your tanks, did you follow Robyns method or did you remove the bed?


I'm currently leaning towards removing the bed bolts and raising the bed slightly to allow more room to work. Both of my tanks rusted from the inside out.

[bleucrew6.2]

Wow. This is an oldy but goody. I ended up using a modified Robyn technique. (I attached a metal cutting sawzall blade to a stick using a small screw and electrical tape) It worked like a charm to cut the fuel lines. When I installed the new tanks, I used just enough rubber fuel line to allow a comfortable installation- per Robyn. I was pleased with the fit and quality of the MTS poly tanks, and highly recommend them.
Getting those bed bolts loose, and removing the bed can be a tough job if you're working by yourself. Kind of impossible in my case...

Best of luck, whichever way you go!
John

[Robyn]

Glad everything came out OK for you.

The more I work on rigs and the deeper I get into things, the more I have begun to see just how stuff is "layered" on as the truck is assembled.

Most stuff in the engine bay can be removed and replaced with relative ease, especially on the older trucks (pre GMT400)

The fuel tanks on Pickups can be a tad nasty to get at the lines as you have seen.

The other area thats a bloody PITA is anything under the dash farther in then about 4 Inches :eek:

In my recent disassembly of the Blazer I have really picked up on just how a lot of this stuff goes in and when.

Your use of the poly tanks is a great choice. The original tanks are thin metal and will fail (as you have seen) from corosion from the outside as well as from the inside.

Small amounts of water accumulate over time due to condensation.

This small amount of water will lay on the bottom of the tank and over time start rust spots. As the rust continues its just a matter of time until it gets through.

My old 86 dually rotted through from the outside but, after replacing the tank I cut it open (after filling with water to prevent a fire or explosion)
I found several spots inside that would have resulted in leaks too within a short time.

The manufactures have taken most of these things into account and understand that the design will last a "reasonable" amount of years under most circumstances.

Large amounts of salt, mud, dust and such will hasten the demise of the tanks.

Had the tanks simply been sprayed with an asphalt type undercoating, the issue of outer rot through would have been much less prevalent.

Oh well, there are still a lot of mid 80's trucks out there plying the highways that retain the stock tanks.

Rigs that see use in dusty areas seem to have just as much issue as those used in very sloppy muddy areas.

The dust settles into the tank guard and then over time gets wet from the rain. Not all that different than sloppy mud to start with.


I have seen a few rigs that folks carefully cut an access port in the floor of the bed so they could get to the hose connections. A handy little cover plate had been fashioned and installed over the hole to allow access in the future if need be.

In salt country the big issue is usually getting the retaining hardware to come loose without breaking off :eek:

Out here in the Northwest, even with all the rain and wet, the underside of most rigs stays fairly pristine, allowing tanks strap fasteners to come off readily.

Plastic is a good thing.

Missy

[wthif]

Finished getting the fuel tanks in today. Took longer than I wanted, work got in the way. Anyways I ended up using Robyn's method of the longer fuel lines. I'm a little worried about chaffing of the lines, so I will try and secure them. I also wrapped the lines in convoluted tubing to give them a little more protection from chaffing.

The one thing I noticed that was different after replacing the tanks is the engine is smoking at idle. Like it is burning oil; hopefully this is just residue inside the tank from the manufacturing process. If I had known about the plastic tanks before starting this project I would have ordered them.

[Robyn]

Just changing the tanks should not have any affect on things. Smoking at idle is not related to the tank swap, unless you have a little air in the system that has not purged out.

Any residue (oil) in the tanks will mix with the diesel fuel and you would not know it.

Run the truck good and warm it up to temps and the issue may resolve.


Missy